The inner dust rim of protoplanetary disks as probed by GRAVITY

Understanding the observed diversity of planetary systems requires to better probe the initial conditions of their formation, which are intrinsically linked to the physical conditions at play in protoplanetary disks. The nature and the interplay of the different processes as accretion flows, winds, dust grain coagulation within the innermost central regions (< 5 au) are still poorly constrained. Only optical long-baseline interferometry can bring spatially resolved constraints on this region and on the mechanisms that shape it. As an illustration, the broad H-band interferometric observations of the PIONIER Large Program of about 50 Herbig AeBe stars have shown that the sublimation front is generally rather smooth, wide, in agreement with the presence of multiple dust grain populations, and that its thickness is larger than predicted by hydrostatic models. The GRAVITY YSO Large Program based on GTO time aims at completing this statistical study by probing the inner disk thermal emission in the K band, in a systematic and homogeneous approach. In this talk we will present the first results obtained by analyzing the continuum observations of a sample of about 20 HAEBEs and T Tauris.