September 9, 2020
Volume 2020, Dated: 9 September 2020
[Initiated by Prof. Dr. K. Lakshmi Narayana]
In Memory of
Late Professor Kotcherlakota Rangadhama Rao
D.Sc. (Madras).a D.Sc. (London).
(Birth on 9 September 1899 Early Morning, Berhampur
Demise on 20 June 1972 at 9 h 09 m at Visakhapatnam),
at his residence, Narasimha Ashram, Official Colony,
Maharanipeta. P. O., Visakhapatnam 530002.
[Mrs. Peramma Rangadhama Rao demise on 31 Dec 1971 around 10 AM.]
TRUWIZ-121b.
Q61.arXiv:2002.03086 [astro-ph.GA]: Impact of an Active Sgr A* on the Synthesis of Water and Organic Molecules Throughout the Milky Way. Chang Liu (PKU), Xian Chen (PKU), Fukun Du (PMO): Submitted on 8 Feb 2020): ABSTRACT: Sgr A*, the supermassive black hole (SMBH) in our Galaxy, is dormant today, but it should have gone through multiple gas-accretion episodes in the past to grow to its current mass of 4×10^6 M⊙. Each episode temporarily ignites the SMBH and turns the Galactic Center into an active galactic nucleus (AGN). Recently, we showed that the AGN could produce large amount of hard X-rays that can penetrate the dense interstellar medium in the Galactic plane. Here we further study the impact of the X-rays on the molecular chemistry in our Galaxy. We use a chemical reaction network to simulate the evolution of several molecular species including H2O, CH3OH, and H2CO, both in the gas phase and on the surface of dust grains. We find that the X-ray irradiation could significantly enhance the abundances of these species. The effect is the most significant in those young, high-density molecular clouds, and could be prominent at a Galactic distance of 8kpc or smaller. The imprint in the chemical abundance is visible even several million years after the AGN turns off. The potential impact on the origin and evolution of organic and prebiotic molecules in the Milky Way deserves further
a. details b. investigation c. research d. abundances.
Q62. arXiv:2002.03096 [astro-ph.HE]: Discovery of annular X-ray emission centered on MAXI J1421-613: Dust-scattering X-rays?Kumiko K. Nobukawa, Masayoshi Nobukawa, Shigeo Yamauchi. (Submitted on 8 Feb 2020):ABSTRACT: We report the discovery of an annular emission of ~3'-9' radius around the center of a transient source, an X-ray burster MAXI J1421-613, in the Suzaku follow-up analysis. The spectrum of the annular emission shows no significant emission-line structure, and is well explained by an absorbed power law model with a photon index of ~4.2. These features exclude the possibility that the annular emission is a shell-like component of a supernova remnant. The spectral shape, the time history, and the X-ray flux of the annular emission agree with the scenario that the emission is due to a dust-scattering echo. The annular emission is made under a rare condition of the dust-scattering echo, where the central X-ray source, MAXI J1421-613, exhibits a short time outburst with three X-ray bursts and immediately re-enters a long quiescent period. The distribution of the hydrogen column density along the annular emission follows that of the CO intensity, which means that MAXI J1421-613 is located behind the CO cloud. We estimate the distance to MAXI J1421-613 to be ~3~kpc assuming that the dust layer responsible for the annular emission is located at the same position as the CO
a. formation b. source c. cloud d. density.
Q63.arXiv:2002.03693 [astro-ph.HE]: The remnant of neutron star-white dwarf merger and the repeating fast radio bursts. iang Liu (XAO, CAS): (Submitted on 10 Feb 2020): ABSTRACT: Fast radio bursts (FRBs) at cosmological distances still hold concealed physical origins. Previously Liu (2018) proposes a scenario that the collision between a neutron star (NS) and a white dwarf (WD) can be one of the progenitors of non-repeating FRBs and notices that the repeating FRBs can also be explained if a magnetar formed after such NS-WD merger. In this paper, we investigate this channel of magnetar formation in more detail. We propose that the NS-WD post-merger, after cooling and angular momentum redistribution, may collapse to either a black hole or a new NS or even remains as a hybrid WDNS, depending on the total mass of the NS and WD. In particular, the newly formed NS can be a magnetar if the core of the WD collapsed into the NS while large quantities of degenerate electrons of the WD compressed to the outer layers of the new NS. A strong magnetic field can be formed by the electrons and positive charges with different angular velocities induced by the differential rotation of the newborn magnetar. Such a magnetar can power the repeating FRBs by the magnetic reconnections due to the crustal movements or
a. star collapse b. star outburst c. magnetars d. starquakes.
Q64. arXiv:2002.04216 [physics.optics]: Optical analogues of black-hole horizons. Yuval Rosenberg. (Submitted on 10 Feb 2020): ABSTRACT: Hawking radiation is unlikely to be measured from a real black-hole, but can be tested in laboratory analogues. It was predicted as a consequence of quantum mechanics and general relativity, but turned out to be more universal. A refractive index perturbation produce an optical analogue of the black-hole horizon and Hawking radiation that is made of light. We discuss the central and recent experiments of the optical analogue, using hands-on physics. We stress the roles of classical fields, negative frequencies, 'regular optics' and dispersion. DETAILS: This paper discusses the optical analogues that use a refractive index perturbation to establish an artificial black-hole horizon. Extensive reviews of analogue gravity exist [14,15], but they pay little attention to optical analogues and substantial progress was made after their publication. CONCLUSIONS: . The reality of optical horizons and negative frequencies became clear, and multiple optical interpretations made their physics more tangible. The crucial role of dispersion was stressed, determining the Hawking spectrum. Both a phase and a group velocity horizon are necessary for Hawking radiation. The universality of the Hawking effect separates it from gravity and high-energy physics, and emphasises the central role of classical fields to the process. This hints to more possibilities in gravity and in optics, even before going fully
a. stressed b. quantum c. tangible d. Hawking radiation.
Q65.arXiv:2002.04382 [physics.ed-ph]: Using smartphones as hydrophones: two experiments in underwater acoustics. Martin Monteiro, Arturo C. Marti. (Submitted on 11 Feb 2020): ABSTRACT: During the last years, it has become increasingly clear that smartphones are valuable tools to be used almost everywhere. Until recently, a place that still resisted smartphone onslaught was the aquatic media. However, nowadays, many modern smartphones are waterproof and the performance of their microphones results sufficiently adequate to employ them as hydrophones. This capability gives rise to several interesting applications. Here, we describe two experiments in underwater acoustics which require two smartphones -- at least one should be waterproof. The first experiment consists in a simple time-of-flight measurement of the sound speed in water and the comparison with the corresponding value in air. The second experiment deals with the acoustic location -- or ranging -- of a distant object by comparing the time it takes for the sound to reach the object travelling in two different media (air and water in this case) with known sound speed. Closing remarks To sum up, we have described a simple and inexpensive experiment in underwater acoustics, an area usually little explored in Physics courses. At least one waterproof smartphone is needed and the experiments can be performed in a small pool or pond. Data analysis requires only a sound editor, however, due to the noise inherent to the aquatic media, special attention should be paid to the experimental
a. details b. results c. pool d. courses.
Q66.arXiv:2002.05218 [astro-ph.IM]: The variable shadow of M87*. Philipp Arras, et al., (Submitted on 12 Feb 2020): ABSTRACT: Observing the dynamics of compact astrophysical objects provides insights into their inner workings and allows to probe physics under extreme conditions. The immediate vicinity of an active supermassive black hole with its event horizon, photon ring, accretion disk, and relativistic jets is a perfect place to study general relativity, magneto-hydrodynamics, and high energy plasma physics. The recent observations of the black hole shadow of M87* with Very Long Baseline Interferometry (VLBI) by the Event Horizon Telescope (EHT) open the possibility to investigate dynamical processes there on timescales of days. In this regime, radio astronomical imaging algorithms are brought to their limits. Compared to regular radio interferometers, VLBI networks have fewer antennas. The resulting sparser sampling of the Fourier sky can only be partly compensated by co-adding observations from different days, as the source changes. Here, we present an imaging algorithm that copes with the data scarcity and the source's temporal evolution, while simultaneously providing uncertainty quantification on all results. Our algorithm views the imaging task as a Bayesian inference problem of a time-varying flux density, exploits the correlation structure between time frames, and reconstructs a whole, (2+1+1)-dimensional time-variable and spectral-resolved image at once. We apply the method to the EHT observation of M87* and validate our approach on synthetic data. The obtained first time-resolved reconstruction of M87* indicates varying structures on and outside the emission ring on a time scale of
a. months b. years c. days d. weeks.
a. details b. investigation c. research d. abundances.
Q62. arXiv:2002.03096 [astro-ph.HE]: Discovery of annular X-ray emission centered on MAXI J1421-613: Dust-scattering X-rays?Kumiko K. Nobukawa, Masayoshi Nobukawa, Shigeo Yamauchi. (Submitted on 8 Feb 2020):ABSTRACT: We report the discovery of an annular emission of ~3'-9' radius around the center of a transient source, an X-ray burster MAXI J1421-613, in the Suzaku follow-up analysis. The spectrum of the annular emission shows no significant emission-line structure, and is well explained by an absorbed power law model with a photon index of ~4.2. These features exclude the possibility that the annular emission is a shell-like component of a supernova remnant. The spectral shape, the time history, and the X-ray flux of the annular emission agree with the scenario that the emission is due to a dust-scattering echo. The annular emission is made under a rare condition of the dust-scattering echo, where the central X-ray source, MAXI J1421-613, exhibits a short time outburst with three X-ray bursts and immediately re-enters a long quiescent period. The distribution of the hydrogen column density along the annular emission follows that of the CO intensity, which means that MAXI J1421-613 is located behind the CO cloud. We estimate the distance to MAXI J1421-613 to be ~3~kpc assuming that the dust layer responsible for the annular emission is located at the same position as the CO
a. formation b. source c. cloud d. density.
Q63.arXiv:2002.03693 [astro-ph.HE]: The remnant of neutron star-white dwarf merger and the repeating fast radio bursts. iang Liu (XAO, CAS): (Submitted on 10 Feb 2020): ABSTRACT: Fast radio bursts (FRBs) at cosmological distances still hold concealed physical origins. Previously Liu (2018) proposes a scenario that the collision between a neutron star (NS) and a white dwarf (WD) can be one of the progenitors of non-repeating FRBs and notices that the repeating FRBs can also be explained if a magnetar formed after such NS-WD merger. In this paper, we investigate this channel of magnetar formation in more detail. We propose that the NS-WD post-merger, after cooling and angular momentum redistribution, may collapse to either a black hole or a new NS or even remains as a hybrid WDNS, depending on the total mass of the NS and WD. In particular, the newly formed NS can be a magnetar if the core of the WD collapsed into the NS while large quantities of degenerate electrons of the WD compressed to the outer layers of the new NS. A strong magnetic field can be formed by the electrons and positive charges with different angular velocities induced by the differential rotation of the newborn magnetar. Such a magnetar can power the repeating FRBs by the magnetic reconnections due to the crustal movements or
a. star collapse b. star outburst c. magnetars d. starquakes.
Q64. arXiv:2002.04216 [physics.optics]: Optical analogues of black-hole horizons. Yuval Rosenberg. (Submitted on 10 Feb 2020): ABSTRACT: Hawking radiation is unlikely to be measured from a real black-hole, but can be tested in laboratory analogues. It was predicted as a consequence of quantum mechanics and general relativity, but turned out to be more universal. A refractive index perturbation produce an optical analogue of the black-hole horizon and Hawking radiation that is made of light. We discuss the central and recent experiments of the optical analogue, using hands-on physics. We stress the roles of classical fields, negative frequencies, 'regular optics' and dispersion. DETAILS: This paper discusses the optical analogues that use a refractive index perturbation to establish an artificial black-hole horizon. Extensive reviews of analogue gravity exist [14,15], but they pay little attention to optical analogues and substantial progress was made after their publication. CONCLUSIONS: . The reality of optical horizons and negative frequencies became clear, and multiple optical interpretations made their physics more tangible. The crucial role of dispersion was stressed, determining the Hawking spectrum. Both a phase and a group velocity horizon are necessary for Hawking radiation. The universality of the Hawking effect separates it from gravity and high-energy physics, and emphasises the central role of classical fields to the process. This hints to more possibilities in gravity and in optics, even before going fully
a. stressed b. quantum c. tangible d. Hawking radiation.
Q65.arXiv:2002.04382 [physics.ed-ph]: Using smartphones as hydrophones: two experiments in underwater acoustics. Martin Monteiro, Arturo C. Marti. (Submitted on 11 Feb 2020): ABSTRACT: During the last years, it has become increasingly clear that smartphones are valuable tools to be used almost everywhere. Until recently, a place that still resisted smartphone onslaught was the aquatic media. However, nowadays, many modern smartphones are waterproof and the performance of their microphones results sufficiently adequate to employ them as hydrophones. This capability gives rise to several interesting applications. Here, we describe two experiments in underwater acoustics which require two smartphones -- at least one should be waterproof. The first experiment consists in a simple time-of-flight measurement of the sound speed in water and the comparison with the corresponding value in air. The second experiment deals with the acoustic location -- or ranging -- of a distant object by comparing the time it takes for the sound to reach the object travelling in two different media (air and water in this case) with known sound speed. Closing remarks To sum up, we have described a simple and inexpensive experiment in underwater acoustics, an area usually little explored in Physics courses. At least one waterproof smartphone is needed and the experiments can be performed in a small pool or pond. Data analysis requires only a sound editor, however, due to the noise inherent to the aquatic media, special attention should be paid to the experimental
a. details b. results c. pool d. courses.
Q66.arXiv:2002.05218 [astro-ph.IM]: The variable shadow of M87*. Philipp Arras, et al., (Submitted on 12 Feb 2020): ABSTRACT: Observing the dynamics of compact astrophysical objects provides insights into their inner workings and allows to probe physics under extreme conditions. The immediate vicinity of an active supermassive black hole with its event horizon, photon ring, accretion disk, and relativistic jets is a perfect place to study general relativity, magneto-hydrodynamics, and high energy plasma physics. The recent observations of the black hole shadow of M87* with Very Long Baseline Interferometry (VLBI) by the Event Horizon Telescope (EHT) open the possibility to investigate dynamical processes there on timescales of days. In this regime, radio astronomical imaging algorithms are brought to their limits. Compared to regular radio interferometers, VLBI networks have fewer antennas. The resulting sparser sampling of the Fourier sky can only be partly compensated by co-adding observations from different days, as the source changes. Here, we present an imaging algorithm that copes with the data scarcity and the source's temporal evolution, while simultaneously providing uncertainty quantification on all results. Our algorithm views the imaging task as a Bayesian inference problem of a time-varying flux density, exploits the correlation structure between time frames, and reconstructs a whole, (2+1+1)-dimensional time-variable and spectral-resolved image at once. We apply the method to the EHT observation of M87* and validate our approach on synthetic data. The obtained first time-resolved reconstruction of M87* indicates varying structures on and outside the emission ring on a time scale of
a. months b. years c. days d. weeks.
