Calibration of the photometric G passband for Gaia Data Release 1⋆
Centro de Astrobiología, CSIC-INTA, campus ESAC, camino bajo del castillo s/n, 28 692 Villanueva de la Cañada, Spain
Received: 25 October 2017
Accepted: 29 November 2017
Context. On September 2016 the first data from Gaia were released (DR1). The first release included photometry for over 109 sources in the very broad G system.
Aims. The aims here are to test the correspondence between G magnitudes in DR1 and the synthetic equivalents derived using spectral energy distributions from observed and model spectrophotometry; to correct the G passband curve; and to measure the zero point in the Vega system.
Methods. I have computed the synthetic G and Tycho-2 BTVT photometry for a sample of stars using the Next Generation Spectral Library (NGSL) and the Hubble Space Telescope (HST) CALSPEC spectroscopic standards.
Results. I have found that the nominal G passband curve is too blue for the DR1 photometry, as shown by the presence of a color term in the comparison between observed and synthetic magnitudes. A correction to the passband applying a power law in λ with an exponent of 0.783 eliminates the color term. The corrected passband has a Vega zero point of 0.070 ± 0.004 mag.
Key words: surveys / methods: data analysis / techniques: photometric
Tables 1 and 2 are only available at the CDS via anonymous ftp to cdsarc.u-strasbg.fr (18.104.22.168) or via http://cdsarc.u-strasbg.fr/viz-bin/qcat?J/A+A/608/L8
© ESO, 2017