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arXiv 2020年

作者： Liu, N.-P. Sarotsakulchai, T. Rattanasoon, S. Zhang, B. Yunnan Observatories Chinese Academy of Sciences P.O. Box 110 Kunming650216 China National Astronomical Research Institute of Thailand 260 Moo 4 T.Donkaew A.MaerimChiangmai50180 Thailand Key Laboratory for the Structure and Evolution of Celestial Objects Chinese Academy of Sciences P.O. Box 110 Kunming650216 China University of Chinese Academy of Sciences Yuquan Road 19# Shijingshan Block Beijing100049 China Department of Physics and Astronomy University of Shelffield Hounsfield Road SheffieldS3 7RH United Kingdom Guizhou Normal University Guiyang550001 China Guizhou Provincial Key Laboratory of Radio Astronomy and Data Processing Guiyang550001 China

Comprehensive photometric investigation was carried out to the early K-type contact binary - IL Cnc. A few light curves from both ground-based telescopes and the Kepler space telescope were obtained (or downloaded) and then analyzed in detail. They are mostly found to be asymmetric and there are even continuously changing O’Connell effect in the light curves from Kepler K2 data, suggesting the system to be highly active. Using the Wilson-Devinney code (version 2013), photometric solutions were derived and then compared. It is found that the calculation of the mass ratio is easily affected by the spot settings. Combining the radial velocities determined from LAMOST median resolution spectral data, the mass ratio of the binary components is found to be M2/M1 = 1.76±0.05. The components are in shallow contact (f ∼ 9%) and have a temperature difference about T2 − T1 = −280 ± 20 K. The system is demonstrated to be W-subtype, which may be a common feature of K-type contact binaries. The masses of the binary components were estimated to be M1 ∼ 0.51 M and M2 ∼ 0.90 M. The values are in good agreement with that deduced from the parallax data of Gaia. The results suggest that the primary component lacks luminosity compared with the zero main sequence. The Hα spectral line of the primary component is found to be peculiar. Combining newly determined minimum light times with those collected from literature, the orbital period of IL Cnc is studied. It is found that the (O−C)s of the primary minima show sinusoidal variation while the secondary do not. The oscillation is more likely to be caused by the starspot activities. Yet this assumption needs more data to support. Copyright © 2020, The Authors. All rights reserved.

关键词： Photometry

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The rate of period change in DAV stars

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Research in Astronomy and Astrophysics 2017年第7期17卷 11-24页

作者： Yan-Hui Chen Cai-Yun Ding Wei-Wei Na Hong Shu Institute of Astrophysics Chuxiong Normal University School of Physics and Electronical Science Chuxiong Normal University Key Laboratory for the Structure and Evolution of Celestial Objects Chinese Academy of Sciences School of Physics and Electronic Engineering Yuxi Normal University

Grids of DAV star models are evolved by WDEC, taking the element diffusion effect into account. The grid parameters are hydrogen mass log（MH/M＊）, helium mass log（MHe/M＊）, stellar mass M＊and effective temperature T_（eff） for DAV stars. The core compositions are from white dwarf models evolved by MESA. Therefore, DAV star models evolved by WDEC have historically viable core compositions. Based on those DAV star models, we studied the rate of period change（P˙（k）） for different values of H, He, M_＊and Teff. The results are consistent with previous work. Two DAV stars G117-B15A and R548 have been observed for around 40 years. The rates of period change of two large-amplitude modes were obtained through the O-C method. We conducted an asteroseismological study on the two DAV stars and then obtained a best-fitting model for each star. Based on the two best-fitting models,the mode identifications（l, k） of the observed modes for G117-B15A and R548 are consistent with previous work. Both the observed modes and the observedP˙ s can be fitted by calculated ones. The results indicate that our method of evolving DAV star models is feasible.

