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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

Stellar kinematics and populations out to 1.5 effective radii in the elliptical galaxy NGC 4636

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Research in Astronomy and Astrophysics 2011年第8期11卷 909-923页

作者： Shi-Bi PU zhan-wen han National Astronomical Observatory/Yunnan Observatory Chinese Academy of Sciences Kunming 650011 China Graduate University of Chinese Academy of Sciences Beijing 100049 China Key Laboratory of the Structure and Evolution of Celestial Objects Chinese Academy of Sciences Kunming 650011 China

We present high quality long slit spectra along the major and minor axes out to 1.5 effective radii of the massive galaxy NGC 4636 taken by the Hobby-Eberly Telescope. Using the Fourier Correlation Quotient method, we measured the stellar line-of-sight velocity distribution along the axes. Furthermore, six Lick/IDS indices （Hβ, Mgb, Fe5015, Fe5270, Fe5335, Fe5406） are derived from the clean spectrum. By comparing the measured absorption line strengths with the predictions of Simple Stellar Population （SSP） models, we derived ages, total metallicity and a abundance profiles of the galaxy. This galaxy presents old and [α/Fe] overabundant stellar populations. Indeed, using the SSP model, we obtained the broadband color profiles. The theoretical colors match well with the measured colors and present red sharp peaks at the galaxy center. The sharp peaks of the colors are mainly shaped by the high metallicity in the galaxy＇s center. Interestingly, the galaxy has steep negative metaUicity gradients, but the trend flattens outwards. This result likely suggests that the center and outer regions of the galaxy formed through different formation processes.

关键词： galaxy: elliptical and lenticular -- galaxy: abundances -- galaxy: kine- matic and dynamics -- galaxy: individual (NGC 4636)

Fitting formulae for the effects of binary interactions on lick indices and colors of stellar populations

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Chinese Journal of Astronomy and Astrophysics 2009年第2期9卷 191-204页

作者： Zhong-Mu Li zhan-wen han Dali Uinversity Dali 671003 China National Astronomical Observatories/Yunnan Observatory Chinese Academy of Sciences Kunming 650011 China

More than about 50% of stars are in binaries, but most stellar population studies take single star stellar population （ssSSP） models, which do not take binary interactions into account. In fact, the integrated peculiarities of ssSSPs are different from those of stellar populations with binary interactions （bsSSPs）. Therefore, it is necessary to investigate the effects of binary interactions on the Lick indices and colors of populations in detail. We show some formulae for calculating the difference between the Lick indices and colors of bsSSPs, and those of ssSSPs. Twenty-five Lick indices and 12 colors are studied in this work. The results can be conveniently used for calculating the effects of binary interactions on stellar population studies and for adding the effects of binary interactions into present ssSSP models. The electronic data and fortran procedures in the paper can be obtained on request from the authors.

关键词： galaxies stellar content -- galaxies elliptical and lenticular, cD

Hydrogen and helium shell burning during white dwarf accretion

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Research in Astronomy and Astrophysics 2018年第5期18卷 111-118页

作者： Xiao Cui Xiang-Cun Meng zhan-wen han Yunnan Observatories Chinese Academy of Sciences Kunming 650216 China Key Laboratory for the Structure and Evolution of Celestial Objects Chinese Academy of Sciences Kunming 650216 China University of Chinese Academy of Sciences Beijing 100049 China

