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The early-type stars from LAMOST survey: Atmospheric parameters

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arXiv 2021年

作者： Guo, YanJun Zhang, Bo Liu, Chao Li, Jiao Li, JiangDan Wang, Luqian Liu, ZhiCun Hou, Yong-Hui Han, ZhanWen Chen, XueFei Yunnan Observatories Chinese Academy of Sciences P.O. Box 110 Kunming650011 China School of Astronomy and Space Science University of Chinese Academy of Sciences Beijing100049 China Key Laboratory for Structure and Evolution of Celestial Objects Chinese Academy of Sciences P.O. Box 110 Kunming650216 China Department of Astronomy Beijing Normal University Beijing100875 China Key Laboratory of Space Astronomy and Technology National Astronomical Observatories Chinese Academy of Sciences Beijing100101 China University of Chinese Academy of Sciences Beijing100049 China Nanjing Institute of Astronomical Optics & Technology National Astronomical Observatories Chinese Academy of Sciences Nanjing210042 China Center for Astronomical Mega-Science Chinese Academy of Sciences Beijing100012 China

Massive stars play key roles in many astrophysical processes. Deriving atmospheric parameters of massive stars is important to understand their physical properties and thus are key inputs to trace their evolution. Here we report our work on adopting the data-driven technique Stellar LAbel Machine (SLAM) with the non-LTE TLUSTY synthetic spectra as the training dataset to estimate the stellar parameters of LAMOST optical spectra for early-type stars. We apply two consistency tests to verify this machine learning method and compare stellar labels given by SLAM with that in literature for several objects having high-resolution spectra. We provide the stellar labels of effective temperature (Teff), surface gravity (log g), metallicity ([M/H]), and projected rotational velocity (v sin i) for 3,931 and 578 early-type stars from LAMOST Low-Resolution Survey (LAMOST-LRS) and Medium-Resolution Survey (LAMOST-MRS), respectively. To estimate the average statistical uncertainties of our results, we calculated the standard deviation between the predicted stellar label and the pre-labeled published values from the high-resolution spectra. The uncertainties of the four parameters are σ(Teff) = 2, 185K, σ(log g) = 0.29 dex, and σ(v sin i) = 11 km s−1 for MRS, and σ(Teff) = 1, 642K, σ(log g) = 0.25 dex, and σ(v sin i) = 42 km s−1 for LRS spectra, respectively. We notice that parameters of Teff, log g and [M/H] can be better constrained using LRS spectra rather than using MRS spectra, most likely due to their broad wavelength coverage, while v sin i is constrained better by MRS spectra than by LRS spectra, probably due to the relatively accurate line profiles of MRS spectra. Copyright © 2021, The Authors. All rights reserved.

关键词： Surveys

Long-term evolution of post-explosion Helium-star Companions of Type Iax Supernovae

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arXiv 2022年

作者： Zeng, Yaotian Liu, Zheng-Wei Heger, Alexander McCully, Curtis Röpke, Friedrich K. Han, Zhanwen Kunming650216 China Key Laboratory for the Structure and Evolution of Celestial Objects CAS Kunming650216 China University of Chinese Academy of Science Beijing100012 China Center for Astronomical Mega-Science CAS Beijing100012 China School of Physics and Astronomy Monash University 19 Rainforest Walk VIC3800 Australia Joint Institute for Nuclear Astrophysics National Superconducting Cyclotron Laboratory Michigan State University 1 Cyclotron Laboratory East LansingMI48824-1321 United States ClaytonVIC3800 Australia Stromlo ACT2611 Australia Las Cumbres Observatory 6740 Cortona Dr Ste 102 GoletaCA93117-5575 United States Department of Physics University of California Santa BarbaraCA93106-9530 United States Zentrum für Astronomie Universität Heidelberg Institut für Theoretische Astrophysik Philosophenweg 12 HeidelbergD-69120 Germany Heidelberger Institut für Theoretische Studien Schloss-Wolfsbrunnenweg 35 HeidelbergD-69118 Germany

Supernovae of Type Iax (SNe Iax) are an accepted faint subclass of hydrogen-free supernovae. Their origin, the nature of the progenitor systems, however, is an open question. Recent studies suggest that the weak deflagration explosion of a near-Chandrasekhar-mass white dwarf in a binary system with a helium star donor could be the origin of SNe Iax. In this scenario, the helium star donor is expected to survive the explosion. We use the one-dimensional stellar evolution codes MESA and Kepler to follow the post-impact evolution of the surviving helium companion stars. The stellar models are based on our previous hydrodynamical simulations of ejecta-donor interaction, and we explore the observational characteristics of these surviving helium companions. We find that the luminosities of the surviving helium companions increase significantly after the impact: They could vary from 2,500 Lo to 16,000 Lo for a Kelvin-Helmholtz timescale of about 104 yr. After the star reaches thermal equilibrium, it evolves as an O-type hot subdwarf (sdO) star and continues its evolution along the evolutionary track of a normal sdO star with the same mass. Our results will help to identify the surviving helium companions of SNe Iax in future observations and to place new constraints on their progenitor models. Copyright © 2022, The Authors. All rights reserved.

