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On the Surface Helium Abundance of B-type Hot Subdwarf Stars from the WD+MS Channel of Type Ia Supernovae

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Research in Astronomy and Astrophysics 2024年第5期24卷 21-27页

作者： Rui-Jie Ji xiang-cun meng Zheng-Wei Liu Yunnan Observatories Chinese Academy of SciencesKunming 650216Kunming 650216China University of Chinese Academy of Sciences Beijing 100049China Key Laboratory for the Structure and Evolution of Celestial Objects Chinese Academy of SciencesKunming 650216China International Centre of Supernovae(ICESUN) Yunnan Key LaboratoryKunming 650216China

The origin of intermediate helium (He)-rich hot subdwarfs is still *** studies have suggested that some surviving Type Ia supernovae (SNe Ia) companions from the white dwarf+main-sequence (WD+MS)channel may contribute to the intermediate He-rich hot ***,previous studies ignored the impact of atomic diffusion on the post-explosion evolution of surviving companion stars of SNe Ia,leading to the aspect that they could not explain the observed surface He abundance of intermediate He-rich hot *** this work,by taking the atomic diffusion and stellar wind into account,we trace the surviving companions of SNe Ia from the WD+MS channel using the one-dimensional stellar evolution code MESA until they evolve into hot *** find that the surface He-abundances of our surviving companion models during their core He-burning phases are in a range of-1■log(N_(He) N_(H))■0,which are consistent with those observed in intermediate He-rich hot *** seems to further support the notion that it is possible for surviving companions of SNe Ia in the WD+MS channel to form some intermediate He-rich hot subdwarfs.

关键词： (stars:)subdwarfs-atomic processes-diffusion

Formation of accreting millisecond X-ray pulsars

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Research in Astronomy and Astrophysics 2019年第8期19卷 45-55页

作者： xiang He xiang-cun meng Hai-Liang Chen Yunnan Observatories Chinese Academy of SciencesKunming650216China Key Laboratory for the Structure and Evolution of Celestial Objects Chinese Academy of SciencesKunming650216China University of Chinese Academy of Sciences Beijing100049China

Accreting millisecond X-ray pulsars(AMXPs) are an important subclass of low-mass X-ray binaries(LMXBs), in which coherent millisecond X-ray pulsations can be observed during outburst *** have dual characteristics of LMXBs and millisecond pulsars, providing a direct confirmation for the recycling scenario. However, their formation is not well understood. In this work, we simulate the evolution of LMXBs with the MESA code to explore the formation and evolution of AMXPs. Based on the binary evolutionary model of LMXBs and the model of accretion disk instability, we find that most of the observed AMXPs can be produced from LMXBs with orbital periods at the onset of Roche lobe overflow close to the bifurcation period and their observed properties can be explained by our models. The AMXPs with main sequence(MS) donors ultimately evolve into AMXPs with extremely low-mass He white dwarf ***, our results indicate that these AMXPs with MS donors are likely to have donor stars near the terminal-age main sequence.

关键词： binaries:close stars:evolution stars:neutron X-ray:binaries

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

Machine Learning to Search for Accreting Neutron Star Binary Candidates Using Chinese Space Station Telescope Photometric System

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Research in Astronomy and Astrophysics 2022年第12期22卷 322-334页

作者： Shun-Yi Lan Kai-Fan Ji xiang-cun meng 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

Accreting neutron star binary(ANSB)systems can provide some important information about neutron stars(NSs),especially on the structure and the equation of state of ***,only a few ANSBs are known so *** upcoming Chinese Space Station Telescope(CSST)provides an opportunity to search for a large number of ANSB *** aim to investigate whether or not a machine learning method may efficiently search for ANSBs based on CSST photometric *** this paper,we generate some ANSBs and normal binaries under CSST photometric system by binary evolution and binary population synthesis method and use a machine learning method to train a classification *** consider the classical multi-color disk and the irradiated accretion disk,then compare their effects on the classification *** find that no matter whether the X-ray reprocessing effect is included or not,the machine learning classification accuracy is always very high,i.e.,higher than 96%.If a significant magnitude difference exists between the accretion disk and the companion of an ANSB,machine learning may not distinguish it from some normal stars such as massive main sequence stars,white dwarf binaries,*** classifications of the ANSBs and the normal stars highly overlap in a color–color *** results indicate that machine learning would be a powerful way to search for potential ANSB candidates from the CSST survey.

关键词： stars:neutron X-rays:binaries methods:analytical

The cooling time of white dwarfs produced from type Iasupernovae

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Research in Astronomy and Astrophysics 2010年第9期10卷 927-934页

作者： xiang-cun meng Wu-Ming Yang Zhong-Mu Li School of Physics and Chemistry Henan Polytechnic University Jiaozuo 454000 China College of Physics and Electronic Information Dali University Dali 671003 China National Astronomical Observatories Chinese Academy of Sciences Beijing 100012 China

Type Ia supernovae （SNe Ia） play a key role in measuring cosmological parameters, in which the Phillips relation is adopted. However, the origin of the relation is still unclear. Several parameters are suggested, e.g. the relative content of carbon to oxygen （C/O） and the central density of the white dwarf （WD） at ignition. These parameters are mainly determined by the WD＇s initial mass and its cooling time, respectively. Using the progenitor model developed by meng ＆ Yang, we present the distributions of the initial WD mass and the cooling time. We do not find any correlation between these parameters. However, we notice that as the range of the WD＇s mass decreases, its average value increases with the cooling time. These results could provide a constraint when simulating the SN Ia explosion, i.e. the WDs with a high C/O ratio usually have a lower central density at ignition, while those having the highest central density at ignition generally have a lower C/O ratio. The cooling time is mainly determined by the evolutionary age of secondaries, and the scatter of the cooling time decreases with the evolutionary age. Our results may indicate that WDs with a long cooling time have more uniform properties than those with a short cooling time, which may be helpful to explain why SNe Ia in elliptical galaxies have a more uniform maximum luminosity than those in spiral galaxies.

