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gaia data release 3 documentation

6 Spectroscopy

6.1 Introduction

Author(s): Paola Sartoretti, George Seabroke, Ronny Blomme and Marc David

This chapter summarises the processing and validation of the Radial Velocity Spectrometer (RVS) data released in Gaia DR3.

A description of the RVS instrument is provided in Cropper et al. (2018) and a description of the calibration of the instrument is in Section 5 of Sartoretti et al. (2018). The products of the RVS pipeline, their properties and their validation are described in more detail in dedicated papers: the radial velocities are described in Katz et al. (2023), the specific treatments to obtain the hot star radial velocities in Blomme et al. (2023), and the radial velocities of the double-lined spectra in Damerdji et al. (2022). The mean spectra are described in Seabroke et al. (2022), the broadening velocities in Frémat et al. (2023) and the magnitudes in the RVS passband in Sartoretti et al. (2023).

Gaia DR2, based on 22 months of data, was the first release to include radial velocities from the RVS. These were for 7.2 million stars brighter than GRVS=12 and with effective temperature Teff in the range from about 3550 to 6900 K. The Gaia DR2 radial velocities have been copied for convenience to Gaia EDR3, leaving aside some identified spurious cases (see Seabroke et al. 2021).

Gaia DR3, based on 34 months of data, contains radial velocities for about 33.8 million stars brighter than GRVS14 and with effective temperature Teff in the range from about 3100 to 14 500 K. In addition to the radial velocities, other products of the RVS pipeline are published for the first time: broadening velocities for about 3.5 million stars, magnitudes GRVS for about 32 million stars, mean spectra for about 1 million stars, and epoch radial velocities for about 2000 Cepheid and RR Lyrae stars (Clementini et al. (2023) and Chapter 10). All the other epoch data will be published in Gaia DR4.

The mean spectra and the epoch radial velocities produced by the RVS pipeline were used and analysed by other downstream pipelines and resulted in data products published in Gaia DR3 and described respectively in Chapter 11 and Chapter 7.

It is recommended to treat the Gaia DR3 radial velocity catalogue as independent from Gaia DR2.