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Minute-cadence Observations of the LAMOST Fields with the TMTS: III. Statistic Study of the Flare Stars from the First Two Years

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arXiv 2023年

作者： Liu, Qichun Lin, Jie Wang, Xiaofeng Gu, Shenghong Shi, Jianrong Zhang, Liyun Xi, Gaobo Mo, Jun Cai, Yongzhi Chen, Liyang Chen, Zhihao Guo, Fangzhou Jiang, Xiaojun Li, Gaici Li, Wenxiong Lin, Han Lin, Weili Liu, Jialian Miao, Cheng Ma, Xiaoran Peng, Haowei Xiang, Danfeng Yan, Shengyu Zhang, Jicheng Zhang, Xinhan Physics Department Tsinghua Center for Astrophysics 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 CAS 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 Beijing100049 China College of Physics College of Big Data and Information Engineering Guizhou University Guiyang550025 China Center for Astronomical Mega-Science Chinese Academy of Sciences 20A Datun Road Chaoyang District Beijing100012 China The School of Physics and Astronomy Tel Aviv University Tel Aviv69978 Israel Department of Astronomy Beijing Normal University Beijing100875 China

Tsinghua University-Ma Huateng Telescopes for Survey (TMTS) aims to detect fast-evolving transients in the Universe, which has led to the discovery of thousands of short-period variables and eclipsing binaries since 2020. In this paper, we present the observed properties of 125 flare stars identified by TMTS within the first two years, with an attempt to constrain their eruption physics. As expected, most of these flares were recorded in late-type red stars with GBP − GRP > 2.0 mag;however, the flares associated with bluer stars tend to be on average more energetic and have broader profiles. The peak flux (Fpeak) of the flare is found to depend strongly on the equivalent duration (ED) of the energy release, i.e., Fpeak ∝ ED0.72±0.04, which is consistent with results derived from the Kepler and Evryscope samples. This relation is likely related to the magnetic loop emission, while, for the more popular non-thermal electron heating model, a specific time evolution may be required to generate this relation. We notice that flares produced by hotter stars have a flatter Fpeak ∝ ED relation compared to that from cooler stars. This is related to the statistical discrepancy in light-curve shape of flare events with different colors. In spectra from LAMOST, we find that flare stars have apparently stronger Hα emission than inactive stars, especially at the low temperature end, suggesting that chromospheric activity plays an important role in producing flares. On the other hand, the subclass with frequent flares is found to show Hα emission of similar strength in its spectra to that recorded with only a single flare but similar effective temperature, implying that the chromospheric activity may not be the only trigger for eruptions. Copyright © 2023, The Authors. All rights reserved.

关键词： Stars

A systematic study of the high-frequency bump in the black-hole low-mass X-ray binary GX 339−4

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arXiv 2023年

作者： Zhang, Yuexin Méndez, Mariano Motta, Sara E. Zdziarski, Andrzej A. Marcel, Grégoire García, Federico Altamirano, Diego Belloni, Tomaso M. Zhang, Liang Timmermans, Thimo Zhang, Guobao Kapteyn Astronomical Institute University of Groningen P.O. BOX 800 Groningen9700 AV Netherlands Center for Astrophysics Harvard & Smithsonian 60 Garden St CambridgeMA02138 United States MerateI-23807 Italy Nicolaus Copernicus Astronomical Center Polish Academy of Sciences Bartycka 18 WarszawaPL-00-716 Poland Institute of Astronomy University of Cambridge Madingley Road CambridgeCB3 0HA United Kingdom Villa Elisa Buenos Aires1894 Argentina School of Physics and Astronomy University of Southampton SouthamptonSO17 1BJ United Kingdom Key Laboratory of Particle Astrophysics Institute of High Energy Physics Chinese Academy of Sciences Beijing100049 China Yunnan Observatories Chinese Academy of Sciences Kunming650216 China Key Laboratory for the Structure and Evolution of Celestial Objects CAS Kunming650216 China

