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SOLAR MODELS WITH CONVECTIVE OVERSHOOT, THE SOLAR-WIND MASS LOSS, AND A PMS DISK ACCRETION: HELIOSEISMIC QUANTITIES, LI DEPLETION AND NEUTRINO FLUXES

arXiv

引用

arXiv 2019年

作者： Zhang, Qian-Sheng Li, Yan Christensen-Dalsgaard, Jørgen Yunnan Observatories Chinese Academy of Sciences 396 Yangfangwang Guandu District Kunming650216 China Center for Astronomical Mega-Science Chinese Academy of Sciences 20A Datun Road Chaoyang District Beijing100012 China Key Laboratory for the Structure and Evolution of Celestial Objects Chinese Academy of Sciences 396 Yangfangwang Guandu District Kunming650216 China University of Chinese Academy of Sciences Beijing100049 China Stellar Astrophysics Centre Department of Physics and Astronomy Aarhus University Aarhus CDK-8000 Denmark Kavli Institute for Theoretical Physics University of California Santa Barbara CA93106-4030 United States

Helioseismic observations have revealed many properties of the Sun: the depth and the helium abundance of the convection zone, the sound-speed and the density profiles in the solar interior. Those constraints have been used to judge the stellar evolution theory. With the old solar composition (e.g., GS98), the solar standard model is in reasonable agreement with the helioseismic constraints. However, a solar model with revised composition (e.g., AGSS09) with low abundance Z of heavy elements cannot be consistent with those constraints. This is the so-called "solar abundance problem", standing for more than ten years even with the recent upward revised Ne abundance. Many mechanisms have been proposed to mitigate the problem. However, there is still not a low-Z solar model satisfying all helioseismic constraints. In this paper, we report a possible solution to the solar abundance problem. With some extra physical processes that are not included in the standard model, solar models can be significantly improved. Our new solar models with convective overshoot, the solar wind, and an early mass accretion show consistency with helioseismic constraints, the solar Li abundance, and observations of solar neutrino fluxes. Copyright © 2019, The Authors. All rights reserved.

关键词： Solar wind

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Eclipsing binaries observed by LAMOST 2

Eclipsing binaries observed by LAMOST

引用

2nd Accretion Processes in Cosmic Sources, APCS 2018

作者： Zhu, Liying Qian, Shengbang Shi, Xiangdong Yunnan Observatories Chinese Academy of Sciences 396 Yangfangwang Guandu District Kunming 650216 P. R. ChinaCenter for Astronomical Mega-Science Chinese Academy of Sciences 20A Datun Road Chaoyang District Beijing 100012 P. R. ChinaKey Laboratory for the Structure and Evolution of Celestial Objects Chinese Academy of Sciences 396 Yangfangwang Guandu District Kunming 650216 P. R. ChinaUniversity of the Chinese Academy of Sciences Yuquan Road 19# Sijingshang Block 100049 Beijing P. R. China

LAMOST has a wide field of view and a very high spectrum acquiring rate. More than 9 millions spectra were obtained by LAMOST till now. Among them, more than 8 millions are stellar spectra. Such huge stellar spectra database will stimulate the deep study of stellar physics and corresponding fields. Eclipsing binaries are very important sources in astrophysics because they provide precise information about absolute parameters of the components. LAMOST observed 12923 eclipsing binary stars, which greatly expanded the spectroscopic information of eclipsing binaries. We provided the eclipsing binary catalogue with stellar atmospheric parameters and spectral types obtained by LAMOST. In this paper, we introduce the different kinds of eclipsing binaries observed by LAMOST. As an example of the follow-up observation, we present the study of the EW-type eclipsing binary NSVS4692753. Combined the complete light curves and the parameters obtained by LAMOST, we analyzed its muli-color light *** results show that NSVS4692753 is a low mass ratio (mass ratio 5.0) and deep contact (fill-out factor 64%) W-type contact binary system. The third light contribution was detected in all bands and the asymmetric light variation detected in the light curve was explained by a dark spot in the secondary. NSVS4692753 is the special system at the late evolutionary stage of contact binaries, and maybe the progenitor of the luminous red nova, which is a rare class of optical transients. © Copyright owned by the author(s) under the terms of the Creative Commons

