The VLTI/GRAVITY view of the innermost regions of protoplanetary disks

Karine Perraut (Institut de Planétologie et d'Astrophysique de Grenoble) - hybrid seminar (in-person in Salle NEF + remote via Zoom)

Abstract:
Probing the inner rim of the protoplanetary disks where micron-sized dust grains grow to pebbles and larger bodies producing the first building blocks of planets, and investigating star-disk interactions at sub-astronomical unit scale are of utmost interest as they define the initial and environmental conditions for planet formation.
Since its installation in 2016, VLTI/GRAVITY has brilliantly illustrated the potential of the high angular and spectral resolutions to constrain these innermost regions of protoplanetary disks in the near-infrared K-band. With a sample of a hundred young stellar objects (YSO), from solar-like (namely the T Tauri) to high-mass YSO, the YSO GTO Large Program has gathered a large homogeneous data set allowing us to extend the Radius-Luminosity relation over more than 4 decades and to look for trends with the properties of the central star and the disk morphology. We have investigated the origins of gaps in the innermost regions, measure (mis-)alignments between the inner and the outer disks over a sample of 20 transitional disks, and tested proxies to investigate a potential evolutionary scenario between the different morphologies of the dusty disks. Thanks to its spectroscopic ability, GRAVITY has also led to the spatial resolution of the Hydrogen Br emitting regions around a sample of YSO, leading to the first resolution of the magnetospheric accretion regions around T Tauri stars.
In a near future, with its improved sensitivity and sky coverage, GRAVITY+ will drastically increase our sample: a more representative population of YSO, including the bulk of T Tauri stars in different star forming regions, will be reachable, as long as lower-mass young stars and younger embedded sources that would become observable with near-infrared interferometry for the first time. Combined within multi-technique and multi-wavelength campaigns, and with advanced radiative transfer and MHD simulations, the GRAVITY+ observations will be key to obtain a global picture of the inner parts of the protoplanetary disks.
In this talk, I will review the most striking results obtained with GRAVITY during its first 5 years of operation and illustrate the opportunities opened by GRAVITY+.