Q67.arXiv:2002.06207 [astro-ph.GA]: Spectroscopic Confirmation of a Coma Cluster Progenitor at z ∼ 2.2. Behnam Darvish, et al., (Submitted on 14 Feb 2020): ABSTRACT: We report the spectroscopic confirmation of a new protocluster in the COSMOS field at z ∼ 2.2, COSMOS Cluster 2.2 (CC2.2), originally identified as an overdensity of narrow-band selected Hα emitting candidates. With only two masks of Keck/MOSFIRE near-IR spectroscopy in both H(∼ 1.47-1.81μm) and K(∼1.92-2.40 μm) bands (∼ 1.5 hour each), we confirm 35 unique protocluster members with at least two emission lines detected with S/N >3. Combined with 12 extra members from the zCOSMOS-deep spectroscopic survey (47 in total), we estimate a mean redshift and a line-of-sight velocity dispersion of zmean=2.23224±0.00101 and σlos=645±69 km s^−1 for this protocluster, respectively. Assuming virialization and spherical symmetry for the system, we estimate a total mass of Mvir∼(1−2)×10^14M⊙ for the structure. We evaluate a number density enhancement of δg∼7 for this system and we argue that the structure is likely not fully virialized at z∼2.2. However, in a spherical collapse model, δgis expected to grow to a linear matter enhancement of ∼1.9 by z=0, exceeding the collapse threshold of 1.69, and leading to a fully collaped and virialized Coma-type structure with a total mass of Mdyn(z=0) ∼9.2×10^14M⊙by now. This observationally efficient confirmation suggests that large narrow-band emission-line galaxy surveys, when combined with ancillary photometric data, can be used to effectively trace the large-scale structure and protoclusters at a time when they are mostly dominated by star-forming
a. supernovae b. galaxies c. emission lines d. clusters.
Q68. arXiv:2002.06214 [astro-ph.SR]: Two new Double-lined Spectroscopic Binary White Dwarfs. Mukremin Kilic, A. Bedard, P. Bergeron, Alekzander Kosakowski. (Submitted on 14 Feb 2020): ABSTRACT: We present radial velocity observations of four binary white dwarf candidates identified through their over-luminosity. We identify two new double-lined spectroscopic binary systems, WD 0311-649 and WD 1606+422, and constrain their orbital parameters. WD 0311-649 is a 17.7 h period system with a mass ratio of 1.44±0.06 and WD 1606+422 is a 20.1 h period system with a mass ratio of 1.33±0.03. An additional object, WD 1447-190, is a 43 h period single-lined white dwarf binary, whereas WD 1418-088 does not show any significant velocity variations over timescales ranging from minutes to decades. We present an overview of the 14 over-luminous white dwarfs that were identified by Bedard et al., and find the fraction of double- and single-lined systems to be both 31%. However, an additional 31% of these over-luminous white dwarfs do not show any significant radial velocity variations. We demonstrate that these must be in long-period binaries that may be resolved by Gaia astrometry. We also discuss the over-abundance of single low-mass white dwarfs identified in the SPY survey, and suggest that some of those systems are also likely long period binary systems of more massive white
a. dwarfs b. stars c. objects d. galaxies.
Q69. arXiv:2002.08001 [astro-ph.SR]: Physical Parameters of Late-type Contact Binaries in the Northern Catalina Sky Survey. Weijia Sun, Xiaodian Chen, Licai Deng, Richard de Grijs. (Submitted on 19 Feb 2020): ABSTRACT: We present the physical parameters of 2335 late-type contact binary (CB) systems extracted from the Catalina Sky Survey (CSS). Our sample was selected from the CSS Data Release 1 by strictly limiting the prevailing temperature uncertainties and light-curve fitting residuals, allowing us to almost eliminate any possible contaminants. We developed an automatic Wilson--Devinney-type code to derive the relative properties of CBs based on their light-curve morphology. By adopting the distances derived from CB (orbital) period--luminosity relations (PLRs), combined with the well-defined mass--luminosity relation for the systems' primary stars and assuming solar metallicity, we calculated the objects' masses, radii, and luminosities. Our sample of fully eclipsing CBs contains 1530 W-, 710 A-, and 95 B-type CBs. A comparison with literature data and with the results from different surveys confirms the accuracy and coherence of our measurements. The period distributions of the various CB subtypes are different, hinting at a possible evolutionary sequence. W-type CBs are clearly located in a strip in the total mass versus mass ratio plane, while A-type CBs may exhibit a slightly different dependence. There are no significant differences among the PLRs of A- and W-type CBs, but the PLR zero points are affected by their mass ratios and fill-out factors. Determination of zero-point differences for different types of CBs may help us improve the accuracy of the resulting
a. subtypes b. measurements c. CBs d. PLRs.
Q70. arXiv:2002.08033 [physics.atom-ph]: Theoretical study of the spectroscopic properties of mendelevium (Z=101). Jiguang Li, Vladimir Dzuba. (Submitted on 19 Feb 2020):ABSTRACT: Using recently developed version of the configuration interaction method for atoms with open shells we calculate electron structure and spectroscopic properties of the mendelevium atom (Md, Z=101). These include energy levels, first and second ionisation potentials, electron affinity, hyperfine structure and electric dipole transition amplitudes between ground and low lying states of opposite parity. The accuracy of the calculations is controlled by performing similar calculations for lighter analog of mendelevium, thulium atom and comparing the results with experiment and other calculations. The calculations for Md are to address the lack of experimental data and help in planing and interpreting the
a. data b. measurements c. calculations. d. mendelevium.
Q71. Astrophysics of Galaxies (astro-ph.GA): Exploring galaxy colour in different environments of the cosmic web with SDSS. Biswajit Pandey, Suman Sarkar. (Submitted on 19 Feb 2020): ABSTRACT: We analyze a set of volume limited samples from the SDSS to study the dependence of galaxy colour on different environments of the cosmic web. We measure the local dimension of the galaxies to determine their embedding environments and find that the filaments host a higher fraction of red galaxies than the sheets at each luminosity. At a fixed luminosity, the fraction of red galaxies in filaments and sheets increases with the size of these structures. This suggests that the bigger structures have a larger baryon reservoir favouring higher accretion rate and larger stellar mass. At a fixed length scale, the fraction of red galaxies monotonically increases in all the environments with increasing luminosity. We also find that the average colour of the red and blue populations are systematically higher in the environments with smaller local dimension and increases monotonically in all the environments with luminosity. We observe that the bimodal nature of the galaxy colour distribution persists in all environments and all luminosities suggesting that the transformation from blue to red galaxy can occur in all
a. environments b. populations c. masses d. luminosity.
Q72. arXiv:2002.08401 [astro-ph.CO]: Determining the Neutrino Lifetime from Cosmology. Zackaria Chacko, Abhish Dev, Peizhi Du, Vivian Poulin, Yuhsin Tsai. (Submitted on 19 Feb 2020):ABSTRACT: We explore the cosmological signals of theories in which the neutrinos decay into invisible dark radiation after becoming non-relativistic. We show that in this scenario, near-future large scale structure measurements from the Euclid satellite, when combined with cosmic microwave background data from Planck, may allow an independent determination of both the lifetime of the neutrinos and the sum of their masses. These parameters can be independently determined because the Euclid data will cover a range of redshifts, allowing the growth of structure over time to be tracked. If neutrinos are stable on cosmological timescales, these observations can improve the lower limit on the neutrino lifetime by seven orders of magnitude, from O(10) years to 2×10^8 years (95% C.L.), without significantly affecting the measurement of neutrino mass. On the other hand, if neutrinos decay after becoming non-relativistic but on timescales less than O(100) million years, these observations may allow, not just the first measurement of the sum of neutrino masses, but also the determination of the neutrino lifetime from cosmology. DETAILS: In both cases, Majorana and Dirac neutrinos, the lifetime of the heavier neutrino is of order τν ∼ 10^50s (0.05eV/mν)^5, in the limit that the daughter neutrino mass is neglected. Therefore,at present there is no evidence that neutrinos are stable on cosmological timescales, and the lifetime of the neutrino remains an open question. In summary, we have considered the cosmological signatures of theories in which the neutrinos decay into invisible radiation on cosmological timescales. We have shown that in this scenario, observations of large scale structure made at multiple redshifts may allow two fundamental parameters, the sum of neutrino masses and the neutrino lifetime, to be determined independently. To assess the prospects for near future experiments, we have performed an MCMC analysis based on mock data from the Planck and Euclid experiments. Trading Planck data for the mock data from an ext-generation CMB experiment would strengthen our conclusions. In the case of neutrinos that are stable on timescales of order the age of the universe, we find that these measurements can improve the lower limit on the neutrino lifetime in this scenario by seven orders of magnitude, from O(10) years to 200 million years, without significantly impacting the measurement of neutrino mass. In the case of neutrinos that decay on timescales shorter than O(100) million years, these measurements may allow the neutrino lifetime to be determined from cosmology, provided the neutrinos decay after becoming non-relativistic. We find that in this case, requiring that neutrinos are stable when performing the fit can lead to a significant bias in the reconstructed neutrino mass. Therefore the possibility that neutrinos are unstable on cosmological timescales should be taken into account in the analysis of future Euclid
a. summary b. years c. data d. experiments. .
a. supernovae b. galaxies c. emission lines d. clusters.
Q68. arXiv:2002.06214 [astro-ph.SR]: Two new Double-lined Spectroscopic Binary White Dwarfs. Mukremin Kilic, A. Bedard, P. Bergeron, Alekzander Kosakowski. (Submitted on 14 Feb 2020): ABSTRACT: We present radial velocity observations of four binary white dwarf candidates identified through their over-luminosity. We identify two new double-lined spectroscopic binary systems, WD 0311-649 and WD 1606+422, and constrain their orbital parameters. WD 0311-649 is a 17.7 h period system with a mass ratio of 1.44±0.06 and WD 1606+422 is a 20.1 h period system with a mass ratio of 1.33±0.03. An additional object, WD 1447-190, is a 43 h period single-lined white dwarf binary, whereas WD 1418-088 does not show any significant velocity variations over timescales ranging from minutes to decades. We present an overview of the 14 over-luminous white dwarfs that were identified by Bedard et al., and find the fraction of double- and single-lined systems to be both 31%. However, an additional 31% of these over-luminous white dwarfs do not show any significant radial velocity variations. We demonstrate that these must be in long-period binaries that may be resolved by Gaia astrometry. We also discuss the over-abundance of single low-mass white dwarfs identified in the SPY survey, and suggest that some of those systems are also likely long period binary systems of more massive white
a. dwarfs b. stars c. objects d. galaxies.
Q69. arXiv:2002.08001 [astro-ph.SR]: Physical Parameters of Late-type Contact Binaries in the Northern Catalina Sky Survey. Weijia Sun, Xiaodian Chen, Licai Deng, Richard de Grijs. (Submitted on 19 Feb 2020): ABSTRACT: We present the physical parameters of 2335 late-type contact binary (CB) systems extracted from the Catalina Sky Survey (CSS). Our sample was selected from the CSS Data Release 1 by strictly limiting the prevailing temperature uncertainties and light-curve fitting residuals, allowing us to almost eliminate any possible contaminants. We developed an automatic Wilson--Devinney-type code to derive the relative properties of CBs based on their light-curve morphology. By adopting the distances derived from CB (orbital) period--luminosity relations (PLRs), combined with the well-defined mass--luminosity relation for the systems' primary stars and assuming solar metallicity, we calculated the objects' masses, radii, and luminosities. Our sample of fully eclipsing CBs contains 1530 W-, 710 A-, and 95 B-type CBs. A comparison with literature data and with the results from different surveys confirms the accuracy and coherence of our measurements. The period distributions of the various CB subtypes are different, hinting at a possible evolutionary sequence. W-type CBs are clearly located in a strip in the total mass versus mass ratio plane, while A-type CBs may exhibit a slightly different dependence. There are no significant differences among the PLRs of A- and W-type CBs, but the PLR zero points are affected by their mass ratios and fill-out factors. Determination of zero-point differences for different types of CBs may help us improve the accuracy of the resulting
a. subtypes b. measurements c. CBs d. PLRs.
Q70. arXiv:2002.08033 [physics.atom-ph]: Theoretical study of the spectroscopic properties of mendelevium (Z=101). Jiguang Li, Vladimir Dzuba. (Submitted on 19 Feb 2020):ABSTRACT: Using recently developed version of the configuration interaction method for atoms with open shells we calculate electron structure and spectroscopic properties of the mendelevium atom (Md, Z=101). These include energy levels, first and second ionisation potentials, electron affinity, hyperfine structure and electric dipole transition amplitudes between ground and low lying states of opposite parity. The accuracy of the calculations is controlled by performing similar calculations for lighter analog of mendelevium, thulium atom and comparing the results with experiment and other calculations. The calculations for Md are to address the lack of experimental data and help in planing and interpreting the
a. data b. measurements c. calculations. d. mendelevium.
Q71. Astrophysics of Galaxies (astro-ph.GA): Exploring galaxy colour in different environments of the cosmic web with SDSS. Biswajit Pandey, Suman Sarkar. (Submitted on 19 Feb 2020): ABSTRACT: We analyze a set of volume limited samples from the SDSS to study the dependence of galaxy colour on different environments of the cosmic web. We measure the local dimension of the galaxies to determine their embedding environments and find that the filaments host a higher fraction of red galaxies than the sheets at each luminosity. At a fixed luminosity, the fraction of red galaxies in filaments and sheets increases with the size of these structures. This suggests that the bigger structures have a larger baryon reservoir favouring higher accretion rate and larger stellar mass. At a fixed length scale, the fraction of red galaxies monotonically increases in all the environments with increasing luminosity. We also find that the average colour of the red and blue populations are systematically higher in the environments with smaller local dimension and increases monotonically in all the environments with luminosity. We observe that the bimodal nature of the galaxy colour distribution persists in all environments and all luminosities suggesting that the transformation from blue to red galaxy can occur in all
a. environments b. populations c. masses d. luminosity.
Q72. arXiv:2002.08401 [astro-ph.CO]: Determining the Neutrino Lifetime from Cosmology. Zackaria Chacko, Abhish Dev, Peizhi Du, Vivian Poulin, Yuhsin Tsai. (Submitted on 19 Feb 2020):ABSTRACT: We explore the cosmological signals of theories in which the neutrinos decay into invisible dark radiation after becoming non-relativistic. We show that in this scenario, near-future large scale structure measurements from the Euclid satellite, when combined with cosmic microwave background data from Planck, may allow an independent determination of both the lifetime of the neutrinos and the sum of their masses. These parameters can be independently determined because the Euclid data will cover a range of redshifts, allowing the growth of structure over time to be tracked. If neutrinos are stable on cosmological timescales, these observations can improve the lower limit on the neutrino lifetime by seven orders of magnitude, from O(10) years to 2×10^8 years (95% C.L.), without significantly affecting the measurement of neutrino mass. On the other hand, if neutrinos decay after becoming non-relativistic but on timescales less than O(100) million years, these observations may allow, not just the first measurement of the sum of neutrino masses, but also the determination of the neutrino lifetime from cosmology. DETAILS: In both cases, Majorana and Dirac neutrinos, the lifetime of the heavier neutrino is of order τν ∼ 10^50s (0.05eV/mν)^5, in the limit that the daughter neutrino mass is neglected. Therefore,at present there is no evidence that neutrinos are stable on cosmological timescales, and the lifetime of the neutrino remains an open question. In summary, we have considered the cosmological signatures of theories in which the neutrinos decay into invisible radiation on cosmological timescales. We have shown that in this scenario, observations of large scale structure made at multiple redshifts may allow two fundamental parameters, the sum of neutrino masses and the neutrino lifetime, to be determined independently. To assess the prospects for near future experiments, we have performed an MCMC analysis based on mock data from the Planck and Euclid experiments. Trading Planck data for the mock data from an ext-generation CMB experiment would strengthen our conclusions. In the case of neutrinos that are stable on timescales of order the age of the universe, we find that these measurements can improve the lower limit on the neutrino lifetime in this scenario by seven orders of magnitude, from O(10) years to 200 million years, without significantly impacting the measurement of neutrino mass. In the case of neutrinos that decay on timescales shorter than O(100) million years, these measurements may allow the neutrino lifetime to be determined from cosmology, provided the neutrinos decay after becoming non-relativistic. We find that in this case, requiring that neutrinos are stable when performing the fit can lead to a significant bias in the reconstructed neutrino mass. Therefore the possibility that neutrinos are unstable on cosmological timescales should be taken into account in the analysis of future Euclid
a. summary b. years c. data d. experiments. .
