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Asteroseismology of the DBV star CBS 114

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Research in Astronomy and Astrophysics 2016年第8期16卷 17-24页

作者： Yan-Hui Chen Institute of Astrophysics Chuxiong Normal University School of Physics and Electronical Science Chuxiong Normal University Key Laboratory for the Structure and Evolution of Celestial Objects Chinese Academy of Sciences

Asteroseismology is a unique and powerful tool to investigate the internal structure of stars. CBS 114 is the sixth known pulsating DBV star. It was observed by Handler, Metcalfe, ＆ Wood at the South African Astronomical Observatory over three weeks in 2001. Then, it was observed by Metcalfe et al. for seven nights （2004 Feb. 19-25） on the 1.8 m telescope at the Bohyunsan Optical Astronomy Observatory and seven nights （2004 Feb. 21-27） on the 2.1 m telescope at the McDonald Observatory. Totally two triplets, four doublets, and five singlets were identified. The frequency splitting values are very different, from 5.2 *** to 11.9 ~tHz, which may reflect differential rotations. We evolve grids of white dwarf models by MESA. Cores, added with He/C envelopes, of those white dwarf models are inserted into WDEC to evolve grids of DBV star models. With those DBV star models, we calculate eigenperiods. Those calculated periods are used to fit observed periods. A best-fitting model is selected. The parameters are T^ff ----- 25 000 K, M, = 0.740 MG and log（MHe/M,） = -4.5. With the relatively large stellar mass, the effective temperature is close to the previous spectroscopic result. In addition, kinetic energy distributions are calculated for the best-fitting model. We find that the observed modes with large frequency splitting values are fitted by the calculated modes with a large amount of kinetic energy distributed in the C/O core. After preliminary analysis, we suggest that the C/O core may rotate at least two times faster than the helium layer for CBS 114.

关键词： stars： oscillations （including pulsations） -- stars： individual （CBS 114） -- white dwarfs

Eclipsing binaries observed by LAMOST 2

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Eclipsing binaries observed by LAMOST

2nd Accretion Processes in Cosmic Sources, APCS 2018

作者： Zhu, Liying Qian, Shengbang Shi, Xiangdong Yunnan Observatories Chinese Academy of Sciences 396 Yangfangwang Guandu District Kunming 650216 P. R. ChinaCenter for Astronomical Mega-Science Chinese Academy of Sciences 20A Datun Road Chaoyang District Beijing 100012 P. R. ChinaKey Laboratory for the Structure and Evolution of Celestial Objects Chinese Academy of Sciences 396 Yangfangwang Guandu District Kunming 650216 P. R. ChinaUniversity of the Chinese Academy of Sciences Yuquan Road 19# Sijingshang Block 100049 Beijing P. R. China

LAMOST has a wide field of view and a very high spectrum acquiring rate. More than 9 millions spectra were obtained by LAMOST till now. Among them, more than 8 millions are stellar spectra. Such huge stellar spectra database will stimulate the deep study of stellar physics and corresponding fields. Eclipsing binaries are very important sources in astrophysics because they provide precise information about absolute parameters of the components. LAMOST observed 12923 eclipsing binary stars, which greatly expanded the spectroscopic information of eclipsing binaries. We provided the eclipsing binary catalogue with stellar atmospheric parameters and spectral types obtained by LAMOST. In this paper, we introduce the different kinds of eclipsing binaries observed by LAMOST. As an example of the follow-up observation, we present the study of the EW-type eclipsing binary NSVS4692753. Combined the complete light curves and the parameters obtained by LAMOST, we analyzed its muli-color light *** results show that NSVS4692753 is a low mass ratio (mass ratio 5.0) and deep contact (fill-out factor 64%) W-type contact binary system. The third light contribution was detected in all bands and the asymmetric light variation detected in the light curve was explained by a dark spot in the secondary. NSVS4692753 is the special system at the late evolutionary stage of contact binaries, and maybe the progenitor of the luminous red nova, which is a rare class of optical transients. © Copyright owned by the author(s) under the terms of the Creative Commons

