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TY Pup: a low-mass-ratio and deep contact binary as a progenitor candidate of luminous red novae

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arXiv 2018年

作者： Sarotsakulchai, T. Qian, S.-B. Soonthornthum, B. Zhou, X. Zhang, J. Reichart, D.E. Haislip, J.B. Kouprianov, V.V. Poshyachinda, S. Yunnan Observatories Chinese Academy of Sciences Kunming650216 China Key Laboratory of the Structure and Evolution of Celestial Objects Chinese Academy of Sciences Kunming650216 China Center for Astronomical Mega-Science Chinese Academy of Sciences 20A Datun Rd. Chaoyang District Beijing100012 China University of Chinese Academy of Sciences 19 A Yuquan Rd. Shijingshan Beijing100049 China National Astronomical Research Institute of Thailand Ministry of Science and Technology Bangkok Thailand Department of Physics and Astronomy University of North Carolina CB #3255 Chapel HillNC27599 United States

TY Pup is a well-known bright eclipsing binary with an orbital period of 0.8192 days. New light curves in B, V, (RI)C bands were obtained with the 0.61-m reflector robotic telescope (PROMPT-8) at CTIO in Chile during 2015 and 2017. By analysing those photometric data with the W-D method, it is found that TY Pup is a low-mass-ratio (q ∼ 0.184) and deep contact binary with a high fill-out factor (84.3 %). An investigation of all available times of minimum light including three new ones obtained with the 60-cm and the 1.0-m telescopes at Yunnan Observatories in China indicates that the period change of TY Pup is complex. An upward parabolic variation in the O − C diagram is detected to be superimposed on a cyclic oscillation. The upward parabolic change reveals a long-term continuous increase in the orbital period at a rate of dP/dt = 5.57(±0.08) × 10−8 d yr−1. The period increase can be explained by mass transfer from the less massive component (M2 ∼ 0.3M☉) to the more massive one (M1 ∼ 1.65M☉). The binary will be merging when it meets the criterion that the orbital angular momentum is less than 3 times the total spin angular momentum, i.e., Jorb rot. This suggests that the system will finally merge into a rapid-rotating single star and may produce a luminous red nova. The cyclic oscillation in the O − C diagram can be interpreted by the light-travel time effect (LITE) via the presence of a third body. Copyright © 2018, The Authors. All rights reserved.

关键词： Stars

Study of the X-ray properties of the neutron-star binary 4U 1728-34 from the soft to hard state

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arXiv 2019年

作者： Wang, Yanan Méndez, Mariano Altamirano, Diego Zhang, Guobao Belloni, T.M. Ribeiro, Evandro M. Linares, M. Sanna, Andrea Motta, S.E. Tomsick, John A. Kapteyn Astronomical Institute University of Groningen PO BOX 800 GroningenNL-9700 AV Netherlands Physics & Astronomy University of Southampton Southampton HampshireSO17 1BJ United Kingdom 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 Istituto Nazionale di Astrofisica Osservatorio Astronomico di Brera Via E. Bianchi 46 MerateI-23807 Italy Departament de Física EEBE Universitat Politècnica de Catalunya Av. Eduard Maristany 16 BarcelonaE-08019 Spain BarcelonaE-08034 Spain Dipartimento di Fisica Universitá degli Studi di Cagliari SP Monserrato-Sestu km 0.7 MonserratoI-09042 Italy University of Oxford Department of Physics Astrophysics Denys Wilkinson Building Keble Road OxfordOX1 3RH United Kingdom Space Sciences Laboratory University of California 7 Gauss Way BerkeleyCA94720-7450 United States

We studied five XMM-Newton observations of the neutron-star binary 4U 1728-34 covering the hard, intermediate and soft spectral states. By jointly fitting the spectra with several reflection models, we obtained an inclination angle of 25◦ − 53◦ and an iron abundance up to 10 times the solar. From the fits with reflection models, we found that the fluxes of the reflection and the Comptonised components vary inconsistently;since the latter is assumed to be the illuminating source, this result possibly indicates the contribution of the neutron star surface/boundary layer to the disc reflection. As the source evolved from the relatively soft to the intermediate state, the disc inner radius decreased, opposite to the prediction of the standard accretion disc model. We also explore the possible reasons why the supersolar iron abundance is required by the data and found that this high value is probably caused by the absence of the hard photons in the XMM-Newton data. Copyright © 2019, The Authors. All rights reserved.

