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The double blue straggler sequence in NGC 2173: a field contamination artefact?

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arXiv 2018年

作者： Li, Chengyuan Deng, Licai de Grijs, Richard Jiang, Dengkai Xin, Yu Department of Physics and Astronomy Macquarie University Balaclava Road SydneyNSW2109 Australia Department of Astronomy China West Normal University Nanchong637002 China School of Astronomy and Space Science University of the Chinese Academy of Sciences 20A Datun Road Beijing100012 China International Space Science Institute–Beijing 1 Nanertiao Zhongguancun Beijing100190 China Yunnan Observatories Chinese Academy of Sciences Kunming650216 China Key Laboratory for the Structure and Evolution of Celestial Objects Chinese Academy of Sciences Kunming650011 China Center for Astronomical Mega-Science Chinese Academy of Sciences Beijing100012 China

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

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

Application of screened Coulomb potential in fitting DBV star PG 0112+104

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arXiv 2017年

作者： Chen, H. Institute of Astrophysics Chuxiong Normal University Chuxiong675000 China School of Physics and Electronical Science Chuxiong Normal University Chuxiong675000 China Key Laboratory for the Structure and Evolution of Celestial Objects Chinese Academy of Sciences P.O. Box 110 Kunming650011 China

With 78.7 days of observations for PG 0112+104, a pulsating DB star, from Campaign 8 of Kepler 2 mission, Hermes et al. made a detailed mode identification. A reliable mode identification, with 5 l = 1 modes, 3 l = 2 modes, and 3 l = 1 or 2 modes, was identified. Grids of DBV star models are evolved by WDEC with element diffusion effect of pure Coulomb potential and screened Coulomb potential. Fitting the identified modes of PG 0112+104 by the calculated ones, we studied the difference of element diffusion effect between adopting pure Coulomb potential and screened Coulomb potential. Our aim is to reduce the fitting error by studying new input physics. The starting models including their chemical composition profile are from white dwarf models evolved by MESA. They were calculated following the stellar evolution from the main sequence to the start of the white dwarf cooling sequences. The optimal parameters are basically consistent with that of previous spectroscopic and asteroseismological studies. The pure and screened Coulomb potential lead to different composition profiles of the C/O-He interface area. High k modes are very sensitive to the area. However, most of the observed modes for PG 0112+104 are low k modes. The σRMS taking the screened Coulomb potential is reduced by 4% compared with taking the pure Coulomb potential when fitting the identified low k modes of PG 0112+104. Fitting the Kepler 2 data with our models improved the σRMS of the fit by 27%. Copyright © 2017, The Authors. All rights reserved.

关键词： White dwarfs

Lunar-based Ultraviolet Telescope study of the well-known Algol-type binary TW Dra

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Research in Astronomy and Astrophysics 2016年第6期16卷 93-98页

作者： Wen-Ping Liao Sheng-Bang Qian Miloslav Zejdat Li-Ying Zhu Lin-Jia Li Yunnan Observatories Chinese Academy of Sciences Kunming 650216 China Key Laboratory of the Structure and Evolution of Celestial Objects Chinese Academy of Sciences Kunming 650216China University of Chinese Academy of Sciences Beijing 100049 China Department of Theoretical Physics and Astrophysics Masaryk University Kotlarska 2 CZ-611 37 Brno Czech Republic

By using the Lunar-based Ultraviolet Telescope （LUT） from 2014 December 2 to December 4, the first near-UV light curve of the well-known Algol-type binary TW Dra is reported, which is analyzed with the 2013 version of the W-D code. Our solutions confirmed that TW Dra is a semi-detached binary system where the secondary component fills its Roche lobe. The mass ratio and a high inclination are obtained （q = 0.47, i = 86.68°）. Based on 589 available data spanning more than one century, the complex period changes are studied. Secular increase and three cyclical changes are found in the corresponding orbital period analysis. The secular increase changes reveal mass transfer from the secondary component to the primary one at a rate of 6.8 × 10-7 M yr-1. One large cyclical change of 116.04 yr may be caused by disturbance of visual component ADS 9706B orbiting TW Dra （ADS 9706A）, while the other two cyclical changes with shorter periods of 22.47 and 37.27 yr can be explained as the result of two circumbinary companions that are orbiting around TW Dra, where the two companions are in simple 3 ： 5 orbit-rotation resonances. TW Dra itself is a basic binary in a possible sextuple system with the configuration （1 ＋ 1）＋（1 ＋ 1）＋（1 ＋ 1）, which further suggests that multiplicity may be a fairly common phenomenon in close binary systems.