Q73.arXiv:2002.12123 [physics.gen-ph]: isco-elastic Cosmology for a Sparkling Universe?. Germain Rousseaux, Stefan C. Mancas. (Submitted on 12 Feb 2020): ABSTRACT: We show the analogy between a generalization of the Rayleigh-Plesset equation of bubble dynamics including surface tension, elasticity and viscosity effects with a reformulation of the Friedmann-Lemaître set of equations describing the expansion of space in cosmology assuming a homogeneous and isotropic universe. By comparing both fluid and cosmic equations, we propose a bold generalization of the newly-derived cosmic equation mapping three continuum mechanics contributions. Conversely, the addition of a cosmological constant-like term in the fluid equation would lead also to a new phenomenology. Our work is purely speculative and does not rely on any observations or theoretical derivations from first principles. DETAILS: Banerjee et al. proposed recently a new model of cosmic dynamics to solve the enigma of the so-called dark energy in order to cope with the observed expansion of the Universe with an ever-accelerating rate. The energy-momentum tensor Tµν in General Relativity does not feature dissipative effects usually so a generalization of the Friedmann-Lemaˆıtre equations is not obvious. Here, we show, thanks to an analogy with the extended Rayleigh-Plesset equation which describes the radial dynamics of a bubble in a classical viscous fluid with surface tension. CONCLUSIONS: Our generalized visco-elastic-capillary Friedman-Lemaˆıtre model is audacious, but the history of science tells us about many examples of the use of analogies (see the recent example of Analogue Gravity for instance) to construct heuristic models which have been later on recognized as discovery tools. It is savoury to notice that Lemaˆıtre and other funders of cosmology pondered about the existence of so-called phoenix universes whose radius varies cycloidally with alternance of Big Bangs and Big Crushes: a typical bubble-like
a. behavior b. discovery c. construct d. analog gravity.
a. behavior b. discovery c. construct d. analog gravity.
Q74.arXiv:2002.11734 [astro-ph.EP]: Frequency of Planets in Binaries. Mariangela Bonavita, Silvano Desidera. (Submitted on 26 Feb 2020): ABSTRACT: The frequency of planets in binaries is an important issue in the field of extrasolar planet studies because of its relevance in the estimation of the global planet population of our galaxy and the clues it can give to our understanding of planet formation and evolution. Multiple stars have often been excluded from exoplanet searches, especially those performed using the radial velocity technique, due to the technical challenges posed by such targets. As a consequence and despite recent efforts, our knowledge of the frequency of planets in multiple stellar systems is still rather incomplete. On the other hand, the lack of knowledge about the binarity at the time of the compilation of the target samples means that our estimate of the planet frequency around single stars could be tainted by the presence of unknown binaries, especially if these objects have a different behavior in terms of planet occurrence. In a previous work we investigated the binarity of the objects included in the Uniform Detectability sample defined by Fisher and Valenti (2005), showing how more than 20% of their targets were, in fact, not single stars. Here, we present an update of this census, made possible mainly by the information now available thanks to the second Gaia Data Release. The new binary sample includes a total of 313 systems, of which 114 were added through this work. We were also able to significantly improve the estimates of masses and orbital parameters for most of the pairs in the original list, especially those at close separations. A few new systems with white dwarf companions were also identified. The results of the new analysis are in good agreement with the findings of our previous work, confirming the lack of difference in the overall planet frequency between binaries and single stars but suggesting a decrease in the planet frequency for very close
a. work b. estimates c. pairs d. thresholds.
Q75.arXiv:2002.12111 [astro-ph.HE]: Fast moving pulsars as probes of interstellar medium. Maxim Barkov, Maxim Lyutikov, Dmitry Khangulyan. (Submitted on 27 Feb 2020): Pulsars moving through ISM produce bow shocks detected in hydrogen Hα line emission. The morphology of the bow shock nebulae allows one to probe the properties of ISM on scales ∼0.01pc and smaller. We performed 2D RMHD modeling of the pulsar bow shock and simulated the corresponding Hα emission morphology. We find that even a mild spatial inhomogeneity of ISM density, δρ/ρ∼1, leads to significant variations of the shape of the shock seen in Hα line emission. We successfully reproduce the morphology of the Guitar Nebula. We infer quasi-periodic density variations in the warm component of ISM with a characteristic length of ∼0.1∼pc. Structures of this scale might be also responsible for the formation of the fine features seen at the forward shock of Tycho SNR in X-rays. Formation of such short periodic density structures in the warm component of ISM is puzzling, and bow-shock nebulae provide unique probes to study this
a. features b. phenomenon c. structures d. variations.
a. work b. estimates c. pairs d. thresholds.
Q75.arXiv:2002.12111 [astro-ph.HE]: Fast moving pulsars as probes of interstellar medium. Maxim Barkov, Maxim Lyutikov, Dmitry Khangulyan. (Submitted on 27 Feb 2020): Pulsars moving through ISM produce bow shocks detected in hydrogen Hα line emission. The morphology of the bow shock nebulae allows one to probe the properties of ISM on scales ∼0.01pc and smaller. We performed 2D RMHD modeling of the pulsar bow shock and simulated the corresponding Hα emission morphology. We find that even a mild spatial inhomogeneity of ISM density, δρ/ρ∼1, leads to significant variations of the shape of the shock seen in Hα line emission. We successfully reproduce the morphology of the Guitar Nebula. We infer quasi-periodic density variations in the warm component of ISM with a characteristic length of ∼0.1∼pc. Structures of this scale might be also responsible for the formation of the fine features seen at the forward shock of Tycho SNR in X-rays. Formation of such short periodic density structures in the warm component of ISM is puzzling, and bow-shock nebulae provide unique probes to study this
a. features b. phenomenon c. structures d. variations.
Q76. arXiv:2003.02477 [physics.app-ph]: Characterization of bulk nanobubbles formed by using a porous alumina film with ordered nanopores. Teng Ma, Yasuo Kimura, Hideaki Yamamoto, Xingyao Feng, Ayumi Hirano-Iwata, Michio Niwano. (Submitted on 5 Mar 2020):ABSTRACT: Gaseous nanobubbles (NBs), with their unique physicochemical properties and promising applications, have become an important research topic. Generation of monodispersed bulk NBs with specified gas content remains a challenge. We developed a simple method for generating bulk NBs, using porous alumina films with ordered straight nano-scaled holes. Different techniques, such as nanoparticle tracking analysis (NTA), atomic force microscopy (AFM), and infrared absorption spectroscopy (IRAS), are used to confirm NB formation. The NTA data demonstrates that the minimum size of the NBs formed is less than 100 nm, which is comparable to the diameter of nanoholes in the porous alumina film. By generating NBs with different gases, including CO2, O2, N2, Ar, and He, we discovered that the minimum size of NBs negatively correlated with the solubility of encapsulated gases in water. Due to the monodispersed size of NBs generated from the highly ordered porous alumina, we determined that NB size is distributed discretely with a uniform increment factor of sqrt(2). To explain the observed characteristic size distribution of NBs, we propose a simple model in which two NBs of the same size are assumed to preferentially coalesce. This characteristic bubble size distribution is useful for elucidating the basic characteristics of nanobubbles, such as the long-term stability of NBs. This distribution can also be used to develop new applications of NBs, for example, nano-scaled reaction fields through bubble coalescence. CONCLUSIONS: We have developed a simple method to form NBs, using a porous alumina film with straight nanoholes penetrating the film. In order to confirm the NB formation by our method, we used nanoparticle tracking analysis (NTA), infrared absorption spectroscopy in the multiple internal reflection geometry (MIR-IRAS) and atomic force microscope (AFM). NTA data showed that the minimum size of generated NBs is less than 100 nm, which is comparable to the diameter of nanoholes in the porous alumina film. We showed that the minimum size of NBs depends on the solubility of the encapsulated gases in water. We found that the size (diameter) of NBs is discrete, and that there is a specific rule which the bubble size obeys. To explain the observed distribution of the bubble sizes, we proposed a simple model in which two NBs of the same size are assumed to preferentially coalescence. We hypothesized that the repulsive force of two colliding bubbles is smallest when the bubble diameters are the same, which would explain why bubbles of the same size preferentially
a. encapsulated b. Alumina c. coalescence d. coalesce.
a. encapsulated b. Alumina c. coalescence d. coalesce.
Q77. arXiv:2003.02383 [astro-ph.GA]: Dark matter Annihilation in Most Luminous and the Most Massive Ultracompact Dwarf Galaxies (UCD). Elaine C. F. S. Fortes, Oswaldo D. Miranda, Floyd W. Stecker, Carlos A. Wuensche. (Submitted on 5 Mar 2020): ABSTRACT: In this paper we explore the potential astrophysical signatures of dark matter (DM) annihilations in ultracompact dwarf galaxies (UCDs) considering two of the richest known galaxy clusters within 100 million light-years, nominally, Virgo and Fornax. Fornax UCD3 is the most luminous UCD and M59 UCD3 is the most massive UCD. With the detection of a 3.5 million solar mass black hole (BH) in Fornax UCD3, we carefully model several DM enhanced profiles scenarios, considering both the presence of the supermassive black hole (SMBH) and DM. For Fornax UCD3, the comparison of the stellar and dynamical masses suggests that there is little content of DM in UCDs. M59 UCD3 did not receive the same attention in simulations as Fornax UCD3, but deep radio imaging and X-ray observations were performed for M59 UCD3 and can be used to place limits in DM content of these UCDs. We work with an average estimative of dark matter content considering the Salpeter and Kroupa mass functions. We model Fornax UCD3 and M59 UCD3 to have a DM content that is the average of these mass functions. We then analyze the constraints for Fornax and M59 UCD3 coming from gamma-ray and radio sources considering in our simulations, a dark matter particle with mass between 10−34 GeV. In the absence of strong γ-ray signatures, we show that synchrotron emission from electrons and positrons produced by DM annihilations can be very sensitive to indirect DM search. We find that DM parameters can be significantly constrained at radio frequencies and the spike profiles play an interesting rule in order to deep study the enhancements of DM \& BH interactions in ultracompact
a. stars b. galaxies c. gamma rays d. DM annihilations.
a. stars b. galaxies c. gamma rays d. DM annihilations.
Q78. arXiv:2003.03380 [astro-ph.SR]: Silicate grain growth due to ion trapping in oxygen-rich supernova remnants like Cassiopeia A. Florian Kirchschlager, M. J. Barlow, Franziska D. Schmidt. (Submitted on 6 Mar 2020):ABSTRACT: Core-collapse supernovae can condense large masses of dust post-explosion. However, sputtering and grain-grain collisions during the subsequent passage of the dust through the reverse shock can potentially destroy a significant fraction of the newly formed dust before it can reach the interstellar medium. Here we show that in oxygen-rich supernova remnants like Cassiopeia~A the penetration and trapping within silicate grains of the same impinging ions of oxygen, silicon and magnesium that are responsible for grain surface sputtering can significantly reduce the net loss of grain material. We model conditions representative of dusty clumps (density contrast χ=100) passing through the reverse shock in the oxygen-rich Cassiopeia~A remnant and find that, compared to cases where the effect is neglected, as well as facilitating the formation of grains larger than those that had originally condensed, ion trapping increases the surviving masses of silicate dust by factors of up to two to four, depending on initial grain radii. For higher density contrasts (χ≳180), we find that the effect of gas accretion on the surface of dust grains surpasses ion trapping, and the survival rate increases to ∼55%of the initial dust mass for χ=256. RESULTS: The dust grain growth processes can produce a significant amount of grains that have sizes above the initial grain sizes. Therefore, ion trapping and gas accretion can play a crucial role in the surviving dust budget of oxygen-rich SNRs and thereby contribute to the dust budget in the interstellar medium. Finally,the increased grain sizes might account for the discrepancy between observed and theoretically predicted dust grain sizes in some
a. SNRs b. SPRs c. SNES d. SBRs.
Q79. arXiv:2003.03539 [astro-ph.SR]: A high-resolution spectroscopic study of two new Na- and Al-rich field giants -- likely globular cluster escapees in the Galactic halo. Avrajit Bandyopadhyay, Sivarani Thirupathi, Timothy C. Beers, A.Susmitha. (Submitted on 7 Mar 2020): ABSTRACT: The stars SDSS J064655.6+411620.5 and SDSS J193712.01+502455.5 are relatively bright stars that were initially observed as part of the SDSS/MARVELS pre-survey. They were selected, on the basis of their weak CHG -bands, along with a total of 60 others, in the range of halo globular cluster metallicities for high-resolution spectroscopic follow-up as a part of the HESP-GOMPA survey (Hanle Echelle SPectrograph -- Galactic survey Of Metal Poor stArs). The stars exhibit typical nucleosynthesis signatures expected from the so-called second-generation stars of globular clusters. The light-element anti-correlation of Mg-Al is detected, along with elevated abundances of Na. Carbon is found to be depleted, which is compatible with expectation. Lithium is also detected in SDSS J064655.6+411620.5 and SDSS J193712.01+502455.5; the measured abundances are similar to those of normal halo giant stars. These bright escapees provide a unique opportunity to study the nucleosynthesis events of globular clusters in great detail, and shed light on their chemical-enrichment
a. clusters b. depletions c. histories d. attachments.
Q80.arXiv:2003.03767 [physics.atm-clus]: The gamma-ray spectra in the room-temperature positron annihilation process of molecules. Lin Tang, Xiaoguang Ma, Jipeng Sui, Meishan Wang, Chuanlu Yang. (Submitted on 8 Mar 2020):ABSTRACT: fully self-consistent method has been developed to obtain the wavefunctions of the positron and the electrons in molecules simultaneously in the present work. The room-temperature positron wavefunction with the characteristic energy about 0.04eV has been used to translate the latest experimental annihilation results in helium, neon, hydrogen and methane molecules as examples. The interactions between a positron and a molecule give a remarkable correction on the gamma-ray spectra of the annihilating electron-positron pairs. The present study also finds that the high-order correlations have almost no correction on the spectra, because that the interaction between the low-energy positron and the electrons cannot bump the electrons into the excited electronic states. More accurate study should take the coupling of the positron-electron pair states and the vibration states of nuclei into account. CONCLUSION. The present work is the first step to obtain the accurate positron wavefunction in annihilation process of many-atomic molecules. The fully self-consistent method has been developed to study the positron annihilation process in
a. electrons b. molecules c. atoms d. pairs.
Q81.arXiv:2003.08547 [astro-ph.GA]: Effects of rotational disruption on the evolution of grain size distribution in galaxies. Hiroyuki Hirashita, Thiem Hoang. (Submitted on 19 Mar 2020): ABSTRACT: Interstellar dust grains can be spun up by radiative torques, and the resulting centrifugal force may be strong enough to disrupt large dust grains. We examine the effect of this rotational disruption on the evolution of grain size distribution in galaxies. To this goal, we modify our previous model by assuming that rotational disruption is the major small-grain production mechanism. We find that rotational disruption can have a large influence on the evolution of grain size distribution in the following two aspects especially for composites and grain mantles (with tensile strength ~10^7 erg cm^-3). First, because of the short time-scale of rotational disruption, the small-grain production occurs even in the early phase of galaxy evolution. Therefore, even though stars produce large grains, the abundance of small grains can be large enough to steepen the extinction curve. Secondly, rotational disruption is important in determining the maximum grain radius, which regulates the steepness of the extinction curve. For compact grains with tensile strength >=10^9 erg cm^-3, the size evolution is significantly affected by rotational disruption only if the radiation field is as strong as (or the dust temperature is as high as) expected for starburst galaxies. For compact grains, rotational disruption predicts that the maximum grain radius becomes less than 0.2 mum for galaxies with a .......... temperature >~ 50 K. (Fill the gap)
a. dust b. grain c. extinction d. tensile.