关键词： Stars

Discovery of an active intermediate-mass black hole candidate in the barred bulgeless galaxy NGC 3319

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arXiv 2018年

作者： Jiang, Ning Wang, Tinggui Zhou, Hongyan Shu, Xinwen Yang, Chenwei Dou, Liming Sun, Luming Dong, Xiaobo Wang, Shaoshao Yang, Huan Key Laboratory for Research in Galaxies and Cosmology Department of Astronomy University of Science and Technology of China Chinese Academy of Sciences Hefei Anhui230026 China School of Astronomy and Space Sciences University of Science and Technology of China Hefei Anhui230026 China Polar Research Institute of China 451 Jinqiao Road Shanghai200136 China Department of Physics Anhui Normal University Wuhu Anhui241000 China Center for Astrophysics Guangzhou University Guangzhou510006 China Yunnan Observatories Chinese Academy of Sciences Kunming Yunnan650011 China Key Laboratory for the Structure and Evolution of Celestial Objects Chinese Academy of Sciences Kunming Yunnan650011 China Las Campanas Observatory Carnegie Institution for Science Casilla 601 La Serena Chile

We report the discovery of an active intermediate-mass black hole (IMBH) candidate in the center of nearby barred bulgeless galaxy NGC 3319. The point X-ray source revealed by archival Chandra and XMM−Newton observations is spatially coincident with the optical and UV galactic nuclei from Hubble Space Telescope observations. The spectral energy distribution derived from the unresolved X-ray and UV-optical flux is comparable with active galactic nuclei (AGNs) rather than ultra-luminous X-ray sources, although its bolometric luminosity is only 3.6 × 1040 erg s−1. Assuming an Eddington ratio range between 0.001 and 1, the black hole mass (MBH) will be located at 3 × 102 − 3 × 105 M☉, placing it in the so-called IMBH regime and could be the one of the lowest reported so far. Estimates from other approaches (e.g., fundamental plane, X-ray variability) also suggest MBH. 105 M☉. Similar to other BHs in bulgeless galaxies, the discovered IMBH resides in a nuclear star cluster with mass of ∼ 6 × 106 M☉. The detection of such a low-mass BH offers us an ideal chance to study the formation and early growth of SMBH seeds, which may result from the bar-driven inflow in late-type galaxies with a prominent bar such as NGC 3319. Copyright © 2018, The Authors. All rights reserved.

关键词： Galaxies

A search for exoplanets around northern circumpolar stars. IV. Six planet candidates to the K giants, HD 44385, HD 97619, HD 106574, HD 118904, HD 164428, and HD 202432

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arXiv 2018年

作者： Jeong, Gwanghui Han, Inwoo Park, Myeong-Gu Hatzes, Artie P. Bang, Tae-Yang Gu, Shenghong Bai, Jinming Lee, Byeong-Cheol Korea Astronomy and Space Science Institute 776 Daedeokdae-Ro Youseong-Gu Daejeon34055 Korea Republic of Korea University of Science and Technology 217 Gajeong-ro Yuseong-gu Daejeon34113 Korea Republic of Department of Astronomy and Atmospheric Sciences Kyungpook National University Daegu41566 Korea Republic of Thüringer Landessternwarte Tautenburg Sternwarte 5 TautenburgD-07778 Germany Yunnan Observatories Chinese Academy of Sciences Kunming650216 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

We report the discovery of long-period radial velocity (RV) variations in six intermediate mass K giant stars using precise RV measurements. These discoveries are part of the Search for Exoplanets around Northern Circumpolar Stars (SENS) survey being conducted at the Bohyunsan Optical Astronomy Observatory (BOAO). The nature of the RV variations was investigated by looking for photometric and line shape variations. We can find no variability with the RV period in these quantities and conclude that RV variations are most likely due to unseen sub-stellar companions. Orbital solutions for the six stars yield orbital periods in the range 418 - 1065 d and minimum masses in the range 1.9 - 8.5 MJ. These properties are typical on planets around intermediate mass stars. Our SENS survey so far has about an 8% confirmed planet occurrence rate, and it will provide better statistics on planets around giant stars when the survey is completed. Copyright © 2018, The Authors. All rights reserved.

