Precise calibration of the dependence of surface brightness-colour relations on colour and class for late-type stars. (arXiv:2007.01906v1 [astro-ph.SR])
<a href="http://arxiv.org/find/astro-ph/1/au:+Salsi_A/0/1/0/all/0/1">A. Salsi</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Nardetto_N/0/1/0/all/0/1">N. Nardetto</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Mourard_D/0/1/0/all/0/1">D. Mourard</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Creevey_O/0/1/0/all/0/1">O. Creevey</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Huber_D/0/1/0/all/0/1">D. Huber</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+White_T/0/1/0/all/0/1">T. R. White</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Hocde_V/0/1/0/all/0/1">V. Hocd&#xe9;</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Morand_F/0/1/0/all/0/1">F. Morand</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Tallon_Bosc_I/0/1/0/all/0/1">I.Tallon-Bosc</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Farrington_C/0/1/0/all/0/1">C. D. Farrington</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Chelli_A/0/1/0/all/0/1">A. Chelli</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Duvert_G/0/1/0/all/0/1">G. Duvert</a>

Surface brightness-colour relations (SBCRs) are used to derive the stellar
angular diameters from photometric observations. They have various
astrophysical applications, such as the distance determination of eclipsing
binaries or the determination of exoplanet parameters. However, strong
discrepancies between the SBCRs still exist in the literature, in particular
for early and late-type stars. We aim to calibrate new SBCRs as a function of
the spectral type and the luminosity class of the stars. Our goal is also to
apply homogeneous criteria to the selection of the reference stars and in view
of compiling an exhaustive and up-to-date list of interferometric late-type
targets. We implemented criteria to select measurements in the JMMC Measured
Diameters Catalog (JMDC). We then applied additional criteria on the
photometric measurements used to build the SBCRs, together with stellar
characteristics diagnostics. We built SBCRs for F5/K7-II/III, F5/K7-IV/V,
M-II/III and M-V stars, with respective RMS of $sigma_{F_{V}} = 0.0022$ mag,
$sigma_{F_{V}} = 0.0044$ mag, $sigma_{F_{V}} = 0.0046$ mag, and
$sigma_{F_{V}} = 0.0038$ mag. This results in a precision on the angular
diameter of 1.0%, 2.0%, 2.1%, and 1.7%, respectively. These relations cover
a large $V-K$ colour range of magnitude, from 1 to 7.5. Our work demonstrates
that SBCRs are significantly dependent on the spectral type and the luminosity
class of the star. Through a new set of interferometric measurements, we
demonstrate the critical importance of the selection criteria proposed for the
calibration of SBCR. Finally, using the Gaia photometry for our samples, we
obtained (G-K) SBCRs with a precision on the angular diameter between 1.1% and
2.4%.

Surface brightness-colour relations (SBCRs) are used to derive the stellar
angular diameters from photometric observations. They have various
astrophysical applications, such as the distance determination of eclipsing
binaries or the determination of exoplanet parameters. However, strong
discrepancies between the SBCRs still exist in the literature, in particular
for early and late-type stars. We aim to calibrate new SBCRs as a function of
the spectral type and the luminosity class of the stars. Our goal is also to
apply homogeneous criteria to the selection of the reference stars and in view
of compiling an exhaustive and up-to-date list of interferometric late-type
targets. We implemented criteria to select measurements in the JMMC Measured
Diameters Catalog (JMDC). We then applied additional criteria on the
photometric measurements used to build the SBCRs, together with stellar
characteristics diagnostics. We built SBCRs for F5/K7-II/III, F5/K7-IV/V,
M-II/III and M-V stars, with respective RMS of $sigma_{F_{V}} = 0.0022$ mag,
$sigma_{F_{V}} = 0.0044$ mag, $sigma_{F_{V}} = 0.0046$ mag, and
$sigma_{F_{V}} = 0.0038$ mag. This results in a precision on the angular
diameter of 1.0%, 2.0%, 2.1%, and 1.7%, respectively. These relations cover
a large $V-K$ colour range of magnitude, from 1 to 7.5. Our work demonstrates
that SBCRs are significantly dependent on the spectral type and the luminosity
class of the star. Through a new set of interferometric measurements, we
demonstrate the critical importance of the selection criteria proposed for the
calibration of SBCR. Finally, using the Gaia photometry for our samples, we
obtained (G-K) SBCRs with a precision on the angular diameter between 1.1% and
2.4%.

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