利用VLBI观测射电星验证Gaia卫星天体测量结果的研究

国际天文联合会（IAU）采用的国际天球参考系统（ICRS）规定了天体位置坐标系的原点和坐标轴的方向，确定了国际天球参考坐标系（ICRF）。随着Gaia卫星的数据释出，人们发现以Gaia数据为基础的GCRF与ICRF有若干数据偏差，因此，需要对两个参考架进行连接，以提高精确度。用VLBI天体测量的方法观测射电星，是一种可能的方式来连接GCRF和ICRF。国际上大多使用河外天体，例如类星体等，在光学和射电波段都进行观测来连接ICRF与GCRF。但是，基于类星体的连接参考架的工作会受到类星体具有复杂多变结构，核移效应，光学-射电辐射区不同等原因的影响，而射电星具有结构简单，自行视差较宜测量等优点，因此，选取射电星进行GCRF和ICRF的连接，是一个可行的方法。本项目拟使用VLBI网观测数十颗射电星，来得到它们的坐标、自行和视差等信息，以修正视差零点，连接光学-射电参考架。

The International Celestial Reference Frame (ICRS) of the International Astronomical Union (IAU) specifies the origin of the celestial position coordinate system and the direction of the coordinate axis, and defines the International celestial reference coordinate Frame (ICRF). With the release of the Gaia satellite data, it has been found that there are several data deviations between the GCRF and the ICRF based on the Gaia data. Therefore, the two reference frames need to be linked to improve the accuracy. Observing radio stars using the VLBI is a possible way to link GCRF and ICRF. Most of people use extragalactic objects, such as quasars, to observe them in the optical and radio bands to link ICRF and GCRF. However, the work of the quasar-based linked reference frame will be affected by the complex and variable structure of the quasars, nuclear shift effect, and the difference of the optical-radio radiation area. The radio star has the simple structure and convenient measurement of proper motions and parallaxes. Therefore, it is a feasible way to use the radio star to link GCRF and ICRF. This project will use the VLBI to observe dozens of radio stars to obtain their coordinates, proper motions and parallaxes to correct the parallax zero point and link the optical-radio reference frame.