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gaia data release 3 documentation

20.13 Variability tables

20.13.9 vari_epoch_radial_velocity

This table contains the epoch radial velocity data points for a sub-set of variable stars. Each entry is a radial velocity in the solar barycentric reference frame for a given object and observation time.

Columns description:

source_id : Unique source identifier (unique within a particular Data Release) (long)

A unique single numerical identifier of the source obtained from gaia_source (for a detailed description see gaia_source.source_id).

transit_id : Transit unique identifier (long)

The transit_id is a unique identifier assigned to each detected (and confirmed) source as it transits the Gaia focal plane. Each time a given source is detected as Gaia scans and re-scans the sky a new transit_id will be created to badge that apparition. Hence the along–scan time and the across–scan position along with the telescope in which the source was detected are used to form a unique integer with which to label the transit.

The several features of a detection that are encoded in transit_id can be easily retrieved using bit masks (&) and shifts (≫) as follows:

  • •

    On-Board Mission Time line [ns]
    = 204800 * ((transit_id ≫ 17) & (0x000003FFFFFFFFFF))

  • •

    Field-of-view = 1 + (transit_id ≫ 15) & 0x03 [1 for ‘preceding’ and 2 for ‘following’ fields-of-view respectively]

  • •

    CCD row = (transit_id ≫ 12) & 0x07 [dimensionless, in the range 1 to 7]

  • •

    Across-scan ‘reference acquisition pixel’ in strip AF1 = (transit_id) & 0x0FFF [pixels] (this is the across-scan centre of the AF1 window and is odd if immediately below the mid-point of the window and even if immediately above)

where the bit mask prefix ‘0x’ denotes hexadecimal.

For further details see Portell et al. (2020). For convenience a decoder for transit_id is available on-line at

rv_obs_time : Observing time of the transit (double, Time[Barycentric JD in TCB - 2 455 197.5 (day)])

Observation time of the radial velocity in the solar barycentric reference frame. It corresponds to the mean of the observation times of the three CCDs used to collect spectra in the RVS during that transit.

radial_velocity : Barycentric radial velocity (double, Velocity[km s-1])

Radial velocity in the solar barycentric frame for the transit of interest.

radial_velocity_error : Barycentric radial velocity error (double, Velocity[km s-1])

Error on the radial velocity for the transit of interest.

rejected_by_variability : Rejected by DPAC variability processing (or variability analysis) (boolean)

Indicates whether the radial velocity at this transit was rejected by the DPAC variability processing (or variability analysis)

solution_id : Solution Identifier (long)

All Gaia data processed by the Data Processing and Analysis Consortium comes tagged with a solution identifier. This is a numeric field attached to each table row that can be used to unequivocally identify the version of all the subsystems that were used in the generation of the data as well as the input data used. It is mainly for internal DPAC use but is included in the published data releases to enable end users to examine the provenance of processed data products. To decode a given solution ID visit https://gaia.esac.esa.int/decoder/solnDecoder.jsp.