Distances to OH/IR stars

我申请一笔补助金，以支持PostDoc职位，用于对20颗OH/IR星的无线电观测进行数据简化和数据分析，这些恒星的距离有待确定。这些观测包括一个1612 MHz OH脉泽谱线的监测计划，该计划自2008年以来一直使用法国的Nancay射电望远镜进行，至少到2012年底。目的是利用不同OH脉泽谱线光变曲线之间的相位滞后来确定星周壳层的线性直径。这些观测得到了自2010年以来在恒星通过其OH脉泽通量密度变化最大值时获得的干涉测量的补充。这些测量被用来构建脉泽发射区域的空间分布图，以确定发射壳层的角直径。线直径和角直径的组合给出了星星的距离。确定OH/IR星的距离是非常重要的，因为它们是渐近巨星分支（AGB）上最新演化阶段的大质量恒星（~2 - 10个太阳质量），由于不确定的距离和光度，很难与恒星演化模型进行比较。因此，对AGB向后AGB演化过渡的观测检验并不令人满意。

I apply for a grant supporting a PostDoc position for data reduction and data analysis of radio observations of 20 OH/IR stars, for which distances are to be determined. The observations comprise a monitor program of the 1612 MHz OH maser lines, which is made since 2008 until at least end of 2012 with the Nancay Radio Telescope in France. The aim is the determination of the linear diameter of the circumstellar shell using the phase lag between the light curves of the varying OH maser lines. These observations are supplemented with interferometric measurements, which are obtained since 2010 while the stars pass the maximum of their OH maser flux density variations. These measurements are used to construct maps of the spatial distribution of the maser emission regions, to determine the angular diameter of the emitting shell. The combination of linear and angular diameter gives the distance of the star. The determination of distances to OH/IR stars is of great importance, because they are massive stars (~2-10 solar masses) in the latest evolutionary phase on the Asymptotic Giant Branch (AGB), for which the comparison with stellar evolutionary models is difficult, because of the uncertain distances and hence luminosities. The observational tests of the transition of the AGB to post-AGB evolution are therefore unsatisfactory.