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arXiv 2023年

作者： Liu, Zheng-Wei Röpke, Friedrich K. Han, Zhanwen Kunming650216 China Key Laboratory for the Structure and Evolution of Celestial Objects CAS Kunming650216 China International Centre of Supernovae Yunnan Key Laboratory Kunming650216 China University of Chinese Academy of Science Beijing100012 China Zentrum für Astronomie Universität Heidelberg Institut für Theoretische Astrophysik Philosophenweg 12 Heidelberg69120 Germany Heidelberger Institut für Theoretische Studien Schloss-Wolfsbrunnenweg 35 Heidelberg69118 Germany

Type Ia supernovae (SNe Ia) play a key role in the fields of astrophysics and cosmology. It is widely accepted that SNe Ia arise from thermonuclear explosions of white dwarfs (WDs) in binary systems. However, there is no consensus on the fundamental aspects of the nature of SN Ia progenitors and their actual explosion mechanism. This fundamentally flaws our understanding of these important astrophysical objects. In this review, we outline the diversity of SNe Ia and the proposed progenitor models and explosion mechanisms. We discuss the recent theoretical and observational progress in addressing the SN Ia progenitor and explosion mechanism in terms of the observables at various stages of the explosion, including rates and delay times, pre-explosion companion stars, ejecta–companion interaction, early excess emission, early radio/X-ray emission from circumstellar material (CSM) interaction, surviving companion stars, late-time spectra and photometry, polarization signals, and supernova remnant properties, etc. Despite the efforts from both the theoretical and observational side, the questions of how the WDs reach an explosive state and what progenitor systems are more likely to produce SNe Ia remain open. No single published model is able to consistently explain all observational features and the full diversity of SNe Ia. This may indicate that either a new progenitor paradigm or the improvement of current models is needed if all SNe Ia arise from the same origin. An alternative scenario is that different progenitor channels and explosion mechanisms contribute to SNe Ia. In the next decade, the ongoing campaigns with the James Webb Space Telescope (JWST), Gaia and the Zwicky Transient Facility (ZTF), and upcoming extensive projects with the Vera C. Rubin Observatory Legacy Survey of Space and Time (LSST) and the Square Kilometre Array (SKA) will allow us to conduct not only studies of individual SNe Ia in unprecedented detail but also systematic investigations for di

关键词： Explosions

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Prominence activation, optical flare, and post-flare loops on the RS Canum Venaticorum star SZ Piscium

arXiv

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arXiv 2024年

作者： Cao, Dongtao Gu, Shenghong Ge, Jian Wang, Tinggui Zhou, Jilin Chang, Liang Wolter, U. Mittag, M. Schmitt, J.H.M.M. Perdelwitz, V. 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 Chinese Academy of Sciences Beijing100049 China Department of Astronomy University of Florida Bryant Space Science Center GainesvilleFL32611 United States Key Laboratory for Research in Galaxies and Cosmology Department of Astronomy University of Science and Technology of China Chinese Academy of Sciences Hefei230026 China Department of Astronomy Key Laboratory of Modern Astronomy and Astrophysics in Ministry of Education Nanjing University Nanjing210093 China Hamburger Sternwarte Universität Hamburg Hamburg21029 Germany

We present the results of time-resolved high-resolution spectroscopic observations of the very active RS Canum Venaticorum (RS CVn) star SZ Piscium (SZ Psc), obtained during two consecutive observing nights on October 24 and 25, 2011. Several optical chromospheric activity indicators are analyzed using the spectral subtraction tech- nique, which show the remarkably different behavior between two nights. Gradually blue-shifted and strengthened excess absorption features presented in the series of the subtracted spectra (especially for the Hα, He i D3 and Hβ lines), as a result of active stellar prominence that is rising its height along the line of our sight, was detected in the observations on October 24. This prominence activation event was probably associated with the subsequently occurred optical flare, and part of that flare decay phase was hunted in the observations on October 25. The flare was characterized by the prominent He i D3 line emission, as well as stronger chromospheric emission in the Hα, Hβ and other active lines. The gradual decay of flare was accompanied by an obviously developmental absorption feature in the blue wing of the H_ and other active lines, which could be explained as cool post-flare loops which projected against the bright flare background. Therefore, a series of possibly associated magnetic activity phenomena, including flare-related prominence activation, optical flare and post-flare loops, were detected during our observations. Copyright © 2024, The Authors. All rights reserved.

