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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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Measuring clock jumps using pulsar timing

arXiv

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arXiv 2019年

作者： Li, Zhi Xuan Lee, Ke Jia Caballero, Ricardo Nicolaos Xu, Yong Hua Hao, Long Fei Wang, Min Wang, Jian Cheng Yunnan Observatories Chinese Academy of Sciences Kunming650216 China Kavli Institute for Astronomy and Astrophysics Peking University Beijing100871 China University of Chinese Academy of Sciences 19A Yuquan Road Shijingshan District Beijing100049 China Key Laboratory for the Structure and Evolution of Celestial Objects Chinese Academy of Sciences Kunming650216 China

In this paper, we investigate the statistical signal-processing algorithm to measure the instant local clock jump from the timing data of multiple pulsars. Our algorithm is based on the framework of Bayesian statistics. In order to make the Bayesian algorithm applicable with limited computational resources, we dedicated our efforts to the analytic marginalization of irrelevant parameters. We found that the widely used parameter for pulsar timing systematics, the 'Efac' parameter, can be analytically marginalized. This reduces the Gaussian likelihood to a function very similar to the Student's t-distribution. Our iterative method to solve the maximum likelihood estimator is also explained in the paper. Using pulsar timing data from the Yunnan Kunming 40m radio telescope, we demonstrate the application of the method, where 80-ns level precision for the clock jump can be achieved. Such a precision is comparable to that of current commercial time transferring service using satellites. We expect that the current method could help developing the autonomous pulsar time scale. Copyright © 2019, The Authors. All rights reserved.

关键词： Pulsars

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Optical flare events on the RS Canum Venaticorum star UX Arietis

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Research in Astronomy and Astrophysics 2017年第6期17卷 55-66页

作者： Dong-Tao Cao Sheng-Hong Gu 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

Based on long-term high-resolution spectroscopic observations obtained during five observing runs from 2001 to 2004, we study optical flare events and chromospheric activity variability of the very active RS CVn star UX Ari. By means of the spectral subtraction technique, several optical chromospheric activity indicators （including the He IDa, Na I D1, D2 doublet, Ha and Ca II IRT lines） covered in our echelle spectra were analyzed. Four large optical flare events were detected on UX Ari during our observations, which show prominent He I D3 line emission together with great enhancement in emission of the Ha and Ca II IRT lines and strong filled-in or emission reversal features in the Na ! D1, D2 doublet lines. The newly detected flares are much more energetic than previous discoveries, especially for the flare identified during the 2002 December observing run. Optical flare events on UX Ari are more likely to be observed around two quadratures of the system, except for our optical flares detected during the 2004 November observing run. Moreover, we have found rotational modulation of chromospheric activity in the Ha and Ca II IRT lines, which suggests the presence of chromospherically active longitudes over the surface of UX Ari. The change in chromospherically active longitudes among our observing runs, as well as the variation in chromospheric activity level from 2001 to 2004, indicates a long-term evolution of active regions.

关键词： stars activity - stars chromospheres - stars binaries spectroscopic -stars flare -stars individual （UX Ari）

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The interaction of core-collapse supernova ejecta with a stellar companion

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Proceedings of the International Astronomical Union 2019年第S346期14卷 55-58页

作者： Liu, Zheng-Wei Tauris, T.M. Röpke, F.K. Moriya, T.J. Kruckow, M. Stancliffe, R.J. Izzard, R.G. Yunnan Observatories Key Laboratory for the Structure and Evolution of Celestial Objects CAS Kunming 650216 China Center for Astronomical Mega-Science CAS Beijing China Argelander-Institut für Astronomie Auf dem Hügel 71 Bonn D-53121 Germany Heidelberger Institut für Theoretische Studien Schloss-Wolfsbrunnenweg 35 Heidelberg D-69118 Germany Zentrum für Astronomie der Universität Heidelberg Institut für Theoretische Astrophysik Philosophenweg 12 Heidelberg D-69120 Germany National Astronomical Observatory of Japan Japan University of Surrey Guildford Surrey GU2 7XH United Kingdom

The progenitors of many core-collapse supernovae (CCSNe) are expected to be in binary systems. By performing a series of three-dimensional hydrodynamical simulations, we investigate how CCSN explosions affect their binary companion. We find that the amount of removed stellar mass, the resulting impact velocity, and the chemical contamination of the companion that results from the impact of the SN ejecta, strongly increases with decreasing binary separation and increasing explosion energy. Also, it is foud that the impact effects of CCSN ejecta on the structure of main-sequence (MS) companions, and thus their long term post-explosion evolution, are in general not dramatic. © International Astronomical Union 2019.

