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First Chromospheric Activity and Doppler Imaging Study of PW And Using a New Doppler Imaging Code: SpotDIPy

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arXiv 2023年

作者： Bahar, Engin Şenavcı, Hakan V. Işık, Emre Hussain, Gaitee A.J. Kochukhov, Oleg Montes, David Xiang, Yue Department of Astronomy and Space Sciences Faculty of Science Ankara University Beşevler Ankara06100 Turkey Max-Planck-Institut für Sonnensystemforschung Justus-von-Liebig-Weg 3 Göttingen37077 Germany Department of Computer Science Turkish-German University Beykoz Istanbul34820 Turkey Keplerlaan 1 Noordwijk2201 AZ Netherlands Department of Physics and Astronomy Uppsala University Box 516 UppsalaSE-75120 Sweden Facultad de Ciencias Físicas Universidad Complutense de Madrid MadridE-28040 Spain Yunnan Observatories Chinese Academy of Sciences Kunming650216 China Key Laboratory for the Structure and Evolution of Celestial Objects Chinese Academy of Sciences Kunming650216 China

Measuring coverage of dark spots on cool stars is important in understanding how stellar magnetic activity scales with the rotation rate and convection zone depth. In this respect, it is crucial to infer surface magnetic patterns on G and K stars, to reveal solar-like stellar dynamos in action. Molecular bands serve as invaluable indicators of cool spots on the surfaces of stars, as they play a crucial role in enabling accurate assessments of the extent of spot coverage across the stellar surface. Therefore, more reliable surface images can be obtained considering the inversion of atomic lines with molecular bands. In this context, we simultaneously carry out Doppler imaging (DI) using atomic lines as well as Titanium Oxide (TiO) band profiles of PW And (K2 V) and also investigate chromospheric activity indicators for the first time in the literature, using the high-resolution spectra. The surface spot distribution obtained from the inversion process represents both atomic line and TiO-band profiles quite accurately. The chromospheric emission is also correlated with photospheric spot coverage, except during a possible flare event during the observations. We detect frequent flare activity, using TESS photometry. We also introduce a new open-source, Python-based DI code SpotDIPy that allows performing surface reconstructions of single stars using the maximum entropy method. We test the code by comparing surface reconstruction simulations with the extensively used DoTS code. We show that the surface brightness distribution maps reconstructed via both codes using the same simulated data are consistent with each other. © 2023, CC BY.

关键词： Stars

Minute-Cadence Observations of the LAMOST Fields with the TMTS: IV— Catalog of Cataclysmic Variables from the First 3-yr Survey

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arXiv 2024年

作者： Liu, Qichun Lin, Jie Wang, Xiaofeng Dai, Zhibin Sun, Yongkang Xi, Gaobo Mo, Jun Liu, Jialian Yan, Shengyu Filippenko, Alexei V. Brink, Thomas G. Yang, Yi Patra, Kishore C. Cai, Yongzhi Chen, Zhihao Chen, Liyang Guo, Fangzhou Jiang, Xiaojun Li, Gaici Li, Wenxiong Lin, Weili Miao, Cheng Ma, Xiaoran Peng, Haowei Xia, Qiqi Xiang, Danfeng Zhang, Jicheng Physics Department Tsinghua Center for Astrophysics Tsinghua University Beijing100084 China CAS Key Laboratory for Research in Galaxies and Cosmology Department of Astronomy University of Science and Technology of China Hefei230026 China School of Astronomy and Space Sciences University of Science and Technology of China Hefei230026 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 National Astronomical Observatories Chinese Academy of Sciences Beijing100101 China School of Astronomy and Space Science University of Chinese Academy of Sciences Beijing100049 China Department of Astronomy University of California BerkeleyCA94720-3411 United States International Centre of Supernovae Yunnan Key Laboratory Kunming650216 China CAS Key Laboratory of Optical Astronomy National Astronomical Observatories Chinese Academy of Sciences Beijing100101 China Center for Astronomical Mega-Science Chinese Academy of Sciences 20A Datun Road Chaoyang District Beijing100101 China Department of Astronomy Xiamen University Xiamen361005 China Department of Astronomy Beijing Normal University Beijing100875 China