Q82. arXiv:2003.08586 [astro-ph.IM]: Pulsar Timing Observations with Haoping Radio Telescope. Jintao Luo, Yuping Gao, Tinggao Yang, Chengshi Zhao, Minglei Tong, Yongnan Rao, Yifeng Li, Bian Li, Xingzhi Zhu, Haihua Qiao, Xiaochun Lu. (Submitted on 19 Mar 2020): ABSTRACT: We report pulsar timing observations carried out in L-band with NTSC's 40-meter Haoping Radio Telescope (HRT), which was constructed in 2014. The observations were carried out using the pulsar machine we developed. Timing observations toward millisecond pulsar J0437-4715 obtains a timing residual (r.m.s) of 397ns in the time span of 284 days. SUMMARY: We have developed a pulsar timing observing system at our 40-meter radio telescope. Using this system several millisecond pulsars and glitch pulsars are being observed. Timing observations toward millisecond pulsar J0437−4715 obtained a timing residual (r.m.s) of 397ns in the time span of 284 days. And timing observations toward Crab pulsar, J0534+2200, has successfully detected this pulsar’s glitch in July, 2019. High-quality profiles of these two pulsars obtained with our system, together with the good timing residual on millisecond pulsar J0437−4715 and the detection of Crab pulsar’s glitch, indicate that this system has a pretty good receiving sensitivity and system stability for pulsar timing observations. After installing the receiving system for the LCP signal, we are working on the calibration capability of our pulsar timing system. This effort is expected to improve the timing result of millisecond pulsars like J0437−4715. Note: And our observations successfully detected Crab pulsar's glitch that happened on
a. 23 July 2017 b. 24 June 2015 c. 23 July 2019. d. 24 July 2018
a. SNRs b. SPRs c. SNES d. SBRs.
Q79. arXiv:2003.03539 [astro-ph.SR]: A high-resolution spectroscopic study of two new Na- and Al-rich field giants -- likely globular cluster escapees in the Galactic halo. Avrajit Bandyopadhyay, Sivarani Thirupathi, Timothy C. Beers, A.Susmitha. (Submitted on 7 Mar 2020): ABSTRACT: The stars SDSS J064655.6+411620.5 and SDSS J193712.01+502455.5 are relatively bright stars that were initially observed as part of the SDSS/MARVELS pre-survey. They were selected, on the basis of their weak CHG -bands, along with a total of 60 others, in the range of halo globular cluster metallicities for high-resolution spectroscopic follow-up as a part of the HESP-GOMPA survey (Hanle Echelle SPectrograph -- Galactic survey Of Metal Poor stArs). The stars exhibit typical nucleosynthesis signatures expected from the so-called second-generation stars of globular clusters. The light-element anti-correlation of Mg-Al is detected, along with elevated abundances of Na. Carbon is found to be depleted, which is compatible with expectation. Lithium is also detected in SDSS J064655.6+411620.5 and SDSS J193712.01+502455.5; the measured abundances are similar to those of normal halo giant stars. These bright escapees provide a unique opportunity to study the nucleosynthesis events of globular clusters in great detail, and shed light on their chemical-enrichment
a. clusters b. depletions c. histories d. attachments.
Q80.arXiv:2003.03767 [physics.atm-clus]: The gamma-ray spectra in the room-temperature positron annihilation process of molecules. Lin Tang, Xiaoguang Ma, Jipeng Sui, Meishan Wang, Chuanlu Yang. (Submitted on 8 Mar 2020):ABSTRACT: fully self-consistent method has been developed to obtain the wavefunctions of the positron and the electrons in molecules simultaneously in the present work. The room-temperature positron wavefunction with the characteristic energy about 0.04eV has been used to translate the latest experimental annihilation results in helium, neon, hydrogen and methane molecules as examples. The interactions between a positron and a molecule give a remarkable correction on the gamma-ray spectra of the annihilating electron-positron pairs. The present study also finds that the high-order correlations have almost no correction on the spectra, because that the interaction between the low-energy positron and the electrons cannot bump the electrons into the excited electronic states. More accurate study should take the coupling of the positron-electron pair states and the vibration states of nuclei into account. CONCLUSION. The present work is the first step to obtain the accurate positron wavefunction in annihilation process of many-atomic molecules. The fully self-consistent method has been developed to study the positron annihilation process in
a. electrons b. molecules c. atoms d. pairs.
Q81.arXiv:2003.08547 [astro-ph.GA]: Effects of rotational disruption on the evolution of grain size distribution in galaxies. Hiroyuki Hirashita, Thiem Hoang. (Submitted on 19 Mar 2020): ABSTRACT: Interstellar dust grains can be spun up by radiative torques, and the resulting centrifugal force may be strong enough to disrupt large dust grains. We examine the effect of this rotational disruption on the evolution of grain size distribution in galaxies. To this goal, we modify our previous model by assuming that rotational disruption is the major small-grain production mechanism. We find that rotational disruption can have a large influence on the evolution of grain size distribution in the following two aspects especially for composites and grain mantles (with tensile strength ~10^7 erg cm^-3). First, because of the short time-scale of rotational disruption, the small-grain production occurs even in the early phase of galaxy evolution. Therefore, even though stars produce large grains, the abundance of small grains can be large enough to steepen the extinction curve. Secondly, rotational disruption is important in determining the maximum grain radius, which regulates the steepness of the extinction curve. For compact grains with tensile strength >=10^9 erg cm^-3, the size evolution is significantly affected by rotational disruption only if the radiation field is as strong as (or the dust temperature is as high as) expected for starburst galaxies. For compact grains, rotational disruption predicts that the maximum grain radius becomes less than 0.2 mum for galaxies with a .......... temperature >~ 50 K. (Fill the gap)
a. dust b. grain c. extinction d. tensile.
Q82. arXiv:2003.08586 [astro-ph.IM]: Pulsar Timing Observations with Haoping Radio Telescope. Jintao Luo, Yuping Gao, Tinggao Yang, Chengshi Zhao, Minglei Tong, Yongnan Rao, Yifeng Li, Bian Li, Xingzhi Zhu, Haihua Qiao, Xiaochun Lu. (Submitted on 19 Mar 2020): ABSTRACT: We report pulsar timing observations carried out in L-band with NTSC's 40-meter Haoping Radio Telescope (HRT), which was constructed in 2014. The observations were carried out using the pulsar machine we developed. Timing observations toward millisecond pulsar J0437-4715 obtains a timing residual (r.m.s) of 397ns in the time span of 284 days. SUMMARY: We have developed a pulsar timing observing system at our 40-meter radio telescope. Using this system several millisecond pulsars and glitch pulsars are being observed. Timing observations toward millisecond pulsar J0437−4715 obtained a timing residual (r.m.s) of 397ns in the time span of 284 days. And timing observations toward Crab pulsar, J0534+2200, has successfully detected this pulsar’s glitch in July, 2019. High-quality profiles of these two pulsars obtained with our system, together with the good timing residual on millisecond pulsar J0437−4715 and the detection of Crab pulsar’s glitch, indicate that this system has a pretty good receiving sensitivity and system stability for pulsar timing observations. After installing the receiving system for the LCP signal, we are working on the calibration capability of our pulsar timing system. This effort is expected to improve the timing result of millisecond pulsars like J0437−4715. Note: And our observations successfully detected Crab pulsar's glitch that happened on
a. 23 July 2017 b. 24 June 2015 c. 23 July 2019. d. 24 July 2018
Q83. arXiv:2003.08701 [astro-ph.HE]: EeV Astrophysical neutrinos from FSRQs? C. Righi, A. Palladino, F. Tavecchio, F. Vissani. (Submitted on 19 Mar 2020):ABSTRACT: Flat Spectrum Radio Quasars (FSRQ) are the most powerful blazars in the gamma-ray band. Although they are supposed to be good candidates in producing high energy neutrinos, no secure detection of FSRQs has been obtained up to now, except for a possible case of PKS B1424-418. In this work, we compute the expected flux of high energy neutrinos from FSRQs using standard assumptions for the properties of the radiation fields filling the regions surrounding the central supermassive black hole. We obtain as a result that high energy neutrinos are naturally expected from FSRQs in the sub-EeV-EeV energy range and not at PeV energies. This justifies the non-observation of neutrinos from FSRQs with the present technology, since only neutrinos below 10 PeV have been observed. We found that for a non-negligible range of the parameters the cumulative flux from FSRQs is comparable to or even exceeds the expected cosmogenic neutrino flux. This result is intriguing and highlights the importance to disentangle these point-source emissions from the diffuse cosmogenic
a.scenario b. neutinos c. quasars d. background.
Q84. arXiv:2003.08733 [physics.gen-ph]: Dirac Equation as a Bridge to the Gravitational Interaction of Antimatter: Antimatter Gravity and Charge Asymmetry. Ulrich D. Jentschura. (Submitted on 12 Mar 2020):ABSTRACT: We show that, because the Dirac equation describes both matter as well as anti-matter composed of the same kind of particle simultaneously, it can be used as a "bridge" toward the description of gravitational interaction of antimatter. We find a symmetry, on the level of the gravitationally coupled Lagrangian, connecting the gravitational interaction terms for particles to those for antiparticles. As a result, we find that, on the level of canonical gravity, there is no room for a deviation of the gravitational interactions of matter to those of antimatter. A natural question arises: Given these observations, how do we interpret upcoming gravitational experiments with anti-matter? We find that a very attractive possibility to reinterpret the tests consists in a connection to a potential charge excess in either matter or anti-matter, a hypothesis discussed by Einstein in 1924 and by Lyttleton and Bondi in [Proc. Roy. Soc. London, Ser. A 252, pp. 313-333 (1959)]. A gravitational test of antimatter is shown to drastically limit the available parameter space for charge excess in the combined matter-antimatter system. This is because the charge excess in either hydrogen or anti-hydrogen, interacting with a potential excess charge of the entire Earth, is being compared to the gravitational
a. field b. force c. interaction d. charge.
Q85. arXiv:2003.08738 [physics.gen-ph]: An Axion Interpretation of the ANITA Events. A. Nicolaidis. (Submitted on 10 Mar 2020): ABSTRACT: We suggest that the unusual events observed by the ANITA experiment originate from axion particles traversing the Earth. Under the influence of the geomagnetic field, the axion may oscillate into a photon and vice-versa. To amplify the axion transition into photon, we consider that the phenomenon takes place at resonance, where the effective photon mass is equal to the axion mass. This requirement fixes the axion mass at 200 eV. An axion at this mass scale reproduces the cold dark matter scenario. If our interpretation prevails, with the help of axions we can establish an axion tomography of the
a. Earth b. axion mass c. photon d. field.
Q86. arXiv:2003.08510 [astro-ph.IM]: An improved analysis framework for axion dark matter searches. D. A. Palken, et al., (Submitted on 18 Mar 2020): ABSTRACT: In experiments searching for axionic dark matter, the use of the standard threshold-based data analysis discards valuable information. We present a Bayesian analysis framework that builds on an existing processing protocol to extract more information from the data of coherent axion detectors such as operating haloscopes. The analysis avoids logical subtleties that accompany the standard analysis framework and enables greater experimental flexibility on future data runs. Performing this analysis on the existing data from the HAYSTAC experiment, we find improved constraints on the axion-photon coupling g γ while also identifying the most promising regions of parameter space within the 23.15 --24.0μ eV mass range. A comparison with the standard threshold analysis suggests a 36% improvement in scan rate from our analysis, demonstrating the utility of this framework for future axion haloscope
a. results b.operations c. detectors d. analyses.
a. results b.operations c. detectors d. analyses.
Q87. arXiv:2003.09492 [astro-ph.GA]: First spectroscopic study of ionized gas emission lines in the extreme low surface brightness galaxy Malin 1: Junais, S. Boissier, B. Epinat, P. Amram, B. F. Madore, A. Boselli, J. Koda, A. Gil de Paz, J. C. Muños Mateos, L. Chemin. (Submitted on 20 Mar 2020): ABSTRACT: Malin 1 is the largest known low surface brightness (LSB) galaxy, the archetype of so-called giant LSBs. The structure and the origin of such galaxies are still poorly understood, especially due to the lack of high-resolution kinematics and spectroscopic data. We use emission lines from spectroscopic observations of Malin 1 aiming to bring new constraints on the internal dynamics and star formation history of Malin 1. We have extracted a total of 16 spectra from different regions of Malin 1 and calculated the rotational velocities of these regions from the wavelength shifts and star formation rates from the observed Hα emission line fluxes. We compare our data with existing data and models for Malin 1. For the first time we present the inner rotation curve of Malin 1, characterized in the radial range r < 10 kpc by a steep rise in the rotational velocity up to at least 350 km/s (with a large dispersion), which had not been observed previously. We use these data to study a suite of new mass models for Malin 1. We show that in the inner regions dynamics may be dominated by the stars (although none of our models can explain the highest velocities measured) but that at large radii a massive dark matter halo remains necessary. The Hα fluxes derived star formation rates are consistent with an early-type disk for the inner region, and with the level found in extended UV galaxies for the outer parts of the giant disk of Malin 1. We also find signs of high metallicity but low dust content for the inner
a. cores b. regions c. parts d. radii.
Q88. arXiv:2003.09646 [astro-ph.EP]: Unveiling the secrets of the mid-infrared Moon. Yunzhao Wu, et al., (Submitted on 21 Mar 2020): ABSTRACT: The Moon's optical characteristics in visible and long-wavelength infrared (LWIR) have long been observed with our eyes or with instruments. What the mid-infrared (MIR) Moon looks like is still a mystery. For the first time we present detailed appearance of the MIR Moon observed by a high-resolution geostationary satellite and reveal the essence behind its appearance. The appearance of the MIR Moon is opposite to its normal visible appearance. In addition the MIR Moon shows limb darkening. Both the absolute and the relative brightness distribution of the MIR lunar disk changes with the solar incidence angle. The signatures of the MIR Moon are controlled by both the reflection and emission of the lunar surface. We also show first-ever brightness temperature maps of the lunar disk without needing a mosaic, which better show the temperature variation across the lunar disk. They reveal that the relationship between brightness temperature and solar incidence angle i is cos1/bi, and the power parameter is smaller than the Lambertian temperature model of cos1/4i observed for lunar orbit-based measurements. The slower decrease of the brightness temperature when moving away from the sub-solar point than the Lambertian model is due to topographic effects. The brightness temperature is dominated by albedo and the solar incidence angle and influenced by the topography. Our results indicate that the Moon in the MIR exhibits many interesting phenomena which were previously unknown, and contains abundant information about lunar reflection and thermal emission for future
a. study b. investigation c. exploration d. topography.