关键词： Astrophysics

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Sn 2018hti: A nearby superluminous supernova discovered in a metal-poor galaxy

arXiv

引用

arXiv 2020年

作者： Lin, W.L. Wang, X.F. Li, W.X. Zhang, J.J. Mo, J. Sai, H.N. Zhang, X.H. Filippenko, A.V. Zheng, W.K. Brink, T.G. Baron, E. DerKacy, J.M. Ehgamberdiev, S.A. Mirzaqulov, D. Li, X. Zhang, J.C. Yan, S.Y. Xi, G.B. Hsiao, Y. Zhang, T.M. Wang, L.J. Liu, L.D. Xiang, D.F. Wu, C.Y. Rui, L.M. Chen, Z.H. Tsinghua University Beijing100084 China Beijing Planetarium Beijing Academy of Science and Technology Beijing100044 China Yunnan Observatories Chinese Academy of Sciences Kunming650216 China Key Laboratory for the Structure and Evolution of Celestial Objects Chinese Academy of Sciences Kunming650216 China Center for Astronomical Mega-Science Chinese Academy of Sciences 20A Datun Road Chaoyang District Beijing100012 China Department of Astronomy University of California BerkeleyCA94720-3411 United States Miller Institute for Basic Research in Science University of California BerkeleyCA94720 United States Homer L. Dodge Department of Physics and Astronomy University of Oklahoma NormanOK73019 United States Ulugh Beg Astronomical Institute Uzbekistan Academy of Sciences Uzbekistan Tashkent100052 Uzbekistan Key Laboratory of Optical Astronomy National Astronomical Observatories Chinese Academy of Sciences Beijing10101 China School of Astronomy and Space Science University of Chinese Academy of Sciences Beijing101408 China Astroparticle Physics Institute of High Energy Physics Chinese Academy of Sciences Beijing100049 China Department of Astronomy Beijing Normal University Beijing100875 China

SN 2018hti is a Type I superluminous supernova (SLSN I) with an absolute g-band magnitude of −22.2 at maximum brightness, discovered in a metal-poor galaxy at a redshift of 0.0612. We present extensive photometric and spectroscopic observations of this supernova, covering the phases from ∼ −35 days to more than +340 days from the r-band maximum. Combining our BVgri-band photometry with Swift UVOT optical/ultraviolet photometry, we calculated the peak luminosity as ∼ 3.5 × 1044 erg s−1. Modeling the observed light curve reveals that the luminosity evolution of SN 2018hti can be produced by an ejecta mass of 5.8 M and a magnetar with a magnetic field of B = 1.8 × 1013 G having an initial spin period of P0 = 1.8 ms. Based on such a magnetar-powered scenario and a larger sample, a correlation between the spin of the magnetar and the kinetic energy of the ejecta can be inferred for most SLSNe I, suggesting a self-consistent scenario. Like for other SLSNe I, the host galaxy of SN 2018hti is found to be relatively faint (Mg = −17.75 mag) and of low metallicity (Z = 0.3 Z ), with a star-formation rate of 0.3 M yr−1. According to simulation results of single-star evolution, SN 2018hti could originate from a massive, metal-poor star with a zero-age main sequence (ZAMS) mass of 25–40 M , or from a less massive rotating star with MZAMS ≈ 16–25 M . For the case of a binary system, its progenitor could also be a star with MZAMS & 25 M . Copyright © 2020, The Authors. All rights reserved.