关键词： Astrophysics

A comprehensive bayesian discrimination of the simple stellar population model, star formation history and dust attenuation law in the spectral energy distribution modeling of galaxies

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arXiv 2018年

作者： Han, Yunkun Han, Zhanwen Yunnan Observatories 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 Key Laboratory for the Structure and Evolution of Celestial Objects Chinese Academy of Sciences 396 Yangfangwang Guandu District Kunming650216 China

When modeling and interpreting the spectral energy distributions (SEDs) of galaxies, the simple stellar population (SSP) model, star formation history (SFH) and dust attenuation law (DAL) are three of the most important components. However, each of them carries significant uncertainties which have seriously limited our ability to reliably recover the physical properties of galaxies from the analysis of their SEDs. In this paper, we present a Bayesian framework to deal with these uncertain components simultaneously. Based on the Bayesian evidence, a quantitative implement of the principle of Occam's razor, the method allows a more objective and quantitative discrimination among the different assumptions about these uncertain components. With a Ks-selected sample of 5467 lowredshift (mostly with z . 1) galaxies in the COSMOS/UltraVISTA field and classified into passively evolving galaxies (PEGs) and star-forming galaxies (SFGs) with UVJ diagram, we present a Bayesian discrimination of a set of 16 SSP models from five research groups (BC03 and CB07, M05, GALEV, Yunnan-II, BPASS V2.0), five forms of SFH (Burst, Constant, Exp-dec, Exp-inc, Delayed-t), and four kinds of DAL (Calzetti law, MW, LMC, SMC). We show that the results obtained with the method are either obvious or understandable in the context of galaxy physics. We conclude that the Bayesian model comparison method, especially that for a sample of galaxies, is very useful for discriminating the different assumptions in the SED modeling of galaxies. The new version of the BayeSED code, which is used in this work, is publicly available at https://***/hanyk/bayesed/. Copyright © 2018, The Authors. All rights reserved.

关键词： Spectroscopy

Physical properties and evolutionary states of binaries and variable stars observed by LAMOST 2

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Physical properties and evolutionary states of binaries and ...

2nd Accretion Processes in Cosmic Sources, APCS 2018

作者： Qian, Shengbang Zhu, Liying Zhao, Ergang Shi, Xiangdong Zhihua, Wang Yunnan Observatories Chinese Academy of Sciences 396 Yangfangwang Guandu District Kunming 650216 P. R. ChinaCenter for Astronomical Mega-Science Chinese Academy of Sciences 20A Datun Road Chaoyang District Beijing 100012 P. R. ChinaKey Laboratory for the Structure and Evolution of Celestial Objects Chinese Academy of Sciences 396 Yangfangwang Guandu District Kunming 650216 P. R. ChinaUniversity of the Chinese Academy of Sciences Yuquan Road 19# Sijingshang Block 100049 Beijing P. R. China

About eighteen thousand known variables were observed by LAMOST during the first stage of the spectroscopic survey from October 24, 2011 to July 16, 2017. Stellar atmospheric parameters for about eleven thousands of them were determined including the temperature (T), the gravitational acceleration (log g), the metallicity [Fe/H] and the radial velocity Vr. Those parameters are introduced in the paper. The locations of those variables including δ Sct and γ Dor stars on the Log g-T diagram are presented where EA- and EW-type eclipsing binaries are also shown for comparison. Meanwhile, new photometric results on two special sample stars ROTSE1 J144111.82+382750.0 and CSS_J034112.5+035336 were obtained by follow-up observations. The former was originally found as a δ Sct with a period of 0.191291 days. However, the LAMOST parameters reveal that it is far beyond the red edge of pulsational instability trip of δ Sct stars. By using those new photometric data, we detect that is an EW-type eclipsing binary with an orbital period of 0.382583. As for CSS_J034112.5+035336, it was listed as an EW-type binary in VSX with a period of 0.285554 days. However, the LAMOST data showed that it is a special target because its temperature is very higher when compared with the short period. Our new photometric observations reveal it is a pulsating star rather than an EW-type binary. These results indicate that they the LAMOST data are very useful to understand their physical properties and evolutionary states. © Copyright owned by the author(s) under the terms of the Creative Commons

关键词：

Binary population synthesis for the core-degenerate scenario of SN ia progenitors

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Binary population synthesis for the core-degenerate scenario...