The high-frequency bump, characterized by a frequency exceeding ∼30 Hz, represents a seldom-explored time-variability feature in the power density spectrum (PDS) of black-hole X-ray binaries. In the 2002, 2004, 2007 and 2010 outbursts of GX 339−4, the bump has been occasionally observed in conjunction with type-C quasi-periodic oscillations (QPOs). We systematically study the properties of the bump during these four outbursts observed by Rossi X-ray Timing Explorer (RXTE) in the 2-60 keV bands and detect the bump in 39 observations. While the frequencies of the type-C QPOs are in the range of ∼0.1-9 Hz, the root-mean-square (rms) amplitude of the bump shows an evolution in the hardness ratio versus the type-C QPO frequency plot. By comparing the rms amplitude of the bump with the corona temperature and simultaneous radio jet flux of the source, as previously studied in GRS 1915+105, we establish that in the hard state of GX 339−4, the bump is always strong, with the measurements of the rms amplitude in the range of 4-10%. At the same time, the corona temperature is high and the radio flux is low. These findings indicate that, using the bump as a proxy, the majority of the accretion energy is directed towards the hot corona rather than being channeled into the radio jet. We discuss this phenomenon in terms of an inefficient energy transfer mechanism between the corona and jet in GX 339−4. © 2023, CC BY.

关键词： Black holes

MULTI-COLOR AND TESS PHOTOMETRIC INVESTIGATION OF FOUR LOW MASS-RATIO CONTACT BINARY SYSTEMS

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arXiv 2024年

作者： Zubairi, Ahmed Waqas Ergang, Zhao Shengbang, Qian Xiao, Zhou Lajús, Eduardo Fernández Kunming650216 China University of Chinese Academy of Sciences No.1 Yanqihu East Rd Huairou District Beijing101408 China Center for Astronomical Mega-Science Chinese Academy of Sciences 20A Datun Road Chaoyang District Beijing100012 China Key Laboratory of the Structure and Evolution of Celestial Objects Chinese Academy of Sciences P. O. Box 110 Kunming650216 China Department of Astronomy Yunnan University Kunming650091 China Facultad de Ciencias Astronómicas y Geofísicas Universidad Nacional de La Plata Paseo del Bosques/n Buenos Aires La Plata1900 Argentina Instituto de Astrofísica de La Plata CCT La Plata CONICET UNLP La Plata1900 Argentina

We present the TESS and BV RcIc light curves solution of four low mass-ratio contact binary systems TIC 159102550), V1068 Her, MW Pav and TIC 321576458. Except MW Pav, all three systems have been studied for the first time. The BV RcIc observations of southern contact binary system, MW Pav, is carried out using 60cm Helen Sawyer Hogg (HSH) telescope located at Argentina. The TIC 321576458 is observed in BV RcIc with 70cm Sino-Thai telescope at Lijiang station of Yunnan Observatories. The period analysis of TIC 159102550 show anti-correlation between primary and secondary minima and no long term variation is reported. The systems V1068 Her and MW Pav show increasing period at dP/dt = 1.247(9) × 10−7days/yr and dP/dt = 2.256(6) × 10−7days/yr, respectively. Data for TIC 321576458 is too few to determine any periodic variations. The light curve analysis using Wilson-Divinney model shows that systems are low mass-ratio contact binaries. Out of four targets, two systems TIC 159102550 and V1068 Her, are shallow contact binary systems with fill-out factor of 20% and 14%, respectively. The two contact binaries MW Pav and TIC 321576458 are in deep contact state with fill-out factor 63% and 61%, respectively. V1068 Her shows EB-type light curve, however the temperature difference between the primary secondary component is only 17K, which indicates that system is in thermal contact. To understand the evolutionary status of these systems, the components are plotted on the mass-luminosity diagram. The primary companions are in the ZAMS zone while the secondary components of all the systems are away from TAMS which indicates that secondary is more evolved than the primary components. V1068 Her and MW Pav are expected to evolve into a single rapidly rotating star provided that they meet the well-know Hut's criterion. Through statistical investigation of more than hundred low mass-ratio contact binary systems including our targets, we have found that all of the low mass-ratio contac