关键词： Luminance

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Search for γ-ray emission from dark matter particle interactions from the Andromeda and Triangulum galaxies with the Fermi Large Area Telescope

引用

Physical Review D 2019年第12期99卷 123027-123027页

作者： Mattia Di Mauro Xian Hou Christopher Eckner Gabrijela Zaharijas Eric Charles NASA Goddard Space Flight Center Greenbelt Maryland 20771 USA Catholic University of America Department of Physics Washington D.C. 20064 USA Yunnan Observatories Chinese Academy of Sciences 396 Yangfangwang Guandu District Kunming 650216 People’s Republic of China Key Laboratory for the Structure and Evolution of Celestial Objects Chinese Academy of Sciences 396 Yangfangwang Guandu District Kunming 650216 People’s Republic of China Center for Astronomical Mega-Science Chinese Academy of Sciences 20A Datun Road Chaoyang District Beijing 100012 People’s Republic of China Center for Astrophysics and Cosmology University of Nova Gorica Vipavska 13 SI-5000 Nova Gorica Slovenia SLAC National Accelerator Laboratory Stanford University Stanford California 94305 USA

The Andromeda (M31) and Triangulum (M33) galaxies are the closest Local Group galaxies to the Milky Way, being only 785 and 870 kpc away. These two galaxies provide an independent view of high-energy processes that are often obscured in our own Galaxy, including possible signals of dark matter (DM) particle interactions. The Fermi Large Area Telescope (Fermi-LAT) preliminary eight year list of sources includes both M31, which is detected as extended with a size of about 0.4°, and M33, which is detected as a pointlike source. The spatial morphology of M31 γ-ray emission could trace a population of unresolved sources and energetic particles originating in sources not related to massive star formation. Alternatively, the γ-ray emission could also be an indication of annihilation or decay of DM particles. We investigate these two possibilities using almost 10 years of data from the Fermi-LAT. An interpretation that involves only a DM γ-ray emission is in tension with the current limits from other searches, such as those targeting Milky Way dwarf spheroidal galaxies. When we include a template of astrophysical emission, tuned on γ-ray data or from observations of these galaxies in other wavelengths, we do not find any significant evidence for a DM contribution and we set limits for the annihilation cross section that probe the thermal cross section for DM masses up to a few tens of GeV in the bb¯ and τ+τ− channels. For models where the DM substructures have masses above 10−6 solar masses our limits probe the DM interpretation of the Fermi-LAT Galactic center excess. We provide also the lower limit for the DM lifetime assuming the same spatial models of the DM distribution in M31 and M33.

关键词： Cosmic ray sources Gamma ray astronomy Particle dark matter

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Formation of hot subdwarf B stars with neutron star components

arXiv

引用

arXiv 2018年

作者： Wu, You Chen, Xuefei Li, Zhenwei Han, Zhanwen Yunnan Observatories Chinese Academy of Sciences Kunming650216 China Key Laboratory for the Structure and Evolution of Celestial Objects Chinese Academy of Sciences Kunming650216 China University of the Chinese Academy of Science Beijing100049 China Center for Astronomical Mega-Science Chinese Academy of Sciences 20A Datun Road Chaoyang District Beijing100012 China

