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The Photometric Study of Neglected Short-Period Eclipsing Binary BS Vulpeculae

Proceedings of the International Astronomical Union 2012年第S282期7卷 83-84页

作者： Miloslav Zejda Zdeněk Mikulášek Liying Zhu Shengbang Qian Jiří Liška Department of Theoretical Physics and Astrophysics Masaryk University CZ-611 37 Brno Czech Republic e-mail: zejda@physics.muni.cz mikulas@physics.muni.cz VŠB – Technical Univ. Observatory and Planetarium of J. Palisa Ostrava Czech Rep. National Astronomical Observatories/Yunnan Observatory Chinese Academy of Sciences P.O. Box 110 650011 Kunming China e-mail: zhuly@*** qsb@*** Key Laboratory for the Structure and Evolution of Celestial Objects Chinese Academy of Sciences P.O. Box 110 650011 Kunming China

The preliminary results of a study of a neglected, relatively bright, short-periodic (P=0.48 d), near contact eclipsing binary BS Vulpeculae is given. We present our new complete (BVRI) light curves, and physical para... 详细信息

关键词： stars: binaries: eclipsing stars: fundamental parameters stars: individual BS Vul

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Infrared spectral evolution of carbon stars

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Research in Astronomy and Astrophysics 2010年第4期10卷 363-382页

作者： Pei-Sheng Chen Xiao-Hong Yang Hong-Guang Shan National Astronomical Observatories /Yunnan Observatory and Key Laboratory for the Structure and Evolution of Celestial Objects Chinese Academy of SciencesKunming 650011China Department of Physics Chongqing UniversityChongqing 400044China

We collected almost all Highly Processed Data Products （HPDP） of ISO SWS01 spectra for the Galactic visual carbon stars,infrared carbon stars,extreme carbon stars and carbon-rich proto-planetary nebulae （PPNs）.Those infrared spectra are primarily analyzed and *** is shown that either spectral shapes/peaks,or main molecular/dust features are evidenced to change in the sequence of visual carbon stars,infrared carbon stars,extreme carbon stars and carbon-rich ***,in this sequence,continua are gradually changed from blue to red and locations of spectral peaks of continua are also gradually changed from short wavelengths to long *** addition,in this sequence,intensities of main molecular/dust features are also gradually changed from prominent in the short wavelengths to prominent in the long ***,from 2MASS and IRAS photometric data,the sequence is also *** in this paper strongly support the previous suggestion for the evolution sequence of carbon-rich objects in our Galaxy,that is the sequence of visual carbon stars → infrared carbon stars → extreme carbon stars → carbon-rich PPNs.

关键词： infrared：stars - stars：carbon - stars：late type

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Is Low-Frequency-Peaked BL Lac Object OJ 287 a TeV Emitter？

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Chinese Physics Letters 2010年第11期27卷 205-207页

作者：陈亮白金明 National Astronomical Observatories Yunnan Observatory Chinese Academy of Sciences Kunming 650011 Key Laboratory for the Structure and Evolution of Celestial Objects Chinese Academy of Sciences Kunming 650011 The Graduate School of Chinese Academy of Sciences Beijing 100049

It is well known that there are only two low-frequency-peaked BL Lac objects （LBLs： BL Lacertae and S5 0716＋714） and one flat spectrum radio quasar （FSRQ： 3C 279） among more than 30 active galactic nuclei （AGNs） with detected TeV emissions. We study the spectral energy distribution （SED） of a famous LBL OJ 287, whose light curve has a 12-y period. Using a homogeneous one-zone synchrotron ＋ synchrotron-self Compton model, we model the quasi-simultaneous broad-band SED of OJ 287. With some reasonable assumptions, we extrapolate the model to the high state of OJ 287 and predict its γ？ray emissions. Taking into account the absorption of γ-ray by the extragalactic background light （EBL）, we find that the TeV emission of OJ 287 in high state is slightly higher than the sensitivity of H.E.S.S. The study on SEDs of OJ 287 has implications to unveil the origin of jet activity during its 12-y period and the properties of EBL.

关键词： Astrophysics and astroparticles

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A likely candidate of type Ia supernova progenitors: the X-ray pulsating companion of the hot subdwarf HD 49798

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Research in Astronomy and Astrophysics 2010年第7期10卷 681-688页

作者： Bo Wang Zhan-Wen Han National Astronomical Observatories / Yunnan Observatory Chinese Academy of Sciences Kunming 650011 China Key Laboratory for the Structure and Evolution of Celestial Objects Chinese Academy of Sciences Kunming 650011 China Graduate University of Chinese Academy of Sciences Beijing 100049 China

HD 49798 is a hydrogen depleted subdwarf 06 star and has an X-ray pulsating companion （RX J0648.0-4418）. The X-ray pulsating companion is a massive white dwarf. Employing Eggleton＇s stellar evolution code with the optically thick wind assumption, we find that the hot subdwarf HD 49798 and its X-ray pulsating companion could produce a type Ia supernova （SN Ia） in future evolution. This implies that the binary system is a likely candidate of an SN Ia progenitor. We also discuss the possibilities of some other WD ＋ He star systems （e.g. V445 Pup and KPD 1930＋2752） for producing SNe Ia.