Q89. arXiv:2003.09842 [astro-ph.GA]: Near-Infrared Photometry of Superthin Edge-on Galaxies. D. Bizyaev, A.M.Tatarnikov, N.I. Shatsky, A.E. Nadjip, M.A. Burlak, O.V. Vozyakova. (Submitted on 22 Mar 2020):ABSTRACT: We perform near-infrared photometry of a large sample of 49 superthin edge-on galaxies. These galaxies are selected based on optical photometry because of high radial-to-vertical scale ratio in their stellar disks. The Near Infrared (NIR) H and K observations were conducted with the cryogenic-cooled camera ASTRONIRCAM on the 2.5m telescope at the Caucasus Mountain Observatory of Lomonosov Moscow State University. A majority of galaxies in our sample show comparable or better photometric depth than the Sloan Digital Sky Survey (SDSS) optical images. We estimate the structural parameters of stellar disks in the galaxies and find that the NIR scale height of stellar disks is comparable to that estimated from the optical, SDSS g, r and i, whereas the H and K scale length of the stellar disks is significantly shorter than in the g, r and i. We investigate if a realistic distribution of dust alone can explain the difference in the scale length and find that in the majority of the galaxies the radial variation of the stellar population is actually responsible for the color distribution. The latter suggests a younger age of the disks periphery, and the inside out building up of stellar disks in the superthin
a. stars b. distribution c. galaxies d. stellars.
Q90. arXiv:2003.12640 [astro-ph.EP]: Meteoroid Bombardment of Lunar Poles. Petr Pokorny, Menelaos Sarantos, Diego Janches, Erwan Mazarico. (Submitted on 27 Mar 2020):ABSTRACT: While the floors of deep lunar craters are largely shielded from solar radiation and thus provide an ideal thermal environment for water ice accumulation, meteoroids on highly inclined orbits can easily access permanently shadowed regions and alter the surface properties via hyper-velocity impacts. Here we consider the detailed topography of lunar poles and a dynamical model of meteoroids to quantify the meteoroid mass fluxes, energy deposition, and impact ejecta mass production rates. Our analysis of regions within $5^\circ$ from the two lunar poles shows that the variations of the meteoroid mass flux, energy flux and ejecta production rate are within $50\%$ of their median values. We find that lunar poles are easily accessible by meteoroid impacts including permanently shadowed regions. We find a positive correlation between the surface slope and the meteoroid ejecta production rate, a finding that suggests a higher impact gardening rate on steep crater walls can facilitate mass
a. dependence b, wasting c. flux d. rate.
Q91. arXiv:2003.12831 [astro-ph.GA]: Active Galactic Nuclei in polarized light. Elena Shablovinskaya, Viktor Afanasiev. (Submitted on 28 Mar 2020): ABSTRACT: Due to the compactness active galactic nuclei (AGNs) are still unresolved with optical observations. However, structure and physical conditions of the matter in their central parts are especially important to study the processes of the matter accretion to supermassive black holes and eventually these investigations are essential to understand the galaxy evolution. Polarization contains information about the interaction of electromagnetic waves with the environment and provides information about the physical processes in the central regions of the AGNs that could not be found with the help of other optical observations. In this paper, the importance of applying polarimetry methods to the study of geometry, kinematics, and physical processes in active galactic nuclei (AGN) in polarized light is discussed. An overview of the mechanisms of polarization formation, their connection with different structures and scales are provided. Also, we overview the polarimetric investigations based on different assumptions that are done using the observations conducted in Special Astrophysical Observatory of the Russian Academy of
a. Light b. Paper c. Sciences d. Mathematics.
Q92. arXiv:2003.13007 [physics.optics]: Perfect absorption of a focused light beam by a single nanoparticle. Alexey Proskurin, Andrey Bogdanov, Denis G. Baranov. (Submitted on 29 Mar 2020):ABSTRACT: Absorption of electromagnetic energy by a dissipative material is one of the most fundamental electromagnetic processes that underlies a plethora of applied problems, including sensing and molecular detection, radar detection, wireless power transfer, and photovoltaics. Perfect absorption is a particular regime when all of the incoming electromagnetic energy is absorbed by the system without scattering. Commonly, the incident energy is delivered to the absorbing system by a plane wave, hence perfect absorption of this wave requires an infinitely extended planar structure. Here, we demonstrate theoretically that a confined incident beam carrying a finite amount of electromagnetic energy can be perfectly absorbed by a finite size deep subwavelength scatterer on a substrate. We analytically solve the self-consistent scattering problem in the dipole approximation and find a closed-form expression for the spatial spectrum of the incident field and the required complex polarizability of the particle. All analytical predictions are confirmed with full-wave
a. simulations b. analysis c. study d. exploration.
Q93. arXiv:2003.13185 [physics.app-ph]: Bi2Te3/Si thermophotovoltaic cells converting low temperature radiation into electricity. Xiaojian Li, Chaogang Lou, Xin Li, Yujie Zhang, Zongkai Liu, Bo Yin. (Submitted on 30 Mar 2020):ABSTRACT: The thermophotovoltaic cells which convert the low temperature radiation into electricity are of significance due to their potential applications in many fields. In this work, Bi2Te3/Si thermophotovoltaic cells which work under the radiation from the blackbody with the temperature of 300 K-480 K are presented. The experimental results show that the cells can output electricity even under the radiation temperature of 300 K. The band structure of Bi2Te3/Si heterojunctions and the defects in Bi2Te3 thin films lower the conversion efficiency of the cells. It is also demonstrated that the resistivity of Si and the thickness of Bi2Te3 thin films have important effects on Bi2Te3/Si thermophotovoltaic cells. Although the cells' output power is small, this work provides a possible way to utilize the low temperature
a. data b.cells c. fields d. radiation.
Q94. arXiv:2003.12638 [cs.CV]: Combining Visible and Infrared Spectrum Imagery using Machine Learning for Small Unmanned Aerial System Detection. Vinicius G. Goecks, Grayson Woods, Niladri Das, John Valasek. (Submitted on 27 Mar 2020):ABSTRACT: Advances in machine learning and deep neural networks for object detection, coupled with lower cost and power requirements of cameras, led to promising vision-based solutions for sUAS detection. However, solely relying on the visible spectrum has previously led to reliability issues in low contrast scenarios such as sUAS flying below the treeline and against bright sources of light. Alternatively, due to the relatively high heat signatures emitted from sUAS during flight, a long-wave infrared (LWIR) sensor is able to produce images that clearly contrast the sUAS from its background. However, compared to widely available visible spectrum sensors, LWIR sensors have lower resolution and may produce more false positives when exposed to birds or other heat sources. This research work proposes combining the advantages of the LWIR and visible spectrum sensors using machine learning for vision-based detection of sUAS. Utilizing the heightened background contrast from the LWIR sensor combined and synchronized with the relatively increased resolution of the visible spectrum sensor, a deep learning model was trained to detect the sUAS through previously difficult environments. More specifically, the approach demonstrated effective detection of multiple sUAS flying above and below the treeline, in the presence of heat sources, and glare from the sun. Our approach achieved a detection rate of 71.2 +- 8.3%, improving by 69% when compared to LWIR and by 30.4% when visible spectrum alone, and achieved false alarm rate of 2.7 +- 2.6%, decreasing by 74.1% and by 47.1% when compared to LWIR and visible spectrum alone, respectively, on average, for single and multiple drone scenarios, controlled for the same confidence metric of the machine learning object detector of at least 50%. Videos of the solution's performance can be seen at this https
a. BRL b. URL c. MRL d. YRL.
a. cores b. regions c. parts d. radii.
Q88. arXiv:2003.09646 [astro-ph.EP]: Unveiling the secrets of the mid-infrared Moon. Yunzhao Wu, et al., (Submitted on 21 Mar 2020): ABSTRACT: The Moon's optical characteristics in visible and long-wavelength infrared (LWIR) have long been observed with our eyes or with instruments. What the mid-infrared (MIR) Moon looks like is still a mystery. For the first time we present detailed appearance of the MIR Moon observed by a high-resolution geostationary satellite and reveal the essence behind its appearance. The appearance of the MIR Moon is opposite to its normal visible appearance. In addition the MIR Moon shows limb darkening. Both the absolute and the relative brightness distribution of the MIR lunar disk changes with the solar incidence angle. The signatures of the MIR Moon are controlled by both the reflection and emission of the lunar surface. We also show first-ever brightness temperature maps of the lunar disk without needing a mosaic, which better show the temperature variation across the lunar disk. They reveal that the relationship between brightness temperature and solar incidence angle i is cos1/bi, and the power parameter is smaller than the Lambertian temperature model of cos1/4i observed for lunar orbit-based measurements. The slower decrease of the brightness temperature when moving away from the sub-solar point than the Lambertian model is due to topographic effects. The brightness temperature is dominated by albedo and the solar incidence angle and influenced by the topography. Our results indicate that the Moon in the MIR exhibits many interesting phenomena which were previously unknown, and contains abundant information about lunar reflection and thermal emission for future
a. study b. investigation c. exploration d. topography.
Q89. arXiv:2003.09842 [astro-ph.GA]: Near-Infrared Photometry of Superthin Edge-on Galaxies. D. Bizyaev, A.M.Tatarnikov, N.I. Shatsky, A.E. Nadjip, M.A. Burlak, O.V. Vozyakova. (Submitted on 22 Mar 2020):ABSTRACT: We perform near-infrared photometry of a large sample of 49 superthin edge-on galaxies. These galaxies are selected based on optical photometry because of high radial-to-vertical scale ratio in their stellar disks. The Near Infrared (NIR) H and K observations were conducted with the cryogenic-cooled camera ASTRONIRCAM on the 2.5m telescope at the Caucasus Mountain Observatory of Lomonosov Moscow State University. A majority of galaxies in our sample show comparable or better photometric depth than the Sloan Digital Sky Survey (SDSS) optical images. We estimate the structural parameters of stellar disks in the galaxies and find that the NIR scale height of stellar disks is comparable to that estimated from the optical, SDSS g, r and i, whereas the H and K scale length of the stellar disks is significantly shorter than in the g, r and i. We investigate if a realistic distribution of dust alone can explain the difference in the scale length and find that in the majority of the galaxies the radial variation of the stellar population is actually responsible for the color distribution. The latter suggests a younger age of the disks periphery, and the inside out building up of stellar disks in the superthin
a. stars b. distribution c. galaxies d. stellars.
Q90. arXiv:2003.12640 [astro-ph.EP]: Meteoroid Bombardment of Lunar Poles. Petr Pokorny, Menelaos Sarantos, Diego Janches, Erwan Mazarico. (Submitted on 27 Mar 2020):ABSTRACT: While the floors of deep lunar craters are largely shielded from solar radiation and thus provide an ideal thermal environment for water ice accumulation, meteoroids on highly inclined orbits can easily access permanently shadowed regions and alter the surface properties via hyper-velocity impacts. Here we consider the detailed topography of lunar poles and a dynamical model of meteoroids to quantify the meteoroid mass fluxes, energy deposition, and impact ejecta mass production rates. Our analysis of regions within $5^\circ$ from the two lunar poles shows that the variations of the meteoroid mass flux, energy flux and ejecta production rate are within $50\%$ of their median values. We find that lunar poles are easily accessible by meteoroid impacts including permanently shadowed regions. We find a positive correlation between the surface slope and the meteoroid ejecta production rate, a finding that suggests a higher impact gardening rate on steep crater walls can facilitate mass
a. dependence b, wasting c. flux d. rate.
Q91. arXiv:2003.12831 [astro-ph.GA]: Active Galactic Nuclei in polarized light. Elena Shablovinskaya, Viktor Afanasiev. (Submitted on 28 Mar 2020): ABSTRACT: Due to the compactness active galactic nuclei (AGNs) are still unresolved with optical observations. However, structure and physical conditions of the matter in their central parts are especially important to study the processes of the matter accretion to supermassive black holes and eventually these investigations are essential to understand the galaxy evolution. Polarization contains information about the interaction of electromagnetic waves with the environment and provides information about the physical processes in the central regions of the AGNs that could not be found with the help of other optical observations. In this paper, the importance of applying polarimetry methods to the study of geometry, kinematics, and physical processes in active galactic nuclei (AGN) in polarized light is discussed. An overview of the mechanisms of polarization formation, their connection with different structures and scales are provided. Also, we overview the polarimetric investigations based on different assumptions that are done using the observations conducted in Special Astrophysical Observatory of the Russian Academy of
a. Light b. Paper c. Sciences d. Mathematics.
Q92. arXiv:2003.13007 [physics.optics]: Perfect absorption of a focused light beam by a single nanoparticle. Alexey Proskurin, Andrey Bogdanov, Denis G. Baranov. (Submitted on 29 Mar 2020):ABSTRACT: Absorption of electromagnetic energy by a dissipative material is one of the most fundamental electromagnetic processes that underlies a plethora of applied problems, including sensing and molecular detection, radar detection, wireless power transfer, and photovoltaics. Perfect absorption is a particular regime when all of the incoming electromagnetic energy is absorbed by the system without scattering. Commonly, the incident energy is delivered to the absorbing system by a plane wave, hence perfect absorption of this wave requires an infinitely extended planar structure. Here, we demonstrate theoretically that a confined incident beam carrying a finite amount of electromagnetic energy can be perfectly absorbed by a finite size deep subwavelength scatterer on a substrate. We analytically solve the self-consistent scattering problem in the dipole approximation and find a closed-form expression for the spatial spectrum of the incident field and the required complex polarizability of the particle. All analytical predictions are confirmed with full-wave
a. simulations b. analysis c. study d. exploration.
Q93. arXiv:2003.13185 [physics.app-ph]: Bi2Te3/Si thermophotovoltaic cells converting low temperature radiation into electricity. Xiaojian Li, Chaogang Lou, Xin Li, Yujie Zhang, Zongkai Liu, Bo Yin. (Submitted on 30 Mar 2020):ABSTRACT: The thermophotovoltaic cells which convert the low temperature radiation into electricity are of significance due to their potential applications in many fields. In this work, Bi2Te3/Si thermophotovoltaic cells which work under the radiation from the blackbody with the temperature of 300 K-480 K are presented. The experimental results show that the cells can output electricity even under the radiation temperature of 300 K. The band structure of Bi2Te3/Si heterojunctions and the defects in Bi2Te3 thin films lower the conversion efficiency of the cells. It is also demonstrated that the resistivity of Si and the thickness of Bi2Te3 thin films have important effects on Bi2Te3/Si thermophotovoltaic cells. Although the cells' output power is small, this work provides a possible way to utilize the low temperature
a. data b.cells c. fields d. radiation.
Q94. arXiv:2003.12638 [cs.CV]: Combining Visible and Infrared Spectrum Imagery using Machine Learning for Small Unmanned Aerial System Detection. Vinicius G. Goecks, Grayson Woods, Niladri Das, John Valasek. (Submitted on 27 Mar 2020):ABSTRACT: Advances in machine learning and deep neural networks for object detection, coupled with lower cost and power requirements of cameras, led to promising vision-based solutions for sUAS detection. However, solely relying on the visible spectrum has previously led to reliability issues in low contrast scenarios such as sUAS flying below the treeline and against bright sources of light. Alternatively, due to the relatively high heat signatures emitted from sUAS during flight, a long-wave infrared (LWIR) sensor is able to produce images that clearly contrast the sUAS from its background. However, compared to widely available visible spectrum sensors, LWIR sensors have lower resolution and may produce more false positives when exposed to birds or other heat sources. This research work proposes combining the advantages of the LWIR and visible spectrum sensors using machine learning for vision-based detection of sUAS. Utilizing the heightened background contrast from the LWIR sensor combined and synchronized with the relatively increased resolution of the visible spectrum sensor, a deep learning model was trained to detect the sUAS through previously difficult environments. More specifically, the approach demonstrated effective detection of multiple sUAS flying above and below the treeline, in the presence of heat sources, and glare from the sun. Our approach achieved a detection rate of 71.2 +- 8.3%, improving by 69% when compared to LWIR and by 30.4% when visible spectrum alone, and achieved false alarm rate of 2.7 +- 2.6%, decreasing by 74.1% and by 47.1% when compared to LWIR and visible spectrum alone, respectively, on average, for single and multiple drone scenarios, controlled for the same confidence metric of the machine learning object detector of at least 50%. Videos of the solution's performance can be seen at this https
a. BRL b. URL c. MRL d. YRL.