Context. Binary population synthesis predicts the existence of subdwarf B stars (sdBs) with neutron star (NS) or black hole (BH) companions. Several works have been dedicated to finding such systems, but none has been confirmed yet. Theoretically, the formation of sdBs with white dwarf (WD) and main sequence (MS) companions has been well investigated, while those with NS or BH companions remain to be explored further. Aims. We systematically investigate the formation of sdB+NS binaries from binary evolution and aim to obtain some clues for a search for such systems. Methods. We started from a series of MS+NS systems and determined the parameter spaces for producing sdB+NS binaries from the stable Roche-lobe overflow (RLOF) channel and from the common envelope (CE) ejection channel. The parameters for sdB+NS binaries were obtained from detailed binary evolution calculation with the code called modules for experiments in stellar astrophysics (MESA), and the CE parameters were given by the standard energy budget for CE evolution. The MS star had an initial mass ranging from 0.8 to 5 M. Various NS accretion efficiencies and NS masses were examined to investigate the effects they have. We show the characteristics of the produced sdB+NS systems, such as the mass of components, orbital period, the semi-amplitude of the radial velocity (K), and the spin of the NS component. Results. sdB+NS binaries can be produced either from stable RLOF or from CE ejection. In the stable RLOF channel, sdBs can be formed when the donor starts mass transfer close to the tip of the giant branch if the donor has an initial mass ≤ 2.0M. For more massive donors, sdBs can be formed when the donor starts mass transfer during the Hertzsprung gap or near the end of the MS. The orbital period of sdB+NS binaries produced in this way ranges from several days to more than 1000 days and moves toward the short-period (∼ hr) side with increasing initial MS mass. The highest K is about 150km s−1 for an MS s

关键词： Neutrons

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White dwarf deflagrations for Type Iax supernovae: Polarisation signatures from the explosion and companion interaction

arXiv

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arXiv 2020年

作者： Bulla, M. Liu, Z.-W. Röpke, F.K. Sim, S.A. Fink, M. Kromer, M. Pakmor, R. Seitenzahl, I.R. Nordita KTH Royal Institute of Technology Stockholm University Roslagstullsbacken 23 StockholmSE-106 91 Sweden Kunming650216 China Key Laboratory for the Structure and Evolution of Celestial Objects CAS Kunming650216 China Center for Astronomical Mega-Science CAS Beijing100012 China Zentrum für Astronomie der Universität Heidelberg Institut für Theoretische Astrophysik Philosophenweg 12 Heidelberg69120 Germany Heidelberger Institut für Theoretische Studien Schloss-Wolfsbrunnenweg 35 Heidelberg69118 Germany Astrophysics Research Centre School of Mathematics and Physics Queen's University BelfastBT7 1NN United Kingdom Institut für Theoretische Physik und Astrophysik Universität Würzburg Emil-Fischer-Straße 31 WürzburgD-97074 Germany Max-Planck-Institut für Astrophysik Karl-Schwarzschild-Str. 1 GarchingD-85748 Germany School of Science University of New South Wales Australian Defence Force Academy Northcott Drive CanberraACT2600 Australia

Growing evidence suggests that Type Iax supernovae might be the result of thermonuclear deflagrations of Chandrasekhar-mass white dwarfs in binary systems. We carry out Monte Carlo radiative transfer simulations and predict spectropolarimetric features originating from the supernova explosion and subsequent ejecta interaction with the companion star. Specifically, we calculate viewing-angle dependent flux and polarisation spectra for a 3D model simulating the deflagration of a Chandrasekhar-mass white dwarf and, for a second model, simulating the ejecta interaction with a main-sequence star. We find that the intrinsic signal is weakly polarised and only mildly viewing-angle dependent, owing to the overall spherical symmetry of the explosion and the depolarising contribution of iron-group elements dominating the ejecta composition. The interaction with the companion star carves out a cavity in the ejecta and produces a detectable, but modest signal that is significant only at relatively blue wavelengths (. 5000 Å). In particular, increasingly fainter and redder spectra are predicted for observer orientations further from the cavity, while a modest polarisation signal P ∼ 0.2 per cent is found at blue wavelengths for orientations 30◦ and 45◦ away from the cavity. We find a reasonable agreement between the interaction model viewed from these orientations and spectropolarimetric data of SN 2005hk and interpret the maximum-light polarisation signal seen at blue wavelengths for this event as a possible signature of the ejecta-companion interaction. We encourage further polarimetric observations of SNe Iax to test whether our results can be extended and generalised to the whole SN Iax class. Copyright © 2020, The Authors. All rights reserved.