关键词： binaries close -- stars individual （HD 49798） -- stars evolution -- supernovae general -- white dwarfs

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Birthrates and delay times of Type Ia supernovae

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Science China(Physics,Mechanics & Astronomy) 2010年第3期53卷 586-590页

作者： WANG Bo1,2,3, LIU ZhengWei1,2,3, HAN YunKun1,2,3, LEI ZhenXin1,2,3, LUO YangPing1,2,3 & HAN ZhanWen1,2 1National Astronomical Observatories/Yunnan Observatory, Chinese Academy of Sciences, Kunming 650011, China 2key laboratory for the structure and evolution of celestial objects, Chinese Academy of Sciences, Kunming 650011, China 3Graduate University of Chinese Academy of Sciences, Beijing 100049, China 1. National Astronomical Observatories/Yunnan Observatory Chinese Academy of Sciences Kunming 650011 China2. Key Laboratory for the Structure and Evolution of Celestial Objects Chinese Academy of Sciences Kunming 650011 China3. Graduate University of Chinese Academy of Sciences Beijing 100049 China

Type Ia supernovae (SNe Ia) play an important role in diverse areas of astrophysics, from the chemical evolution of galaxies to observational cosmology. However, the nature of the progenitors of SNe Ia is still unclear. In this paper, according to a detailed binary population synthesis study, we obtained SN Ia birthrates and delay times from different progenitor models, and compared them with observations. We find that the Galactic SN Ia birthrate from the double-degenerate (DD) model is close to those inferred from observations, while the birthrate from the single-degenerate (SD) model accounts for only about 1/2-2/3 of the observations. If a single starburst is assumed, the distribution of the delay times of SNe Ia from the SD model is a weak bimodality, where the WD + He channel contributes to the SNe Ia with delay times shorter than 100 Myr, and the WD + MS and WD + RG channels to those with age longer than 1 Gyr.

关键词： binaries: close stars: evolution supernovae: general white dwarfs

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Possible γ-ray emission of radio intermediate AGN Ⅲ Zw 2 and its implication on the evolution of jets in AGNs

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Research in Astronomy and Astrophysics 2010年第8期10卷 707-712页

作者： Liang Chen Jin-Ming Bai Jin Zhang Hong-Tao Liu National Astronomical Observatories/Yunnan Observatory Chinese Academy of Sciences Kunming 650011 China Key Laboratory for the Structure and Evolution of Celestial Objects Chinese Academy of Sciences Kunming 650011 China Graduate University of Chinese Academy of Sciences Beijing 100049 China College of Physics and Electronic Engineering Guangxi Teachers Education University Nanning 530001 China

AGNs with hard γ-ray emission identified so far are radio-loud. Ⅲ Zw 2 is a radio intermediate AGN with a relativistic jet. We study its spectral energy distribution （SED） and find that the broad band emissions are dominated by the nonthermal emissions from the jet. We model its SED through a synchrotron ＋ inverse Compton （IC） model. The results show that the IC component of Ⅲ Zw 2 peaks at a few MeV, and the flux density drops rapidly at higher energy with photon index F 3.3 above 0.1 GeV. The predicted flux is slightly over the sensitivity of Fermi/LAT, but it was not included in the first Fermi/LAT AGN catalog. The reason for this may be： 1） that the IC peak is low and the spectrum is very steep above 0.1 GeV, 2） that Ⅲ Zw 2 is in the low state during the period of the Fermi/LAT operation. We also find that Ⅲ Zw 2 follows similar jet processes as those in γ-ray AGNs, e.g., the relation between jet power and radiation power, which is called the blazar sequence. We suggest that Ⅲ Zw 2 may be a young source at an earlier stage of jet activity.

关键词： galaxies active -- galaxies Seyfert- galaxies jets -- radiation mechanisms non-thermal

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ERRATUM: 'TIDALLY ENHANCED STELLAR WIND: A WAY TO MAKE THE SYMBIOTIC CHANNEL TO TYPE Ia SUPERNOVA VIABLE' (2011, ApJ, 735, L31)

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The Astrophysical Journal Letters 2011年第2期736卷

作者： X. Chen Z. Han C. A. Tout National Astronomical Observatories/Yunnan Observatory CAS Kunming 650011 China Key Laboratory for the Structure and Evolution of Celestial Objects CAS Kunming 650011 China Institute of Astronomy Madingley Road Cambridge CB3 0HA UK

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A statistical study of the relation between soft X-ray excess and accretion disk

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Science China(Physics,Mechanics & Astronomy) 2010年第S1期53卷 102-105页

