美国海军天文台照相星表第五批数据释放（UCAC5)

美国海军天文台CCD照相星表（UCAC）的全天观测数据进行了新的天体测量归算，从头开始使用8至11星等范围内的TGAS恒星作为参考星表。天体测量解决方案得到了显著改进，并生成了以2001年为平均历元的UCAC5平均位置星表。通过将UCAC5与Gaia DR1数据相结合，我们为超过1.07亿颗恒星在Gaia坐标系上获得了新的自行数据，其典型精度为1至2毫角秒每年（星等11至15），以及在16星等时约为5毫角秒每年。大多数TGAS恒星的自行数据相较于使用仅Gaia数据时有所改进，数百万颗更暗的恒星自行的精度达到了TGAS恒星的自行精度水平。我们利用星团场和河外源进行了外部比较。TGAS数据使我们能够推导出UCAC x，y数据的极限精度，该精度明显优于1/100像素。New astrometric reduction was performed on the all-sky observational data of the US Naval Observatory CCD Astrograph Catalog (UCAC), adopting TGAS stars within the magnitude range of 8 to 11 as reference catalogs from scratch. The astrometric solution was significantly improved, and the UCAC5 mean position catalog with a mean epoch of 2001 was generated. By combining UCAC5 with Gaia Data Release 1 (Gaia DR1) data, we obtained new proper motion data for over 107 million stars in the Gaia coordinate system, with typical precisions of 1 to 2 milliarcseconds per year for stars of magnitude 11 to 15, and approximately 5 milliarcseconds per year at magnitude 16. The proper motion data for most TGAS stars were improved compared to using only Gaia data, and the proper motion precisions of millions of fainter stars reached the level of TGAS stars' proper motion precisions. We conducted external comparisons using cluster fields and extragalactic sources. The TGAS data allowed us to derive the limiting precision of the UCAC x, y data, which is significantly better than 1/100 of a pixel.