Shp. Alencar et Lpr. Vaz, THE GRAVITY-BRIGHTENING EFFECT AND STELLAR ATMOSPHERES .1. RESULTS FOR MODELS WITH 3700K-LESS-THAN-T-EFF-LESS-THAN-7000K, Astronomy and astrophysics, 326(1), 1997, pp. 257-262
The gravity-brightening exponent (beta) is studied using the UMA (Upps
ala Model Atmosphere) code in nonilluminated convective grey (in the s
ense of ''continuum only'' opacity) and non-grey (line blanketed) atmo
spheres, for 3700 K < T-eff < 7000 K. The value beta=0.32 proposed by
Lucy was confirmed only for T-eff similar to 6500 K. beta depends upon
T-eff (an analytical expression is given), being rather insensitive t
o variations of the mixing length parameter, of the stellar mass and t
o the use of grey or non-grey atmospheres. A comparison with empirical
determinations and a preliminary test of the use of the proposed beta
values in eclipsing binary light curve analysis are presented. A depe
ndence of beta on external illumination (''reflection effect'') for co
nvective models is evidenced for the first time, the larger the amount
of incident flux the larger the beta exponent.