利用测地观测中搭载式相位参考模式观测射电星Del Lib和HR 1099

Observation of Radio Stars Del Lib and HR 1099 Using Piggy-back Phase Referencing Mode in Geodetic Observation

基于盖亚(Gaia)天体测量数据建立的盖亚天体参考系(Gaia Celestial Reference Frame,GCRF)与基于甚长基线干涉测量(Very Long Baseline Interferometry,VLBI)建立的国际天球参考系(International Celestial Reference Frame,ICRF)具有一定的系统差异,需要对盖亚的数据进行外部的独立评估,以建立光学和射电参考架连接。国际上对参考架的连接普遍采用在光学和射电波段都有辐射的天体,在暗端(星等G≥15)使用类星体,在亮端(G≤13)使用射电星。由于普通VLBI观测申请批准的周期长,难度大,因此,我们尝试将一部分射电星的观测转向数量较多的测地观测,在测地观测中搭载相位参考模式来观测射电星。为了测试这种观测的可行性,我们在IVS(The International VLBI Service for Geodesy and Astrometry)和LBA(Large Baseline Array)的测地观测中搭载相位参考观测,选取Del Lib和HR 1099作为实验的目标源。观测得到了这两颗射电星的VLBI图像、流量和单历元坐标,且坐标精度高于前人;同时结合前人的数据,对这两颗射电星进行了视差和自行拟合,结果与前人和盖亚的结果相符,且部分精度更高。验证了测地模式中搭载相位参考观测射电星的可行性,为后续丰富射电星VLBI天体测量样本,连接光学与射电参考架奠定了一定的基础。

The GCRF(Gaia Celestial Reference Frame)based on Gaia astrometric data has systematic differences from the ICRF(International Celestial Reference Frame)based on VLBI(Very Long Baseline Interferometry).An external independent evaluation of the data from Gaia is required to link optical and radio reference frame.Celestial bodies with both optical and radio radiation are generally used to link the two frames,quasars are used at the dark end(magnitude G≥15),and radio stars are used at the bright end(G≤13).It is very difficult to apply for the ordinary VLBI observations,so we try to focus on some geodesic observations that can use phase reference mode to observe radio stars in geodesic observations.In order to test the feasibility of this kind of observation,we use piggy-back phase referencing mode in geodetic observation of IVS(The International VLBI Service for Geodesy and Astrometry)and LBA(Large Baseline Array),and select Del Lib and HR 1099 as the targets.Our observations have obtained the VLBI images,flux densities and single-epoch coordinates of these two radio stars,and the coordinate accuracy is higher than that of the previous work;at the same time,we also combine the data of the previous work to fit parallax and proper motion of the two radio stars.Our results are consistent with the results of the previous VLBI work and Gaia′s,and some of the accuracy is higher.Our work verify the feasibility of observing radio stars with piggy-back phase referencing mode in geodetic observation,and lay a certain foundation for the subsequent enrichment of VLBI astrometric samples of radio stars and linking of optical and radio reference frames.