关键词： stars oscillations （including pulsations） - stars individual （G117-B 15A and R548） -white dwarfs

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The escape of hydrogen-rich atmosphere of exoplanet: mass loss rates and the absorptions of stellar lyman α

arXiv

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arXiv 2019年

作者： Yan, D.D. Guo, J.H. Yunnan Observatories Chinese Academy of Sciences P.O. Box 110 Kunming650011 China Yunnan Observatories Chinese Academy of Sciences P.O. Box 110 Kunming650011 China School of Astronomy and Space Science University of Chinese Academy of Sciences Beijing China Key Laboratory for the Structure and Evolution of Celestial Objects CAS Kunming650011 China

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XMM-Newton and NICER measurement of the rms spectrum of the millihertz quasi-periodic oscillations in the neutron-star low-mass X-ray binary 4U 1636−53

arXiv

引用

arXiv 2020年

作者： Lyu, Ming Zhang, Guobao Méndez, Mariano Altamirano, D. Mancuso, G.C. Xiang, Fu-Yuan Xiao, Huaping Department of Physics Xiangtan University Xiangtan Hunan411105 China Key Laboratory of Stars and Interstellar Medium Xiangtan University Xiangtan Hunan411105 China Kunming650216 China Key Laboratory for the Structure and Evolution of Celestial Objects CAS Kunming650216 China Kapteyn Astronomical Institute University of Groningen PO BOX 800 GroningenNL-9700 AV Netherlands Physics & Astronomy University of Southampton SouthamptonHampshireSO17 1BJ United Kingdom C.C. No. 5 Villa Elisa1894 Argentina Facultad de Ciencias Astronómicas y Geofísicas Universidad Nacional de La Plata Paseo del Bosque s/n La Plata1900 Argentina

We used two XMM-Newton and six Neutron Star Interior Composition Explorer (NICER) observations to investigate the fractional rms amplitude of the millihertz quasi-periodic oscillations (mHz QPOs) in the neutron-star low-mass X-ray binary 4U 1636–53. We studied, for the first time, the fractional rms amplitude of the mHz QPOs vs. energy in 4U 1636–53 down to 0.2 keV. We find that, as the energy increases from ∼0.2 keV to ∼3 keV, the rms amplitude of the mHz QPOs increases, different from the decreasing trend that has been previously observed above 3 keV. This finding has not yet been predicted by any current theoretical model, however, it provides an important observational feature to speculate whether a newly discovered mHz oscillation originates from the marginally stable nuclear burning process on the neutron star surface. Copyright © 2020, The Authors. All rights reserved.

关键词： Stars

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Populations of accreting white dwarfs

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Proceedings of the International Astronomical Union 2019年第S343期14卷 371-372页

作者： Chen H.-L. Woods T.E. Yungelson L. Gilfanov M. Han Z. Yunnan Observatories CAS Kunming 650011 China Key Laboratory for the Structure and Evolution of Celestial Objects CAS Kunming 650011 China Center for Astronomical Mega-Science Chinese Academy of Science Beijing 100012 China Institute of Gravitational Wave Astronomy School of Physics and Astronomy University of Birmingham Birmingham B15 2TT United Kingdom Institute of Astronomy RAS 48 Pyatnitskaya Str. Moscow 119017 Russian Federation Max Planck Institute for Astrophysics Karl-Schwarzschild-Str. 1 Garching b. München 85741 Germany Space Research Institute of Russian Academy of Sciences Profsoyuznaya 84/32 Moscow 117997 Russian Federation

Using a hybrid binary population synthesis approach, we modelled the formation and evolution of populations of accreting white dwarfs (WDs) for differing star formation histories. We found that the delay time distribution of SNe Ia in the single degenerate scenario is inconsistent with observations. Additionally, we found that our predicted X-ray and UV emission of populations of accreting WDs are consistent with the X-ray luminosities of early-type galaxies observed by Chandra and the HeII 4686 Å/Hβ line ratio measured in stacked SDSS spectra of passively evolving galaxies. Moreover, we found that the majority of current novae in elliptical-like galaxies have low-mass WDs, long decay times, long recurrence periods and are relatively faint. In contrast, the majority of current novae in spiral-like galaxies have massive WDs, short decay times, short recurrence periods and are relatively bright. Our predicted distribution of mass-loss timescales in an M31-like galaxy is consistent with observations for Andromeda. © International Astronomical Union 2019.