The Tsinghua University–Ma Huateng Telescopes for Survey (TMTS) started to monitor the LAMOST plates in 2020, leading to the discovery of numerous short-period eclipsing binaries, peculiar pulsators, flare stars, and other variable objects. Here, we present the uninterrupted light curves for a sample of 64 cataclysmic variables (CVs) observed/discovered using the TMTS during its first three-year observations, and we introduce new CVs and new light-variation periods (from known CVs) revealed through the TMTS observations. Thanks to the high-cadence observations of TMTS, diverse light variations, including superhumps, quasi-periodic oscillations, large-amplitude orbital modulations, and rotational modulations, are able to be detected in our CV samples, providing key observational clues for understanding the fast-developing physical processes in various CVs. All of these short-timescale light-curve features help further classify the subtypes of CV systems. We highlight the light-curve features observed in our CV sample and discuss further implications of minute-cadence light curves for CV identifications and classifications. Moreover, we examine the Hα emission lines in the spectra from our nonmagnetic CV samples (i.e., dwarf novae and nova-like subclasses) and find that the distribution of Hα emission strength shows significant differences between the sources with orbital periods above and below the period gap, which agrees with the trend seen from the SDSS nonmagnetic CV sample. Copyright © 2024, The Authors. All rights reserved.

关键词： Seismology

Core overshoot constrained by the absence of a solar convective core and some solar-like stars

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arXiv 2022年

作者： Zhang, Qian-Sheng Christensen-Dalsgaard, Jørgen Li, Yan Yunnan Observatories Chinese Academy of Sciences 396 Yangfangwang Guandu District Kunming650216 China Stellar Astrophysics Centre Department of Physics and Astronomy Aarhus University Aarhus CDK-8000 Denmark Center for Astronomical Mega-Science Chinese Academy of Sciences 20A Datun Road Chaoyang District Beijing100012 China Key Laboratory for the Structure and Evolution of Celestial Objects Chinese Academy of Sciences 396 Yangfangwang Guandu District Kunming650216 China University of Chinese Academy of Sciences Beijing100049 China

Convective-core overshoot mixing is a significant uncertainty in stellar evolution. Because numerical simulations and turbulent convection models predict exponentially decreasing radial rms turbulent velocity, a popular treatment of the overshoot mixing is to apply a diffusion process with exponentially decreasing diffusion coefficient. It is important to investigate the parameters of the diffusion coefficient because they determine the efficiency of the mixing in the overshoot region. In this paper, we have investigated the effects of the core overshoot mixing on the properties of the core in solar models and have constrained the parameters of the overshoot model by using helioseismic inferences and the observation of the solar 8B neutrino flux. For solar-mass stars, the core overshoot mixing helps to prolong the lifetime of the convective core developed at the ZAMS. If the strength of the mixing is sufficiently high, the convective core in a solar model could survive till the present solar age, leading to large deviations of the sound-speed and density profiles comparing with the helioseismic inferences. The 8B neutrino flux also favours a radiative solar core. Those provide a constraint on the parameters of the exponential diffusion model of the convective overshoot mixing. A limited asteroseismic investigation of 13 Kepler low-mass stars with 1.0 © 2022, CC BY.

关键词： Mixing

MODELING Hα AND HE 10830 TRANSMISSION SPECTRUM OF WASP-52B

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arXiv 2022年

作者： Yan, Dongdong Seon, Kwang-Il Guo, Jianheng Chen, Guo Li, Lifang 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 Korea Astronomy and Space Science Institute 776 Daedeokdae-ro Yuseong-gu Daejeon34055 Korea Republic of Astronomy and Space Science Major University of Science and Technology 217 Gajeong-ro Yuseong-gu Daejeon34113 Korea Republic of Key Laboratory of Planetary Sciences Purple Mountain Observatory Chinese Academy of Sciences Nanjing210023 China

Escaping atmosphere has been detected by the excess absorption of Lyα, Hα and He triplet (10830Å) lines. Simultaneously modeling the absorption of the Hα and He 10830 lines can provide useful constraints about the exoplanetary atmosphere. In this paper, we use a hydrodynamic model combined with a non-local thermodynamic model and a new Monte Carlo simulation model to obtain the H(2) and He(23S) populations. The Monte Carlo simulations of Lyα radiative transfer are performed with assumptions of a spherical stellar Lyα radiation and a spherical planetary atmosphere, for the first time, to calculate the Lyα mean intensity distribution inside the planetary atmosphere, necessary in estimating the H(2) population. We model the transmission spectra of the Hα and He 10830 lines simultaneously in hot Jupiter WASP-52b. We find that models with many different H/He ratios can reproduce the Hα observations well if the host star has (1) a high X-ray/extreme ultraviolet (XUV) flux (FXUV) and a relatively low X-ray fraction in XUV radiation (βm), or (2) a low FXUV and a high βm. The simulations of He 10830 Å triplet suggest that a high H/He ratio (∼ 98/2) is required to fit the observation. The models that fit both lines well confine FXUV to be about 0.5 times the fiducial value and βm to have a value around 0.3. The models also suggest that hydrogen and helium originate from the escaping atmosphere, and the mass-loss rate is about 2.8×1011 g s−1 © 2022, CC BY-NC-ND.