关键词： stars： binaries： close -- stars： binaries： eclipsing -- stars： individual （TW Draco）

Physical parameters and orbital period variation of a newly discovered cataclysmic variable GSC 4560-02157

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Research in Astronomy and Astrophysics 2016年第10期16卷 55-62页

作者： Zhong-Tao Han Sheng-Bang Qian Irina Voloshina Vladimir G. Metlov Li-Ying Zhu Lin-Jia Li Yunnan Observatories Chinese Academy of Sciences Kunming 650216 China Key Laboratory of the Structure and Evolution of Celestial Objects Chinese Academy of Sciences Kunming 650216China University of Chinese Academy of Sciences Beijing 100049 China Sternberg Astronomical Institute Moscow State University Universitetskij prospect 13 Moscow 119992 Russia

GSC 4560-02157 is a new eclipsing cataclysmic variable with an orbital period of 0.265359 days. By using the published V- and R-band data together with our observations, we discovered that the O - C curve of GSC 4560-02157 may show a cyclic variation with a period of 3.51 years and an amplitude of 1.40 min. If this variation is caused by a light travel-time effect via the existence of a third body, then its mass can be derived as M3 sin i1≈ 91.08 Mjup, and it should be a low-mass star. In addition, several physical parameters were measured. The color of the secondary star was determined to be V - R = 0.77（±0.03） which corresponds to a spectral type of K2-3. The secondary star＇s mass was estimated as M2 = 0.73（±0.02） Mo by combing the derived V - R value around phase 0 with the assumption that it obeys the mass-luminosity relation for main sequence stars. This mass is consistent with the mass-period relation for CV donor stars. For the white dwarf, the eclipse durations and contacts of the white dwarf yield an upper limit on the white dwarf＇s radius corresponding to a lower limit on mass of M1 ≈ 0.501 M⊙. The overestimated radius and previously published spectral data indicate that the boundary layer may have a very high temperature.

关键词： techniques： photometric -- stars： binaries： cataclysmic variables -- stars： individual：GSC 4560-02157

The progenitors of type Ia supernovae in the semidetached binaries with red giant donors

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arXiv 2017年

作者： Liu, D. Wang, B. Ge, H. Chen, X. Han, Z. Yunnan Observatories Chinese Academy of Sciences 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 Center for Astronomical Mega-Science Chinese Academy of Sciences Beijing100012 China

Context. The companions of the exploding carbon-oxygen white dwarfs (CO WDs) for producing type Ia supernovae (SNe Ia) are still not conclusively confirmed. A red-giant (RG) star has been suggested to be the mass donor of the exploding WD, named as the symbiotic channel. However, previous studies on the this channel gave a relatively low rate of SNe Ia. Aims. We aim to systematically investigate the parameter space, Galactic rates and delay time distributions of SNe Ia from the symbiotic channel by employing a revised mass-transfer prescription. Methods. We adopted an integrated mass-transfer prescription to calculate the mass-transfer process from a RG star onto the WD. In this prescription, the mass-transfer rate varies with the local material states. Results. We evolved a large number of WD+RG systems, and found that the parameter space of WD+RG systems for producing SNe Ia is significantly enlarged. This channel could produce SNe Ia with intermediate and old ages, contributing to at most 5% of all SNe Ia in the Galaxy. Our model increases the SN Ia rate from this channel by a factor of 5. We suggest that the symbiotic systems RS Oph and T CrB are strong candidates for the progenitors of SNe Ia. Conclusions. Copyright © 2017, The Authors. All rights reserved.

关键词： White dwarfs

A Polarization Sequence for Type Ia Supernovae?

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arXiv 2017年

作者： Meng, X. Zhang, J. Han, Z. 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

Early polarization observations on Type Ia supernovae (SNe Ia) may reveal the geometry of supernova ejecta, and then put constraints on their explosion mechanism and their progenitor model. We performed a literature search of SNe Ia with polarization measurements and determined the polarization and relative equivalent width (REW) of Si II 635.5-nm absorption feature at -5 days after the maximum light. We found that either the distribution of observed polarization degree is bimodal, i.e. the broad line SNe Ia have systematically higher polarization than all other SNe Ia, or all kind of SNe Ia share the same polarization sequence, i.e. the polarization of Si II 635.5-nm absorption feature increases with the REW. We also discussed the potential meaning of the discovery on the explosion mechanism and progenitor model of SNe Ia. Copyright © 2017, The Authors. All rights reserved.

关键词： Supernovae

The first photometric study of the short period shallow contact system LO Comae

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arXiv 2017年

作者： Zhang, Y. Han, Q.W. Liu, J.Z. Xinjiang Astronomical Observatory Chinese Academy of Sciences Urumqi830011 China Yunnan Observatory Chinese Academy of Sciences 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

In this paper, the first complete photometric light curves in the B, V, and R passbands for an eclipsing binary LO Com are presented, and the photometric solution for the LO Com is derived by analyzing these light curves by using the Wilson and Devinney code. From the photometric solution, it is found that the LO Com is a W-type W UMa binary with a mass ratio of q = m2=m1= 2:478 and a contact degree of f = (3.2±0.25)%. By combining the two new minimum times with those published earlier in the literature, we have found that the (O-C) curve shows a downward parabolic variation corresponding to a long-term decrease in the orbital period with a rate of dP/dt = -1.18×10-7days yr-1. This long-term decrease in its orbital period may be caused by mass transfer from the more massive component to the less massive one. Copyright © 2017, The Authors. All rights reserved.

关键词： Photometry