关键词： Extrasolar planets

Reddening and he I∗ λ10830 absorption lines in three narrow-line seyfert 1 galaxies

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arXiv 2017年

作者： Zhang, Shaohua Zhou, Hongyan Shi, Xiheng Liu, Wenjuan Pan, Xiang Jiang, Ning Ji, Tuo Jiang, Peng Wang, Shufen Polar Research Institute of China 451 Jinqiao Road Shanghai200136 China Key Laboratory for Researches in Galaxies and Cosmology Department of Astronomy University of Sciences and Technology of China Chinese Academy of Sciences Hefei Anhui230026 China Key Laboratory for the Structure and Evolution of Celestial Objects Yunnan Observatories Chinese Academy of Sciences Kunming Yunnan650011 China

We report the detection of heavy reddening and the He I∗ λ10830 absorption lines at the AGNs' redshift in three Narrow-line Seyfert 1 galaxies: SDSS J091848.61+211717.0, SDSS J111354.66+124439.0, and SDSS J122749.13+321458.9. They exhibit very red optical to nearinfrared colors, narrow Balmer/Paschen broad emission lines and He I∗ λ10830 absorption lines. The ultraviolet-optical-infrared nucleus continua are reddened by the SMC extinction law of E(B - V ) ∼ 0.74, 1.17, and 1.24 mag for three objects, which are highly consistent with the values obtained from the broad-line Balmer decrements, but larger than those of narrow emission lines. The reddening analysis suggests the extinction dust simultaneously obscure the accretion disk, the broad emission line region, and the hot dust from the inner edge of the torus. It is possible that the dust obscuring the AGN structures are the dusty torus itself. Furthermore, the Cloudy analysis of the He I∗ λ10830 absorption lines propose the distance of the absorption materials to be the extend scale of the torus. That greatly increases probabilities of the obscure and absorption materials being the dusty torus. Copyright © 2017, The Authors. All rights reserved.

关键词： Galaxies

Applications of the k-ω model in stellar evolutionary models

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arXiv 2017年

作者： Li, Yan Yunnan Observatories Chinese Academy of Sciences Kunming650216 China Key Laboratory for the Structure and Evolution of Celestial Objects Chinese Academy of Sciences University of Chinese Academy of Sciences Beijing100049 China Center for Astronomical Mega-Science Chinese Academy of Sciences Beijing100012 China

The k-ω model for turbulence was first proposed by Kolmogorov (1942). A new k-ω model for stellar convection was developed by Li (2012), which could reasonably describe turbulent convection not only in the convectively unstable zone but also in the overshooting regions. We have revised the k-ω model by improving several model assumptions (including the macro-length of turbulence, convective heat flux, and turbulent mixing diffusivity, etc.), making it applicable for not only convective envelopes but also convective cores. Eight parameters are introduced in the revised k-ω model. It should be noted that the Reynolds stress (turbulent pressure) is neglected in the equation of hydrostatic support. We have applied it into solar models and 5M stellar models, in order to calibrate the eight model parameters, as well as to investigate the effects of the convective overshooting on the sun and intermediate mass stellar models. Copyright © 2017, The Authors. All rights reserved.

关键词： Turbulence

Linear polarization, circular polarization, and depolarization of gamma-ray bursts: A simple case of jitter radiation

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arXiv 2017年

作者： Mao, Jirong Wang, Jiancheng Yunnan Observatories Chinese Academy of Sciences Kunming Yunnan Province650011 China Center for Astronomical Mega-Science Chinese Academy of Sciences 20A Datun Road Beijing100012 Key Laboratory for the Structure and Evolution of Celestial Objects Chinese Academy of Sciences Kunming650011

Linear and circular polarizations of gamma-ray bursts (GRBs) have been detected during recent years. We adopt a simplified model to investigate GRB polarization characteristics in this paper. A compressed two-dimensional turbulent slab containing stochastic magnetic fields is considered, and jitter radiation can produce the linear polarization under this special magnetic field topology. Turbulent Faraday rotation measure (RM) of this slab makes strong wavelengthdependent depolarization. The jitter photons can also scatter with those magnetic clumps inside the turbulent slab, and a nonzero variance of the Stokes parameter V can be generated. Furthermore, the linearly and circularly polarized photons in the optical and radio bands may suffer heavy absorptions from the slab. Thus we consider the polarized jitter radiation transfer processes. Finally, we compare our model results with the optical detections of GRB 091018, GRB 121024A, and GRB 131030A. We suggest simultaneous observations of GRB multi-wavelength polarization in the future. Copyright © 2017, The Authors. All rights reserved.