关键词： stars white dwarfs -- stars supernovae general

Grids of rotating stellar models with masses between 1.0 and 3.0 M_⊙

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Research in Astronomy and Astrophysics 2013年第5期13卷 579-592页

作者： Wu-Ming Yang Shao-Lan Bi xiang-cun meng Department of Astronomy Beijing Normal University School of Physics and Chemistry Henan Polytechnic University

We calculated a grid of evolutionary tracks of rotating models with masses between 1.0 and 3.0 M⊙ and resolution δM 〈 0.02 M⊙, which can be used to study the effects of rotation on stellar evolution and on the characteristics of star clusters. The value of ～ 2.05 Me is a critical mass for the effects of rotation on stellar struc- ture and evolution. For stars with M 〉 2.05 Me, rotation leads to an increase in the convective core and prolongs their lifetime on the main sequence （MS）; rotating mod- els evolve more slowly than non-rotating ones; the effects of rotation on the evolution of these stars are similar to those of convective core overshooting. However for stars with 1.1 〈 M/M⊙ 〈 2.05, rotation results in a decrease in the convective core and shortens the duration of the MS stage; rotating models evolve faster than non-rotating ones. When the mass has values in the range ～ 1.7 - 2.0 M⊙, the mixing caused by rotationally induced instabilities is not efficient; the hydrostatic effects dominate pro- cesses associated with the evolution of these stars. For models with masses between about 1.6 and 2.0 M⊙, rotating models always exhibit lower effective temperatures than non-rotating ones at the same age during the MS stage. For a given age, the lower the mass, the smaller the change in the effective temperature. Thus rotations could lead to a color spread near the MS turnoff in the color-magnitude diagram for intermediate-age star clusters.

关键词： stars: evolution -- stars: rotation m stars: interiors

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)

Distribution of ^(56)Ni Yields of Type Ia Supernovae and its Implication for Progenitors

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Chinese Journal of Astronomy and Astrophysics 2008年第1期8卷 71-80页

作者： Bo Wang xiang-cun meng Xiao-Feng Wang Zhan-Wen Han National Astronomical Observatories / Yunnan Observatory Chinese Academy of Sciences Kunming 650011 Graduate School of Chinese Academy of Sciences Beijing 100049 Tsinghua Center for Astrophysics （THCA） and Department of Physics Tsinghua University Beijing 100084 Astronomy Department University of California at Berkeley CA 94720 USA

The amount of 56↑Ni produced in Type Ia supernova （SN Ia） explosion is probably the most important physical parameter underlying the observed correlation of SN Ia luminosities with their light curves. Based on an empirical relation between the 56↑Ni mass and the light curve parameter △m15, we obtained rough estimates of the 56↑Ni mass for a large sample of nearby SNe Ia with the aim of exploring the diversity in SN Ia. We found that the derived 56↑Ni masses for different SNe Ia could vary by a factor of ten （e.g., MNi = 0.1 - 1.3 M⊙）, which cannot be explained in terms of the standard Chandrasekhar-mass model （with a 56↑Ni mass production of 0.4 - 0.8 M⊙）. Different explosion and/or progenitor models are clearly required for various SNe Ia, in particular, for those extremely nickel-poor and nickel-rich producers. The nickel-rich （with MNi 〉 0.8 M⊙） SNe Ia are very luminous and may have massive progenitors exceeding the Chandrasekhar-mass limit since extra progenitor fuel is required to produce more 56↑Ni to power the light curve. This is also consistent with the finding that the intrinsically bright SNe Ia prefer to occur in stellar environments of young and massive stars. For example, 75% SNe Ia in spirals have △ml5 〈 1.2 while this ratio is only 18% in E/S0 galaxies. The nickel-poor SNe Ia （with MNi 〈 0.2 M⊙） may invoke the sub- Chandrasekhar model, as most of them were found in early-type E/S0 galaxies dominated by the older and low-mass stellar populations. This indicates that SNe Ia in spiral and E/S0 galaxies have progenitors of different properties.

关键词： stars evolution - supernovae general - white dwarfs

The Relation between the Critical Accretion Rate of Progenitors of SNe Ia and Metallicity

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Chinese Journal of Astronomy and Astrophysics 2006年第4期6卷 461-469页

作者： xiang-cun meng Xue-Fei Chen Christopher A. Tout Zhan-Wen Han National Astronomical Observatories / Yunnan Observatory Chinese Academy of Sciences Kunming 650011 Graduate School of Chinese Academy of Sciences Beijing 100049 Institute of Astronomy The Observatories Madingley Road Cambridge CB3 0HA England Centre for Stellar and Planetary Astrophysics School of Mathematics Monash University Clayton Victoria 3800 Australia

A carbon-oxygen white dwarf may *** a Type Ia supernova by accreting matter from its companion via either Roche lobe overflow or from winds, but there exists a critical accretion rate of the progenitor system for the explosion. We study the relation between the critical accretion rate and the metallicity via an AGB star approach. The result indicates that the critical accretion rate depends not only on the hydrogen mass fraction and the white dwarf mass, but also on the metallicity. The effect of the metallicity is smaller than that of the white dwarf mass. We show that it is reasonable to use the model with stellar mass 1.6 M⊙ for real white dwarfs.

关键词： stars: evolution -- star: AGB -- star: supernova: general