Study of environment and photosphere of 51 Oph

The main objective of this work is to improve our understanding of young fast-rotating stars evolving from the Herbig Ae/Be class to the Vega-like one. We observed with the VEGA instrument on CHARA one object so-called 51 Oph that is probably in such an evolutionary phase, allowing us to measure a mean stellar radius for the first time for this star and to show that the Hα emission was produced in a Keplerian rotating disc. However, additional observations are needed to improve our (u,v) plan coverage in order to measure the flattening of this close-to-critically rotating star and to probe the inner region of its circumstellar gaseous disc. These studies will help to disentangle the gas and dust emission around this late young star and will finally improve our understanding of the planet formation conditions in the inner regions of protoplanetary discs.