LAM Seminar by Karine Perraut: Probing the star-disk interaction regions around young stellar objects with VLTI/GRAVITY

Deciphering the physical processes occurring in the innermost region of protoplanetary disks is key to understand the environmental conditions of (terrestrial) planet formation and evolution. Thanks to its unique milliarcsecond angular resolution, VLTI/GRAVITY has allowed us to resolve the ~0.1 – 5AU disk region where most of the planets have been detected so far.

We led a Large Program in a homogeneous sample of nearly hundred young stellar objects covering the T-Tauri (~40), Herbig AeBe (~60), and high-mass YSO (a few) classes. This K-band GRAVITY YSO survey started 8 years ago has made significant contributions to the field: we extended the near-infrared disk radius-luminosity relation over four orders of magnitude, which has permitted to evidence trends with the properties of the central star (mass, accretion rate); we evidenced the month-scale morphological variability of the inner disk for few sources and the potential connection between the inner and the outer scales of the protoplanetary disks.

Furthermore, thanks to its spectral resolution ability in the K-band, GRAVITY has allowed us to spatially resolve, in a sample of T Tauri stars, the Brg emitting regions associated to hot hydrogen gas, giving us new insights in the star-disk interaction regions through direct monitoring of accretion flows and disentangling of the various accretion-ejection mechanisms.

We will finally discuss the potential yield of the new GRAVITY+ upgrade, in particular towards the study of early Class I phases of YSOs in various star forming regions, as well as the possible legacy of GRAVITY(+) observations to refine theoretical models of protoplanetary disks.

A few references:

GRAVITY Coll. Perraut et al. 2019, A&A, 632, 53

GRAVITY Coll. Perraut et al. 2021, A&A, 655, 73

Bohn, Benisty, Perraut et al. 2022, A&A, 658, 183

Bouvier, Perraut et al. 2020, A&A, 636, 108

GRAVITY Coll. Garcia-Lopez et al. 2020, Nature, 584, 547-550

GRAVITY Coll. Wojtczak et al. 2023, A&A, 669, 59

GRAVITY Coll. Nowacki, Perraut et al. 2024, A&A, 690, 123