关键词： cataclysmic variables stars:novae white dwarfs

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Using the Extragalactic Gamma-Ray Background to Constrain the Hubble Constant and Matter Density of the Universe

arXiv

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arXiv 2019年

作者： Zeng, Houdun Yan, Dahai Key Laboratory of Dark Matter and Space Astronomy Purple Mountain Observatory Chinese Academy of Sciences Nanjing210008 China Key Laboratory for the Structure and Evolution of Celestial Objects Yunnan Observatories 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 Key Laboratory of Astroparticle Physics of Yunnan Province Yunnan University Kunming650091 China

The attenuation produced by extragalactic background light (EBL) in γ-ray spectra of blazars has been used to constrain the Hubble constant (H0) and matter density (Ωm) of the Universe. We propose to estimate H0 and Ωm using the well measured >10 GeV extragalactic γ-ray background (EGB). This suggestion is based on the facts that the >10 GeV EGB is totally explained by the emissions from blazars, and an EBL-absorption cutoff occurs at ∼50 GeV in the EGB spectrum. We fit the >10 GeV EGB data with modeled EGB spectrum. This results in H0 = 64.9+4−4..63 km s−1 Mpc−1 and Ωm = 0.31−+00..1314. Note that the uncertainties may be underestimated due to the limit of our realization for EBL model. H0 and Ωm are degenerate in our method. Independent determination of Ωm by other methods would improve the constraint on H0. Copyright © 2019, The Authors. All rights reserved.

关键词： Gamma rays

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Performance of the Stellar Abundances and atmospheric Parameters Pipeline adapted for M dwarfs I. Atmospheric parameters from the spectroscopic module

arXiv

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arXiv 2025年

作者： Olander, Terese Gent, Matthew R. Heiter, Ulrike Kochukhov, Oleg Bergemann, Maria Magg, Ekaterina Cassisi, Santi Kovalev, Mikhail Morel, Thierry Miller, Nicola J. Souto, Diogo Shan, Yutong Rojas-Ayala, Bárbara Delgado-Mena, Elisa Wang, Haiyang S. Department of Physics and Astronomy Uppsala University Box 516 UppsalaSE-751 20 Sweden Max Planck Institute for Astronomy Heidelberg69117 Germany Institut de Recherche en Astrophysique et Planétologie Université de Toulouse CNRS IRAP UMR 5277 14 Avenue Edouard Belin Toulouse31400 France INAF Osservatorio Astronomico d’Abruzzo Via M. Maggini s/n Teramo64100 Italy INFN Sezione di Pisa Largo Pontecorvo 3 Pisa56127 Italy Yunnan Observatories China Academy of Sciences Kunming650216 China Key Laboratory for the Structure and Evolution of Celestial Objects Chinese Academy of Sciences Kunming650011 China Institute Université de Liège Quartier Agora Allée du 6 Août 19c Bât. B5c LiègeB4000 Belgium Departamento de Física Universidade Federal de Sergipe Av. Marcelo Deda Chagas S/N SE São CristóvãoCep 49.107-230 Brazil Centre for Planetary Habitability Department of Geosciences University of Oslo Sem Sælands Vei 2b Oslo0315 Norway Institut für Astrophysik Georg-August-Universität Friedrich-Hund-Platz 1 Göttingen37077 Germany Instituto de Alta Investigación Universidad de Tarapacá Casilla 7D Arica Chile CAUP Universidade do Porto Rua das Estrelas PortoPT4150-762 Portugal CSIC-INTA Camino Bajo del Castillo s/n Madrid Villanueva de la Cañada28692 Spain Center for Star and Planet Formation Globe Institute The University of Copenhagen Øster Voldgade 5-7 København K1350 Denmark

