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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）

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

Investigations into the thermal non-equilibrium of W UMa-type contact binaries

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Research in Astronomy and Astrophysics 2018年第5期18卷 83-92页

作者： Xiao Xiong Liang Liu Sheng-Bang Qian Yunnan Observatories Chinese Academy of Sciences Kunming 650011 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 100101 China University of Chinese Academy of Sciences Beijing 100049 China

Traditionally, some physical details（e.g., magnetic braking, energy transfer, angular momentum loss, etc.） have to be taken into consideration during investigations into the evolution of contact binaries. However, the real evolutionary processes which usually contain several of these physical mechanisms are very complicated as a result of strong interaction between components. To avoid dealing with these factors, a linear relationship is applied to the temperatures of components. It is found that the higher the mass ratio（M2/M1） of a contact system, the weaker the deviation from thermal *** this basis, a variation trend of fill-out factor（f） changing with mass ratio can be inferred, which is consistent with observations. Moreover, if we stick to this point of view, it should be natural that the number of semi-detached binaries in the predicted broken-contact phase of relaxation oscillations is less than the number in the contact phase.

关键词： stars binaries close - stars binaries eclipsing - stars evolution

Multi-color light curves and orbital period research of eclipsing binary V1073 Cyg

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Research in Astronomy and Astrophysics 2018年第2期18卷 83-92页

作者： Xiao-Man Tian Li-Ying Zhu Sheng-Bang Qian Lin-Jia Li Lin-Qiao Jiang 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 University of Chinese Academy of Sciences Beijing 100049 China School of Physics and Electronic Engineering Sichuan University of Science & Engineering Zigong 643000 China

New multi-color BVRcIc photometric observations are presented for the W UMa type eclips- ing binary V1073 Cyg. The multi-color light curve analysis with the Wilson-Devinney procedure yielded the absolute parameters of this system, showing that V 1073 Cyg is a shallow contact binary system with a fill-out factor f = 0.124（±0.011）. We collected all available times of light minima spanning 119yr, including CCD data to construct the O - C curve, and performed detailed O - C analysis. The O - C diagram shows that the period change is complex. A long-term continuous decrease and a cyclic vari- ation exist. The period is decreasing at a rate ofP = -1.04（±0.18） × 10-10 d cycle-land, with the period decrease, V1073 Cyg will evolve to the deep contact stage. The cyclic variation with a period of P3 = 82.7（±3.6） yr and an amplitude of A = 0.028（±0.002） d may be explained by magnetic activ- ity of one or both components or the light travel time effect caused by a distant third companion with M3（i1 = 90°） = 0.511 M⊙.

关键词： stars： binaries： close -- stars： binaries： eclipse -- stars： binaries： individual （V1073 Cyg）

Blue large-amplitude pulsators: The possible surviving companions of type ia supernovae

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arXiv 2020年

作者： Meng, Xiang-Cun Han, Zhan-Wen Podsiadlowski, Philipp 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 Department of Astronomy Oxford University OxfordOX1 3RH United Kingdom Key Laboratory of Space Astronomy and Technology National Astronomical Observatories Chinese Academy of Sciences Beijing100101 China

The single degenerate (SD) model, one of the leading models for the progenitors of Type Ia supernovae (SNe Ia), predicts that there should be binary companions that survive the supernova explosion which, in principle, should be detectable in the Galaxy. The discovery of such surviving companions could therefore provide conclusive support for the SD model. Several years ago, a new type of mysterious variables was discovered, the so-called blue large-amplitude pulsators (BLAPs). Here we show that all the properties of BLAPs can be reasonably well reproduced if they are indeed such surviving companions, in contrast to other proposed channels. This suggests that BLAPs could potentially be the long-sought surviving companions of SNe Ia. Our model also predicts a new channel for forming single hot subdwarf stars, consistent with a small group in the present hot-subdwarf-star sample. Copyright © 2020, The Authors. All rights reserved.

关键词： White dwarfs

Searching for multiple populations in star clusters using the China Space Station Telescope

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arXiv 2022年

作者： Li, Chengyuan Zheng, Zhenya Li, Xiaodong Pang, Xiaoying Tang, Baitian Milone, Antonino P. Wang, Yue Wang, Haifeng Jiang, Dengkai School of Physics and Astronomy Sun Yat-sen University Daxue Road Guangdong Zhuhai519082 China CSST Science Center for the Guangdong-Hong Kong-Macau Greater Bay Area Zhuhai519082 China CAS Key Laboratory for Research in Galaxies and Cosmology Shanghai Astronomical Observatory Shanghai200030 China Division of Optical Astronomical Technologies Shanghai Astronomical Observatory Shanghai200030 China Department of Physics Xi'an Jiaotong-Liverpool University 111 Ren'ai Road Jiangsu Suzhou215123 China Shanghai Key Laboratory for Astrophysics Shanghai Normal University 100 Guilin Road Shanghai200234 China Dipartimento di Fisica e Astronomia 'Galileo Galilei' Universita di Padova Vicolo dell'Osservatorio 3 PaduaI-35122 Italy Istituto Nazionale di Astrofisica Osservatorio Astronomico di Padova Vicolo dell'Osservatorio 5 PaduaIT-35122 Italy Key Laboratory of Optical Astronomy National Astronomical Observatories Chinese Academy of Sciences Beijing100101 China GEPI Observatoire de Paris Université PSL CNRS Place Jules Janssen Meudon92195 France 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 Kunming650216 China Center for Astronomical Mega-Science Chinese Academy of Sciences Beijing100012 China