关键词： Helium

NSVS 01286630:a detached binary with a close-in companion

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Research in Astronomy and Astrophysics 2018年第9期18卷 123-132页

作者： Bin Zhang Sheng-Bang Qian Nian-Ping Liu Wen-Ping Liao Li-Ying Zhu Ai-Jun Dong Qi-Jun Zhi Yunnan Observatories Chinese Academy of SciencesKunming 650216China Key Laboratory of the Structure and Evolution of Celestial Objects Chinese Academy of SciencesKunming 650216China University of Chinese Academy of Sciences Beijing 100049China School of Physics and Electronic Science Guizhou Normal UniversityGuiyang 550001China

New photometric observations of NS VS 01286630 were performed and two sets of fourcolor（B, V, Rc, Ic） light curves（LCs） were obtained. Using the 2013 version of the Wilson-Devinney（W-D） code, we analyzed these data. The photometric solutions reveal that NS VS 01286630 is an active detached eclipsing binary（EB） with a high orbital inclination（nearly 90°）. Remarkably, the temperature of the primary component（the hotter star） is higher than the secondary one, but the value of mass ratio q（M2/M1）for NS VS 0128663 is more than 1, which can be explained in that the surface of the secondary component of NSVS 01286630 is covered with big cool starspots. Based on our new CCD mid-eclipse times and the data published until now, variations in the mid-eclipse times were reanalyzed in detail using a weighted least-squares method. It is discovered that the（O-C） diagram of the system shows a cyclic oscillation with a period of 3.61 yr and an amplitude of 0.001 d. The cyclic variation may be caused by the light-travel time effect（LTTE） due to the presence of a third companion, whose mass we calculated as M3 sin（i3） =0.11 M（⊙）. The third body may affect the orbital evolution of the central binary system by transferring angular momentum.

关键词： stars binaries close- stars binaries eclipsing-stars individual （NSVS 01286630）

Magnetic-reconnection-heated corona in active galactic nuclei: refined disc–corona model and application to broad-band radiation

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arXiv 2020年

作者： Cheng, Huaqing Liu, B.F. Liu, Jieying Liu, Zhu Qiao, Erlin Yuan, Weimin School of Astronomy and Space Sciences University of Chinese Academy of Sciences Beijing100049 China National Astronomical Observatories/Yunnan Observatory Chinese Academy of Sciences Kunming650011 China Key Laboratory for the Structure and Evolution of Celestial Objects Chinese Academy of Sciences Kunming650011 China Center for Astronomical Mega-Science Chinese Academy of Sciences Beijing100012 China Key Laboratory of Space Astronomy and Technology National Astronomical Observatories Chinese Academy of Sciences Beijing100012 China

A long-standing question in active galactic nucleus (AGN) research is how the corona is heated up to produce X-ray radiation much stronger than that arising from the viscous heating within the corona. In this paper, we carry out detailed investigations of magnetic-reconnection heating to the corona, specifically, studying how the disc and corona are self-consistently coupled with the magnetic field, and how the emergent spectra depend on the fundamental parameters of AGN. It is shown that diverse spectral shapes and luminosities over a broad bandpass from optical to X-ray can be produced from the coupled disc and corona within a limited range of the black hole mass, accretion rate and magnetic field strength. The relative strength of X-ray emission with respect to optical/ultraviolet (UV) depends on the strength of the magnetic field in the disc, which, together with accretion rate, determines the fraction of accretion energy transported and released in the corona. This refined disc–corona model is then applied to reproduce the broad-band spectral energy distributions (SEDs) of a sample of 20 bright local AGNs observed simultaneously in X-ray and optical/UV. We find that, in general, the overall observed broad-band SEDs can be reasonably reproduced, except for rather hard X-ray spectral shapes in some objects. The radiation pressure-dominant region, as previously predicted for the standard accretion disc in AGN, disappears for strong X-ray sources, revealing that AGN accretion discs are indeed commonly stable as observed. Our study suggests the disc–corona coupling model involving magnetic fields to be a promising approach for understanding the broad-band spectra of bright AGNs. Copyright © 2020, The Authors. All rights reserved.