关键词： Stars

New zz ceti stars from the lamost survey

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arXiv 2017年

作者： Su, Jie Fu, Jianning Lin, Guifang Chen, Fangfang Khokhuntod, Pongsak Li, Chunqian Department of Astronomy Beijing Normal University Beijing100875 China Key Laboratory for the Structure and Evolution of Celestial Objects Chinese Academy of Sciences Yunnan Observatories Chinese Academy of Sciences Kunming650216 China Center for Astronomical Mega-Science Chinese Academy of Sciences Beijing100012 China

The spectroscopic sky survey carried out by the Large Sky Area Multi-object Fiber Spectroscopic Telescope (LAMOST) provides the largest stellar spectra library in the world until now. A large number of new DA white dwarfs had been identified based on the LAMOST spectra. The effective temperature (Teff) and surface gravity (log g) of most DA white dwarfs were determined and published in the catalogs, e.g. Zhao et al. (2013), Rebassa-Mansergas et al. (2015), Gentile Fusillo et al. (2015) and Guo et al. (2015). We selected ZZ Ceti candidates from the published catalogs by considering whether their Teff are situated in the ZZ Ceti instability strip. The follow-up time-series photometric observations for the candidates were performed in 2015 and 2016. Four stars: LAMOST J004628.31+343319.90, LAMOST J062159.49+252335.9, LAMOST J010302.46+433756.2 and LAMOST J013033.90+273757.9 are finally confirmed to be new ZZ Ceti stars. They show dominant peaks with amplitudes rising above the 99.9% confidence level in the amplitude spectra. As LAMOST J004628.31+343319.90 has an estimated mass of ∼ 0.40 M* and LAMOST J013033.90+273757.9 has a mass of ∼ 0.45 M* derived from their log g values, these two stars are inferred to be potential helium-core white dwarfs. Copyright © 2017, The Authors. All rights reserved.

关键词： White dwarfs

The discrepancy between Einstein mass and dynamical mass for sis and power-law mass models

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arXiv 2018年

作者： Li, Rui Wang, Jiancheng Shu, Yiping Xu, Zhaoyi Yunnan Observatories Chinese Academy of Sciences 396 Yangfangwang Guandu District Kunming650216 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 Key Laboratory for the Structure and Evolution of Celestial Objects Chinese Academy of Sciences 396 Yangfangwang Guandu District Kunming650216 China Purple Mountain Observatory Chinese Academy of Sciences 2 West Beijing Road Nanjing Jiangsu210008 China Institute of Astronomy Madingley Road CambridgeCB3 0HA United Kingdom

We investigate the discrepancy between the two-dimensional projected lensing mass and the dynamical mass for an ensemble of 97 strong gravitational lensing systems discovered by the Sloan Lens ACS (SLACS) Survey, the BOSS Emission-Line Lens Survey (BELLS), and the BELLS for GALaxy-Lyα EmitteR sYstems (BELLS GALLERY) Survey. We fit the lensing data to obtain the Einstein mass, and use the velocity dispersion of the lensing galaxies provided by the Sloan Digital Sky Survey (SDSS) to get the projected dynamical mass within the Einstein radius by assuming the power-law mass approximation. The discrepancy is found to be obvious and quantified by Bayesian analysis. For the singular isothermal sphere (SIS) mass model, we obtain that the Einstein mass is 20.7% more than the dynamical mass, and the discrepancy increases with the redshift of the lensing galaxies. For more general power-law mass model, the discrepancy still exists within 1σ credible region. The main reason of the the discrepancy could be mass contamination, including all invisible masses along the line of sight. In addition, the measurement errors and the approximation of the mass models could lead to part of the discrepancy. Copyright © 2018, The Authors. All rights reserved.

关键词： Galaxies