关键词： binaries: close stars: kinematics stars: supernovae: general

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CIV emission line properties and uncertainties in black hole mass estimates of z ~ 3.5 quasars

arXiv

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arXiv 2020年

作者： Zuo, Wenwen Wu, Xue-Bing Fan, Xiaohui Green, Richard Yi, Weiming Schulze, Andreas Wang, Ran Bian, Fuyan Shanghai Astronomical Observatory Chinese Academy of Sciences 80 Nandan Road Shanghai200030 China Department of Astronomy School of Physics Peking University Beijing100871 China Kavli Institute for Astronomy and Astrophysics Peking University Beijing100871 China Steward Observatory University of Arizona TucsonAZ85721 United States Yunnan Observatories Kunming650216 China Key Laboratory for the Structure and Evolution of Celestial Objects Chinese Academy of Sciences Kunming650216 China National Astronomical Observatory of Japan Mitaka181-8588 Japan European Southern Observatory Alonso de CÃşrdova 3107 Casilla 19001 Vitacura Santiago 19 Chile

Using a high luminosity (Lbol ∼ 1047.5 − 1048.3 erg s−1), high redshift (3.2 BH). The median logarithm of the CIV- and Hβ-based MBH ratios is 0.110 dex with the scatter of 0.647 dex. The CIV-to-Hβ BH mass differences are significantly correlated with the CIV FWHMs, blueshifts and asymmetries. Corrections of the CIV FWHM using the blueshift and asymmetry reduce the scatter of the mass differences by ∼ 0.04-0.2 dex. Quasars in our sample accrete at the Eddington ratio REDD > 0.3 and cover a considerable range of blueshifts, with 18/19 of the quasars showing CIV blueshifts (with the median value of 1126 km s−1) and 14/19 of the quasars showing CIV blueshifts larger than 500 km s−1. It suggests that not all quasars with high Eddington ratios show large blueshifts. The Baldwin effect between the CIV rest-frame equivalent width (REW) and the continuum luminosity at 1350 Å is not seen, likely due to the limited luminosity range of our sample. We find a lack of flux in the red wing of the composite spectrum with larger CIV blueshift, and detect a higher ratio of [OIII] quasars with REW[OIII] > 5 Å in the subsample with lower CIV blueshift. It is more likely that they are caused by the combination of the Eddington ratio and the orientation effect. Copyright © 2020, The Authors. All rights reserved.

关键词： Galaxies

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GRB x-ray flare properties among different GRB subclasses

arXiv

引用

arXiv 2019年

作者： Liu, Chuanxi Mao, Jirong Yunnan Observatories Chinese Academy of Sciences Yunnan Province Kunming650011 China Center for Astronomical Mega-Science Chinese Academy of Sciences 20A Datun Road Chaoyang District Beijing100012 China University of Chinese Academy of Sciences Beijing100049 China Key Laboratory for the Structure and Evolution of Celestial Objects Chinese Academy of Sciences Kunming650011 China

Gamma-ray bursts (GRBs) can be divided into three subclasses: X-ray flash (XRF), X-ray rich (XRR), and classical GRB (C-GRB). An X-ray flare is the rebrightening emission shown in the early X-ray afterglow of some GRBs. In this paper, we comprehensively examine the X-ray flare properties among XRF, XRR, and C-GRB subclasses. We utilize the XRF, XRR, and C-GRB subclass samples obtained from the Swift-BAT3 catalog, and the X-ray flare observational properties are collected from Falcone et al., Chincarini et al., and Yi et al. We find that XRFs and XRRs have more bright X-ray flares than C-GRBs. The ratio of the X-ray flare fluence to the prompt emission fluence has different distributions between XRF and C-GRB subclasses. The linear correlation between the duration and the peak time of the X-ray flares is also different between XRF and C-GRB subclasses. We are inclined to identify the GRBs with the bright X-ray flares as XRFs or XRRs. We discuss some issues that are related to the XRF/XRR/C-GRB classification. We also caution the selection effects and the instrument bias in our investigation. Large samples are required in the future to further confirm our results. Copyright © 2019, The Authors. All rights reserved.