关键词： Chemical activation

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ASAS J174406+2446.8 is identified as a marginal-contact binary with a possible cool third body

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Research in Astronomy and Astrophysics 2020年第6期20卷 265-272页

作者： Xiang-Dong Shi Sheng-Bang Qian Lin-Jia Li Wei-Wei Na Xiao Zhou Yunnan Observatories Chinese Academy of SciencesKunming 650216China University of Chinese Academy of Sciences Beijing 100049China Key Laboratory of the Structure and Evolution of Celestial Objects Chinese Academy of SciencesKunming 650216China Center for Astronomical Mega-Science Chinese Academy of SciencesBeijing 100101China Yuxi Normal University Yuxi 653100China

ASAS J174406+2446.8 was originally found as aδScuti-type pulsating star with the period P=0.189068 d by ASAS ***,the LAMOST stellar parameters reveal that it is far beyond the red edge of pulsational instability strip on the log g-T diagram ofδScuti pulsating *** understand the physical properties of the variable star,we observed it by the 1.0-m Cassegrain reflecting telescope at Yunnan ***-color light curves in B,V,R_c and I_c bands were obtained and are analyzed by using the W-D *** is found that this variable star is a shallow-contact binary with an EB-type light curve and an orbital period of 0.3781 d rather than aδScuti *** is a W-subtype contact binary with a mass ratio of 1.135(±0.019)and a fill-out factor of 10.4%(±5.6)%.The situation of ASAS J174406+2446.8 resembles those of other EB-type marginal-contact binaries such as UU Lyn,ⅡPer and GW *** of them are at a key evolutionary phase from a semi-detached configuration to a contact system predicted by the thermal relaxation oscillation *** linear ephemeris was corrected by using 303 new determined times of light *** is detected that the O-C curve shows a sinusoidal variation that could be explained by the light-travel-time effect via the presence of a cool red *** present investigation reveals that some of theδScuti-type stars beyond the red edge of pulsating instability strip on the log g-T diagram are misclassified eclipsing *** understand their structures and evolutionary states,more studies are required in the future.

关键词： stars binaries close-stars binaries eclipsing-stars δScuti-stars individual(ASAS J174406+2446.8)

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The Distribution of Semi-Detached Binaries. *** Efficient Pipeline

arXiv

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arXiv 2023年

作者： Xiong, Jianping Ding, Xu Li, Jiadong Ge, Hongwei Cheng, Qiyuan Ji, Kaifan Han, Zhanwen Chen, Xuefei Yunnan Observatories Chinese Academy of Sciences 396 YangFangWang Guandu District Kunming650216 China Max-Planck-Institut für Astronomie Königstuhl 17 HeidelbergD-69117 Germany Key Laboratory for Structure and Evolution of Celestial Objects Chinese Academy of Sciences P.O. Box 110 Kunming650216 China International Centre of Supernovae Yunnan Key Laboratory Kunming650216 China University of Chinese Academy of Sciences Beijing100049 China

Semi-detached binaries are in the stage of mass transfer and play a crucial role in studying mass transfer physics between interacting binaries. Large-scale time-domain surveys provide massive light curves of binary systems, while Gaia offers high-precision astrometric data. In this paper, we develop, validate, and apply a pipeline that combines the MCMC method with a forward model and DBSCAN clustering to search for semi-detached binary and estimate its inclination, relative radius, mass ratio, and temperature ratio using light curve. We train our model on the mock light curves from PHOEBE, which provides broad coverage of light curve simulations for semi-detached binaries. Applying our pipeline to TESS sectors 1-26, we have identified 77 semi-detached binary candidates. Utilizing the distance from Gaia, we determine their masses and radii with median fractional uncertainties of ∼26% and ∼7%, respectively. With the added 77 candidates, the catalog of semi-detached binaries with orbital parameters has been expanded by approximately 20%. The comparison and statistical results show that our semi-detached binary candidates align well with the compiled samples and the PARSEC model in Teff-L and M-R relations. Combined with the literature samples, comparative analysis with stability criteria for conserved mass transfer indicates that ∼ 97.4% of samples are undergoing nuclear-timescale mass transfer, and two samples (GO Cyg and TIC 454222105) are located within the limits of stability criteria for dynamical- and thermal-timescale mass transfer, which are currently undergoing thermal-timescale mass transfer. Additionally, one system (IR Lyn) is very close to the upper limit of delayed dynamical-timescale mass transfer. Copyright © 2023, The Authors. All rights reserved.

