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Research in Astronomy and Astrophysics 2018年第6期18卷 17-26页

作者： Tarun Kumar Arvind Kumar Lal Ankush Pathania School of Mathematics Thapar University

Anharmonic oscillations of rotating stars have been studied by various authors in literature to explain the observed features of certain variable stars. However, there is no study available in literature that has discussed the combined effect of rotation and tidal distortions on the anharmonic oscillations of stars. In this paper, we have created a model to determine the effect of rotation and tidal distortions on the anharmonic radial oscillations associated with various polytropic models of pulsating variable stars. For this study we have used the theory of Rosseland to obtain the anharmonic pulsation equation for rotationally and tidally distorted polytropic models of pulsating variable stars. The main objective of this study is to investigate the effect of rotation and tidal distortions on the shapes of the radial velocity curves for rotationally and tidally distorted polytropic models of pulsating variable stars. The results of the present study show that the rotational effects cause more deviations in the shapes of radial velocity curves of pulsating variable stars as compared to tidal effects.

关键词： stars: rotation stars: oscillations stars: binaries technique: radial velocities

rotation Profiles of Solar-like stars with Magnetic Fields

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Chinese Journal of Astronomy and Astrophysics 2008年第6期8卷 677-685页

作者： Wu-Ming Yang Shao-Lan Bi Department of Physics and Chemistry Henan Polytechnic University Jiaozuo 454000 China Department of Astronomy Beijing Normal University Beijing 100875 China National Astronomical Observatories/Yunnan Observatoryl Chinese Academy of Sciences Kunming 650011 China

We investigate the rotation profile of solar-like stars with magnetic fields. A diffu- sion coefficient of magnetic angular momentum transport is deduced. Rotating stellar models with different mass incorporating the coefficient are computed to give the rotation profiles. The total angular momentum of a solar model with only hydrodynamic instabilities is about 13 times larger than that of the Sun at the age of the Sun, and this model can not reproduce quasi-solid rotation in the radiative region. However, the solar model with magnetic fields not only can reproduce an almost uniform rotation in the radiative region, but also a total angular momentum that is consistent with the helioseismic result at the 3 tr level at the age of the Sun. The rotation of solar-like stars with magnetic fields is almost uniform in the radiative region, but for models of 1.2-1.5 MG, there is an obvious transition region between the convective core and the radiative region, where angular velocity has a sharp radial gradient, which is different from the rotation profile of the Sun and of massive stars with magnetic fields. The change of angular velocity in the transition region increases with increasing age and mass.

关键词： stars evolution stars: rotation stars: magnetic fields

Chromospheric activity in several single late-type stars

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Research in Astronomy and Astrophysics 2015年第2期15卷 252-274页

作者： Li-Yun Zhang Qing-Feng Pi Zhong-Zhong Zhu Department of Physics & NAOC-GZU Sponsored Center for Astronomy Research College of Science Guizhou University Guizhou Province Big Data Industry Development Application Research Institute Guizhou University

New high-resolution echelle spectra of six single late-type Pleiades-like stars （V368 Cep, EP Eri, DX Leo, GJ 211, PW And and V383 Lac） were obtained with the 2.16 meter telescope at Xinglong Station in 2008-2010. Using the spectral subtraction technique, we analyzed our spectroscopic data and calculated the equiva- lent widths of excess emission from several indicators of chromospheric activity （Na I D1, D2, Hoz and Ca II infrared triplet lines）. All our results using chromospheric activ- ity indicators confirmed the previous findings. In addition, the maximum amplitudes of chromospheric rotational modulation and the ratio of EW8542/EW8498 were found to rise with increasing v sin i velocity.

关键词： stars: chromospheres stars: spectroscopic stars: activity stars: rotation late-type

Test of a low-mass contact binary model by comparing the relations obtained from theory with those from observations

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Science China(Physics,Mechanics & Astronomy) 2012年第4期55卷 706-716页

作者： SONG Fen HUANG RunQian Department of Astronomy Beijing Normal UniversityBeijing 100875China National Astronomical Observatories/Yunnan Observatory Chinese Academy of SciencesKunming 650011China Key Laboratory of the Structure and Evolution of Celestial Objects Chinese Academy of SciencesKunming 650011China

The W UMa-type contact binaries have been observed for several *** construct the evolutionary model for W UMa-type contact binaries,many difficulties were encountered due to the existence of complicated physical processes in such *** model introduced by Huang,Song and Bi includes some special and unique understandings of the physical processes of contact *** is necessary to test whether this model can be used for W UMa-type contact *** best way to test a theoretical model is to know whether this model can explain the observational phenomena of such *** this aim,a comparison is performed for the relations of mass-luminosity,mass-radius,and the distribution in the HR diagram obtained from the model introduced by Huang et *** those from the astronomical *** result of the comparison indicates that this model can be applied to W UMa-type contact binaries and can explain the observational phenomena of such binaries.

关键词： binaries: close stars: evolution stars: fundamental parameters stars: rotation

On the non-synchronous rotation of binary systems

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Science China(Physics,Mechanics & Astronomy) 2014年第6期57卷 1194-1200页

作者： LI ZhiXiong HUANG RunQian WANG ShuMin Department of Physics Yunnan University Yunnan Observatory Chinese Academy of Sciences Key Laboratory for the Structure and Evolution of Celestial Objects Chinese Academy of Sciences Graduate University of Chinese Academy of Sciences

During the evolution of the binary system, many physical processes occur, which can influence the orbital angular velocity and the spin angular velocities of the two components, and influence the non-synchronous or synchronous rotation of the system. These processes include the transfer of masses and angular momentums between the component stars, the loss of mass and angular momentum via stellar winds, and the deformation of the structure of component stars. A study of these processes indicates that they are closely related to the combined effects of tide and rotation. This means, to study the synchronous or non-synchronous rotation of binary systems, one has to consider the contributions of different physical processes simultaneously, instead of the tidal effect alone. A way to know whether the rotation of a binary system is synchronous or non-synchronous is to calculate the orbital angular velocity and the spin angular velocities of the component stars. If all of these angular velocities are equal, the rotation of the system is synchronous. If not, the rotation of the system is non-synchronous. For this aim, a series of equations are developed to calculate the orbital and spin angular velocities. The evolutionary calculation of a binary system with masses of 10M~ ＋ 6Me shows that the transfer of masses and angular momentums between the two components, and the deformation of the components structure in the semidetached or in the contact phase can change the rotation of the system from synchronous into non-synchronous rotation.

关键词： stars: rotation stars: evolution stars: binaries

A test of an early-type contact binary model by comparing the relations obtained from theory with those from observations

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Science China(Physics,Mechanics & Astronomy) 2012年第2期55卷 320-328页

Contact binary systems,including massive,middle-mass and low-mass systems,have been *** is necessary to construct the evolutionary model for contact binary systems with all different *** model introduced by Huang,Song and Bi indicates some special and unique understandings of the physical processes occurring in the contact *** is necessary to test whether this model can be applied to the early-type contact *** best way to test a theoretical model is to know whether this model can explain the observational phenomena of such *** this aim,a comparison is performed for the relations of mass-luminosity,mass-radius,and the distribution in the HR diagram obtained from the model introduced by Huang et *** those from the astronomical observations.A good result is obtained by the *** means the model can be used in calculating the evolution of early-type contact binaries,and can explain the observational phenomena of such binaries.

关键词： binaries: eclipsing stars: evolution stars: fundamental parameters stars: rotation