Type Ia supernovae（SNe Ia） are believed to be thermonuclear explosions of carbon oxygen（CO） white dwarfs（WDs） with masses close to the Chandrasekhar mass limit. How a CO WD accretes matter and grows in mass to this limit is not well understood, hindering our understanding of SN Ia explosions and the reliability of using SNe Ia as a cosmological distance indicator. In this work, we employed the stellar evolution code MESA to simulate the accretion process of hydrogen-rich material onto a 1.0 M⊙CO WD at a high rate（over the Eddington limit） of 4.3 × 10^-7 M⊙yr^-1. The simulation demonstrates the characteristics of the double shell burning on top of the WD, with a hydrogen shell burning on top of a helium burning shell. The results show that helium shell burning is not steady（*** flashes）. Flashes from the helium shell are weaker than those in the case of accretion of helium-rich material onto a CO WD. The carbon to oxygen mass ratio resulting from the helium shell burning is higher than what was previously thought. Interestingly, the CO WD growing due to accretion has an outer part containing a small fraction of helium in addition to carbon and oxygen. The flashes become weaker and weaker as the accretion continues.

关键词： stars evolution - supernovae general - white dwarfs

The Effect of Method of Constructing the Mass Distribution on Single Stellar Populations

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Chinese Journal of Astronomy and Astrophysics 2005年第4期5卷 371-378页

作者： Feng-Hui zhang Li-Fang Li zhan-wen han National Astronomical Observatories Yunnan Observatory Chinese Academy of SciencesKunming 650011

We use two methods of constructing the initial mass distribution, the traditional way and Monte Carlo simulation, to obtain integrated U - B, B - V,V-R and V-I colours and absorption-line indices defined by the Lick Observatory image dissector scanner （referred to as Lick/IDS）, for instantaneous burst solarmetallicity single stellar populations with ages in the range 1-15Gyr. We find that the evolutionary curves of all colours obtained by the traditional method are smoother than those by Monte Carlo simulation, that the U- B and B- V colours obtained by the two methods agree with one another, while the V - R and V - I colours by the traditional method are bluer than those by Monte Carlo simulation.A comparison of the Lick/IDS absorption-line indices shows that the variations in all the indices by the traditional method are smoother than that for the Monte Carlo simulation, and that all the indices except for TiO1 and TiO2 are consistent with those for the Monte Carlo simulation.

关键词： star: evolution - galaxies: star clusters- galaxies: stellar content

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Mira Symbiotic Stars

Chinese Journal of Astronomy and Astrophysics 2007年第1期7卷 101-110页

作者： Guo-Liang Lu Chun-Hua Zhu zhan-wen han National Astronomical Observatories / Yunnan Observatory Chinese Academy of Sciences Kunming 650011 Department of Physics Xinjiang University Urumqi 830046

We have carried out a detailed study of Mira symbiotic stars by means of a population synthesis code. We estimate the number of Mira symbiotic stars in the Galaxy as 1700 - 3100 and the Galactic occurrence rate of Mira symbiotic novae as from -0.9 to 6.0 yr^-1, depending on the model assumptions. The distributions of the orbital periods, the masses of the components, mass-loss rates of cool components, mass-accretion rates of hot components and Mira pulsation periods in Mira symbiotic stars are simulated. By a comparison of the number ratio of Mira symbiotic stars to all symbiotic stars, we find the model with the stellar wind model of Winters et al. to be reasonable.

关键词： binaries symbiotic-Galaxy stellar content-stars Mira variables

A Study of Binary Stellar Population Synthesis of Elliptical Galaxies

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Chinese Journal of Astronomy and Astrophysics 2006年第6期6卷 669-679页

作者： Zhong-Mu Li Feng-Hui zhang zhan-wen han National Astronomical Observatories / Yunnan Observatory Chinese Academy of Sciences Kunming 650011 Graduate School of Chinese Academy of Sciences Beijing 100049

We determined the relative stellar ages and metallicities of about 80 elliptical galaxies in both low and high density environments using the latest binary stellar population （BSP） synthesis model and tested the predictions of a recent hierarchical formation model that adopted the new ACDM cosmology. The stellar ages and metallicities were estimated from two high-quality published spectra line indices, the Hβ and [MgFe] indices. The results show that the stellar populations of elliptical galaxies are older than 3.9 Gyr and more metal rich than 0.02. Most of our results are in agreement with the model predictions; （1） elliptical galaxies in denser environment are redder and have older populations than field galaxies; （2） elliptical galaxies with more massive stellar components are redder and have older and more metal rich populations than less massive ones; （3） the most massive galaxies have the oldest and most metal rich stars. However, some of our results differ from the model predictions on the metallicity distributions of low- and high-density elliptical galaxies and the dependence on the distance to the cluster center.

