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arXiv 2024年

作者： Sun, Luming Jiang, Ning Dou, Liming Shu, Xinwen Zhu, Jiazheng Dong, Subo Buckley, David Cenko, S. Bradley Fan, Xiaohui Gromadzki, Mariusz Liu, Zhu Wang, Jianguo Wang, Tinggui Wang, Yibo Wu, Tao Yang, Lei Zhang, Fabao Zhang, Wenjie Zhang, Xiaer Department of Physics Anhui Normal University Anhui Wuhu241002 China CAS Key Laboratory for Researches in Galaxies and Cosmology Department of Astronomy University of Science and Technology of China Anhui Hefei230026 China School of Astronomy and Space Sciences University of Science and Technology of China Hefei230026 China Center for Astrophysics Guangzhou University Guangzhou510006 China Department of Astronomy School of Physics Peking University 5 Yiheyuan Road Haidian District Beijing100871 China Kavli Institute of Astronomy and Astrophysics Peking University 5 Yiheyuan Road Haidian District Beijing100871 China National Astronomical Observatories Chinese Academy of Science 20A Datun Road Chaoyang District Beijing100101 China South African Astronomical Observatory P.O. Box 9 Observatory Cape Town7935 South Africa Astrophysics Science Division NASA Goddard Space Flight Center MC 661 GreenbeltMD20771 United States Steward Observatory University of Arizona 933 North Cherry Avenue Rm. N204 TucsonAZ85721-0065 United States Astronomical Observatory University of Warsaw Al. Ujazdowskie 4 Warszawa00-478 Poland Max-Planck-Institut für Extraterrestrische Physik Gießenbachstraße 1 Garching85748 Germany Key Laboratory for the Structure and Evolution of Celestial Objects Yunnan Observatories Kunming650011 China

Context. In theory, recurring tidal disruption events (TDEs) may occur when a close stellar binary encounters a supermassive black hole, if one star is captured and undergoes repeating partial TDEs, or if both stars are tidally disrupted (double TDEs). In addition, independent TDEs may be observed over decades in some special galaxies where the TDE rate is extremely high. Exploring the diversity of recurring TDEs and probing their natures with rich observational data help to understand these mechanisms. Aims. We report the discovery of a second optical flare that occurred in September 2021 in IRAS F01004-2237, where the first flare occurred in 2010 has been reported, and present a detailed analysis of multi-band data. We aim to understand the nature of the flare and explore the possible causes of the recurring flares. Methods. We describe our analysis of the position of the flare, the multi-band light curves (LCs), the optical and ultraviolet (UV) spectra, and the X-ray LC and spectra. Results. The position of the flare coincides with the galaxy centre with a precision of 650 pc. The flare peaks in ∼ 50 days with an absolute magnitude of ∼ −21 and fades in two years roughly following L ∝ t−5/3. It maintains a nearly constant blackbody temperature of ∼22,000 K in the late time. Its optical and UV spectra show hydrogen and helium broad emission lines with full width at half maxima of 7,000–21,000 km s−1 and He II/Hα ratio of 0.3–2.3. It shows weak X-ray emission relative to UV emission, with X-ray flares lasting for +1.4. These characters are consistent with a TDE, ruling out the possibilities of a supernova or an active galactic nuclei flare. With a TDE model, we infer a peak UV luminosity of 3.3 ± 0.2 × 1044 erg s−1 and an energy budget of 4.5 ± 0.2 × 1051 erg. Conclusions. A TDE caused the flare that occurred in 2021. The two optical flares separated by 10.3 ± 0.3 years can be interpreted as repeating partial TDEs, double TDEs, or two independent TDEs. Although no

关键词： Budget control

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Accreting CO material onto ONe white dwarfs towards accretion-induced collapse

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Research in Astronomy and Astrophysics 2018年第3期18卷 121-128页

作者： Cheng-Yuan Wu Bo Wang Yunnan Observatories Chinese Academy of Sciences Kunming 650216 China Key Laboratory for the Structure and Evolution of Celestial Objects Chinese Academy of Sciences Kunming 650216 China University of Chinese Academy of Sciences Beijing 100049 China Center for Astronomical Mega-Science Chinese Academy of Sciences Beijing 100012 China

The final outcomes of accreting ONe white dwarfs（ONe WDs） have been studied for several decades,but there are still some issues that are not resolved. Recently,some studies suggested that the deflagration of oxygen would occur for accreting ONe WDs with Chandrasekhar masses. In this paper,we aim to investigate whether ONe WDs can experience accretion-induced collapse（AIC） or explosions when their masses approach the Chandrasekhar limit. Employing the stellar evolution code Modules for Experiments in Stellar Astrophysics（MESA）,we simulate the longterm evolution of ONe WDs with accreting CO material. The ONe WDs undergo weak multicycle carbon flashes during the mass-accretion process,leading to mass increase of the WDs. We found that different initial WD masses and mass-accretion rates influence the evolution of central density and temperature. However,the central temperature cannot reach the explosive oxygen ignition temperature due to neutrino cooling. This work implies that the final outcome of accreting ONe WDs is electroncapture induced collapse rather than thermonuclear explosion.

关键词： stars evolution - binaries close - supernovae general - white dwarfs

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The harmonic component of the millihertz quasi-periodic oscillations in 4U 1636-53

arXiv

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arXiv 2021年

作者： Fei, Zhenyan Lyu, Ming Méndez, Mariano Altamirano, D. Zhang, Guobao Mancuso, G.C. Xiang, Fu-Yuan Yang, X.J. Department of Physics Xiangtan University Hunan Xiangtan411105 China Key Laboratory of Stars and Interstellar Medium Xiangtan University Hunan Xiangtan411105 China Kapteyn Astronomical Institute University of Groningen PO BOX 800 GroningenNL-9700 AV Netherlands Physics & Astronomy University of Southampton Hampshire SouthamptonSO17 1BJ United Kingdom Kunming650216 China Key Laboratory for the Structure and Evolution of Celestial Objects Cas Kunming650216 China 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 studied the harmonics of the millihertz quasi-periodic oscillations (mHz QPOs) in the neutron-star low-mass X-ray binary 4U 1636-53 using the Rossi X-ray Timing Explorer observations. We detected the harmonics of the mHz QPOs in 73 data intervals, with most of them in the transitional spectra state. We found that the ratio between the rms amplitude of the harmonic and that of the fundamental remains constant in a wide range of the fundamental frequency. More importantly, we studied, for the first time, the rms amplitude of the harmonics vs. energy in 4U 1636-53 in the 2-5 keV range. We found that the rms amplitude of both the harmonic and the fundamental shows a decreasing trend as the energy increases, which is different from the behaviors reported in QPOs in certain black hole systems. Furthermore, our results suggest that not all observations with mHz QPOs have the harmonic component, although the reason behind this is still unclear. Copyright © 2021, The Authors. All rights reserved.

关键词： Stars

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The early-type stars from LAMOST survey: Atmospheric parameters

arXiv

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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

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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）

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

arXiv

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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

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

arXiv

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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

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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）

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Astronomical site monitoring system at lijiang observatory

arXiv

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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

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

arXiv

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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

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