关键词： Radiative transfer

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Subdwarf B stars as possible surviving companions in Type Ia supernova remnants

arXiv

引用

arXiv 2018年

作者： Meng, Xiangcun Li, Jiao Yunnan Observatories Chinese Academy of Sciences Kunming650216 China Key Laboratory for the Structure and Evolution of Celestial Objects Chinese Academy of Sciences Kunming650216 China Center for Astronomical Mega-Science Chinese Academy of Sciences 20A Datun Road Chaoyang District Beijing100012 China University of Chinese Academy of Sciences Beijing100049 China

Although type Ia supernovae (SNe Ia) are so important in many astrophysical fields, a debate on their progenitor model is still endless. Searching the surviving companion in a supernova remnant (SNR) may distinguish different progenitor models, since a companion still exists in the remnant for the single-degenerate (SD) model, but does not for the double degenerate (DD) model. However, some recent surveys do not discover the surviving companions in the remnant of SN 1006 and Kepler’s supernova, which seems to disfavor the SD model. Such a result could be derived from an incorrect survey target. Here, based on the common-envelope wind SD model for SNe Ia, in which the initial binary system consists of a white dwarf (WD) and a main-sequence (MS) star, we found that the companion at the moment of supernova explosion may be a MS, red-giant (RG) or subdwarf B (sdB) star if a spin-down timescale of less than 107 yr is assumed. We show the properties of the companions at the moment of supernova explosion, which are key clues to search the surviving companions in SNRs. Here, we suggest that the sdB star may be the surviving companion in some SNRs, even if the progenitor systems are the WD + MS systems. The SNe Ia with the sdB companions may contribute to all SNe Ia as much as 22%. Copyright © 2018, The Authors. All rights reserved.

关键词： White dwarfs

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Disruption of a planet spiralling into its host star

arXiv

引用

arXiv 2018年

作者： Jia, Shi Spruit, H.C. Yunnan Observatories Chinese Academy of Sciences Kunming650011 China Max-Planck-Institut für Astrophysik Karl-Schwarzschild-Str. 1 GarchingD-85748 Germany Key Laboratory for the Structure and Evolution of Celestial Objects Chinese Academy of Sciences Kunming650011 China University of Chinese Academy of Sciences Beijing100049 China

The processes leading deformation and destruction of planets spiraling into the convective envelope of their host stars are described. The planet is compressed by the ram pressure, and deformed into a attened shape for which a quantitative model is developed. Compression increases the planet's density contrast with the envelope and its gravitational binding energy. This increases the survivability especially of gas planets. An estimate is given for the depth of disruption by ram pressure, and for the subsequent fragmentation of the remnants. We show how the debris of rocky or iron planets, instead of mixing through the convection zone, sinks below the base of the convection zone. The time scale of the entire sequence of events is of the order of a few orbital times of the planet. If spiral-in of (partly) icy, rocky or iron planets has happened to the pre-main sequence Sun, it could account for the higher opacity below the base of the convection zone as inferred from helioseismology. Copyright © 2018, The Authors. All rights reserved.

关键词： Planets

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Search for γ-ray emission from dark matter particle interactions from Andromeda and Triangulum Galaxies with the Fermi Large Area Telescope

arXiv

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arXiv 2019年

作者： Mauro, Mattia Di Hou, Xian Eckner, Christopher Zaharijas, Gabrijela Charles, Eric NASA Goddard Space Flight Center GreenbeltMD20771 United States Catholic University of America Department of Physics WashingtonDC20064 United States Yunnan Observatories Chinese Academy of Sciences 396 Yangfangwang Guandu District Kunming650216 China Key Laboratory for the Structure and Evolution of Celestial Objects Chinese Academy of Sciences 396 Yangfangwang Guandu District Kunming650216 China Center for Astronomical Mega-Science Chinese Academy of Sciences 20A Datun Road Chaoyang District Beijing100012 China Center for Astrophysics and Cosmology University of Nova Gorica Vipavska 13 Nova GoricaSI-5000 Slovenia SLAC National Accelerator Laboratory Stanford University StanfordCA94305 United States