Context. M dwarfs are important targets in the search for Earth-like exoplanets due to their small masses and low luminosities. Several ongoing and upcoming space missions are targeting M dwarfs for this reason, and the ESA Plato mission is one of these. Aims. In order to fully characterise a planetary system the properties of the host star must be known. For M dwarfs we can derive effective temperature, surface gravity, metallicity, and abundances of various elements from spectroscopic observations in combination with photometric data. Methods. The Stellar Abundances and atmospheric Parameters Pipeline (SAPP) has been developed to serve as a prototype for one of the stellar science softwares within the Plato consortium. The pipeline combines results from a spectroscopy, a photometry, an interferometry, and an asteroseismology module to derive stellar parameters for FGK-type stars. We have modified the pipeline to be able to analyse the M dwarf part of the Plato target sample. The current version of the pipeline for M dwarfs mostly relies on spectroscopic observations. The module processing these data is based on the machine learning algorithm The Payne and fits a grid of model spectra to an observed spectrum to derive effective temperature and metallicity. We use spectra in the H-band, as the near-infrared region is beneficial for M dwarfs because there are fewer molecular lines and they are brighter in this wavelength region than in the optical. A method based on synthetic spectra was developed for the continuum normalisation of the spectra, taking into account the pseudo-continuum formed by numerous lines of the water molecule. Photometry is used to constrain the surface gravity. Results. We tested the modified SAPP on spectra of M dwarfs from the APOGEE survey. Our validation sample of 26 stars includes stars with interferometric observations and binaries. We found a good agreement between our derived values and reference values from a range of previous studies.

关键词： Photometers

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Spectroscopic properties of the dwarf nova-type cataclysmic variables observed by LAMOST

arXiv

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arXiv 2020年

作者： Zhongtao, Han Soonthornthum, Boonrucksar Shengbang, Qian Xiaohui, Fang Qishan, Wang Liying, Zhu Aijun, Dong Qijun, Zhi P. O. Box 110 Kunming650216 China National Astronomical Research Institute of Thailand Higher Education Science Research and Innovation 260 Moo 4 T. Donkaew A. MaerimChiangmai50180 Thailand Guizhou Provincial Key Laboratory of Radio Data Processing School of Physics and Electronic Sciences Guizhou Education University Guiyang550001 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 Chinese Academy of Sciences Yuquan Road 19# Sijingshang Block Beijing100049 China

Spectra of 76 known dwarf novae from the LAMOST survey were presented. Most of the objects were observed in quiescence, and about 16 systems have typical outburst spectra. 36 of these systems were observed by SDSS, and most of their spectra are similar to the SDSS spectra. 2 objects, V367 Peg and V537 Peg, are the first to observe their spectra. The spectrum of V367 Peg shows a contribution from a M-type donor and its spectral type could be estimated as M3-5 by combining its orbital period. The signature of white dwarf spectrum can be seen clearly in four low-accretion-rate WZ Sge stars. Other special spectral features worthy of further observations are also noted and discussed. We present a LAMOST spectral atlas of outbursting dwarf novae. 6 objects have the first outburst spectra, and the others were also compared with the published outburst spectra. We argue that these data will be useful for further investigation of the accretion disc properties. The HeII λ4686 emission line can be found in the outburst spectra of seven dwarf novae. These objects are excellent candidates for probing the spiral asymmetries of accretion disc. Copyright © 2020, The Authors. All rights reserved.

关键词： White dwarfs

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Followup ground-based observations of the dwarf nova KZ Gem

arXiv

引用

arXiv 2020年

作者： Dai, Zhibin Szkody, Paula Thorstensen, John R. Medagangoda, N. Indika 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 Yuquan Road Shijingshan District Beijing100049 China Key Laboratory of Optical Astronomy National Astronomical Observatories Chinese Academy of Sciences Beijing100101 China Department of Astronomy University of Washington SeattleWA98195 United States Department of Physics and Astronomy Dartmouth College 6127 Wilder Laboratory Hanover NH03755 United States Astronomy Division Arthur C. Clarke Institute for Modern Technologies Sri Lanka