作者： LIU JieYing1,2,3 & QIAO ErLin1,2 1 National Astronomical Observatories/Yunnan Observatory,Chinese Academy of Science,Kunming 650011,China 2 key laboratory for the structure and evolution of celestial objects,Chinese Academy of Sciences,Kunming 650011,China 3 Graduate University of Chinese Academy of Sciences,Beijing 100049,China 1. National Astronomical Observatories/Yunnan Observatory Chinese Academy of Science Kunming 650011 China 2. Key Laboratory for the Structure and Evolution of Celestial Objects Chinese Academy of Sciences Kunming 650011 China 3. Graduate University of Chinese Academy of Sciences Beijing 100049 China

To study the origin of the soft X-ray excess,we compile a sample of 94 unobscured,radio-quiet QSOs and Seyfert galaxies with available data from GALEX and *** find that 50 sources show strong soft X-ray excess and the other 44 show weak/no soft X-ray *** analyses of the data indicate that the difference in soft X-rays is mainly but not only resulting from different accretion rates(in units of Eddington rate).The statistical study of the sources with soft X-ray excess shows that the strength of soft X-ray excess weakly and positively correlates with the Eddington ratio and increases with the increase of the strength of UV radiations relative to the *** that the UV emissions are from the thin disk,the correlations imply that the origin of soft X-ray excess is associated with the thin disk,either by means of Comptonization of the disk photons or in some other ways.

关键词： accretion:accretion disks ultraviolet:galaxies X-rays:galaxies

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Mass transfer and loss of the massive semi-detached binary AI Crucis

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Research in Astronomy and Astrophysics 2010年第5期10卷 438-444页

作者： Er-Gang Zhao Sheng-Bang Qian E. Femanindez Lajus Carolina von Essen Li-Ying Zhu National Astronomical Observatories / Yunnan Observatory Chinese Academy of SciencesKunming 650011 China Key Laboratory for the Structure and Evolution of Celestial Objects Chinese Academy ofSciences Kunming 650011 China Graduate University of Chinese Academy of Sciences Beijing 100049 China Facultad de Ciencias Astron6micas y Geoffsicas Universidad Nacional de La Plata 1900 LaPlata Buenos Aires Argentina

AI Crucis is a short-period semi-detached massive close binary （P = 1.41771d, Sp.=B1.5） in the open cluster NGC 4103. It is a good astrophysical laboratory for investigating the formation and evolution of massive close binary stars via case A mass transfer. Orbital period variations of the system were analyzed based on one newly determined eclipse time and the others compiled from the literature. It is discovered that the orbital period of the binary is continuously increasing at a rate of dP/dt = ＋1.00（±0.04） × 10-7 d yr-1. After the long-term increase is subtracted from the O - C diagram, weak evidence indicates the presence of a cyclic oscillation with a period of 30.1yr, which may reveal a very cool stellar companion in the system. The long-term period increase can be explained by mass transfer from the less massive component to the more massive one. This is in agreement with the semidetached configuration of the binary, indicating that the system is undergoing a slow mass-transfer stage on the nuclear time scale of the secondary. However, it is found that the slow mass transfer is insufficient to cause the observed period increase, which suggests that the stellar wind from the hot component should contribute to the amount of period increase dP/dt = ＋0.54× 10-7 d yr-1 that corresponds to a mass loss rate of M˙1 = 2.72 × 10-7 M yr-1. It is estimated that the hot component lost a total mass of 4.1M during the slow mass-transfer stage and, thus, the evolution of the binary system should be changed greatly by the mass loss.

关键词： stars： binaries： close — stars： binaries： eclipsing — stars： individual （AI Crucis） — stars： early-type — stars： evolution

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The Helium Star Donor Channel for the Progenitors of Type Ia Supernovae and their Surviving Companion Stars

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AIP Conference Proceedings 2010年第1期1314卷 244-249页

作者： Bo Wang Zhanwen Han aNational Astronomical Observatories/Yunnan Observatory CAS Kunming 650011 China bKey Laboratory for the Structure and Evolution of Celestial Objects CAS Kunming 650011 China

The nature of type Ia supernovae (SNe Ia) is still unclear. Employing Eggleton’s stellar evolution code with the optically thick wind assumption, we systematically studied the He star donor channel of SNe Ia, in which a carbon‐oxygen white dwarf accretes material from a He main‐sequence star or a He subgiant to increase its mass to the Chandrasekhar mass. We mapped out the initial parameters for producing SNe Ia in the orbital period‐secondary mass plane for various WD masses from this channel. According to a detailed binary population synthesis approach, we find that this channel can produce SNe Ia with short delay times (∼100 Myr) implied by recent observations. We obtained many properties of the surviving companions of this channel after SN explosion, which can be verified by future observations. We also find that the surviving companions from the SN explosion scenario have a high spatial velocity (>400 km/s), which could be an alternative origin for hypervelocity stars (HVSs), especially for HVSs such as US 708.

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