关键词： Mass transfer

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On the narrow spectral feature at ∼3 TeV in the MAGIC spectrum of Mrk 501

arXiv

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arXiv 2021年

作者： Hu, Wen Yan, Dahai Department of Physics Jinggangshan University Jiangxi Province Ji'an343009 China Key Laboratory for the Structure and Evolution of Celestial Objects Yunnan Observatories Chinese Academy of Sciences Kunming650011 China

Using a time-dependent one-zone leptonic model that incorporates both shock acceleration and stochastic acceleration processes, we investigate the formation of the narrow spectral feature at ∼ 3 TeV of Mrk 501 which was observed during the X-ray and TeV flaring activity in July 2014. It is found that the broadband spectral energy distribution (SED) can be well interpreted as the synchrotron and synchrotron-self-Compton emission from the electron energy distribution (EED) that is composed by a power-law (PL) branch and a pileup branch. The PL branch produces synchrotron photons which are scattered by the electrons of the pileup branch via inverse-Compton scattering and form the narrow spectral feature observed at the TeV energies. The EED is produced by two injection episodes, and the pileup branch in EED is caused by shock acceleration rather than stochastic acceleration. Copyright © 2021, The Authors. All rights reserved.

关键词： Stochastic systems

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MHD simulations of inward shocks in Cassiopeia A

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Research in Astronomy and Astrophysics 2020年第4期20卷 39-43页

作者： Chu-Yuan Yang Bi-Wen Bao Si-Ming Liu Yunnan Observatories Chinese Academy of SciencesKunming 650216China Key Laboratory for the Structure and Evolution of Celestial Objects Chinese Academy of SciencesKunming 650216China Center for Astronomical Mega-Science Chinese Academy of SciencesBeijing 100101China Department of Astronomy Key Laboratory of Astroparticle Physics of Yunnan ProvinceYunnan UniversityKunming 650091China Key Laboratory of Dark Matter and Space Astronomy Purple Mountain ObservatoryChinese Academy of SciencesNanjing 210033China

Cassiopeia A,the brightest radio supernova remnant(SNR)in the sky,has several unique characteristics in comparison to its *** its radio brightness and prominent soft-concave radio spectrum,itsγ-ray spectrum appears to have a low-energy cutoff near 2 GeV,and it is the only SNR with prominent hard X-ray *** the unusual radio properties may be attributed to strong emission from reverse shocks,the hard X-ray emission has been associated with high-speed inward shocks induced by high density ***,the low-energyγ-ray spectral cutoff could be attributed to slow penetration of lower energy particles accelerated near the inward shocks into high-density emission *** this paper,we carry out magneto-hydrodynamic(MHD)simulations of shocks in Cassiopeia A and demonstrate that its inward shock structure can indeed be reproduced via shock interactions with clumps of gases with a density of 20 cm-3.

关键词： acceleration of particles supernovae:individual(Cassiopeia A) ISM:supernova remnants X-rays:ISM

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A method for estimating masses of W Ursae Majoris-type binaries

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Research in Astronomy and Astrophysics 2020年第12期20卷 243-253页

作者： Li-Na Lu Jin-Zhong Liu Deng-Kai Jiang Ya-Hui Wang Xinjiang Astronomical Observatory Chinese Academy of SciencesUrumqi 830011China University of Chinese Academy of Sciences Beijing 100049China Yunnan Observatories Chinese Academy of SciencesKunming 650216China Key Laboratory for the Structure and Evolution of Celestial Objects Chinese Academy of SciencesKunming 650216China Laboratory of New Energy and Materials Xinjiang Institute of EngineeringUrumqi 830091China

Masses of W Ursae Majoris-type(W UMa) binaries play a critical role in investigating stellar dynamical evolutionary status. In this paper, we combine the PARSEC(PAdova and TRieste Stellar evolution Code) with the Roche geometric model to provide a method to determine the masses of W UMa systems. To verify the validity of this method, we compile a sample of 140 spectrum binaries from the literature, which includes 76 W-and 64 A-subtype systems with reliable physical parameters. We find that the average fractional difference and the standard deviation(σM) of the residuals for W-subtype and Asubtype approximately amount to 15.66% and 0.1218, 16.03% and 0.2094, respectively. Meanwhile, we also perform detailed analyses in accordance with the orbital period, the effective temperatures and the mass ratio. We find that the method is more applicable to determine masses for W UMa systems with low effective temperature and short period.

关键词： stars:binaries:eclipsing W Ursae Majoris(W UMa)binaries masses

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The carbon-to-H2, CO-to-H2 conversion factors and carbon abundance on kiloparsec scales in nearby galaxies

arXiv

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arXiv 2021年

作者： Jiao, Qian Gao, Yu Zhao, Yinghe Nanjing210023 China Department of Astronomy Xiamen University XiamenFujian361005 China Yunnan Observatories & Key Laboratory for the Structure and Evolution of Celestial Objects CAS Kunming650011 China

