Gaia Data Release 3. GRVS photometry from the RVS spectra
Résumé
Context.Gaia Data Release 3 (DR3) contains the first release of magnitudes estimated from the integration of Radial Velocity Spectrometer (RVS) spectra for a sample of about 32.2 million stars brighter than GRVS ∼ 14 mag (or G ∼ 15 mag).
Aims: In this paper, we describe the data used and the approach adopted to derive and validate the GRVS magnitudes published in DR3. We also provide estimates of the GRVS passband and associated GRVS zero-point.
Methods: We derived GRVS photometry from the integration of RVS spectra over the wavelength range from 846 to 870 nm. We processed these spectra following a procedure similar to that used for DR2, but incorporating several improvements that allow a better estimation of GRVS. These improvements pertain to the stray-light background estimation, the line spread function calibration, and the detection of spectra contaminated by nearby relatively bright sources. We calibrated the GRVS zero-point every 30 h based on the reference magnitudes of constant stars from the HIPPARCOS catalogue, and used them to transform the integrated flux of the cleaned and calibrated spectra into epoch magnitudes. The GRVS magnitude of a star published in DR3 is the median of the epoch magnitudes for that star. We estimated the GRVS passband by comparing the RVS spectra of 108 bright stars with their flux-calibrated spectra from external spectrophotometric libraries.
Results: The GRVS magnitude provides information that is complementary to that obtained from the G, GBP, and GRP magnitudes, which is useful for constraining stellar metallicity and interstellar extinction. The median precision of GRVS measurements ranges from about 0.006 mag for the brighter stars (i.e. with 3.5≲ GRVS ≲6.5 mag) to 0.125 mag at the faint end. The derived GRVS passband shows that the effective transmittance of the RVS is approximately 1.23 times better than the pre-launch estimate.
Aims: In this paper, we describe the data used and the approach adopted to derive and validate the GRVS magnitudes published in DR3. We also provide estimates of the GRVS passband and associated GRVS zero-point.
Methods: We derived GRVS photometry from the integration of RVS spectra over the wavelength range from 846 to 870 nm. We processed these spectra following a procedure similar to that used for DR2, but incorporating several improvements that allow a better estimation of GRVS. These improvements pertain to the stray-light background estimation, the line spread function calibration, and the detection of spectra contaminated by nearby relatively bright sources. We calibrated the GRVS zero-point every 30 h based on the reference magnitudes of constant stars from the HIPPARCOS catalogue, and used them to transform the integrated flux of the cleaned and calibrated spectra into epoch magnitudes. The GRVS magnitude of a star published in DR3 is the median of the epoch magnitudes for that star. We estimated the GRVS passband by comparing the RVS spectra of 108 bright stars with their flux-calibrated spectra from external spectrophotometric libraries.
Results: The GRVS magnitude provides information that is complementary to that obtained from the G, GBP, and GRP magnitudes, which is useful for constraining stellar metallicity and interstellar extinction. The median precision of GRVS measurements ranges from about 0.006 mag for the brighter stars (i.e. with 3.5≲ GRVS ≲6.5 mag) to 0.125 mag at the faint end. The derived GRVS passband shows that the effective transmittance of the RVS is approximately 1.23 times better than the pre-launch estimate.
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