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gaia data release 3 documentation

20.13 Variability tables

20.13.5 vari_agn

This table provides information on AGN properties.

Columns description:

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

source_id : Unique source identifier (long)

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

fractional_variability_g : Fractional variability in the G band (float)

The fractional variability is calculated as MAD2(F)-RMS2(σF)/median(F), where MAD(F) is the Median Absolute Deviation (MAD) of the field-of-view transit fluxes F in the G band, RMS2(σF) the mean square of flux uncertainties σF, and median(F) is the median flux of the field-of-view transits in the G band.

structure_function_index : Index of the first-order structure function in the G band (float)

Index of the first-order structure function (SF; Simonetti et al. 1985), i.e., slope in the logSF vs logTau space, where Tau is the time lag. The SF is expressed in magnitude squared and computed from field-of-view transit magnitudes in the G band. The index is linked to that of the Fourier power spectrum and indicates the type of noise process at work.

structure_function_index_scatter : Standard deviation of the index of the structure function (float)

Standard deviation of the index α of the structure function (i.e., slope in the logSF vs logTau space). The structure function is expressed in magnitude square. The index is linked to the power of the Fourier power spectrum and indicates the type of noise process at work. AGN should show α=0.5, in between flicker noise (α=0) and shot (random walk) noise (α=1).

qso_variability : Quasar variability metric in the G band (float)

Quasar variability metric from field-of-view transit magnitudes in the G band in log format, log(χQSO2/ν), from Butler and Bloom (2011), after adaptation to Gaia data.

non_qso_variability : Non-quasar variability metric in the G band (float)

Non-quasar variability metric from field-of-view transit magnitudes in the G band in log format, log(χfalse2/ν), from Butler and Bloom (2011), after adaptation to Gaia data.