GEPI

Sujet: The rapid rotation of stars induces a deformation of their envelope which, combined with centrifugal acceleration, produces a gravity gradient from the pole to the equator, on the surface of the star. This effect produces a temperature and luminosity gradient: the equator is cooler and fainter than the polar regions (gravity darkening). Rapidly rotating stars with rotation axis close to the line-of-sight will be observed with a low v sin i (projected rotational velocity) and will be seen from the pole, brighter than the equator. The spectroscopic signature of gravity darkening is detectable in line profiles, but the effect on the magnitude is difficult to observe for field stars, due to the lack of comparison element.

The aim of this internship is the search for “pole-on” rapid rotator candidates, in nearby open clusters containing A-type stars (T_eff between 7500 and 10000 K) on the main sequence. The work will be based on the data mining of Gaia DR3 catalogue, combined with v sin i determined by spectroscopy. The identification of binary stars and the observation of differences in magnitude will provide constrains to the models of rapidly rotating stars. The student will work in Python and use Topcat.