Verifying reddening and extinction for Gaia DR1 TGAS main sequence stars
  We compare eight sources of reddening and extinction estimates for
approximately 60,000 {\it Gaia} DR1 Tycho--Gaia Astrometric Solution (TGAS)
main sequence stars younger than 3~Gyr with a relative error of the {\it Gaia}
parallax less than 0.1. For the majority of the stars, the best 2D dust
emission-based reddening maps show considerable differences between the
reddening to infinity and the one calculated to the stellar distance using the
barometric law of the dust distribution. This proves that the majority of the
TGAS stars are embedded in to the Galactic dust layer and a proper 3D treatment
of the reddening/extinction is required to reliably calculate their de-reddened
colors and absolute magnitudes. The sources with the 3D estimates of reddening
are tested in their ability to put the stars among the PARSEC and MIST
theoretical isochrones in the Hertzsprung--Russell diagram based on the precise
{\it Gaia}, {\it Tycho-2}, 2MASS and {\it WISE} photometry. Only the
reddening/extinction estimates by Arenou et al. (1992), Gontcharov (2012), and
Gontcharov (2017), being appropriate for nearby stars within 280~pc, provide
both the minimal number of outliers bluer than any reasonable isochrone and the
correct number of stars younger than 3~Gyr in agreement with the Besan\c{c}on
Galaxy model.