Q95.arXiv:2004.03617 [cond-mat.str-el]: Strongly coupled quantum phonon fluid in a solvable model. Evyatar Tulipman, Erez Berg. (Submitted on 7 Apr 2020): ABSTRACT: We study a model of a large number of strongly coupled phonons that can be viewed as a bosonic variant of the Sachdev-Ye-Kitaev model. We determine the phase diagram of the model which consists of a glass phase and a disordered phase, with a first-order phase transition separating them. We compute the specific heat of the disordered phase, with which we diagnose the high-temperature crossover to the classical limit. We further study the real-time dynamics of the disordered phase, where we identify three dynamical regimes as a function of temperature. Low temperatures are associated with a semiclassical regime, where the phonons can be described as long-lived normal modes. High-temperatures are associated with the classical limit of the model. For a large region in parameter space, we identify an intermediate-temperatures regime, where the phonon lifetime is of the order of the Planckian time scale
a. ℏ b. ℏ/ kT c. ℏ/ k d.ℏ/ kBT.
Q96. arXiv:2004.03664 [cond-mat.mes-hall]: Photo-Seebeck effect in single-crystalline bismuth telluride topological insulator. Anand Nivedan, Arvind Singh, Sandeep Kumar, Sunil Kumar. (Submitted on 7 Apr 2020):ABSTRACT: Bismuth telluride is a low energy bulk band-gap topological system with conducting surface states. Besides its very good thermoelectric properties, it also makes a very good candidate for broadband photodetectors. Here, we report temperature-dependent photo-Seebeck effect in a bulk single crystalline bismuth telluride. On light illumination, an electrically biased sample shows distinguishable contributions in the measured current due to both the Seebeck effect and the normal photo-generated carriers within a narrow layer of the sample. Detailed experiments are performed to elucidate the distinction between the Seebeck contribution and the photogenerated current. The temperature-dependence of the photocurrent without Seebeck contribution shows a sign reversal from negative to positive at a specific temperature depending on the wavelength of photoexcitation
a. light b. spectra c. layer d. carrier.
Q97. arXiv:2004.03700 [cond-mat.str-el]: Electronic correlations and transport in iron at Earth's core conditions. L. V. Pourovskii, J. Mravlje, M. Pozzo, D. Alfè. (Submitted on 7 Apr 2020):ABSTRACT: The transport properties of iron under inner core conditions are essential input for the geophysical modeling of the Earth's interior but are poorly constrained experimentally. We calculate the electrical and thermal conductivities of iron at Earth's inner core conditions taking into account consistently the thermal disorder due to the motion of ions and the electronic correlations. We focus mainly on the body-centered cubic (bcc) phase predicted to be stable at the core's conditions by several recent works. The total calculated thermal conductivity is 220 W/(m*K) including both the electron-electron scattering (EES) and electron-lattice scattering (ELS), with the EES contribution of about 20%. Thermal disorder is found to suppress the non-Fermi-liquid behavior characteristic for the perfect bcc iron and thus to reduce the EES. The total conductivity exhibits a markedly weaker sensitivity to increase of the EES as compared to the Matthiessen's rule, hence, the electron-lattice and electron-electron contributions are intertwined and cannot be treated separately. We also calculate the conductivity in the hexagonal close packed (hcp) iron phase, and again find the EES is not increased by the thermal disorder and is found to be weak there, too. Our main finding of a relatively weak EES thus holds for the both likely iron phases at Earth's core
a. status b. conditions c. liquid d. rule.
Q98. arXiv:2004.03884 [cond-mat.mtrl-sci]: Controlled switching of ferroelectric SnSe monolayers at room temperature. Kai Chang, Felix Küster, Brandon J. Miller, Jing-Rong Ji, Jia-Lu Zhang, Paolo Sessi, Salvador Barraza-Lopez, Stuart S. P. Parkin. (Submitted on 8 Apr 2020): ABSTRACT: Two-dimensional (2D) van der Waals ferroelectrics provide an unprecedented architectural freedom for the creation of artificial multiferroics and non-volatile electronic devices based on vertical and co-planar heterojunctions of 2D ferroic materials. Additionally, their non-centrosymmetric structures lead to a strong non-linear optical response, and also add functionalities to designer spintronic and valleytronic devices. Nevertheless, controlled electrical switching of in-plane polarization--a fundamental requirement for realizing in-plane ferroelectric non-volatile memories--has not yet been seen experimentally in any monolayer-thick 2D ferroelectric. Here we report the discovery of robust ferroelectricity with a critical temperature close to 400 K in SnSe monolayer plates, and the demonstration of controlled ferroelectric switching of their in-plane spontaneous polarization at room temperature using a scanning tunneling microscope (STM). The switching was achieved through creating, moving and eliminating 180° domain walls in the SnSe monolayer plates by applying appropriate bias voltage pulses to an STM tip. This study shows that STM is a powerful tool for detecting and manipulating the in-plane polarization in 2D ferroelectric monolayers, which is difficult to characterize by conventional approaches such as piezoresponse force microscopy, thus facilitating the hunt for other 2D ferroelectric monolayers with in-plane polarization with important technological
a. creations b. manipulation c. applications d. devices.
Q99. arXiv.2006.09476: Infrared-detected AGNs in the Local Universe. Tuba İkiz et al. Turkey. Subjects: Astrophysics of Galaxies (astro-ph.GA): ABSTRACT: Spitzer/IRAC color selection is a promising technique to identify hot accreting nuclei, that is to say AGN, in galaxies. We demonstrate this using a small sample of SAURON galaxies, and explore this further. The goal of this study is to find a simple and efficient way to reveal optically obscured nuclear accretion in (nearby) galaxies. We apply an infrared selection method to the Spitzer Survey of Stellar Structures in Galaxies (S4G) sample of more than 2500 galaxies, together with its extension sample of more than 400 galaxies. We use the Spitzer colors to find galaxies in the S4G survey containing a hot core, suggesting the presence of a strong AGN, and study the detection fraction as a function of morphological type. We test this infrared color selection method by examining the radio properties of the galaxies, using the VLA NVSS and FIRST surveys. Using the radio data, we demonstrate that galaxies displaying hot mid-infrared nuclei stand out as being (candidate) active galaxies. When using, instead of Spitzer, colors from the lower spatial resolution WISE mission, we reproduce these results. Hence multi-band infrared imaging represents a useful tool to uncover optically obscured nuclear activity in galaxies.
a. ℏ b. ℏ/ kT c. ℏ/ k d.ℏ/ kBT.
Q96. arXiv:2004.03664 [cond-mat.mes-hall]: Photo-Seebeck effect in single-crystalline bismuth telluride topological insulator. Anand Nivedan, Arvind Singh, Sandeep Kumar, Sunil Kumar. (Submitted on 7 Apr 2020):ABSTRACT: Bismuth telluride is a low energy bulk band-gap topological system with conducting surface states. Besides its very good thermoelectric properties, it also makes a very good candidate for broadband photodetectors. Here, we report temperature-dependent photo-Seebeck effect in a bulk single crystalline bismuth telluride. On light illumination, an electrically biased sample shows distinguishable contributions in the measured current due to both the Seebeck effect and the normal photo-generated carriers within a narrow layer of the sample. Detailed experiments are performed to elucidate the distinction between the Seebeck contribution and the photogenerated current. The temperature-dependence of the photocurrent without Seebeck contribution shows a sign reversal from negative to positive at a specific temperature depending on the wavelength of photoexcitation
a. light b. spectra c. layer d. carrier.
Q97. arXiv:2004.03700 [cond-mat.str-el]: Electronic correlations and transport in iron at Earth's core conditions. L. V. Pourovskii, J. Mravlje, M. Pozzo, D. Alfè. (Submitted on 7 Apr 2020):ABSTRACT: The transport properties of iron under inner core conditions are essential input for the geophysical modeling of the Earth's interior but are poorly constrained experimentally. We calculate the electrical and thermal conductivities of iron at Earth's inner core conditions taking into account consistently the thermal disorder due to the motion of ions and the electronic correlations. We focus mainly on the body-centered cubic (bcc) phase predicted to be stable at the core's conditions by several recent works. The total calculated thermal conductivity is 220 W/(m*K) including both the electron-electron scattering (EES) and electron-lattice scattering (ELS), with the EES contribution of about 20%. Thermal disorder is found to suppress the non-Fermi-liquid behavior characteristic for the perfect bcc iron and thus to reduce the EES. The total conductivity exhibits a markedly weaker sensitivity to increase of the EES as compared to the Matthiessen's rule, hence, the electron-lattice and electron-electron contributions are intertwined and cannot be treated separately. We also calculate the conductivity in the hexagonal close packed (hcp) iron phase, and again find the EES is not increased by the thermal disorder and is found to be weak there, too. Our main finding of a relatively weak EES thus holds for the both likely iron phases at Earth's core
a. status b. conditions c. liquid d. rule.
Q98. arXiv:2004.03884 [cond-mat.mtrl-sci]: Controlled switching of ferroelectric SnSe monolayers at room temperature. Kai Chang, Felix Küster, Brandon J. Miller, Jing-Rong Ji, Jia-Lu Zhang, Paolo Sessi, Salvador Barraza-Lopez, Stuart S. P. Parkin. (Submitted on 8 Apr 2020): ABSTRACT: Two-dimensional (2D) van der Waals ferroelectrics provide an unprecedented architectural freedom for the creation of artificial multiferroics and non-volatile electronic devices based on vertical and co-planar heterojunctions of 2D ferroic materials. Additionally, their non-centrosymmetric structures lead to a strong non-linear optical response, and also add functionalities to designer spintronic and valleytronic devices. Nevertheless, controlled electrical switching of in-plane polarization--a fundamental requirement for realizing in-plane ferroelectric non-volatile memories--has not yet been seen experimentally in any monolayer-thick 2D ferroelectric. Here we report the discovery of robust ferroelectricity with a critical temperature close to 400 K in SnSe monolayer plates, and the demonstration of controlled ferroelectric switching of their in-plane spontaneous polarization at room temperature using a scanning tunneling microscope (STM). The switching was achieved through creating, moving and eliminating 180° domain walls in the SnSe monolayer plates by applying appropriate bias voltage pulses to an STM tip. This study shows that STM is a powerful tool for detecting and manipulating the in-plane polarization in 2D ferroelectric monolayers, which is difficult to characterize by conventional approaches such as piezoresponse force microscopy, thus facilitating the hunt for other 2D ferroelectric monolayers with in-plane polarization with important technological
a. creations b. manipulation c. applications d. devices.
Q99. arXiv.2006.09476: Infrared-detected AGNs in the Local Universe. Tuba İkiz et al. Turkey. Subjects: Astrophysics of Galaxies (astro-ph.GA): ABSTRACT: Spitzer/IRAC color selection is a promising technique to identify hot accreting nuclei, that is to say AGN, in galaxies. We demonstrate this using a small sample of SAURON galaxies, and explore this further. The goal of this study is to find a simple and efficient way to reveal optically obscured nuclear accretion in (nearby) galaxies. We apply an infrared selection method to the Spitzer Survey of Stellar Structures in Galaxies (S4G) sample of more than 2500 galaxies, together with its extension sample of more than 400 galaxies. We use the Spitzer colors to find galaxies in the S4G survey containing a hot core, suggesting the presence of a strong AGN, and study the detection fraction as a function of morphological type. We test this infrared color selection method by examining the radio properties of the galaxies, using the VLA NVSS and FIRST surveys. Using the radio data, we demonstrate that galaxies displaying hot mid-infrared nuclei stand out as being (candidate) active galaxies. When using, instead of Spitzer, colors from the lower spatial resolution WISE mission, we reproduce these results. Hence multi-band infrared imaging represents a useful tool to uncover optically obscured nuclear activity in galaxies.
a. galaxies b. universe c. radio data. d. colors.
Q100. arXiv:2006.09584: Laboratory Optical Spectroscopy of Vibronic Transitions of the Thiophenoxy Radical. Haruka T. Sato, Mitsunori Araki, Takahiro Oyama, Koichi Tsukiyama. Astrophysics of Galaxies (astro-ph.GA). ABSTRACT: The thiophenoxy radical (C6H5S) is a species of possible astrophysical interest due to an electronic transition in a 5000 A region. The B <-- X electronic transition of this radical in the discharge of thiophenol was measured using a cavity ring-down spectrometer. The optical absorption spectrum of this transition was obtained in the range covering from the origin band (0-0) to a frequency of 1750 cm-1. The vibronic bands in the 400-1700 cm-1 region are stronger than the origin band, suggesting structural difference between the ground and excited electronic states. The prominent progression was assigned to the 6a symmetric in-plane CCC bending mode starting from the 6b10 forbidden band. Band origins of individual bands were determined by analysis of the rotational profiles. Although these vibronic bands were not found in optical spectra of diffuse clouds, the upper limits of the column densities for the thiophenoxy radical in the diffuse clouds toward HD 183143 and HD 204827 were evaluated to be
a. 4x10^13 cm-2 b. 4x10^12 cm-2 c.4x10^13 cm-2 d. 4x10^14.
Q101. arXiv. 2006.09898: Evolution of galaxies in groups in the Coma Supercluster. Ruchika Seth, Somak Raychaudhury. publication in MNRAS. Cosmology and Nongalactic Astrophysics (astro-ph.CO). ABSTRACT: We take a close look at the galaxies in the Coma Supercluster and assess the role of the environment (in the form of cluster, group and supercluster filament) in their evolution, in particular examining the role of groups. We characterise the groups according to intrinsic properties such as richness and halo mass, as well as their position in the supercluster and proximity to the two rich clusters, Abell 1656 (Coma) and Abell 1367. We devise a new way of characterising the local environment using a kernel density estimator. We find that apart from the dominant effects of the galaxy mass, the effect of the environment on galaxies is a complex combination of the overdensities on various scales, which is characterised in terms of membership of groups, and also of the position of the galaxy on filaments and their proximity to the infall regions of clusters. Whether the gas can be turned into stars depends upon the level of pre-processing, which plays a role in how star formation is enhanced in a given environment. Our results are consistent with gas accreted in the cold mode from the filaments, being made available to enhance star formation. Finally, we show that the Abell~1367 end of the supercluster is in the process of assembly at present, leading to heightened star formation activity, in contrast with the Coma-end of the filament
a. group b. system. c. environment d. formation.
Q102. arXiv. 2006.09941: On the Diversity of M-Star Astrospheres and the Role of Galactic Cosmic Rays Within. Konstantin Herbst, et al. Subjects: Solar and Stellar Astrophysics (astro-ph.SR): ABSTRACT: With upcoming missions such as the James Webb Space Telescope (JWST), the European Extremely Large Telescope (ELT), and the Atmospheric Remote-sensing Infrared Exoplanet Large-survey (ARIEL), we soon will be on the verge of detecting and characterizing Earth-like exoplanetary atmospheres for the first time. These planets are most likely to be found around smaller and cooler K- and M-type stars. However, recent observations showed that their radiation environment might be much harsher than that of the Sun. Thus, the exoplanets are most likely exposed to an enhanced stellar radiation environment, which could affect their habitability, for example, in the form of a hazardous flux of energetic particles. Knowing the stellar radiation field, and being able to model the radiation exposure on the surface of a planet is crucial to assess its habitability. In this study, we present 3D magnetohydrodynamic (MHD)-based model efforts investigating M-stars, focusing on V374 Peg, Proxima Centauri, and LHS 1140, chosen because of their diverse astrospheric quantities. We show that V374 Peg has a much larger astrosphere (ASP) than our Sun, while Proxima Centauri and LHS 1140 most likely have ASPs comparable or even much smaller than the heliosphere, respectively. Based on a 1D transport model, for the first time, we provide numerical estimates of the modulation of Galactic cosmic rays (GCRs) within the three ASPs. We show that the impact of GCRs on the Earth-like exoplanets Proxima Centauri b and LHS 1140 b cannot be neglected in the context of exoplanetary
a. diversity b. quantities c. situations d. habitability.