关键词： Radiative transfer

The maximum accreted mass of recycled pulsars

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arXiv 2021年

作者： Li, Zhenwei Chen, Xuefei Chen, Hai-Liang Han, Zhanwen Yunnan Observatories Chinese Academy of Sciences Kunming650011 China Key Laboratory for the Structure and Evolution of Celestial Objects Chinese Academy of Science China University of the Chinese Academy of Science Yuquan Road 19 Shijingshan Block Beijing100049 China Center for Astronomical Mega-Science Chinese Academy of Science 20A Datun Road Chaoyang District Beijing100012 China

The maximum mass of neutron stars (NSs) is of great importance for constraining equations of state of NSs and understanding the mass gap between NSs and stellar-mass black holes. NSs in X-ray binaries would increase in mass by accreting material from their companions (known as recycling process), and the uncertainties in the accretion process give challenge to study the NS mass at birth. In this work, we investigate the NS accreted mass with considering the effect of NS spin evolution and give the maximum accreted mass for NSs in the recycling process. By exploring a series of binary evolution calculations, we obtain the final NS mass and the maximum accreted mass for a given birth mass of NS and a mass transfer efficiency. Our results show that the NSs can accrete relatively more material for binary systems with the donor masses in the range of 1.8 ∼ 2.4M☉, the NSs accrete relatively more mass when the remnant WD mass is in the range of ∼ 0.25 − 0.30M☉, and the maximum accreted mass is positively correlated with the initial NS mass. For a 1.4M☉ NS at birth with a moderate mass transfer efficiency of 0.3, the maximum accreted mass could be 0.27M☉. The results can be used to estimate the minimum birth mass for systems with massive NSs in observations. Copyright © 2021, The Authors. All rights reserved.

关键词： Mass transfer

Science objectives of the Einstein Probe mission

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Science China(Physics,Mechanics & Astronomy) 2025年第3期68卷 1-60页

作者： Weimin Yuan Lixin Dai Hua Feng Chichuan Jin Peter Jonker Erik Kuulkers Yuan Liu Kirpal Nandra Paul O’Brien Luigi Piro Arne Rau Nanda Rea Jeremy Sanders Lian Tao Junfeng Wang Xuefeng Wu Bing Zhang Shuangnan Zhang Shunke Ai Johannes Buchner Esra Bulbul Hechao Chen Minghua Chen Yong Chen Yu-Peng Chen Alexis Coleiro Francesco Coti Zelati Zigao Dai Xilong Fan Zhou Fan Susanne Friedrich He Gao Chong Ge Mingyu Ge Jinjun Geng Giancarlo Ghirlanda Giulia Gianfagna Lijun Gou Sebastien Guillot´ Xian Hou Jingwei Hu Yongfeng Huang Long Ji Shumei Jia S.Komossa Albert K.H.Kong Lin Lan An Li Ang Li Chengkui Li Dongyue Li Jian Li Zhaosheng Li Zhixing Ling Ang Liu Jinzhong Liu Liangduan Liu Zhu Liu Jiawei Luo Ruican Ma Pierre Maggi Chandreyee Maitra Alessio Marino Stephen Chi-Yung Ng Haiwu Pan Surangkhana Rukdee Roberto Soria Hui Sun Pak-Hin Thomas Tam Aishwarya Linesh Thakur Hui Tian Eleonora Troja Wei Wang Xiangyu Wang Yanan Wang Junjie Wei Sixiang Wen Jianfeng Wu Ting Wu Di Xiao Dong Xu Renxin Xu Yanjun Xu Yu Xu Haonan Yang Bei You Heng Yu Yunwei Yu Binbin Zhang Chen Zhang Guobao Zhang Liang Zhang Wenda Zhang Yu Zhang Ping Zhou Zecheng Zou National Astronomical Observatories Chinese Academy of SciencesBeijing 100101China School of Astronomy and Space Sciences University of Chinese Academy of SciencesBeijing 100049China Department of Physics University of Hong KongPokfulam RoadHong Kong 999077China Key Laboratory of Particle Astrophysics Institute of High Energy PhysicsChinese Academy of SciencesBeijing 100049China Department of Astrophysics/IMAPP Radboud UniversityNijmegen6500 GLthe Netherlands SRON Netherlands Institute for Space ResearchLeiden2333 CAthe Netherlands ESA/ESTEC Noordwijk2201 AZthe Netherlands Max Planck Institute for Extraterrestrial Physics Garching85748Germany School of Physics and Astronomy University of LeicesterLeicesterLE17RHUK INAF-Istituto di Astrofisica e Planetologia Spaziali Rome00133Italy Institute of Space Sciences(ICE) CSICCampus UABBarcelonaE-08193Spain Institut d’Estudis Espacials de Catalunya(IEEC) BarcelonaE-08034Spain Department of Astronomy Xiamen UniversityXiamen 361005China Purple Mountain Observatory Chinese Academy of SciencesNanjing 210023China School of Astronomy and Space Sciences University of Science and Technology of ChinaHefei 230026China Nevada Center for Astrophysics University of NevadaLas VegasNV 89154USA Department of Physics and Astronomy University of NevadaLas VegasNV 89154USA Department of Astronomy School of Physics and TechnologyWuhan UniversityWuhan 430072China School of Physics and Astronomy Yunnan UniversityKunming 650500China Xinjiang Astronomical Observatory Chinese Academy of SciencesUrumqi 830011China Universit´e Paris Cit´e CNRSAstroparticule et CosmologieParisF-75013France Department of Astronomy University of Science and Technology of ChinaHefei 230026China Institute for Frontier in Astronomy and Astrophysics Beijing Normal UniversityBeijing 102206China Department of Astronomy Beijing Normal UniversityBeijing 100875China INAF-Osservatorio Astronomico di Brera Merate(LC)I-23807Italy INFN-sezione di Milano-Bicocca Milano(M