2017 AGB-Supernovae Mass Transition

作者： Wang, B. 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

The core-degenerate (CD) scenario has been proposed as an alternative way for the production of type Ia supernovae (SNe Ia). In this scenario, SNe Ia are formed at the final stage of common-envelope evolution from a merger of a carbon-oxygen white dwarf (CO WD) with the CO core of an asymptotic giant branch companion. However, the birthrates of SNe Ia from this scenario are still not well determined. In this work, we performed a detailed investigation on the CD scenario based on a binary population synthesis (BPS) approach. The SN Ia delay times for this scenario are mainly in the range of ∼90 Myr−2200 Myr, contributing to the observed SNe Ia with short and intermediate delay times. The Galactic birthrates of SNe Ia from this scenario range from ∼4.6×10−5yr−1 to ∼4.3×10−4yr−1, accounting for ∼2−14% of total SNe Ia. Especially, SNe Ia with circumstellar material from this scenario contribute to ∼1−10% of total SNe Ia, which means that the CD scenario can reproduce the observed birthrates of SNe Ia like PTF 11kx. © SAIt 2017.

关键词： White dwarfs

Early-Time Observations of SN 2023wrk: A Luminous Type Ia Supernova with Significant Unburned Carbon in the Outer Ejecta

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arXiv 2024年

作者： Liu, Jialian Wang, Xiaofeng Andrade, Cristina Duverne, Pierre-Alexandre Zhang, Jujia Li, Liping Wang, Zhenyu Navarete, Felipe Reguitti, Andrea Schuldt, Stefan Cai, Yongzhi Filippenko, Alexei V. Yang, Yi Brink, Thomas G. Zheng, WeiKang Esamdin, Ali Iskandar, Abdusamatjan Bai, Chunhai Liu, Jinzhong Li, Xin Hu, Maokai Li, Gaici Li, Wenxiong Ma, Xiaoran Yan, Shengyu Mo, Jun Adami, Christophe Akl, Dalya Antier, Sarah Broens, Eric Ducoin, Jean-Grégoire Elhosseiny, Eslam Esposito, Thomas M. Freeberg, Michael Gokulass, Priya Hello, Patrice Karpov, Sergey Márquez, Isabel Mašek, Martin Pyshna, Oleksandra Rajabov, Yodgor Saint-Gelais, Denis Serrau, Marc Sokoliuk, Oleksii Takey, Ali Tanasan, Manasanun Turpin, Damien Physics Department Tsinghua University Beijing100084 China School of Physics and Astronomy University of Minnesota MinneapolisMN55455 United States Université Paris Cité CNRS Astroparticule et Cosmologie ParisF-75013 France Yunnan Observatories Chinese Academy of Sciences Kunming650216 China International Centre of Supernovae Yunnan Key Laboratory Kunming650216 China Key Laboratory for the Structure and Evolution of Celestial Objects Chinese Academy of Sciences Kunming650216 China University of Chinese Academy of Sciences Beijing100049 China SOAR Telescope/NSF’s NOIRLab Avda Juan Cisternas 1500 La Serena1700000 Chile Merate23807 Italy INAF – Osservatorio Astronomico di Padova Vicolo dell’Osservatorio 5 Padova35122 Italy Dipartimento di Fisica Università degli Studi di Milano via Celoria 16 MilanoI-20133 Italy INAF - IASF Milano via A. Corti 12 MilanoI-20133 Italy Department of Astronomy University of California BerkeleyCA94720-3411 United States Xinjiang Astronomical Observatory Chinese Academy of Sciences Urumqi Xinjiang830011 China School of Astronomy and Space Science University of Chinese Academy of Sciences Beijing100049 China Beijing Planetarium Beijing Academy of Science and Technology Beijing100044 China Natioal Astronomical Observatories of China Chinese Academy of Sciences Beijing100012 China Aix Marseille Univ CNRS CNES LAM Marseille France Physics Department American University of Sharjah Sharjah United Arab Emirates Université Côte d’Azur Observatoire de la Côte d’Azur CNRS Laboratoire J.-L. Lagrange Boulevard de l’Observatoire Nice06304 France KNC Vereniging Voor Sterrenkunde Balen-Neetlaan 18A MolB-2400 Belgium CPPM Aix Marseille Univ CNRS IN2P3 CPPM Marseille France 1 El-marsad St. Helwan Cairo11421 Egypt ColfaxWI54730 United States iTelescope Utah Desert Remote Observatory Beryl Junction UT84714 United States Department of Physical Sciences College of Arts and Sciences Embry-Riddle