关键词： Gamma rays

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evolution of A Peculiar Type Ibn Supernova SN 2019wep

arXiv

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arXiv 2022年

作者： Gangopadhyay, Anjasha Misra, Kuntal Hosseinzadeh, Griffin Arcavi, Iair Pellegrino, Craig Wang, Xiaofeng Howell, D. Andrew Burke, Jamison Zhang, Jujia Kawabata, Koji Singh, Mridweeka Dastidar, Raya Hiramatsu, Daichi McCully, Curtis Mo, Jun Chen, Zhihao Xiang, Danfeng Hiroshima Astrophysical Science Centre Hiroshima University 1-3-1 Kagamiyama Hiroshima Higashi-Hiroshima739-8526 Japan Aryabhatta Research Institute of Observational Sciences Manora Peak Nainital 263 002 India Steward Observatory University of Arizona 933 North Cherry Avenue TucsonAZ85721 United States The School of Physics and Astronomy Tel Aviv University Tel Aviv69978 Israel CIFAR Azrieli Global Scholars program CIFAR Toronto Canada Las Cumbres Observatory 6740 Cortona Drive Suite 102 GoletaCA93117-5575 United States Department of Physics University of California Santa BarbaraCA93106-9530 United States Physics Department Tsinghua Center for Astrophysics Tsinghua University China Beijing Planetarium Beijing Academy of Sciences Beijing100044 China Yunnan Astronomical Observatory of China Chinese Academy of Sciences Kunming650216 China Key Laboratory for the Structure and Evolution of Celestial Objects CAS Kunming650216 China Indian Institute of Astrophysics 2nd Block 100 Feet Rd Koramangala Karnataka Bengaluru560034 India Korea Astronomy and Space Science Institute 776 Daedeokdae-ro Yuseong-gu Daejeon34055 Korea Republic of Millennium Institute of Astrophysics Nuncio Monsenor Sótero Sanz 100 Providencia Santiago8320000 Chile

We present a high-cadence short term photometric and spectroscopic monitoring campaign of a type Ibn SN 2019wep, which is one of the rare SN Ibn after SNe 2010al and 2019uo to display signatures of flash ionization (He II, C III, N III). We compare the decline rates and rise time of SN 2019wep with other SNe Ibn and fast transients. The post-peak decline in all bands (0.1 mag d−1) are consistent with SNe Ibn but less than the fast transients. On the other hand, the ∆m15 values are slightly lower than the average values for SNe Ibn but consistent with the fast transients. The rise time is typically shorter than SNe Ibn but longer than fast transients. SN 2019wep lies at the fainter end of SNe Ibn but possesses an average luminosity amongst the fast transients sample. The peculiar color evolution places it between SNe Ib and the most extreme SNe Ibn. The bolometric light curve modelling shows resemblance with SN 2019uo with ejecta masses consistent with SNe Ib. SN 2019wep belongs to the "P cygni" sub-class of SNe Ibn and shows faster evolution in line velocities as compared to the "emission" sub-class. The post-maximum spectra show close resemblance with ASASSN-15ed hinting it to be of SN Ib nature. The low He I CSM velocities and residual Hα further justifies it and gives evidence of an intermittent progenitor between WR and LBV star. Copyright © 2022, The Authors. All rights reserved.

关键词： Photometry

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Three new late-type hypervelocity star candidates from gaia DR2 by refined selection criteria

arXiv

引用

arXiv 2020年

作者： Li, Jiao Jia, Shi Gao, Yan Jiang, Dengkai Kupfer, Thomas Heber, Ulrich Liu, Chao Chen, Xuefei Han, Zhanwen Yunnan Observatories Chinese Academy of Sciences P.O. Box 110 Kunming650011 Key Laboratory for the Structure and Evolution of Celestial Objects Yunnan Observatories Chinese Academy of Sciences University of Chinese Academy of Sciences Beijing100049 China Center for Astronomical Mega-Science Chinese Academy of Sciences Beijing100012 China State Key Laboratory of Lunar and Planetary Sciences Macau University of Science and Technology Macau China Kavli Institute for Theoretical Physics University of California Santa BarbaraCA93106 United States Department of Physics University of California Santa BarbaraCA93106 United States Dr. Remeis-Sternwarte and Ecap University of Erlangen-Nürnberg Erlangen Key Lab of Optical Astronomy National Astronomical Observatories Chinese Academy of Sciences Beijing100012 China

Several dozen hypervelocity star (HVS) candidates have been reported based on the second data release of Gaia (Gaia DR2). However, it has been proven that the radial velocities of some Gaia HVS candidates are not reliable. In this paper, we employ refined astrometric criteria to re-examine Gaia DR2, arriving at a more reliable sample of HVS and high velocity star candidates than those found by previous authors. We develop a method called Binary Escape Probability Analysis to identify some HVS candidates. This method allows us to work with stars having only two epochs of measured radial velocity. These stars were usually discarded in previous similar studies. A scrutiny of our final results sheds light on selection effects present in our studies, which we propose to be the focus of future studies. In total, we find three late-type (2 G-type and 1 K-type) HVS and 21 high velocity star candidates, 3 and 11 of which are new, respectively. Judging by their historical trajectories, which we calculate, all three HVS candidates could not have had Galactic centre origins. Copyright © 2020, The Authors. All rights reserved.

关键词： Stars

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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

引用

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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