关键词： Telescopes

Probing the Shock Breakout Signal of SN 2024ggi from the Transformation of Early Flash Spectroscopy

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arXiv 2024年

作者： Zhang, Jujia Dessart, Luc Wang, Xiaofeng Zhai, Qian Yang, Yi Li, Liping Lin, Han Valerin, Giorgio Cai, Yongzhi Guo, Zhen Wang, Lingzhi Zhao, Zeyi Wang, Zhenyu Yan, Shengyu Kunming650216 China International Centre of Supernovae Yunnan Key Laboratory Kunming650216 China Key Laboratory for the Structure and Evolution of Celestial Objects CAS Kunming650216 China Institut d’Astrophysique de Paris CNRS-Sorbonne Université 98 bis boulevard Arago ParisF-75014 France Physics Department Tsinghua University Beijing100084 China Department of Astronomy University of California BerkeleyCA94720-3411 United States INAF-Osservatorio Astronomico di Padova Vicolo dell’Osservatorio 5 Padova35122 Italy Instituto de Física y Astronomía Universidad de Valparaíso ave. Gran Bretaña 1111 Casilla 5030 Valparaíso Chile Centre for Astrophysics Research University of Hertfordshire HatfieldAL10 9AB United Kingdom Millennium Institute of Astrophysics Nuncio Monseñor Sotero Sanz 100 Of. 104 Providencia Santiago Chile National Astronomical Observatories CAS Beijing China

We present early-time, hour-to-day cadence spectroscopy of the nearby type II supernova (SN II) 2024ggi, which was discovered at a phase when the SN shock just emerged from the red-supergiant (RSG) progenitor star. Over the first few days after the first light, SN 2024ggi exhibited prominent narrow emission lines formed through intense and persistent photoionization of the nearby circumstellar material (CSM). In the first 63 hours, spectral lines of He, C, N, and O revealed a rapid rise in ionization, as a result of the progressive sweeping-up of the CSM by the shock. The duration of the IIn-like spectra indicates a dense and relatively confined CSM distribution extending up to ∼ 4 × 1014 cm. Spectral modeling reveals a CSM mass loss rate at this region exceeding 5× 10−3 M☉ yr−1 is required to reproduce low-ionization emissions, which dramatically exceeds that of an RSG. Analyzing Hα emission shift implies the velocity of the unshocked outer CSM to be between 20 and 40 km s−1, matching the typical wind velocity of an RSG. The differences between the inner and outer layers of the CSM and an RSG progenitor highlight a complex mass loss history before the explosion of SN 2024ggi. © 2024, CC BY.

关键词： Supernovae

A potential mass-gap black hole in a wide binary with a circular orbit

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arXiv 2024年

作者： Wang, Song Zhao, Xinlin Feng, Fabo Ge, Hongwei Shao, Yong Cui, Yingzhen Gao, Shijie Zhang, Lifu Wang, Pei Li, Xue Bai, Zhongrui Yuan, Hailong Huang, Yang Yuan, Haibo Zhang, Zhixiang Yi, Tuan Xiang, Maosheng Li, Zhenwei Li, Tanda Zhang, Junbo Zhang, Meng Han, Henggeng Fan, Dongwei Li, Xiangdong Chen, Xuefei Liu, Zhengwei Meng, Xiangcun Liu, Qingzhong Zhang, Haotong Gu, Wei-Min Liu, Jifeng Key Laboratory of Optical Astronomy National Astronomical Observatories Chinese Academy of Sciences Beijing100101 China Institute for Frontiers in Astronomy and Astrophysics Beijing Normal University Beijing102206 China School of Astronomy and Space Sciences University of Chinese Academy of Sciences Beijing100049 China Tsung-Dao Lee Institute Shanghai Jiao Tong University Shanghai201210 China School of Physics and Astronomy Shanghai Jiao Tong University Shanghai200240 China Yunnan Observatories Chinese Academy of Sciences Kunming650216 China International Centre of Supernovae Yunnan Key Laboratory Kunming650216 China Key Laboratory for Structure and Evolution of Celestial Objects Chinese Academy of Sciences Kunming650216 China School of Astronomy and Space Science Nanjing University Nanjing210023 China Ministry of Education Nanjing210023 China CAS Key Laboratory of FAST NAOC Chinese Academy of Sciences Beijing100101 China Department of Astronomy Beijing Normal University Beijing100875 China Department of Astronomy Xiamen University Fujian Xiamen361005 China Department of Astronomy School of Physics Peking University Beijing100871 China Kavli Institute for Astronomy and Astrophysics Peking University Beijing100871 China Center for Astronomical Mega-Science Chinese Academy of Sciences Beijing100012 China Key Laboratory of Dark Matter and Space Astronomy Purple Mountain Observatory Chinese Academy of Sciences Nanjing210008 China College of Physics and Electronic Engineering Qilu Normal University Jinan China New Cornerstone Science Laboratory National Astronomical Observatories Chinese Academy of Sciences Beijing100012 China

