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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

A Close-in Substellar object Orbiting the sdOB-type Eclipsing-Binary System NSVS14256825

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arXiv 2019年

作者： Zhu, L.-Y. Qian, S.-B. Lajús, Fernández E. Wang, Z.-H. Li, L.-J. P. O. Box 110 Kunming650216 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 Facultad de Ciencias AstronómicasyGeofísicas Universidad Nacional de La Plata La PlataBuenos Aires1900 Argentina La Plata BA Paseo del Bosque s/n B1900FWA Argentina

NSVS 14256825 is the second sdOB + dM eclipsing binary systems with an orbital period of 2.65 hours. The special binary was reported to contain circumbinary planets or brown dwarfs by using the timing method. However, different results were derived by different authors because of the insufficient coverage of eclipse timings. Since 2008, we have monitored this binary for about 10 years by using several telescopes and 84 new times of light minimum in high precision were obtained. It is found that the O-C curve is increasing recently and it shows a cyclic variation with a period of 8.83 years and amplitude of 46.31 seconds. The cyclic change cannot be explained by magnetic activity cycles of the red-dwarf component because the required energy is much larger than that radiated by this component in one whole period. This cyclic change detected in NSVS1425 could be explained by the light-travel time effect via the presence of a third body. The lowest mass of the third body is determined as 14.15 Mjup that is in the transition between planets and brown dwarfs. The substellar object is orbiting around this evolved binary at an orbital separation around 3 AU with an eccentricity of 0.12. These results indicate that NSVS 14256825 is the first sdOB-type eclipsing binary consisting of a hierarchical substellar object. The detection of a close-in substellar companion to NSVS 14256825 will provide some insights on the formation and evolution of sdOB-type binaries and their companions. Copyright © 2019, The Authors. All rights reserved.

关键词： Systems (metallurgical)

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

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

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

An extreme X-ray variability event of a weak-line quasar

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arXiv 2020年

作者： Ni, Q. Brandt, W.N. Yi, W. Luo, B. Timlin, J.D. Hall, P.B. Liu, Hezhen Plotkin, R.M. Shemmer, O. Vito, F. Wu, Jianfeng Department of Astronomy & Astrophysics Pennsylvania State University Davey Lab University ParkPA16802 United States Institute for Gravitation and the Cosmos Pennsylvania State University University ParkPA16802 United States Department of Physics Pennsylvania State University University ParkPA16802 United States Yunnan Observatories Kunming650216 China Key Laboratory for the Structure and Evolution of Celestial Objects Chinese Academy of Sciences Kunming650216 China School of Astronomy and Space Science Nanjing University Nanjing Jiangsu210093 China Key Laboratory of Modern Astronomy and Astrophysics Nanjing University Ministry of Education Nanjing Jiangsu210093 China Collaborative Innovation Center of Modern Astronomy and Space Exploration Nanjing210093 China Department of Physics & Astronomy York University 4700 Keele Street TorontoONM3J 1P3 Canada Department of Physics University of Nevada 1664 N. Virginia St RenoNV89557 United States Department of Physics University of North Texas DentonTX76203 United States Instituto de Astrofísica Centro de Astroingeniería Facultad de Física Pontificia Universidad Católica de Chile Casilla 306 Santiago 22 Chile Chinese Academy of Sciences South America Center for Astronomy National Astronomical Observatories CAS Beijing100012 China Department of Astronomy Xiamen University Xiamen Fujian361005 China

We report the discovery of an extreme X-ray ux rise (by a factor of 20) of the weak-line quasar SDSS J153913.47+395423.4 (hereafter SDSS J1539+3954) at z = 1.935. SDSS J1539+3954 is the most-luminous object among radio-quiet type 1 AGNs where such dramatic X-ray variability has been observed. Before the X-ray ux rise, SDSS J1539+3954 appeared X-ray weak compared with the expectation from its UV ux;after the rise, the ratio of its X-ray ux and UV ux is consistent with the majority of the AGN population. We also present a contemporaneous HET spectrum of SDSS J1539+3954, which demonstrates that its UV continuum level remains generally unchanged despite the dramatic increase in the X-ray ux, and its C iv emission line remains weak. The dramatic change only observed in the X-ray ux is consistent with a shielding model, where a thick inner accretion disk can block our line of sight to the central X-ray source. This thick inner accretion disk can also block the nuclear ionizing photons from reaching the high-ionization broad emission-line region, so that weak high-ionization emission lines are observed. Under this scenario, the extreme X-ray variability event may be caused by slight variations in the thickness of the disk. This event might also be explained by gravitational light-bending effects in a reection model. Copyright © 2020, The Authors. All rights reserved.

关键词： Electromagnetic wave emission

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

The Radio and -ray variability analysis of S5 0716+714

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arXiv 2018年

作者： Li, H.Z. Jiang, Y.G. Yi, T.F. Guo, D.F. Chen, X. Zhang, H.M. Gao, Q.G. Lu, F.W. Ren, J.Y. Physics Department Yuxi Normal University Yuxi653100 China Key Laboratory for the Structure and Evolution of Celestial Objects Chinese Academy of Sciences Kunming650011 China Shandong Provincial Key Laboratory of Optical Astronomy and Solar-Terrestrial Environment Institute of Space Sciences Shandong University Weihai264209 China Physics Department Yunan Normal University Kunming Yunnan650092 China GXU-NAOC Center for Astrophysics and Space Sciences Department of Physics Guangxi University Nanning530004 China Guangxi Key Laboratory for the Relativistic Astrophysics Nanning530004 China

We have studied the variability of S5 0716+714 at radio 15 GHz and -ray band using three different methods. A possible periodicity of P15GHz = 266.0 ± 11.5 and P = 344.0 ± 16.4 days are obtained for radio 15 GHz and -ray light curves, respectively. The variability may be related to the intrinsically emission mechanism. The difference between the variability timescales of radio 15 GHz and -ray may be due to that the emission of radio 15 GHz is produced via the synchrotron process, while the -ray is produced by both the SSC and EC processes. Copyright © 2018, The Authors. All rights reserved.

关键词： Galaxies

Verification of the diffusive shock acceleration in Mrk 501

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arXiv 2018年

作者： Zheng, Y.G. Long, G.B. Yang, C.Y. Bai, J.M. Department of Physics Yunnan Normal University Kunming650092 China Yunnan Observatories Chinese Academy of Sciences Kunming650011 China Shandong Prov. Key Lab. of Optical Astronomy and Solar-Terrestrial EnvironmentShandong University Weihai264209 Key Laboratory for Structure and Evolution of Celestial Objects Chinese Academy of Sciences China Department of Physics and Astronomy Sun Yat-Sen University Zhuhai519082 China

The present work considers a plane shock front propagating along a cylindrical jet. Electrons experience the diffusive shock acceleration around the shock front, and sub-sequently drift away into the downstream flow in which they emit most of their energy. Assuming a proper boundary condition at the interface between the shock zone and the downstream zone, we solve the transport equation for the electrons in the down-stream flow zone, where the combined effects of escape, synchrotron and IC cooling in the Thomson regime are taken into account. Using the electron spectrum obtained in this manner we calculate the multi-wavelength spectral energy distribution of Mrk 501 in the synchrotron self-Compton scenario. We check numerically if the Klein-Nishina cross-section could be approximated to the Thomsom regime. We consider whether the model results yield physically reasonable parameters, and further discuss some of implications of the model results. It suggests that the process of diffusive shock acceleration operates in the outflow of Mrk 501. Copyright © 2018, The Authors. All rights reserved.

关键词： Shock waves