The Andromeda (M31) and Triangulum (M33) galaxies are the closest Local Group galaxies to the Milky Way, being only 785 and 870 kpc away. These two galaxies provide an independent view of high-energy processes that are often obscured in our own Galaxy, including possible signals of dark matter (DM) particle interactions. The Fermi Large Area Telescope (Fermi-LAT) preliminary eight year list of sources includes both M31, which is detected as extended with a size of about 0.4◦, and M33, which is detected as a point-like source. The spatial morphology of M31 γ-ray emission could trace a population of unresolved sources and energetic particles originating in sources not related to massive star formation. Alternatively, the γ-ray emission could also be an indication of annihilation or decay of DM particles. We investigate these two possibilities using almost 10 years of data from the Fermi LAT. An interpretation that involves only a DM γ-ray emission is in tension with the current limits from other searches, such as those targeting Milky Way dwarf spheroidal galaxies. When we include a template of astrophysical emission, tuned on γ-ray data or from observations of these galaxies in other wavelengths, we do not find any significant evidence for a DM contribution and we set limits for the annihilation cross section that probe the thermal cross section for DM masses up to a few tens of GeV in the b¯b and τ+τ− channels. For models where the DM substructures have masses above 10−6 solar masses our limits probe the DM interpretation of the Fermi LAT Galactic center excess. We provide also the lower limit for the DM decay time assuming the same spatial models of the DM distribution in M31 and M33. Copyright © 2019, The Authors. All rights reserved.

关键词： Galaxies

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Black hole and neutron star binary mergers in triple systems: Merger fraction and spin-orbit misalignment

arXiv

引用

arXiv 2018年

作者： Liu, Bin Lai, Dong Shanghai Astronomical Observatory Chinese Academy of Sciences 80 Nandan Road Shanghai200030 China Cornell Center for Astrophysics and Planetary Science Cornell University IthacaNY14853 United States Key Laboratory for the Structure and Evolution of Celestial Objects Chinese Academy of Sciences Kunming650011 China Tsung-Dao Lee Institute Shanghai200240 China

Black hole (BH) mergers driven by gravitational perturbations of external companions constitute an important class of formation channels for merging BH binaries detected by LIGO. We have studied the orbital and spin evolution of binary BHs in triple systems, where the tertiary companion excites large eccentricity in the inner binary through Lidov-Kozai oscillations, causing the binary to merge via gravitational radiation. Using the single-averaged and double-averaged secular dynamics of triples (where the equations of motion are averaged over the inner orbit and both orbits, respectively), we perform a large set of numerical integrations to determine the merger window (the range of companion inclinations that allows the inner binary to merge within ∼10 Gyrs) and the merger fraction as a function of various system parameters (e.g., the binary masses m1;m2 and initial semi-major axis a0, the mass, semi-major axis and eccentricity eout of the outer companion). For typical BH binaries (m1;2 20Mo - 30Mo and a0 10 AU), the merger fraction increases rapidly with eout because of the octupole perturbation, ranging from ∼ 1% at eout = 0 to 10 - 20% at eout = 0:9. We derive the analytical expressions and approximate scaling relations for the merger window and merger fraction for systems with negligible octupole effect, and apply them to neutron star binary mergers in triples. We also follow the spin evolution of the BHs during the companion-induced orbital decay, where de-Sitter spin precession competes with Lidov-Kozai orbital precession/nutation. Starting from aligned spin axes (relative to the orbital angular momentum axis), a wide range of final spin-orbit misalignment angle θf sl can be generated when the binary enters the LIGO sensitivity band. For systems where the octupole effect is small (such as those with m1 m2 or eout ∼ 0), the distribution of θf sl peaks around 90_. As the octuple effect increases, a more isotropic distribution of final spin axis is produced. Over

关键词： Merging

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