Q103. arXiv.2006.09405: Non-adiabatic molecular quantum dynamics with quantum computers. Pauline J. Ollitrault, Guglielmo Mazzola, Ivano Tavernelli. Quantum Physics (quant-ph): ABSTRACT: The theoretical investigation of non-adiabatic processes is hampered by the complexity of the coupled electron-nuclear dynamics beyond the Born-Oppenheimer approximation. Classically, the simulation of such reactions is limited by the unfavourable scaling of the computational resources as a function of the system size. While quantum computing exhibits proven quantum advantage for the simulation of real-time dynamics, the study of quantum algorithms for the description of non-adiabatic phenomena is still unexplored. In this work, we propose a quantum algorithm for the simulation of fast non-adiabatic chemical processes together with an initialization scheme for quantum hardware calculations. In particular, we introduce a first-quantization method for the time evolution of a wavepacket on two coupled harmonic potential energy surfaces (Marcus model). In our approach, the computational resources scale polynomially in the system dimensions, opening up new avenues for the study of photophysical processes that are classically
a. Intractable b. unsolved c. comprehensible d. forbidden.
Q104. arXiv:2006.11303 [astro-ph.HE]: Measuring the energy spectrum of neutral pions in ultra--high--energy proton--air interactions. Lorenzo Cazon, Ruben Conceição, Miguel Alexandre Martins, Felix Riehn. [Submitted on 19 Jun 2020]: ABSTRACT: Fluctuations in the muon content of extensive air showers are anti-correlated to the fluctuations of the energy taken by the neutral pions which emerge from the first interaction of the cosmic ray in the atmosphere. We demonstrate that the high-energy tail of the neutral pion spectrum produced in the first proton-air interaction can be measured, within the uncertainties of present cosmic ray experiments, through the analysis of the probability distribution of showers over the shower muon
a. contents b. distribution c. interaction d. correlations.
a. contents b. distribution c. interaction d. correlations.
Q105. arXiv:2006.11779 [astro-ph.SR]: Magnetic Flux Emergence in a Coronal Hole. J. Palacios, et al. [Submitted on 21 Jun 2020]: ABSTRACT: A joint campaign of various space-borne and ground-based observatories, comprising the Japanese Hinode mission (HOP~338, 20\,--\,30~September 2017), the GREGOR solar telescope, and the \textit{Vacuum Tower Telescope} (VTT), investigated numerous targets such as pores, sunspots, and coronal holes. In this study, we focus on the coronal hole region target. On 24~September 2017, a very extended non-polar coronal hole developed patches of flux emergence, which contributed to the decrease of the overall area of the coronal hole. These flux emergence patches erode the coronal hole and transform the area into a more quiet-Sun-like area, whereby bipolar magnetic structures play an important role. Conversely, flux cancellation leads to the reduction of opposite-polarity magnetic fields and to an increase in the area of the coronal hole. Other global coronal hole characteristics, including the evolution of the associated magnetic flux and the aforementioned area evolution in the EUV, are studied using data of the \textit{Helioseismic and Magnetic Imager} (HMI) and \textit{Atmospheric Imaging Assembly} (AIA) onboard the \textit{Solar Dynamics Observatory} (SDO). The interplanetary medium parameters of the solar wind display parameters compatible with the presence of the coronal hole. Furthermore, a particular transient is found in those
a. characteristics b. parameters c. holes d. wind display.
Q106. arXiv:2006.11626 [gr-qc]: A Neutron Star Model with Dark Energy Crust. L. S. M. Veneroni, A. Braz, M. F. A. da Silva.[Submitted on 20 Jun 2020]: ABSTRACT: We investigate stellar models in the presence of the cosmological constant Λ, based on two density profiles, one of them attributed to Stewart and the other one to Durgapal and Bannerji, proposed in the literature to model neutron stars. For them, a nonlocal equation of state with cosmological constant is obtained as a consequence of the chosen metric. In another direction, we obtain a solution for configurations with null radial pressure. The first model (based on the Stewart's density profile) turned out to be the most interesting, since surprisingly it admits the presence of dark energy in the interior of the star, in the outermost layers, for a certain range of mass-radius ratio γ. Still in this case, for other values of γ, all the energy conditions are satisfied. Another advantage of this model over the others studied here is the existence of intervals of γ compatible with physically acceptable models for Λ<0, Λ=0 and Λ>0, which also allowed us to analyze the influence of Λ on the behavior of the fluid with respect to the energy conditions. The other two configurations (Durgapal-Bannerji profile and Pr=0) only allow solutions for Λ<0, in order to ensure a positive mass for the star and to satisfy all the energy conditions in a specific range of
a. γ b. ratio c. analysis d. mass-radius.
Q107. arXiv:2006.13225 [astro-ph.GA]: Rapid Elimination of Small Dust Grains in Molecular Clouds. Kedron Silsbee, Alexei Ivlev, Paola Caselli, Olli Sipila, Bo Zhao. [Submitted on 23 Jun 2020]: ABSTRACT: We argue that impact velocities between dust grains with sizes less than ∼0.1 μm in molecular cloud cores are dominated by drift arising from ambipolar diffusion. This effect is due to the size dependence of the dust coupling to the magnetic field and the neutral gas. Assuming perfect sticking in collisions up to ≈50 m/s, we show that this effect causes rapid depletion of small grains - consistent with starlight extinction and IR/microwave emission measurements, both in the core center (n∼106 cm^−3) and envelope (n∼104 cm^−3). The upper end of the size distribution does not change significantly if only velocities arising from this effect are considered. We consider the impact of an evolved dust size distribution on the gas temperature, and argue that if the depletion of small dust grains occurs as would be expected from our model, then the cosmic ray ionization rate must be well below 10−16 s^−1 at a number density of
a. 104 cm^3 b. 105 cm^-4 c. 103 cm^-2 d. 105 cm^-3.
Q108. arXiv:2006.13229 [astro-ph.SR]: [Submitted on 23 Jun 2020]: Investigating the lack of main-sequence companions to massive Be stars. J. Bodensteiner, T. Shenar, H. Sana. ABSTRACT: About 20% of all B-type stars are classical Be stars. The Be phenomenon is strongly correlated with rapid rotation, the origin of which remains unclear. It may be rooted in single- or binary-star evolution. In the framework of the binary channel, the initially more massive star transfers mass and angular momentum to the original secondary, which becomes a Be star. The system then evolves into a Be binary with a post-main-sequence companion, which may later be disrupted in a supernova event. Hence, if the binary channel dominates the formation of Be stars, one may expect a strong lack of close Be binaries with main sequence (MS) companions. Through an extensive, star-by-star review of the literature of a magnitude-limited sample of Galactic early-type Be stars, we investigate whether Be binaries with MS companions are known to exist. Our sample is constructed from the BeSS database and cross-matched with all available literature on the individual stars. Out of an initial list of 505 Be stars, we compile a final sample of 287 Galactic Be stars earlier than B1.5 with V<=12 mag. Out of those, 13 objects were reported as Be binaries with known post-MS companions and 11 as binaries with unknown, uncertain or debated companions. We find no confirmed reports of Be binaries with MS companions. For the remaining 263 targets, no significant reports of multiplicity exist in the literature, implying that they are either Be binaries with faint companions, or truly single. The clear lack of reported MS companions to Be stars, which stands in contrast to the high number of detected B+B MS binaries, strongly supports the hypothesis that early-type Be stars are binary interaction products that spun up after mass and angular momentum transfer from a companion star. Taken at face value, our results may suggest that a large majority of the early-type Be stars have formed through binary
a. targets b. mass-transfer c. interaction d. truly single.
Q109.arXiv:2006.13830 [physics.gen-ph]: Space-time structure may be topological and not geometrical. Gabriele Carcassi, Christine A. Aidala.[Submitted on 18 Jun 2020]: ABSTRACT: In a previous effort [arXiv:1708.05492] we have created a framework that explains why topological structures naturally arise within a scientific theory; namely, they capture the requirements of experimental verification. This is particularly interesting because topological structures are at the foundation of geometrical structures, which play a fundamental role within modern mathematical physics. In this paper we will show a set of necessary and sufficient conditions under which those topological structures lead to real quantities and manifolds, which are a typical requirement for geometry. These conditions will provide a physically meaningful procedure that is the physical counter-part of the use of Dedekind cuts in mathematics. We then show that those conditions are unlikely to be met at Planck scale, leading to a breakdown of the concept of ordering. This would indicate that the mathematical structures required to describe space-time at that scale, while still topological, may not be
a. geometrical b. geometry c. on Planck scale d. structures.
a. 104 cm^3 b. 105 cm^-4 c. 103 cm^-2 d. 105 cm^-3.
Q108. arXiv:2006.13229 [astro-ph.SR]: [Submitted on 23 Jun 2020]: Investigating the lack of main-sequence companions to massive Be stars. J. Bodensteiner, T. Shenar, H. Sana. ABSTRACT: About 20% of all B-type stars are classical Be stars. The Be phenomenon is strongly correlated with rapid rotation, the origin of which remains unclear. It may be rooted in single- or binary-star evolution. In the framework of the binary channel, the initially more massive star transfers mass and angular momentum to the original secondary, which becomes a Be star. The system then evolves into a Be binary with a post-main-sequence companion, which may later be disrupted in a supernova event. Hence, if the binary channel dominates the formation of Be stars, one may expect a strong lack of close Be binaries with main sequence (MS) companions. Through an extensive, star-by-star review of the literature of a magnitude-limited sample of Galactic early-type Be stars, we investigate whether Be binaries with MS companions are known to exist. Our sample is constructed from the BeSS database and cross-matched with all available literature on the individual stars. Out of an initial list of 505 Be stars, we compile a final sample of 287 Galactic Be stars earlier than B1.5 with V<=12 mag. Out of those, 13 objects were reported as Be binaries with known post-MS companions and 11 as binaries with unknown, uncertain or debated companions. We find no confirmed reports of Be binaries with MS companions. For the remaining 263 targets, no significant reports of multiplicity exist in the literature, implying that they are either Be binaries with faint companions, or truly single. The clear lack of reported MS companions to Be stars, which stands in contrast to the high number of detected B+B MS binaries, strongly supports the hypothesis that early-type Be stars are binary interaction products that spun up after mass and angular momentum transfer from a companion star. Taken at face value, our results may suggest that a large majority of the early-type Be stars have formed through binary
a. targets b. mass-transfer c. interaction d. truly single.
Q109.arXiv:2006.13830 [physics.gen-ph]: Space-time structure may be topological and not geometrical. Gabriele Carcassi, Christine A. Aidala.[Submitted on 18 Jun 2020]: ABSTRACT: In a previous effort [arXiv:1708.05492] we have created a framework that explains why topological structures naturally arise within a scientific theory; namely, they capture the requirements of experimental verification. This is particularly interesting because topological structures are at the foundation of geometrical structures, which play a fundamental role within modern mathematical physics. In this paper we will show a set of necessary and sufficient conditions under which those topological structures lead to real quantities and manifolds, which are a typical requirement for geometry. These conditions will provide a physically meaningful procedure that is the physical counter-part of the use of Dedekind cuts in mathematics. We then show that those conditions are unlikely to be met at Planck scale, leading to a breakdown of the concept of ordering. This would indicate that the mathematical structures required to describe space-time at that scale, while still topological, may not be
a. geometrical b. geometry c. on Planck scale d. structures.
Q110. arXiv:2007.01302 [astro-ph.HE]: Submitted on 2 Jul 2020: The signature of energy losses on the cosmic ray electron spectrum. Carmelo Evoli, Pasquale Blasi, Elena Amato, Roberto Aloisio. ABSTRACT: We show that the fine structure of the electron spectrum in cosmic rays, especially the excess claimed by AMS-02 at energies ∼42 GeV, is fully accounted for in terms of inverse Compton losses in the photon background dominated by ultraviolet, infrared and CMB photons, plus the standard synchrotron losses in the Galactic magnetic field. The transition to the Klein-Nishina regime on the ultraviolet background causes the feature. Hence, contrary to previous statements, observations do not require the overlap of different components. We stress that the feature observed by AMS-02 at energies ∼42 GeV is not related to the positron excess, which instead requires the existence of positron sources, such as pulsars. Because energy losses are the physical explanation of this feature, we indirectly confirm that the transport of leptons in the Galaxy is loss-dominated down to energies of the order of tens of GeV. This finding imposes strong constraints on the feasibility of alternative theories of cosmic transport in which the grammage is accumulated in cocoons concentrated around sources, requiring that electrons and positrons become loss dominated only at very high energies.
a. spectrum b. pulsars. c. energies d. sources.
Q111. L1330 life member of ISCA, Dr Biresh Guha Street, Kolkata – 700017, The Indian Science Congress Association, The 108 Session year 2021, Mathematics Session (including Statistics) held in Jan 3-7, 2021. Ref: PDF: ANTI PHOTON, Zq MESON AND QUONIC NUMBER n CONSERVATION: ABSTRACT:Anti-Photon, Zq Meson and Quonic Number n Conservation.
Kotcherlakota_l_n. 17-11-10, Narasimha Ashram, Official Colony, Maharanipeta, Visakhapatnam-530002, Andhra Pradesh, Cell: 9491902867 truscincetrutechnology@blogspot.com
It is suggested that a spin one particle decays in 84 atta seconds, involving anti-photon, a gamma, quon and a neutrino of quon. I postulate that quon transforms as Zq meson and an anti neutrino. Zq has zero charge, mass of about 91.2 GeV/c2. The quon negative and quon positive decays are outlined. The neutrino, electron and quon negative have, lepton as plus one, while anti-neutrino, positron and quon positive have, lepton as minus one. S- Matrix with charge conjugation operator is formulated, with the quonic number n conservation. The anti- lepton negative associated with a “Star” in the incoherent scattering is found significant, with R as a target
a. spectrum b. pulsars. c. energies d. sources.
Q111. L1330 life member of ISCA, Dr Biresh Guha Street, Kolkata – 700017, The Indian Science Congress Association, The 108 Session year 2021, Mathematics Session (including Statistics) held in Jan 3-7, 2021. Ref: PDF: ANTI PHOTON, Zq MESON AND QUONIC NUMBER n CONSERVATION: ABSTRACT:Anti-Photon, Zq Meson and Quonic Number n Conservation.
Kotcherlakota_l_n. 17-11-10, Narasimha Ashram, Official Colony, Maharanipeta, Visakhapatnam-530002, Andhra Pradesh, Cell: 9491902867 truscincetrutechnology@blogspot.com
It is suggested that a spin one particle decays in 84 atta seconds, involving anti-photon, a gamma, quon and a neutrino of quon. I postulate that quon transforms as Zq meson and an anti neutrino. Zq has zero charge, mass of about 91.2 GeV/c2. The quon negative and quon positive decays are outlined. The neutrino, electron and quon negative have, lepton as plus one, while anti-neutrino, positron and quon positive have, lepton as minus one. S- Matrix with charge conjugation operator is formulated, with the quonic number n conservation. The anti- lepton negative associated with a “Star” in the incoherent scattering is found significant, with R as a target
a. nucleon b. nucleus c. quonic d. quon.