关键词： Magnetic fields

High amplitude δ Scuti star BO Lyn with evidence of a late A-type companion in an elliptical orbit

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Research in Astronomy and Astrophysics 2018年第1期18卷 119-126页

作者： Lin-Jia Li Sheng-Bang Qian Jia Zhang Li-Ying Zhu Wen-Ping Liao Yunnan Observatories Chinese Academy of Sciences Kunming 650216 China Key Laboratory of the Structure and Evolution of Celestial Objects Chinese Academy of Sciences Kunming 650216 China Center for Astronomical Mega-Science Chinese Academy of Sciences Beijing 100012 China University of Chinese Academy of Sciences Beijing 100049 China

We present 145 times of light maximum for high amplitude δ Scuti star BO Lyn based on several sky surveys（CRTS,DASCH,NSVS,OMC and Super WASP）and our photometric *** with the data in literature,a total of 179 times of light maximum are used to analyze the O-C diagram of BO *** find that it can be described by an upward parabolic component and a periodic variation with a period of 34.5±0.1 *** latter could be caused by the light travel time effect as a result of an additional companion orbiting in a highly elliptical orbit（e=0.64±0.03）.Our study indicates that the companion’s luminosity cannot be ignored,and it should be a late A-type main-sequence *** long-term period change of BO Lyn is also detected,and its value,1.52±0.26×10^（-3）d Myr^（-1）,is consistent with evolutionary *** suggest that more spectroscopic and photometric observations are needed in the future to confirm the nature of the BO Lyn system.

关键词： techniques：photometric stars：variables：δ Scuti stars：individual（BO Lyn）

Astronomical site monitoring system at lijiang observatory

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arXiv 2020年

作者： Xin, Yu-Xin Bai, Jin-Ming Lun, Bao-Li Fan, Yu-Feng Wang, Chuan-Jun Liu, Xiao-Wei Yu, Xiao-Guang Ye, Kai Song, Teng-Fei Chang, Liang He, Shou-Sheng Mao, Ji-Rong Xu, Liang Xiong, Ding-Rong Zhang, Xi-Liang Wang, Jian-Guo Ding, Xu Feng, Hai-Cheng Liu, Xiang-Kun Huang, Yang Chen, Bing-Qiu Yunnan Observatories Chinese Academy of Sciences KunmingYunnan650216 China University of Chinese Academy of Sciences Beijing100049 China Key Laboratory for the Structure and Evolution of Celestial Objects Chinese Academy of Sciences Kunming650216 China Center for Astronomical Mega-Sciences Chinese Academy of Sciences Beijing100012 China South-Western Institute for Astronomy Research Yunnan University Kunming650500 China

We installed two sets of Astronomical Site Monitoring System(ASMS) at Lijiang Observatory(GMG), for the running of the 2.4-meter Lijiang optical telescope(LJT) and the 1.6-meter Multi-channel Photometric Survey Telescope (Mephisto). The Mephistro is under construction. ASMS has been running on robotic mode since 2017. The core instruments: Cloud Sensor, All-Sky Camera and Autonomous-DIMM that are developed by our group, together with the commercial Meteorological Station and Sky Quality Meter, are combined into the astronomical optical site monitoring system. The new Cloud Sensor’s Cloud-Clear Relationship is presented for the first time, which is used to calculate the All-Sky cloud cover. We designed the Autonomous-DIMM located on a tower, with the same height as LJT. The seeing data have been observed for a full year. ASMS’s data for the year 2019 are also analysed in detail, which are valuable to observers. Copyright © 2020, The Authors. All rights reserved.

关键词： Observatories

The origin of UV/optical emission in the black hole low-mass X-ray binary Swift J1753.5-0127

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arXiv 2022年

作者： Yang, Pengcheng Zhang, Guobao Russell, David M. Gelfand, Joseph D. Méndez, Mariano Wang, Jiancheng Lyu, Ming Yunnan Observatories Chinese Academy of Sciences Kunming650216 China Key Laboratory for the Structure and Evolution Celestial Objects Chinese Academy of Sciences Kunming650216 China Center for Astronomical Mega-Science Chinese Academy of Sciences Bejing100012 China University of Chinese Academy of Sciences Bejing100049 China New York University Abu Dhabi P.O. Box 129188 Abu Dhabi United Arab Emirates Center for Astro Particle and Planetary Physics New York University Abu Dhabi P.O. Box 129188 Abu Dhabi United Arab Emirates Center for Cosmology and Particle Physics New York University 726 Broadway New YorkNY10003 United States Kapteyn Astronomical Institute University of Groningen P.O. Box 800 NL-9700 AV Groningen Netherlands Department of Physics Xiangtan University Hunan Xiangtan411105 China Key Laboratory of Stars and Interstellar Medium Xiangtan University Hunan Xiangtan411105 China

