arXiv 1802.002292018-02-01astro-ph.GA

银河系核球的单颗和双颗白矮星的星群

The population of single and binary white dwarfs of the Galactic bulge

S. Torres, E. García-Berro, R. Cojocaru, A. Calamida

备注：: 10 pages, 9 figures, accepted for publication in MNRAS
DOI：: 10.1093/mnras/sty289

摘要：

最近哈勃太空望远镜的观测揭示了银河系隆起的白矮星冷却序列。虽然简并序列可以很好地拟合采用最新的理论冷却序列，观测表明，系统的红色物体，不能解释的理论模型的单碳氧白矮星的适当质量。在这里，我们提出了一个人口综合研究的白矮星冷却序列的银河系的隆起，考虑到人口的单白矮星和双系统包含至少一个白矮星。这些计算包含了最先进的冷却序列，适用于具有富氢和缺氢大气的白矮星，适用于具有碳氧和氦核的白矮星，并且还考虑了双星系统演化历史的详细规定。我们的蒙特卡罗模拟器还包含了所有已知的观测偏差。这使我们能够以高度的真实感来模拟银河系凸出部分的白矮星数量。我们发现，观测到的红色恒星的过剩可以部分归因于白矮星加上主序星，和激变变量或矮新星。我们的最佳拟合是获得较高的二进制分数和初始质量函数斜率比标准值陡峭，以及与微分红化和混合的列入。我们的结果还表明，双简并系统或年轻的厚盘核球星的可能贡献是可以忽略的。

英文摘要：

Recent Hubble Space Telescope observations have unveiled the white dwarf cooling sequence of the Galactic bulge. Although the degenerate sequence can be well fitted employing the most up-to-date theoretical cooling sequences, observations show a systematic excess of red objects that cannot be explained by the theoretical models of single carbon-oxygen white dwarfs of the appropriate masses. Here we present a population synthesis study of the white dwarf cooling sequence of the Galactic bulge that takes into account the populations of both single white dwarfs and binary systems containing at least one white dwarf. These calculations incorporate state-of-the-art cooling sequences for white dwarfs with hydrogen-rich and hydrogen-deficient atmospheres, for both white dwarfs with carbon-oxygen and helium cores, and also take into account detailed prescriptions of the evolutionary history of binary systems. Our Monte Carlo simulator also incorporates all the known observational biases. This allows us to model with a high degree of realism the white dwarf population of the Galactic bulge. We find that the observed excess of red stars can be partially attributed to white dwarf plus main sequence binaries, and to cataclysmic variables or dwarf novae. Our best fit is obtained with a higher binary fraction and an initial mass function slope steeper than standard values, as well as with the inclusion of differential reddening and blending. Our results also show that the possible contribution of double degenerate systems or young and thick-disk bulge stars is negligible.

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