The Einstein Probe(EP)is an interdisciplinary mission of time-domain and X-ray *** with a wide-field lobstereye X-ray focusing imager,EP will discover cosmic X-ray transients and monitor the X-ray variability of known sources in 0.5-4 keV,at a combination of detecting sensitivity and cadence that is not accessible to the previous and current wide-field monitoring *** can perform quick characterisation of transients or outbursts with a Wolter-I X-ray telescope *** this paper,the science objectives of the EP mission are *** is expected to enlarge the sample of previously known or predicted but rare types of transients with a wide range of *** them,fast extragalactic transients will be surveyed systematically in soft X-rays,which includeγ-ray bursts and their variants,supernova shock breakouts,and the predicted X-ray transients associated with binary neutron star *** will detect X-ray tidal disruption events and outbursts from active galactic nuclei,possibly at an early phase of the flares for *** will monitor the variability and outbursts of X-rays from white dwarfs,neutron stars and black holes in our and neighbouring galaxies at flux levels fainter than those detectable by the current instruments,and is expected to discover new objects.A large sample of stellar X-ray flares will also be detected and *** the era of multi-messenger astronomy,EP has the potential of detecting the possible X-ray counterparts of gravitational wave events,neutrino sources,and ultra-high energyγ-ray and cosmic ray *** is expected to help advance the studies of extreme objects and phenomena revealed in the dynamic X-ray universe,and their underlying physical *** EP's strength in time-domain science,its follow-up telescope,with excellent performance,will also enable advances in many areas of X-ray astronomy.

关键词： Einstein Probe X-ray astronomy X-ray telescopes time-domain astronomy transients variability

A long-period pre-ELM system discovered from LAMOST medium-resolution survey

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arXiv 2022年

作者： Zhang, Zhi-Xiang Zheng, Ling-Lin Gu, Wei-Min Sun, Mouyuan Yi, Tuan Shi, Jian-Rong Wang, Song Bai, Zhong-Rui Zhang, Hao-Tong Cui, Wen-Yuan Wang, Junfeng Wu, Jianfeng Li, Xiang-Dong Shao, Yong Lu, Kai-Xing Bai, Yu Li, Chunqian Fu, Jin-Bo Liu, Jifeng Department of Astronomy Xiamen University Fujian Xiamen361005 China Key Laboratory of Optical Astronomy National Astronomical Observatories Chinese Academy of Sciences Beijing100012 China School of Astronomy and Space Science University of Chinese Academy of Sciences Beijing100049 China Department of Physics Hebei Normal University Shijiazhuang050024 China Department of Astronomy Nanjing University Nanjing210023 China Key laboratory of Modern Astronomy and Astrophysics Nanjing University Ministry of Education Nanjing210023 China Yunnan Observatories Chinese Academy of Sciences Kunming650011 China Key Laboratory for the Structure and Evolution of Celestial Objects Chinese Academy of Sciences Kunming650011 China WHU-NAOC Joint Center for Astronomy Wuhan University Wuhan430072 China