The emission from the accreting black holes (BHs) in low-mass X-ray binaries (LMXBs) covers a broad energy band from radio to X-rays. Studying the correlations between emission in different energy bands during outbursts can provide valuable information about the accretion process. We analyse the simultaneous optical, ultraviolet (UV) and X-ray data of the BHLMXB Swift J1753.5-0127 during its ∼ 12-year long outburst with the Neil Gehrels Swift Observatory. We find that the UV/optical and X-ray emission are strongly correlated during the hard states of the outburst. We fit the relation with a power-law function FUV/optical∝ FβXand find that the power-law index β increases from ∼ 0.24 to ∼ 0.33 as the UV/optical wavelength decreases from ∼ 5400 Å (V) to ∼ 2030 Å (UVW2). We explore the possible reasons for this and suggest that in Swift J1753.5-0127 the UV/optical emission is dominated by a viscously heated accretion disc at large radii. We find that the data that deviate from the correlation correspond to the low-intensity peaks appeared in the X-ray band during the outburst, and suggest that these deviations are driven by the emission from the inner part of the accretion disc. Copyright © 2022, The Authors. All rights reserved.

关键词： Stars

The thermal equilibrium mass loss model and its applications in binary evolution

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arXiv 2020年

作者： Webbink, Ronald F. Han, Zhanwen Ge, Hongwei 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 Beijing100012 China University of Chinese Academy of Sciences Beijing100049 China University of Illinois at Urbana-Champaign 1002 W Green St Urbana61801 United States

Binary evolution is indispensable in stellar evolution to understand the formation and evolution of most peculiar and energetic objects, such as binary compact objects, Type Ia supernovae, X-ray binaries, cataclysmic variables, blue stragglers, hot subdwarfs, and central binaries in planetary nebulae. Mass transfer in binary stars can change the evolutionary path and fate of the corresponding objects relative to what is expected from single stellar evolution. What is the critical mass ratio at which unstable mass transfer occurs is an unsolved fundamental problem in binary evolution. To resolve this issue, we construct the thermal equilibrium mass loss model and derive critical mass ratios for both thermal timescale mass transfer and unstable mass transfer, the latter of which occurs when the outer Lagrangian point, L2, is overfilled. Using several 3.2 M stellar models as examples, we study the stellar response to thermal equilibrium mass loss and present the thresholds for thermal timescale mass transfer. We study the possible mass transfer channels of binary systems containing a 3.2 M donor star, taking into account thermal timescale mass transfer, unstable mass transfer through L2, and dynamical timescale mass transfer. We repeat this simulation for a grid of donor stars with different masses (from 0.1 to 100 M with Z = 0.02) and at different evolutionary stages, and present our results. The results show that unstable mass transfer due to the overfilling of the outer Lagrangian point may also play an essential role in the formation of common envelopes for late red giant branch and asymptotic giant branch donors. Copyright © 2020, The Authors. All rights reserved.

关键词： Mass transfer

Breaking the degeneracy between gas inflow and outflows with stellar metallicity: Insights on M 101

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arXiv 2021年

作者： Kang, Xiaoyu Chang, Ruixiang Kudritzki, Rolf-Peter Gong, Xiaobo Zhang, Fenghui 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 Key Laboratory for Research in Galaxies and Cosmology Shanghai Astronomical Observatory Chinese Academy of Sciences 80 Nandan Road Shanghai200030 China LMU München Universitätssternwarte Scheinerstr. 1 München81679 Germany Institute for Astronomy University of Hawaii 2680 Woodlawn Drive HonoluluHI96822 United States University of Chinese Academy of Sciences Beijing100049 China

An analytical chemical evolution model is constructed to investigate the radial distribution of gas-phase and stellar metallicity for star-forming galaxies. By means of the model, the gas-phase and stellar metallicity can be obtained from the stellar-to-gas mass ratio. Both the gas inflow and outflow processes play an important role in building the final gas-phase metallicity, and there exists degeneracy effect between the gas inflow and outflow rates for star-forming galaxies. On the other hand, stellar metallicity is more sensitive to the gas outflow rate than to the gas inflow rate, and this helps to break the parameter degeneracy for star-forming galaxies. We apply this analysis method to the nearby disc galaxy M 101 and adopting the classical χ2 methodology to explore the influence of model parameters on the resulted metallicity. It can be found that the combination of gas-phase and stellar metallicity is indeed more effective for constraining the gas inflow and outflow rates. Our results also show that the model with relatively strong gas outflows but weak gas inflow describes the evolution of M 101 reasonably well. Copyright © 2021, The Authors. All rights reserved.

关键词： Astrophysics