Mass distribution of black holes identified through X-ray emission suggests a paucity of black holes in the mass range of 3 to 5 solar masses. Modified theories have been devised to explain this mass gap, and it is suggested that natal kicks during supernova explosion can more easily disrupt binaries with lower mass black holes. Although recent LIGO observations reveal the existence of compact remnants within this mass gap, the question of whether low-mass black holes can exist in binaries remains a matter of debate. Such a system is expected to be noninteracting without X-ray emission, and can be searched for using radial velocity and astrometric methods. Here we report Gaia DR3 3425577610762832384, a wide binary system including a red giant star and an unseen object, exhibiting an orbital period of approximately 880 days and near-zero eccentricity. Through the combination of radial velocity measurements from LAMOST and astrometric data from Gaia DR2 and DR3 catalogs, we determine a mass of (Equation presented) M☉ of the unseen component. This places the unseen companion within the mass gap, strongly suggesting the existence of binary systems containing low-mass black holes. More notably, the formation of its surprisingly wide circular orbit challenges current binary evolution and supernova explosion theories. Copyright © 2024, The Authors. All rights reserved.

关键词： Supernovae

AT2023lli: A Tidal Disruption Event with Prominent Optical Early Bump and Delayed Episodic X-ray Emission

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arXiv 2024年

作者： Huang, Shifeng Jiang, Ning Zhu, Jiazheng Wang, Yibo Wang, Tinggui Wang, Shan-Qin Gan, Wen-Pei Liang, En-Wei Qin, Yu-Jing Lin, Zheyu Xu, Lin-Na Cai, Min-Xuan Jiang, Ji-An Kong, Xu Li, Jiaxun Li, Long Wang, Jian-Guo Xu, Ze-Lin Xue, Yongquan Yuan, Ye-Fei Cheng, Jingquan Fan, Lulu Gao, Jie Hu, Lei Hu, Weida Li, Bin Li, Feng Liang, Ming Liu, Hao Liu, Wei Lou, Zheng Luo, Wentao Qian, Yuan Tang, Jinlong Wan, Zhen Wang, Hairen Wang, Jian Yang, Ji Yao, Dazhi Zhang, Hongfei Zhang, Xiaoling Zhao, Wen Zheng, Xianzhong Zhu, Qingfeng Zuo, Yingxi 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 Institute of Deep Space Sciences Deep Space Exploration Laboratory Hefei230026 China Guangxi Key Laboratory for Relativistic Astrophysics School of Physical Science and Technology Guangxi University Nanning530004 China Nanjing Hopes Technology Co. Ltd. Pukou District Nanjing210000 China Division of Physics Mathematics and Astronomy California Institute of Technology 1200 E California Blvd. PasadenaCA91125 United States National Astronomical Observatory of Japan National Institutes of Natural Sciences Tokyo181-8588 Japan Yunnan Observatories Chinese Academy of Sciences Kunming650011 China Key Laboratory for the Structure and Evolution of Celestial Objects Yunnan Observatories Kunming650011 China Purple Mountain Observatory Chinese Academy of Sciences Nanjing210023 China State Key Laboratory of Particle Detection and Electronics University of Science and Technology of China Hefei230026 China McWilliams Center for Cosmology Department of Physics Carnegie Mellon University 5000 Forbes Ave PittsburghPA15213 United States Department of Physics University of California Santa Barbara Santa BarbaraCA93106 United States 950 N Cherry Ave TucsonAZ85726 United States Institute of Optics and Electronics Chinese Academy of Sciences Chengdu610209 China

