小质量比深度相接双星的统计分析

基于30颗小质量比深度相接双星的观测数据,获得一些重要的统计结论:(ⅰ)质光关系和质径关系指出,此类双星可能由于演化和膨胀而使光度下降、半径变大,预示它们可能处在演化的最后阶段.(ⅱ)Mtotal-Jtotal关系表明,随着总质量的减小,总的比角动量也相应减小.因此,此类双星系统从深度相接到并合的过程中,不断损失质量和角动量.(ⅲ)由q-f关系和q-Jspin/Jorb关系,确定出过相接双星的最小质量比可能在0.0439~0.0465.这对双星演化并合理论提出了重要的挑战.目前观测到的最小质量比双星V857Her通过次子星到主子星的守恒质量转移的并合时标约为1.07Ga.

A statistical analysis of deep low-mass ratio overcontact binaries

Based on the observations of 30 deep low-mass ratio overcontact binaries, some important results were discovered as follows: (1) The relationships of M-L and M-R imply that due to its evolution and expansion the luminosity of this kind of binary decreases and its radius increases, which suggests that it is in the final stage of its evolution. (2) The relationship between M_total and J_total shows when the mass ratio decreases, the total angular momentum per mass also correspondingly decreases. Therefore, the mass and angular momentum for this kind of binaries are continuously lossing in the process from the contact configuration to the merged configuration. (3) From the relationships of q-f and q-J_spin/J_orb, the minimum mass-ratio for the overcontact binary may be determined as 0.0439?0.0465. It is a key challenge for us to bring forward the evoluionary theory and the merged mechanism of the binary. The observed minimum mass-ratio binary is V857 Her up to now. The merged timescale is around 1.07 Ga through the conservated mass transfer from the more massive component to the less massive one.