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Description
Recently, the first installment of data from ESA's Gaia astrometric satellite mission (Gaia DR1) was released, containing positions of more than 1 billion stars with unprecedented precision, as well as proper motions and parallaxes, however only for a subset of 2 million objects. The second release will include those quantities for most objects. In order to provide a dataset that bridges the time gap between the Gaia DR1 and Gaia DR2 releases and partly remedies the lack of proper motions in the former, HSOY ("Hot Stuff for One Year") was created as a hybrid catalog between Gaia and ground-based astrometry, featuring proper motions (but no parallaxes) for a large fraction of the DR1 objects. While not attempting to compete with future Gaia releases in terms of data quality or number of objects, the aim of HSOY is to provide improved proper motions partly based on Gaia data, allowing studies to be carried out just now or as pilot studies for later projects requiring higher-precision data. The HSOY catalog was compiled using the positions taken from Gaia DR1 combined with the input data from the PPMXL catalog, employing the same weighted least-squares technique that was used to assemble the PPMXL catalog itself. This effect resulted in a four-parameter astrometric catalog containing 583 million stars, with Gaia DR1 quality positions and proper motions with precisions from far less than 1 mas/yr to 5 mas/yr, depending on object brightness and location on the sky.
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