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Simulation of the emission lines radiated from cataclysmic variables

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Research in Astronomy and Astrophysics 2013年第10期13卷 1213-1218页

作者： lin He guo-liang lü Yong-Heng Zhao College of Physical Science and Technology Xinjiang University National Astronomical Observatories Chinese Academy of Sciences

Cataclysmic variables are special celestial bodies because they have particular light curves and *** mechanisms for generating emission lines radiated from dwarf novae in their quiescent phases are *** assume that the incident radiation field which is emitted by a hot source（white dwarf and boundary layer）irradiates the gaseous layer evaporated from the accretion disk,and the emission lines are radiated from the *** model the fluxes of emission lines by using the photoionization code *** this method,we input some reasonable parameters and get a series of simulated *** order to find a simulated spectrum which is the best fit to an observed spectrum,we use a cross-correlation method to match *** the calculation,we use the approximation that the parameters of the simulated spectrum can simulate the observed ***,we learn more about the physical conditions of the system.

关键词： stars:cataclysmic variables accretion disk:emission lines emission lines:photoionization

Contribution of dust produced by binary merger ejecta

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Research in Astronomy and Astrophysics 2015年第1期15卷 55-63页

作者： Zhao-Jun Wang Chun-Hua Zhu guo-liang lü School of Physical Science and Technology Xinjiang University

By means of a population synthesis code and by constructing a simple toy model of dust produced by asymptotic giant branch（AGB） stars, common envelope（CE） ejecta and binary merger ejecta, we estimate the dust product rates（DPRs） of these processes in the Milky Way. The total DPR from AGB stars is～ 6.7 × 10-4M yr-1, in which about 73% of dust grains are carbon, 24% are silicates and 3% are iron. The total DPR from CE ejecta is ～ 4.2 × 10-4M yr-1, in which about 83% of dust grains are silicates, about 12% are carbon and 5% are *** DPR from binary merger ejecta is less than 1/3 that from AGB stars or CE ejecta,and it could even be negligible under certain circumstances. Therefore, compared with AGB stars and CE ejecta, the contribution of dust produced by binary merger ejecta to total dust grains in the Milky Way is smaller or can be negligible.

关键词： binaries: close stars: evolution circumstellar matter dust

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

A Photometric Study of Two Contact Binaries: CRTS J025408.1+265957 and CRTS J012111.1+272933

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Research in Astronomy and Astrophysics 2022年第9期22卷 223-238页

作者： Shuo Ma Jin-Zhong liu Yu Zhang Qingshun Hu guo-liang lü Xinjiang Astronomical Observatory Chinese Academy of SciencesUrumqi 830011China University of Chinese Academy of Sciences Beijing 100049China School of Physical Science and Technology Xinjiang UniversityUrumqi 830064China

We performed new photometric observations for two contact binaries(i.e., CRTS J025408.1+265957 and CRTS J012111.1+272933), which were observed by the 1.0 m telescope at Xingjiang Astronomical Observatory. From our light curves and several survey data, we derived several sets of photometric solutions. We found that CRTS J025408.1+265957 and CRTS J012111.1+272933 were A-and W-type W UMa, respectively. The results imply that the spot migrates or disappears in the two contact binaries, which were identified by chromospheric activity emissions(e.g., Hαemission) from lAMOST spectra. From the O-C curves, the orbital periods of the two contact binaries may be increasing, which is interpreted by the mass transfer from the less massive component to the more massive one. With mass transferring, the two contact binaries may evolve from the contact configurations to semi-detached ones as predicted by the theory of thermal relaxation oscillation.