We present extensive photometric and spectroscopic observations of the nearby Type Ia supernova (SN) 2023wrk at a distance of about 40 Mpc. The earliest detection of this SN can be traced back to a few hours after the explosion. Within the first few days the light curve shows a bump feature, while the B − V color is blue and remains nearly constant. The overall spectral evolution is similar to that of an SN 1991T/SN 1999aa-like SN Ia, while the C ii λ6580 absorption line appears to be unusually strong in the first spectrum taken at t ≈ −15.4 days after the maximum light. This carbon feature disappears quickly in subsequent evolution but it reappears at around the time of peak brightness. The complex evolution of the carbon line and the possible detection of Ni iii absorption around 4700 Å and 5300 Å in the earliest spectra indicate macroscopic mixing of fuel and ash. The strong carbon lines is likely related to collision of SN ejecta with unbound carbon, consistent with the predictions of pulsational delayed-detonation or carbon-rich circumstellar-matter interaction models. Among those carbon-rich SNe Ia with strong C ii λ6580 absorption at very early times, the line-strength ratio of C ii to Si ii and the B − V color evolution are found to exhibit large diversity, which may be attributed to different properties of unbound carbon and outward-mixing 56Ni. Copyright © 2024, The Authors. All rights reserved.

关键词： Supernovae

A new hyper-runaway star discovered from lamost and gaia: Ejected almost in the galactic rotation direction

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arXiv 2018年

作者： Li, Yin-Bi Luo, A-Li Zhao, Gang Lu, You-Jun Zhang, Xue-Sen Zhang, Fu-Peng Du, Bing Zuo, Fang Zhang, Lan Huang, Yang Xiang, Mao-Sheng Zhao, Jing-Kun Zhao, Yong-Heng Han, Zhan-Wen Key Laboratory of Optical Astronomy National Astronomical Observatories Chinese Academy of Sciences Beijing100101 China Technology Co. Ltd Beijing100102 China School of Physics and Astronomy Sun Yat-sen University Guangzhou510275 China South-Western Institute for Astronomy Research Yunnan University Kunming650500 China Key Laboratory for the Structure and Evolution of Celestial Objects Yunnan Observatories Chinese Academy of Sciences Kunming650216 China

In this paper, we report the discovery of a new late-B type unbound hyper-runaway star (LAMOST-HVS4) from the LAMOST spectroscopic surveys. According to its atmospheric parameters, it is either a B-type main-sequence (MS) star or a blue horizontal branch (BHB) star. Its Galactocentric distance and velocity are 30.3 ± 1.6 kpc and 586±7 km s−1 if it is an MS star, and they are 13.2 ± 3.7 kpc and 590±7 km s−1 if a BHB star. We track its trajectories back, and find that the trajectories intersect with the Galactic disk and the Galactic center lies outside of the intersection region at the 3σ confidence level. We investigate a number of mechanisms that could be responsible for the ejection of the star, and find that it is probably ejected from the Galactic disk by supernova explosion or multiple-body interactions in dense young stellar clusters. Copyright © 2018, The Authors. All rights reserved.