High-cadence, multiwavelength observations have continuously revealed the diversity of tidal disruption events (TDEs), thus greatly advancing our knowledge and understanding of TDEs. In this work, we conducted an intensive optical-UV and X-ray follow-up campaign of TDE AT2023lli, and found a remarkable month-long bump in its UV/optical light curve nearly two months prior to maximum brightness. The bump represents the longest separation time from the main peak among known TDEs to date. The main UV/optical outburst declines as t−4.10, making it one of the fastest decaying optically selected TDEs. Furthermore, we detected sporadic X-ray emission 30 days after the UV/optical peak, accompanied by a reduction in the period of inactivity. It is proposed that the UV/optical bump could be caused by the self-intersection of the stream debris, whereas the primary peak is generated by the reprocessed emission of the accretion process. In addition, our results suggest that episodic X-ray radiation during the initial phase of decline may be due to the patched obscurer surrounding the accretion disk, a phenomenon associated with the inhomogeneous reprocessing process. The double TDE scenario, in which two stars are disrupted in sequence, is also a possible explanation for producing the observed early bump and main peak. We anticipate that the multicolor light curves of TDEs, especially in the very early stages, and the underlying physics can be better understood in the near future with the assistance of dedicated surveys such as the deep high-cadence survey of the 2.5-meter Wide Field Survey Telescope (WFST). © 2024, CC BY.

关键词： Luminance

Reverberation Mapping of Two Variable Active Galactic Nuclei: Probing the Distinct Characteristics of the Inner and Outer Broad-line Regions

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arXiv 2024年

作者： Feng, Hai-Cheng Li, Sha-Sha Bai, J.M. Liu, H.T. Lu, Kai-Xing Pang, Yu-Xuan Sun, Mouyuan Wang, Jian-Guo Xu, Yerong Zhang, Yang-Wei Zhou, Shuying Yunnan Observatories Chinese Academy of Sciences Yunnan Kunming650216 China Key Laboratory for the Structure and Evolution of Celestial Objects Chinese Academy of Sciences Yunnan Kunming650216 China Center for Astronomical Mega-Science Chinese Academy of Sciences 20A Datun Road Chaoyang District Beijing100012 China Key Laboratory of Radio Astronomy and Technology Chinese Academy of Sciences 20A Datun Road Chaoyang District Beijing100101 China Department of Astronomy School of Physic Peking University Beijing100871 China Kavli Institute for Astronomy and Astrophysics Peking University Beijing100871 China Department of Astronomy Xiamen University Fujian Xiamen361005 China INAF - IASF Palermo Via U. La Malfa 153 PalermoI-90146 Italy Department of Astronomy & Physics Saint Mary's University 923 Robie Street HalifaxNSB3H 3C3 Canada South-Western Institute for Astronomy Research Yunnan University Kunming650500 China

Current reverberation mapping (RM) studies primarily focus on single emission lines, particularly the Hβ line, which may not fully reveal the geometry and kinematic properties of the broad-line region (BLR). To overcome this limitation, we conducted multiline RM observations on two highly variable active galactic nuclei (AGNs), KUG 1141+371 and UGC 3374, using the Lijiang 2.4 m telescope. Our goal was to investigate the detailed structure of different regions within the BLR. We measured the time lags of multiple broad emission lines (Hα, Hβ, Hγ, He I, and He II) and found clear evidence of radial ionization stratification in the BLRs of both AGNs. Velocity-resolved RM analysis revealed distinct geometry and kinematics between the inner and outer regions of the BLRs. Assuming that velocity-resolved lags reflect the kinematics of BLR, our observations indicate that: (1) in KUG 1141+371, the inner BLR exhibits outflow signatures, while the outer region is consistent with virialized motion;(2) in UGC 3374, the inner region displays virial motion, while the outer region shows inflow. Furthermore, we detected "breathing" behavior in the outer BLR regions of both AGN, while the inner BLR regions show "anti-breathing", which may be linked to intrinsic BLR properties. We discuss these findings in the context of various BLR formation models, highlighting importance of long-term, multiline RM campaigns in understanding of BLR structure and evolution. Additionally, our results suggest that the observed stratification in BLR geometry and kinematics may contribute to the scatter in black hole mass estimates and the rapid changes in velocity-resolved RM signatures reported in recent studies. © 2024, CC BY.