关键词： stars:binaries:eclipsing (stars:)binaries:spectroscopic stars:fundamental parameters stars:distances stars:individual(CRTS J025408.1+265957 CRTS J012111.1+272933)

From multicolor-photometric observations to a guaranteed mass of Al Cas

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Research in Astronomy and Astrophysics 2019年第8期19卷 19-30页

作者： Ya-Hui Wang Jin-Zhong liu li-Na lu guo-liang lü School of Physical Science and Technology Xinjiang UniversityUrumqi830046China Xinjiang Astronomical Observatory Chinese Academy of SciencesUrumqi830011China University of Chinese Academy of Sciences Beijing100049China

We utilize the PAdova and TRieste Stellar Evolution Code(PARSEC) combined with photometric observations to determine a guaranteed mass of Al Cas and re-examine its related physical ***-photometric observations of Al Cas have been performed in 2016 and 2017. We use the WilsonDevinney(W-D) code to analyze the light curves and find that Al Cas is probably an A-subtype contact binary(f = 35.7±0.9%) with a mass ratio q = 0.6399±0.0230 and an effective temperature difference?T = 78 K. The mass-radius relation of a higher luminosity component for Al Cas is obtained by two methods: depending on calculation of the Roche lobe(DCRl method) and depending on calculation of the W-D code(DCWD method). Using this relationship with the PARSEC model, we investigate the component masses of Al Cas as M1 = 1.19±0.23 M⊙ with M2 = 0.76±0.18 M⊙ by the DCRl method and M1 = 1.22±0.26 M⊙ with M2 = 0.78±0.20 M ⊙ by the DCWD method. By means of the photometric studies, we examine the related physical properties of Al Cas with the latest findings. We update the orbital period(Porb = 0.50055593 d) of Al Cas according to six new times of light minimum together with those collected from the literature. Meanwhile, the(O-C)2 curve analysis suggests that the orbital period of Al Cas has a cyclic variation with a period of 81.25 yr and an amplitude of 0.01415 d. This cyclic change would be caused by the light-travel time effect from a third body. A similar mass of the third body(M3 sin i′= 0.279 M⊙) is derived from our two methods.

关键词： stars:binaries:close stars:binaries:eclipsing stars:individual:Al Cassiopeiae

The effects of convective overshooting on naked helium stars

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Research in Astronomy and Astrophysics 2016年第9期16卷 75-82页

作者： Jing-Zhi Yan Chun-Hua Zhu Zhao-Jun Wang guo-liang lü School of Physical Science and Technology Xinjiang University

Using stellar evolutionary models, we investigate the effects of convective overshooting on naked helium stars. We find that a larger value of overshooting parameter δov results in a larger convective core, which prolongs the lifetimes of naked helium stars on the helium main sequence and leads to higher effective temperatures and luminosities. For naked helium stars with masses lower than about 0.8 Mo, they hardly become giant stars as a result of a weak burning shell. However, naked helium stars with masses between about 0.8 M⊙ and 1.1 M⊙ can evolve into giant branch phases, and finally become carbon oxygen white dwarfs.

关键词： stars evolution- stars interiors- stars fundamental parameters

Neutrino luminosity of stars with different masses

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Research in Astronomy and Astrophysics 2020年第1期20卷 35-42页

作者： Yang Shi Xun Xue Chun-Hua Zhu Zhao-Jun Wang He-lei liu lin li guo-liang lü School of Physics and Technology Xinjiang UniversityUrumqi 830046China Department of Physics East China Normal UniversityShanghai 2000062China

Neutrinos play an important role in stellar *** are produced by nuclear reactions or thermal *** the stellar evolution code Modules for Experiments in Stellar Astrophysics(MESA),we study stellar neutrino luminosity with different *** neutrino luminosities of stars with different initial masses at different evolutionary stages are *** find that the neutrino flux of a star with 1 M⊙ mass at an evolutionary age of 4.61×10^9 yr is consistent with that of the *** general,neutrinos are produced by nuclear reactions,and the neutrino luminosity of stars is about one or two magnitudes lower than the photo ***,neutrino luminosity can exceed photo luminosity during the helium flash which can occur for stars with a mass lower than 8 M⊙.Although the helium flash does not produce neutrinos,plasma decay,one of the thermal processes,can efficiently make neutrinos during this *** to the high mass-loss rate,a star with a mass of 9 M⊙ does not undergo the helium *** neutrinos mainly originate from nuclear reactions until the end of the AGB *** the end of the AGB stage,its neutrino luminosity results from plasma decay which is triggered by the gravitational energy release because of the stellar core contracting.

