  We present the flux tables of the spectro-photometric standard stars (SPSS)
used to calibrate in flux the Gaia DR2 and (E)DR3 data releases. The latest
SPSS grid version contains 112 stars, whose flux tables agree to better than 1%
with the CALSPEC spectra of 11 flux standards for the calibration of the Hubble
Space Telescope. The synthetic magnitudes computed on the SPSS spectra also
agree to better than 1% with the Landolt magnitudes of 37 stars in common. The
typical spreads in both comparisons are of the order of 1%. These uncertainties
already meet the initial requirements for the Gaia SPSS project, but further
improvements are expected in the next SPSS versions, that will be used to
calibrate future Gaia releases. We complement the SPSS flux tables with
literature spectra of 60 additional stars that did not pass all the criteria to
be SPSS, the Passband Validation Library (PVL). The PVL contains stars of
extreme spectral types, such as bright O and B stars and late M stars and brown
dwarfs, and was useful to investigate systematic effects in the previous Gaia
DR2 release and to minimize them in the EDR3 one. The PVL literature spectra
are recalibrated as accurately as possible onto the SPSS reference scale, so
that the two sets together can be used in a variety of validation and
comparison studies.