关键词： Active Galactic Nuclei

Evidence of stellar oscillations in the post-common envelop binary candidate ASASSN-V J205543.90+240033.5

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arXiv 2023年

作者： Takata, Jumpei Kong, A.K.H. Wang, X.F. Song, F.F. 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 Yunnan Province Kunming650011 China Key Laboratory for the Structure and Evolution of Celestial Objects Chinese Academy of Sciences Kunming650011 China University of Chinese Academy of Sciences Beijing100049 China Center for Astronomical Mega-Science Chinese Academy of Sciences 20A Datun Road Chaoyang District Beijing100012 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

ASASSN-V J205543.90+240033.5 (ASJ2055) is a possible post-common envelope binary system. Its optical photometric data shows an orbital variation about 0.52 days and a fast period modulation of P0 ∼ 9.77 minute, whose origin is unknown. In this Letter, we report an evidence of the stellar oscillation of the companion star as the origin of the fast period modulation. We analyze the photometric data taken by TESS, Liverpool telescope, and Lulin One-meter Telescope. It is found that the period of the 9.77-minute signal measured in 2022 August is significantly shorter than that in 2021 July/August, and the magnitude of the change is of the order of |P0|/P0 ∼ 0.0008(4). Such a large variation will be incompatible with the scenario of the white dwarf spin as the origin of the 9.77-minute periodic modulation. We suggest that the fast periodic signal is related to the emission from the irradiated companion star rather than that of the white dwarf. Using existing photometric data covering a wide wavelength range, we estimate that the hot white dwarf in ASJ2055 has a temperature of Teff ∼ 80000 K and is heating the oscillating M-type main-sequence star with Teff ∼ 3500 K on its un-irradiated surface. The stellar oscillation of M-type main-sequence star has been predicted in theoretical studies, but no observational confirmation has been done. ASJ2055, therefore, has a potential to be a unique laboratory to investigate the stellar oscillation of a M-type main-sequence star and the heating effect on the stellar oscillation. © 2023, CC0.

关键词： White dwarfs

J115307.93+353528.2—Spectroscopic Twin Binary, Composed of Solar Like Stars. Orbital Solution from Poorly Resolved Double-line structure

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Research Notes of the AAS 2024年第7期8卷 175-175页

作者： Mikhail Yu. Kovalev Xuefei Chen Zhanwen Han Yunnan Observatories China Academy of Sciences Kunming 650216 People’s Republic of China mikhail.kovalev@*** Key Laboratory for the Structure and Evolution of Celestial Objects Chinese Academy of Sciences Kunming 650011 People’s Republic of China Center for Astronomical Mega-Science Chinese Academy of Sciences 20A Datun Road Chaoyang District Beijing 100012 People’s Republic of China

We present a study of double-lined spectroscopic binary (SB2) J115307.93+353528.2 based on data from the Large Sky Area Multi-object fiber Spectroscopic Telescope (LAMOST) medium resolution survey (MRS). We use full-spectrum fitting to derive radial velocities and spectral parameters, which suggest that this is a "twin" system of two nearly identical stars, which are similar to the Sun. The orbital solution tells us that it is relatively wide pair of stars on slightly eccentric orbit with period P ≃ 206 days. This result shows that LAMOST-MRS data can be used to detect such twin binaries even when double-line structure is poorly resolved in the spectra. Changes of $(V\sin i)$ $(V \sin i)$ values from single star model analysis allows us to reliably select su

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