Using the atomic carbon [C i] (3P1 → 3P0) and [C i] (3P2 → 3P1) emission (hereafter [C i] (1−0) and [C i] (2−1), respectively) maps observed with the Herschel Space Observatory, and CO (1−0), Hi, infrared and submm maps from literatures, we estimate the [C i]-to-H2 and CO-to-H2 conversion factors of α[CI] (1−0), α[CI] (2−1), and αCO at a linear resolution ∼ 1 kpc scale for six nearby galaxies of M 51, M 83, NGC 3627, NGC 4736, NGC 5055, and NGC 6946. This is perhaps the first effort, to our knowledge, in calibrating both [C i]-to-H2 conversion factors across the spiral disks at spatially resolved ∼ 1 kpc scale though such studies have been discussed globally in galaxies near and far. In order to derive the conversion factors and achieve these calibrations, we adopt three different dust-to-gas ratio (DGR) assumptions which scale approximately with metallicity taken from precursory results. We find that for all DGR assumptions, the α[CI] (1−0), α[CI] (2−1), and αCO are mostly flat with galactocentric radii, whereas both α[CI] (2−1) and αCO show decrease in the inner regions of galaxies. And the central αCO and α[CI] (2−1) values are on average ∼ 2.2 and 1.8 times lower than its galaxy averages. The obtained carbon abundances from different DGR assumptions show flat profiles with galactocentric radii, and the average carbon abundance of the galaxies is comparable to the usually adopted value of 3 × 10−5. We find that both metallicity and infrared luminosity correlate moderately with the αCO whereas only weakly with either the α[CI] (1−0) or carbon abundance, and not at all with the α[CI] (2−1). © 2021, CC BY.

关键词： Galaxies

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A Method of Rapidly Deriving Late-type Contact Binary Parameters and Its Application in the Catalina Sky Survey

arXiv

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arXiv 2024年

作者： Wang, JinLiang Ding, Xu Li, JiaJia Xiong, JianPing Cheng, QiYuan Ji, KaiFan P.O. Box 110 Kunming650216 China Key Laboratory of the Structure and Evolution of Celestial Objects Chinese Academy of Sciences P.O. Box 110 Kunming650216 China Center for Astronomical Mega-Science Chinese Academy of Sciences 20A Datun Road Chaoyang District Beijing100012 China University of the Chinese Academy of Sciences Yuquan Road 19# Shijingshan Block Beijing100049 China

With the continuous development of large optical surveys, a large number of light curves of late-type contact binary systems (CBs) have been released. Deriving parameters for CBs using the the WD program and the PHOEBE program poses a challenge. Therefore, this study developed a method for rapidly deriving light curves based on the Neural Networks (NN) model combined with the Hamiltonian Monte Carlo (HMC) algorithm (NNHMC). The neural network was employed to establish the mapping relationship between the parameters and the pregenerated light curves by the PHOEBE program, and the HMC algorithm was used to obtain the posterior distribution of the parameters. The NNHMC method was applied to a large contact binary sample from the Catalina Sky Survey, and a total of 19,104 late-type contact binary parameters were derived. Among them, 5172 have an inclination greater than 70◦ and a temperature difference less than 400 K. The obtained results were compared with the previous studies for 30 CBs, and there was an essentially consistent goodness-of-fit (R2) distribution between them. The NNHMC method possesses the capability to simultaneously derive parameters for a vast number of targets. Furthermore, it can provide an extremely efficient tool for rapid derivation of parameters in future sky surveys involving large samples of CBs. Copyright © 2024, The Authors. All rights reserved.

关键词： Hamiltonians

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Photometric analysis of the dwarf nova SU UMa based on TESS

arXiv

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arXiv 2024年

作者： Liu, Wei Shi, Xiang-Dong Fang, Xiao-Hui Wang, Qi-Shan Yunnan Observatories Chinese Academy of Sciences P.O. Box 110 Kunming650216 China University of Chinese Academy of Sciences No.1 Yanqihu East Rd Huairou District Beijing101408 China Key Laboratory of the Structure and Evolution of Celestial Objects Chinese Academy of Sciences P.O. Box 110 Kunming650216 China School of Mathematics Physics and Finance Anhui Polytechnic University Wuhu241000 China

We report the photometric analysis of SU UMa based on the observations of the Transiting Exoplanet Survey Satellite (TESS). TESS has released a large amount of data, which contains the light curves of a complete superoutburst and three normal outbursts of SU UMa. Based on the observations, the evolution of superhumps during the superoutburst was analyzed. By using the O - C method, the three stages were determined, and the superhump period for each stage was calculated. The mass ratio q = 0.137(1) was estimated based on the stage A superhump method. A periodic oscillation with a period of 2.17(9) days was found in the superhump minimum O - C diagram, which is related to the precession of the accretion disk. We investigated the frequency information of quasiperiodic oscillations (QPOs) in the light curves. An ultralong period QPO of 0.18 days at the time of normal outburst and two ultralong periods QPOs of 0.19 days and 0.285 days in quiescence were found. No QPO was found in the superoutburst. © 2024, CC BY.

关键词： Stars

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