关键词： stars:evolution stars:fundamental parameters nuclear reactions nucleosynthesis abundances

Heavy element contributions of rotating massive stars to interstellar medium

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Research in Astronomy and Astrophysics 2021年第5期21卷 287-295页

作者： Rui-Qing Wu Chun-Hua Zhu guo-liang lv Zhao-Jun Wang He-lei liu School of Physical Science and Technology Xinjiang UniversityUrumqi 830046China

Employing the stellar evolution code Modules for Experiments in Stellar Astrophysics(MESA),we calculate yields of heavy elements from massive stars via stellar wind and core−collapse supernova(CCSN)ejecta to the interstellar medium(ISM).In our models,the initial masses(Mini)of massive stars are taken from 13 to 80 M⊙,their initial rotational velocities(V)are 0,300 and 500 km s^(−1),and their metallicities are[Fe/H]=−3,−2,−1 and *** yields of heavy elements coming from stellar winds are mainly affected by stellar rotation which changes the chemical abundances of stellar surfaces via chemically homogeneous evolution,and enhances mass-loss *** estimate that the stellar wind can produce heavy element yields of about 10^(−2)(for low metallicity models)to a mass of severalM⊙(for low metallicity and rapid rotation models).The yields of heavy elements produced by CCSN ejecta also depend on the large amount of remnantmass which is mainly determined by the mass of the *** models calculate that the yields of heavy elements produced by CCSN ejecta can get up to several M⊙.Compared with stellar wind,CCSN ejecta has a greater contribution to the heavy elements in *** also compare the 56Ni yields calculated in this work with the observational *** models only explain the 56Ni masses produced by faint SNe or normal SNe with progenitor mass lower than about 25 M⊙,and greatly underestimate the 56Ni masses produced by stars with masses higher than about 30M⊙.

关键词： Stars:massive rotation ISM:abundances

Forming process chain for manufacturing complex conical-section profiled rings:On a co-design method

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Chinese Journal of Aeronautics 2024年第6期37卷 485-503页

作者： lei liang Chaojiang ZOU lianggang guo State Key laboratory of Solidification Processing School of Materials Science and EngineeringNorthwestern Polytechnical UniversityXi’an 710072China Guizhou Aviation Technology Development Co.ltd Guiyang 550081China

The final quality of complex conical-section rings depends on co-design of multiple processes in forming process *** this study,for a complex aeroengine casing ring with a large slope and a flange on its end,a co-design method of the forming process chain is put forward towards the objective of precision forming,which not only proposes a standard process route composed of multiple processes of upsetting,punching,rectangular ring rolling,loose tooling forging and profiled ring rolling,but also presents co-design methods of dies and blanks for all the *** profiled ring rolling,a design method of preformed blank that makes the blank and the target conical-section ring have the same axial volume distribution is *** the method,the axial metal redistribution during the process can be alleviated greatly thus improving the forming stability and precision of the *** on the geometric features of designed preformed blank,design methods of blanks and dies for loose tolling forging,rectangular ring rolling,punching and upsetting are proposed *** view of the key roles of loose tooling forging(manufacturing the preformed blank)and profiled ring rolling on the final quality of the conical ring parts,inherited FE simulations for these two processes are performed to verify the proposed design methods and determine appropriate design *** is demonstrated that the proposed design method has significant advantages in improving forming ***,a suggestive value 1.5 of the rolling ratio for profiled ring rolling(a key design parameter)is given based on comprehensive consideration of multiple indicators such as ring roundness,deformation uniformity and forming *** corresponding industrial experiments performed illustrate that a high forming precision of the conical-section aeroengine casing ring is achieved.

关键词： Complex conical-section ring Co-design of forming process chain Profiled ringrolling Preformed blank loose tooling forging