关键词： galaxies stellar content- galaxies formation- galaxies elliptical and lenticular, cD

The surviving companions in type Ia supernova remnants

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Research in Astronomy and Astrophysics 2017年第8期17卷 69-80页

作者： li-qing chen xiang-cun meng zhan-wen han yunnan observatories chinese academy of scienceskunming 650216china key laboratory for the structure and evolution of celestial objects chinese academy of scienceskunming 650216china university of chinese academy of sciences beijing 100049china center for astronomical mega-science chinese academy of sciencesbeijing 100012china

The single-degenerate(SD)model is one of the most popular progenitor models of type Ia supernovae(SNe Ia),in which the companion star can survive after an SN Ia explosion and show peculiar ***,searching for the surviving companion in type Ia supernova remnants(SNRs)is a potential method to verify the SD *** the SN 1604 remnant(Kepler’s SNR),although Chandra X-ray observation suggests that the progenitor is most likely a WD+AGB system,the surviving companion has not been *** possible reason is rapid rotation of the white dwarf(WD),causing explosion of the WD to be delayed for a spin-down timescale,and then the companion evolved into a WD before the supernova explosion,so the companion is too dim to be *** aim to verify this possible explanation by carrying out binary evolution *** this paper,we use Eggleton’s stellar evolution code to calculate the evolution of binaries consisting of a WD+red giant(RG).We assume that the rapidly rotating WD can continuously increase its mass when its mass exceeds the Chandrasekhar mass limit(MCh=1.378 M_⊙)until the mass-transfer rate decreases to be lower than a critical ***,we obtain the final masses of a WD in the range 1.378 M_⊙ to 2.707 M_⊙.We also show that if the spin-down time is less than 10~6yr,the companion star will be very bright and easily observed;but if the spin-down time is as long as^10~7 yr,the luminosities of the surviving companion would be lower than the detection *** simulation provides guidance in hunting for the surviving companion stars in SNRs,and the fact that no surviving companion has been found in Kepler’s SNR may not be definite evidence disfavoring the SD origin of Kepler’s SN.

关键词： stars evolution—binaries symbiotic—supernovae individual(SN 1604,SN 1006)

Population Synthesis for the Symbiotic Stars with Main-sequence Accretors

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Chinese Journal of Astronomy and Astrophysics 2006年第4期6卷 447-454页

作者： Guo-Liang Lü Chun-Hua Zhu BinWu zhan-wen han National Astronomical Observatories / Yunnan Observatory Chinese Academy of Sciences Kunming 650011 Graduate School of Chinese Academy of Sciences Beijing 100049 Department of Physics Xinjiang University Urumqi 830046

Using a population synthesis code, we have investigated the formation of symbiotic systems in which the hot component is a main-sequence star that is accreting matter from the cool component via Roche lobe overflow （RLOF）. The RLOF can be divided into two cases： dynamically unstable and stable. In the first case, the birthrate of symbiotic stars is 0.056 yr^- 1 or 0.045 yr^-1 depending on different assumptions; in the stable RLOF case, it is 0.002 yr^-1 or 0.005yr^-1. The number of symbiotic stars with main-sequence accretors and unstable RLOF in our galaxy is about 5, that with stable RLOF is about 60 to 280. Comparison between our results with those of Yungelson et al. shows that symbiotic stars with MS accretors make only a small contribution （ ≤ 8%） to the whole population of symbiotic stars in the Galaxy.

关键词： binaries: symbiotic -- accretion: accretion disks -- stars: evolution -- main-sequence star