Multiple stellar populations (MPs) in most star clusters older than 2 Gyr, as seen by lots of spectroscopic and photometric studies, have led to a significant challenge to the traditional view of star formation. In this field, space-based instruments, in particular the Hubble Space Telescope (HST), have made a breakthrough as they significantly improved the efficiency of detecting MPs in crowding stellar fields by images. The China Space Station Telescope (CSST) and the HST are sensitive to a similar wavelength interval, but it covers a field of view which is about 5-8 times wider than that of HST. One of its instruments, the Multi-Channel Imager (MCI), will have multiple filters covering a wide wavelength range from NUV to NIR, making the CSST a potentially powerful tool for studying MPs in clusters. In this work, we evaluate the efficiency of the designed filters for the MCI/CSST in revealing MPs in different color-magnitude diagrams (CMDs). We find that CMDs made with MCI/CSST photometry in appropriate UV filters are powerful tools to disentangle stellar populations with different abundances of He, C, N, O and Mg. On the contrary, the traditional CMDs are blind to multiple populations in globular clusters (GCs). We show that CSST has the potential of being the spearhead instrument for investigating MPs in GCs in the next decades. Copyright © 2022, The Authors. All rights reserved.

关键词： Space stations

A photmetric study of the high-mass-ratio contact binary av puppis

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arXiv 2019年

作者： Han, Quan-Wang Li, Li-Fang Jiang, Deng-Kai Yunnan Observatories Chinese Academy of Sciences Kunming650216 China Key Laboratory of the Structure and Evolution of Celestial Objects Chinese Academy of Sciences Kunming650216 China University of the Chinese Academy of Sciences Beijing100049 China

The multi-color photometric light curves for a contact binary AV Puppis (AV Pup) in V RcIcbandpasses are presented, and they are analyzed by using of the 2013 version of theWilson-Devinney (W-D) code. The solutions suggest that AV Pup is a peculiar A-subtype W UMa contact binary with a high mass ratio (q = m2/m1= 0.896) and a fill-out factor (f = 10%). Combining with our newly determined times of minimum with those collected from literatures, the orbital period changes of this system are investigated. The O - C analysis shows that the orbital period of AV Pup is increasing at a rate of dP/dt = 4.83× 10-7days yr-1, which can be explained by mass transfer from the less massive component to the more massive one. Copyright © 2019, The Authors. All rights reserved.

关键词： Photometry

SN 2019va: A Type IIP Supernova with Large Influence of Nickel-56 Decay on the Plateau-phase Light Curve

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arXiv 2022年

作者： Zhang, Xinghan Wang, Xiaofeng Sai, Hanna Mo, Jun Nagy, A.P. Zhang, Jicheng Cai, Yongzhi Lin, Han Zhang, Jujia Baron, E. DerKacy, J.M. Zhang, T.-M. Li, Zhitong Graham, Melissa Huang, F. Tsinghua University Beijing100084 China Bejing Planetarium Beijing Academy of Science and Technology Beijing100044 China Department of Optics and Quantum Electronics University of Szeged Szeged6720 Hungary Department of Astronomy Beijing Normal University Beijing100875 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 Homer L. Dodge Department of Physics and Astronomy University of Oklahoma NormanOK73019 United States 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 DiRAC Institute Department of Astronomy University of Washington Box 351580 U.W. SeattleWA98195 United States Department of Astronomy Shanghai Jiao Tong University Shanghai 200240 China

We present multi-band photometric and spectroscopic observations of the type II supernova, (SN) 2019va, which shows an unusually flat plateau-phase evolution in its V-band light curve. Its pseudo-bolometric light curve even shows a weak brightening towards the end of the plateau phase. These uncommon features are related to the influence of 56Ni decay on the light curve during the plateau phase, when the SN emission is usually dominated by cooling of the envelope. The inferred 56Ni mass of SN 2019va is 0.088±0.018 Mo, which is significantly larger than most SNe II. To estimate the influence of 56Ni decay on the plateau-phase light curve, we calculate the ratio (dubbed as ηNi) between the integrated time-weighted energy from 56Ni decay and that from envelope cooling within the plateau phase, obtaining a value of 0.8 for SN 2019va, which is the second largest value among SNe II that have been measured. After removing the influence of 56Ni decay on the plateau-phase light curve, we found that the progenitor/explosion parameters derived for SN 2019va are more reasonable. In addition, SN 2019va is found to have weaker metal lines in its spectra compared to other SNe IIP at similar epochs, implying a low-metallicity progenitor, which is consistent with the metal-poor environment inferred from the host-galaxy spectrum. We further discuss the possible reasons that might lead to SN 2019va-like events. Copyright © 2022, The Authors. All rights reserved.

关键词： Supernovae

A fast point-pattern matching algorithm based on statistical method

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arXiv 2019年

作者： Zhang, Zhen-Jun Zhang, Yi-Gong Cheng, Xiang-Ming Wang, Jian-Cheng Yunnan Observatories Chinese Academy of Sciences Kunming650216 China Key Laboratory of the Structure and Evolution of Celestial Objects Chinese Academy of Sciences Kunming650216 China University of Chinese Academy of Sciences Beijing100049 China

We propose a new pattern-matching algorithm for matching CCD images to a stellar catalogue based statistical method in this paper. The method of constructing star pairs can greatly reduce the computational complexity compared with triangle method. We use a subsample of the brightest objects from the image and reference catalogue, and find a coordinate transformation between the image and reference catalogue based on the statistical information of star pairs. Then all the objects are matched based on the initial plate solution. The matching process can be accomplished in several milliseconds for the observed images taken by Yunnan observatory 1-m telescope. Copyright © 2019, The Authors. All rights reserved.

关键词： Stars