VizieR Online Data Catalog: Dormant 33 solar-masses black hole (Gaia Collaboration, 2024)

We provide here the Gaia epoch astrometry and epoch radial velocity data for the Gaia BH3 system.

The epoch astrometry table (tableb1.dat) presents the individual astrometric Gaia measurements used to produce the binary-orbit solution of Gaia BH3. As explained in the discovery paper, these measurements are derived from preliminary runs of the Gaia Consortium's data reduction pipelines in the development and preparation for Gaia's Data Release 4 (DR4). They used provisional instrument models and calibrations; thus they will not be identical (but similar to) the corresponding data to be produced and published for this star with DR4. Furthermore, the final epoch astrometry table in DR4 will contain many additional details and quality diagnostics on the individual measurements than the present table does. Each row of the present table gives the minimum necessary data for one of the 622 individual astrometric measurements used in the BH3 discovery paper. A Gaia epoch astrometry entry does not give a full 2-dimensional position on the sky, but only a 1-dimensional measurement. Each of these 1-dimensional measurements (denoted centroid_posal) corresponds to the longitude of the observed object in a 2-dimensional coordinate system having its origin at the mean position of the star under consideration, and having the axis of its longitude coordinate rotated with respect to local ICRS North by a precisely known angle (denoted scan_posangle). This angle, as well as the times of the observations, are determined by the rotational motion of the Gaia spacecraft, which closely follows a pre-defined sky coverage pattern known as the Gaia nominal scanning law (NSL).

The details of the definition of scan_posangle and centroid_posal, and thus the precise meaning of the 1-dimensional measurements in the table, are described in the public Gaia Consortium document LL-061 (L. Lindegren & U. Bastian, 'Local plane coordinates for the detailed analysis of complex Gaia sources', https://dms.cosmos.esa.int/COSMOS/doc_fetch.php?id=504573). The mathematical background and the usage of the data in the modelling of astrometric source parameters is described in the publication by L. Lindegren et al., 'The astrometric core solution for the Gaia mission', Lindegren et al. (2012A&A...538A..78L), more specifically in Section 5.1 of that publication.

The epoch RVS radial velocities (tableb2.dat), were produced with the final pipeline, but not finalized with the post-processing; their value or uncertainties may slightly differ from the final DR4 values. Like for astrometry, the final epoch radial velocity table in DR4 will contain additional details and quality diagnostics on the individual measurements. Each epoch radial velocity record corresponds to a transit of the source on the RVS CCDs. The provided observation time of the radial velocity corresponds to the mean of the observation times of the three CCDs used to collect spectra in the RVS during the transit.

(2 data files).