Q112. arXiv:2007.01692 [physics.app-ph]: [Submitted on 3 Jul 2020]: Directed Energy Transfer from Monolayer WS2 to NIR Emitting PbS-CdS Quantum Dots. Arelo O.A Tanoh, et al., : ABSTRACT: Heterostructures of two-dimensional (2D) transition metal dichalcogenides (TMDs) and inorganic semiconducting zero-dimensional (0D) quantum dots (QDs) offer unique charge and energy transfer pathways which could form the basis of novel optoelectronic devices. To date, most has focused on charge transfer and energy transfer from QDs to TMDs, i.e. from 0D to 2D. Here, we present a study of the energy transfer process from a 2D to 0D material, specifically exploring energy transfer from monolayer tungsten disulphide (WS2) to near infrared (NIR) emitting lead sulphide-cadmium sulphide (PbS-CdS) QDs. The high absorption cross section of WS2 in the visible region combined with the potentially high photoluminescence (PL) efficiency of PbS QD systems, make this an interesting donor-acceptor system that can effectively use the WS2 as an antenna and the QD as a tuneable emitter, in this case downshifting the emission energy over hundreds of meV. We study the energy transfer process using photoluminescence excitation (PLE) and PL microscopy, and show that 58% of the QD PL arises due to energy transfer from the WS2. Time resolved photoluminescence (TRPL) microscopy studies show that the energy transfer process is faster than the intrinsic PL quenching by trap states in the WS2, thus allowing for efficient energy transfer. Our results establish that QDs could be used as tuneable and high PL efficiency emitters to modify the emission properties of TMDs. Such TMD/QD heterostructures could have applications in light emitting technologies, artificial light harvesting systems or be used to read out the state of TMD devices optically in various logic and computing
a. methods b. models c. artifacts d. applications.
a. methods b. models c. artifacts d. applications.
Q 113. arXiv:2008.04319 [astro-ph.SR]: Submitted on 10 Aug 2020: Sun-as-a-star Spectral Irradiance Observations of Transiting Active Regions. Shin Toriumi, Vladimir S. Airapetian, Hugh S. Hudson, Carolus J. Schrijver, Mark C.M. Cheung, Marc L. DeRosa: ABSTRACT: Major solar flares are prone to occur in active region atmospheres associated with large, complex, dynamically-evolving sunspots. This points to the importance of monitoring the evolution of starspots, not only in visible but also in ultra violet (UV) and X-rays, in understanding the origin and occurrence of stellar flares. To this end, we perform spectral irradiance analysis on different types of transiting solar active regions by using a variety of full-disk synoptic observations. The target events are an isolated sunspot, spotless plage, and emerging flux in prolonged quiet-Sun conditions selected from the past decade. We find that the visible continuum and total solar irradiance become darkened when the spot is at the central meridian, whereas it is bright near the solar limb; UV bands sensitive to the chromosphere correlate well with the variation of total unsigned magnetic flux in the photosphere; amplitudes of EUV and soft X-ray increase with the characteristic temperature, whose light curves are flat-topped due to their sensitivity to the optically thin corona; the transiting spotless plage does not show the darkening in the visible irradiance, while the emerging flux produces an asymmetry in all light curves about the central meridian. The multi-wavelength sun-as-a-star study described here indicates that such time lags between the coronal and photospheric light curves have the potential to probe the extent of coronal magnetic fields above the starspots. In addition, EUV wavelengths that are sensitive to the transition-region temperature sometimes show anti-phased variations, which may be used for diagnosing plasmas around
a. stars b. galaxies c. starspots d. meridian.
Q114. arXiv:2008.04660 [astro-ph.GA]: [Submitted on 11 Aug 2020] : The Origin of Elements from Carbon to Uranium. Chiaki Kobayashi, Amanda I. Karakas, Maria Lugaro. ABSTRACT: To reach a deeper understanding of the origin of elements in the periodic table, we construct Galactic chemical evolution (GCE) models for all stable elements from C (A=12) to U (A=238) from first principles, i.e., using theoretical nucleosynthesis yields and event rates of all chemical enrichment sources. This enables us to predict the origin of elements as a function of time and environment. In the solar neighborhood, we find that stars with initial masses of M>30M_\odot can become failed supernovae if there is a significant contribution from hypernovae (HNe) at M~20-50M_\odot. The contribution to GCE from super asymptotic giant branch (AGB) stars (with M~8-10M_\odot at solar metallicity) is negligible, unless hybrid white dwarfs from low-mass super-AGB stars explode as so-called Type Iax supernovae, or high-mass super-AGB stars explode as electron-capture supernovae (ECSNe). Among neutron-capture elements, the observed abundances of the second (Ba) and third (Pb) peak elements are well reproduced with our updated yields of the slow neutron-capture process (s-process) from AGB stars. The first peak elements, Sr, Y, and Zr, are sufficiently produced by ECSNe together with AGB stars. Neutron star mergers can produce rapid neutron-capture process (r-process) elements up to Th and U, but the timescales are too long to explain observations at low metallicities. The observed evolutionary trends, such as for Eu, can well be explained if ~3% of 25-50 M_\odot hypernovae are magneto-rotational supernovae producing r-process elements. Along with the solar neighborhood, we also predict the evolutionary trends in the halo, bulge, and thick disk for future comparison with galactic archaeology
a. elements . b. trends c. bulge. d. surveys.
Q115. arXiv:2008.04945 [astro-ph.SR]: [Submitted on 11 Aug 2020]: Spatially Resolved Ultraviolet Spectroscopy of the Great Dimming of Betelgeuse. Andrea K. Dupree et al., ABSTRACT: The bright supergiant, Betelgeuse (Alpha Orionis, HD 39801) experienced a visual dimming during 2019 December and the first quarter of 2020 reaching an historic minimum 2020 February 7−13. During 2019 September-November, prior to the optical dimming event, the photosphere was expanding. At the same time, spatially resolved ultraviolet spectra using the Hubble Space Telescope/Space Telescope Imaging Spectrograph revealed a substantial increase in the ultraviolet spectrum and Mg II line emission from the chromosphere over the southern hemisphere of the star. Moreover, the temperature and electron density inferred from the spectrum and C II diagnostics also increased in this hemisphere. These changes happened prior to the Great Dimming Event. Variations in the Mg II k-line profiles suggest material moved outwards in response to the passage of a pulse or acoustic shock from 2019 September through 2019 November. It appears that this extraordinary outflow of material from the star, likely initiated by convective photospheric elements, was enhanced by the coincidence with the outward motions in this phase of the ∼400 day pulsation cycle. These ultraviolet observations appear to provide the connecting link between the known large convective cells in the photosphere and the mass ejection event that cooled to form the dust cloud in the southern hemisphere imaged in 2019 December, and led to the exceptional optical dimming of Betelgeuse in 2020
a. February b. March c. April d. August
Q116. arXiv:2008.05020 [astro-ph.SR]: [Submitted on 11 Aug 2020]: Heating and Eruption of a Solar Circular Ribbon Flare. Jeongwoo Lee, Judith T. Karpen, Chang Liu, Haimin Wang. ABSTRACT: We studied a circular-ribbon flare, SOL2014-12-17T04:51, with emphasis on its thermal evolution as determined by the Differential Emission Measure (DEM) inversion analysis of the extreme ultraviolet (EUV) images of the Atmospheric Imaging Assembly (AIA) instrument onboard the Solar Dynamics Observatory (SDO). Both temperature and emission measure start to rise much earlier than the flare, along with an eruption and formation of a hot halo over the fan structure. In the main flare phase, another set of ribbons forms inside the circular ribbon, and expands as expected for ribbons at the footpoints of a postflare arcade. An additional heating event further extends the decay phase, which is also characteristic of some eruptive flares. The basic magnetic configuration appears to be a fan-spine topology, rooted in a minority-polarity patch surrounded by majority-polarity flux. We suggest that reconnection at the null point begins well before the impulsive phase, when the null is distorted into a breakout current sheet, and that both flare and breakout reconnection are necessary in order to explain the subsequent local thermal evolution and the eruptive activities in this confined magnetic structure. Using local DEMs, we found a postflare temperature increase inside the fan surface, indicating that the so-called EUV late phase is due to continued heating in the flare
a. signals b. eruptions c. loops d. activities.
Q117. arXiv:2008.05142 [astro-ph.EP]: [Submitted on 12 Aug 2020]: Debris cloud of India Anti-Satellite Test to Microsat-R Satellite. Yu Jiang. Understanding the motion of debris cloud produced by the anti-satellite test can help us to know the danger of these tests. This study presents the orbit status of 57 fragments observed by the CelesTrak and presented in the NORAD Two-Line Element Sets of India Anti-Satellite Test. There are 10 of these observed fragments have altitudes of the apogee larger than 1000.0 km, the maximum one is 1725.7 km. We also numerical calculated the number of debris, the results show that the number of debris with the diameter larger than 0.2m is 14, the number of debris with the diameter larger than 0.01m is 6587, and the number of debris with the diameter larger than 0.001m is 7.22e+5. The results of the secondary collision of the debris will produced more fragments in the space. The life time of the fragments depends on the initial orbit parameters and the sizes of the
a. satellites b. debris c. collisions d. fragments.
Q118. L1330
life member of ISCA, Dr.
Biresh Guha Street, Kolkata – 700017, The
Indian Science Congress Association,The
108 Session year 2021,Physics
Session to be held on Jan 2-7, 2021: ABSTRACT: Lagrangian
Formulation of Outer and Inner Cores
of Earth and Axigra. by Prof.
Dr. Kotcherlakota Lakshmi Narayana, 17-11-10,
Narasimha Ashram, Official
Colony, Maharanipeta, Visakhapatnam-530002,
Andhra Pradesh, Cell:
9491902867
truscincetrutechnology@blogspot.com
Axigra
a combination of axion and gravitin, plays a role in both the inner
and outer covers of Earth. The outer core of liquid state and the
inner core of solid material, have iron, Nickel, Sulphur and
Magnesium apart from minor metals that are negligible. Axigra splits
as spin half and photon of spin one, termed as spo- half and pho –
one for outer core and spi- half and phi- one for the inner core of
earth.
Lagrangian
formulation yields three equations for Ψ̅0,
A and Ψ0
where
represents “axigra’’ mass mA,
and Ψ̅0
and
Ψ0
stand for the four major elements
mentioned
a. above b. below c. three d. earth.
Q119. arXiv:2008.02903 [physics.geo-ph]: Submitted on 6 Aug 2020]: Local earthquakes detection: A benchmark dataset of 3-component seismograms built on a global scale. Fabrizio Magrini, Dario Jozinović, Fabio Cammarano, Alberto Michelini, Lapo Boschi. ABSTRACT: Machine learning is becoming increasingly important in scientific and technological progress, due to its ability to create models that describe complex data and generalize well. The wealth of publicly-available seismic data nowadays requires automated, fast, and reliable tools to carry out a multitude of tasks, such as the detection of small, local earthquakes in areas characterized by sparsity of receivers. A similar application of machine learning, however, should be built on a large amount of labeled seismograms, which is neither immediate to obtain nor to compile. In this study we present a large data set of seismograms recorded along the vertical, north, and east components of 1487 broad-band or very broad-band receivers distributed worldwide; this includes 629,095 3-component seismograms generated by 304,878 local earthquakes and labeled as EQ, and 615,847 ones labeled as noise (AN). Application of machine learning to this data set shows that a simple Convolutional Neural Network of 67,939 parameters allows discriminating between earthquakes and noise single-station recordings, even if applied in regions not represented in the training set. Achieving an accuracy of 96.7, 95.3, and 93.2% on training, validation, and test set, respectively, we prove that the large variety of geological and tectonic settings covered by our data supports the generalization capabilities of the algorithm, and makes it applicable to real-time detection of local events. We make the database publicly available, intending to provide the seismological and broader scientific community with a benchmark for time-series to be used as a testing ground in signal
a. processing b. detection c. effort d. availability.
Q120. arXiv:2008.05424 [astro-ph.GA]: [Submitted on 12 Aug 2020]: Active Galactic Nuclei as seen by the Spitzer Space Telescope. Mark Lacy (1), Anna Sajina (2) ((1) NRAO, (2) Tufts University). ABSTRACT: The Spitzer Space Telescope revolutionized studies of Active Galactic Nuclei (AGNs). Its combined sensitivity and mapping speed at mid-infrared wavelengths revealed a substantial population of highly-obscured AGNs. This population implies a higher radiative accretion efficiency, and thus possibly a higher spin for black holes than indicated by surveys in the optical and X-ray. The unique mid-infrared spectrographic capability of Spitzer gave important insights into the distribution and nature of the dust surrounding AGNs, enabling the separation of AGN and starburst components, the detection of silicate features in emission from hot dust, and the identification of shocked gas associated with AGN activity. The sensitivity of Spitzer allowed almost complete identification of the host galaxies of samples of AGNs selected in the X-ray and radio. As we look forward to the James Webb Space Telescope, the lessons learned from Spitzer studies will inform observational programs with new and upcoming infrared
a. spectra b. illumination c. detection d. facilities.
Q121. arXiv:2008.05081: Automatic Feynman diagram generation for nonlinear optical spectroscopies. Peter A. Rose, Jacob J. Krich. ABSTRACT: Perturbative nonlinear optical spectroscopies are powerful methods to understand the dynamics of excitonic and other condensed phase systems. Feynman diagrams have long provided the essential tool to understand and interpret experimental spectra and to organize the calculation of spectra for model systems. When optical pulses are strictly time ordered, only a small number of diagrams contribute, but in many experiments pulse-overlap effects are important for interpreting results. When pulses overlap, the number of contributing diagrams can increase rapidly, especially with higher order spectroscopies, and human error is especially likely when attempting to write down all of the diagrams. We present an automated Diagram Generator (DG) that generates all of the Feynman diagrams needed to calculate any nth-order spectroscopic signal. We characterize all perturbative nonlinear spectroscopies by their associated phase-discrimination condition as well as the time intervals where pulse amplitudes are nonzero. Although the DG can be used to automate impulsive calculations, its greatest strength lies in automating finite-pulse calculations where pulse overlaps are important. We consider the cases of third-order 2D photon echo spectroscopy and fifth-order exciton-exciton interaction 2D spectroscopy, which are respectively described by 6 or 7 diagrams in the impulsive limit but 16 or 240 diagrams, respectively, when pulses overlap. The DG allows users to automatically include all relevant diagrams at relatively low computational cost, since the extra diagrams are only generated for the inter-pulse delays where they are
a. speculative b. relevant c. overlaps d. diagrams.
Answers: Q61b. Q62c. Q63d. Q64b. Q65a. Q66c. Q67b. Q68a. Q69d. Q70b. Q71a. Q72c. Q73a. Q74c. Q75b. Q76d. Q77b. Q78a. Q79c. Q80b. Q81a. Q82c. Q83d. Q84b. Q85a. Q86d. Q87b. Q88a. Q89c. Q90b. Q91c. Q92a. Q93d. Q94b. Q95d. Q96a. Q97b. Q98c. Q99a. Q100c. Q101b. Q102d. Q103a. Q104a. Q105b. Q106a. Q107d. Q108b. Q109a. Q110c. Q111b. Q112d. Q113c. Q114d. Q115a. Q116c, Q117b. Q118a. Q119a. Q120d. Q121b.
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