关键词： Galaxies

The birthrates of SNe Ia in globular clusters

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Proceedings of the International Astronomical Union 2017年第S316期12卷 343-344页

作者： Bo Wang Dongdong Liu Yunnan Observatories Chinese Academy of Sciences Kunming 650216 China (email: wangbo@***) Key Laboratory for the Structure and Evolution of Celestial Objects Chinese Academy of Sciences Kunming 650216 China

Globular clusters has been proposed as testbeds for type Ia supernovae (SNe Ia). In this work, using a detailed binary population synthesis approach, we studied the birthrates of SNe Ia from various progenitor models in globular clusters, including the single-degenerate model, the double-degenerate model and the Sub-Chandrasekhar model. Here, a single starburst with a total mass of 106M⊙ is assumed.

关键词： binaries: close supernovae: general white dwarfs

Active galactic nuclei with ultra-fast outflows monitoring project: The broad-line region of MRK 79 as a disk wind

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arXiv 2019年

作者： Lu, Kai-Xing Bai, Jin-Ming Zhang, Zhi-Xiang Du, Pu Hu, Chen Kim, Minjin Wang, Jian-Min Ho, Luis C. Li, Yan-Rong Bian, Wei-Hao Yuan, Ye-Fei Xiao, Ming Feng, Hai-Cheng Wang, Jian-Guo Xu, Liang Ding, Xu Yu, Xiao-Guang Xin, Yu-Xin Ye, Kai Wang, Chuan-Jun Lun, Bao-Li Zhang, Ju-Jia Zhang, Xi-Liang Ji, Kai-Fan Fan, Yu-Feng Chang, Liang Yunnan Observatories Chinese Academy of Sciences Kunming650011 China Key Laboratory for the Structure and Evolution of Celestial Objects Chinese Academy of Sciences Kunming650011 China Department of Astronomy Xiamen University Xiamen Fujian361005 China Key Laboratory for Particle Astrophysics Institute of High Energy Physics Chinese Academy of Sciences 19B Yuquan Road Beijing100049 China Department of Astronomy and Atmospheric Sciences Kyungpook National University Daegu702-701 Korea Republic of Korea Astronomy and Space Science Institute Daejeon305-348 Korea Republic of Kavli Institute for Astronomy and Astrophysics Peking University Beijing100871 China Department of Astronomy School of Physics Peking University Beijing100871 China Physics Department Nanjing Normal University Nanjing210097 China Department of Astronomy University of Science and Technology of China Hefei230026 China

We developed a spectroscopic monitoring project to investigate the kinematics of the broad-line region (BLR) in active galactic nuclei (AGN) with ultra-fast outflows (UFOs). Mrk 79 is a radio-quiet AGN with UFOs and warm absorbers, had been monitored by three reverberation mapping (RM) campaigns, but its BLR kinematics is not understood yet. In this paper, we report the results from a new RM-campaign of Mrk 79, which was undertaken by Lijiang 2.4-m telescope. Mrk 79 is seeming to come out the faint state, the mean flux approximates a magnitude fainter than historical record. We successfully measured the lags of the broad emission lines including Hβ λ4861, Hγ λ4340, He II λ4686 and He I λ5876 with respect to the varying AGN continuum. Based on the broad Hβ λ4861 line, we measured black hole (BH) mass of M• = 5.13+1−1..5755×107M, estimated accretion rates of M• = (0.05 ± 0.02) LEdd c−2, indicating that Mrk 79 is a sub-Eddington accretor. We found that Mrk 79 deviates from the canonical Radius−Luminosity relationship. The marginal blueshift of the broad He II λ4686 line detected from rms spectrum indicates outflow of high-ionization gas. The velocity-resolved lag profiles of the broad Hγ λ4340, Hβ λ4861, and He I λ5876 lines show similar signatures that the largest lag occurs in the red wing of the lines then the lag decreases to both sides. These signatures should suggest that the BLR of Keplerian motion probably exists the outflow gas motion. All findings including UFOs, warm absorbers, and the kinematics of high- and low-ionization BLR, may provide an indirect evidence that the BLR of Mrk 79 probably originates from disk wind. Copyright © 2019, The Authors. All rights reserved.

关键词： Kinematics