关键词: 转动/
潮汐/
斜压结构/
引力昏暗
English Abstract
Detail investigation of the inclined pressure structure and gravity darkening in critical rotating star Achernar
Tai Li-Ting1,Song Han-Feng1 2 3,
Wang Jiang-Tao1
1.Department of Physics, College of Science, Guizhou University, Guiyang 550025, China;
2.Key Laboratory for the Structure and Evolution of Celestial Objects, Chinese Academy of Sciences, Kunming 650011, China;
3.Joint Research Centre for Astronomy, National Astronomical Observatory-Guizhou University, Guiyang 550025, China
Fund Project:Project supported by the National Natural Science Foundation of China (Grant No. 11463002), the Key Laboratory for the Structure and Evolution of Celestial Objects, Chinese Academy of Science (Grant No. OP201405), and the Graduate Innovation Fund in Guizhou University, China (Grant No. 2015055).Received Date:27 August 2015
Accepted Date:06 December 2015
Published Online:05 February 2016
Abstract:Rotation and tide are two important factors that have very important impacts on the stellar structure and evolution. Based on the observational data of Achernar, we have derived the inclined pressure structure in a single rotating star or as a member in the binaries. We have given the distributions of the physical quantities on the isobaric surface and these distributions are derived from the Legendre series of expansions. We have also found the relationship between all levels of perturbation potential functions (including rotational and tidal distortions) and the distributions of density and pressure under the condition of inclined pressure structure. In particular, the gravitational darkening with the models including the effects of rotation and tide is investigated. We have found that the critical ratio of equatorial radius to the polar radius is consistent with the observations in rotating binaries better than that in single rotating model. The reason is that the tidal force can make the polar radius shortened because the tidal force exerts an inward force to the two polar points. However, the theoretical angular velocity in binaries is smaller than that observed. It is also shown that the positive shear enhances the centrifugal force and decreases the mean effective gravitational acceleration and effective temperatures whereas the negative shear plays a role to strengthen the effective gravitational acceleration. Moreover, the solid body rotation has not been supported inside Achernar because magnetic fields have not been detected through observations. Furthermore, the theoretical angular velocity in rigid rotation is higher than the angular velocity observed. Achernar has a periodic variation of light curves due to mass outburst, which also supports differential rotation. A positive shear indicates that the mass in accretion disks is falling to Achernar and the Achernar is spun up to critical rotation according to current observations. By comparing the theoretical results with observations, it can be seen that when the theoretical spin angular velocity of Achernar is 4.65 10-5 s-1 and the positive shears / s are 0.7851, the temperature of the polar points is 16041 K and that of equatorial sphere is 12073 K. Relative errors between the theoretical values and observations are less than 3% and are listed in the text. This model is the best and is the most possible one for Achernar.
Keywords: rotation/
tide/
inclined pressure structure/
gravitational darkening