We present spectroscopy of stars in the immediate vicinity of the dwarf nova (DN) KZ Gem to confirm its identification, which had been ambiguous in the literature. Analysis of 73 radial velocities spanning from 2014 to 2019 provides a high-precision orbital period of 0.2224628(2) d (∼ 5.34 hr) and shows KZ Gem to be a double-lined DN. Time series photometry taken from 2016 to 2018 shows a variable double-hump modulation with a full amplitude of ∼ 0.3 mag, along with five Gaussian-like transient events lasting ∼ 30 min or more. Using the light curve code XRBinary and nonlinear fitting code NMfit, we obtain an optimized binary model of the dwarf nova (DN) KZ Gem, from time series photometry, consisting of a Roche-lobe-filling K type dwarf with a mass transfer rate of 2.7 − 7.9×10−10 M☉ yr−1 to a large, cool and thick disk surrounding a white dwarf, in an orbit with an inclination of 51◦.6(±1◦.4). Two hotspots on the disk are demonstrated to cause the observed variations in the ellipsoidal modulations from the secondary star. This physical model is compatible with the Gaia distance of KZ Gem. Copyright © 2020, The Authors. All rights reserved.

关键词： Photometry

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ASASSN-14ms: The most energetic known explosion of a type Ibn supernova and its physical origin

arXiv

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arXiv 2021年

作者： Wang, Xiaofeng Lin, Weili Zhang, Jujia Zhang, Tianmeng Cai, Yongzhi Zhang, Kaicheng Filippenko, Alexei V. Graham, Melissa Maeda, Keiichi Mo, Jun Xiang, Danfeng Xi, Gaobo Yan, Shengyu Wang, Lifan Wang, Lingjun Kawabata, Koji Zhai, Qian 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 Key Laboratory of Optical Astronomy National Astronomical Observatories Chinese Academy of Sciences Beijing100101 China School of Astronomy and Space Science University of Chinese Academy of Sciences Beijing101408 China Department of Astronomy University of California BerkeleyCA94720-3411 United States Miller Institute for Basic Research in Science University of California BerkeleyCA94720 United States Department of Astronomy University of Washington Box 351580 SeattleWA98195-1580 United States Department of Astronomy Kyoto University Kitashirakawa-Oiwake-cho Sakyo-ku Kyoto606-8502 Japan Physics and Astronomy Department Texas A&M University College StationTX77843 United States Astroparticle Physics Institute of High Energy Physics Chinese Academy of Sciences Beijing100049 China Department of Physical Science Hirosima University Kagamiyama Higashi-Hiroshima Hiroshima739-8526 Japan

ASASSN-14ms may represent the most luminous Type Ibn supernova (SN Ibn) ever detected, with an absolute U -band magnitude brighter than −22.0 mag and a total bolometric luminosity > 1.0 × 1044 erg s−1 near maximum light. The early-time spectra of this SN are characterized by a blue continuum on which are superimposed narrow P Cygni profile lines of He i, suggesting the presence of slowly moving (∼ 1000 km s−1), He-rich circumstellar material (CSM). At 1–2 months after maximum brightness, the He i line profiles become only slightly broader, with blueshifted velocities of 2000–3000 km s−1, consistent with the CSM shell being continuously accelerated by the SN light and ejecta. Like most SNe Ibn, the light curves of ASASSN-14ms show rapid post-peak evolution, dropping by ∼ 7 mag in the V band over three months. Such a rapid post-peak decline and high luminosity can be explained with interaction between SN ejecta and helium-rich CSM of 0.9 M☉ at a distance of ∼ 1015 cm. The CSM around ASASSN-14ms is estimated to originate from a pre-explosion event with a mass-loss rate of 6.7 M☉ yr−1 (assuming a velocity of ∼ 1000 km s−1), which is consistent with abundant He-rich material violently ejected during the late Wolf-Rayet (WN9-11 or Opfe) stage. After examining the light curves for a sample of SNe Ibn, we find that the more luminous ones tend to have slower post-peak decline rates, reflecting that the observed differences may arise primarily from discrepancies in the CSM distribution around the massive progenitors. Copyright © 2021, The Authors. All rights reserved.

关键词： Supernovae

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