We present LAMOST J041920.07+072545.4 (hereafter J0419), a close binary consisting of a bloated extremely low mass pre-white dwarf (pre-ELM WD) and a compact object with an orbital period of 0.607189 days. The large-amplitude ellipsoidal variations and the evident Balmer and He I emission lines suggest a filled Roche lobe and ongoing mass transfer. No outburst events were detected in the 15 years of monitoring of J0419, indicating a very low mass transfer rate. The temperature of the pre-ELM, Teff = 5793+124−133 K, is cooler than the known ELMs, but hotter than most CV donors. Combining the mean density within the Roche lobe and the radius constrained from our SED fitting, we obtain the mass of the pre-ELM, M1 = 0.176 ± 0.014 Mo. The joint fitting of light and radial velocity curves yields an inclination angle of i = 66.5+1.4−1.7 degrees, corresponding to the compact object mass of M2 = 1.09 ± 0.05 Mo. The very bloated pre-ELM has a smaller surface gravity (log g = 3.9 ± 0.01, R1 = 0.78 ± 0.02 Ro) than the known ELMs or pre-ELMs. The temperature and the luminosity (Lbol = 0.62+0.11−0.10. Lo) of J0419 are close to the main sequence, which makes the selection of such systems through the HR diagram inefficient. Based on the evolutionary model, the relatively long period and small log g indicate that J0419 could be close to the "bifurcation period" in the orbit evolution, which makes J0419 to be a unique source to connect ELM/pre-ELM WD systems, wide binaries and cataclysmic variables. Copyright © 2022, The Authors. All rights reserved.

关键词： Mass transfer

Searching for cataclysmic variable stars in unidentified X-ray sources

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arXiv 2022年

作者： Takata, Jumpei Wang, X.F. Kong, A.K.H. Mao, J. Hou, X. Hu, C.-P. Lin, L.C.-C. Li, K.L. Hui, C.Y. Department of Astronomy School of Physics Huazhong University of Science and Technology Wuhan430074 China Institute of Astronomy National Tsing Hua University Hsinchu30013 Taiwan Yunnan Observatories Chinese Academy of Sciences Kunming650216 China Key Laboratory for the Structure and Evolution of Celestial Objects Chinese Academy of Sciences Kunming650216 China Department of Physics National Changhua University of Education Changhua50007 Taiwan Department of Physics National Cheng Kung University Tainan701401 Taiwan Department of Astronomy and Space Science Chungnam National University Daejeon305-764 Korea Republic of

We carry out a photometric search for new cataclysmic variable stars (CVs), with the goal of identification for candidates of AR Scorpii-type binary systems. We select GAIA sources that are likely associated with unidentified X-ray sources, and analyze the light curves taken by the Zwicky Transient Facility, Transiting Exoplanet Survey Satellite, and Lulin One-meter Telescope in Taiwan. We investigate eight sources as candidates for CVs, among which six sources are new identifications. Another two sources have been recognized as CVs in previous studies, but no detailed investigations have been done. We identify two eclipsing systems that are associated with an unidentified XMM-Newton or Swift source, and one promising candidate for polar associated with an unidentified ASKA source. Two polar candidates may locate in the so-called period gap of a CV, and the other six candidates have an orbital period shorter than that of the period gap. Although we do not identify a promising candidate for AR Scorpii-type binary systems, our study suggests that CV systems that have X-ray emission and do not show frequent outbursts may have been missed in previous surveys. © 2022, CC0.

关键词： Surveys

The interaction of Type Iax supernova ejecta with a helium companion star

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arXiv 2020年

作者： Zeng, Yaotian Zheng-Wei, Liu 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

Type Iax supernovae (SNe Iax) are an important sub-luminous class of SNe Ia. However, their progenitors and explosion mechanism have not been understood yet. It has been suggested that SNe Iax may be produced from weak deflagration explosions of Chandrasekhar-mass white dwarfs (WDs) in binary systems with a helium (He) star donor. In such progenitor systems, the stripped He companion material caused by the ejecta-companion interaction is expected to present some He features in their late-time spectra. However, the detection of He lines in late-time spectra of SNe Iax has not yet been successful, which gives an upper limit on the amount of stripped He mass of . 2 × 10−3 − 0.1 M . In this work, we study the interaction between SN Iax ejecta and a He star companion by performing three-dimensional hydrodynamical simulations with a weak pure deflagration explosion model. We find that about 4 × 10−3 M of He material can be stripped off from the companion star by SN explosion, which is very close to (or lower than) the observational upper-limit on the total stripped He mass in SNe Iax. We, therefore, conclude that non-detection of He lines in late-time spectra of SNe Iax could be reasonably explained if they are indeed resulted from weak pure deflagration explosions of Chandrasekhar-mass WDs in progenitor systems with a He star donor. Copyright © 2020, The Authors. All rights reserved.

关键词： Helium