The GRAVITY young stellar object survey

Abstract

Context. Protoplanetary disks drive some of the formation process (e.g., accretion, gas dissipation, formation of structures) of stars and planets. Understanding such physical processes is one of the most significant astrophysical questions. HD 163296 is an interesting young stellar object for which infrared and sub-millimeter observations have shown a prominent circumstellar disk with gaps plausibly created by forming planets. Aims. This study aims to characterize the morphology of the inner disk in HD 163296 with multi-epoch, near-infrared interferometric observations performed with GRAVITY at the Very Large Telescope Interferometer. Our goal is to depict the K-band (λ0 ~ 2.2 μm) structure of the inner rim with milliarcsecond (sub-au) angular resolution. Our data is complemented with archival Precision Integrated-Optics Near-infrared Imaging ExpeRiment (H-band; λ0 ~ 1.65 μm) data of the source. Methods. We performed a gradient descent parametric model fitting to recover the sub-au morphology of our source. Results. Our analysis shows the existence of an asymmetry in the disk surrounding the central star of HD 163296. We confirm variability of the disk structure in the inner ~2 mas (0.2 au). While variability of the inner disk structure in this source has been suggested by previous interferometric studies, this is the first time that it is confirmed in the H- and K-bands by using a complete analysis of the closure phases and squared visibilities over several epochs. Because of the separation from the star, position changes, and the persistence of this asymmetric structure on timescales of several years, we argue that it is probably a dusty feature (e.g., a vortex or dust clouds) made by a mixing of silicate and carbon dust and/or refractory grains, inhomogeneously distributed above the mid-plane of the disk.

Two Rings and a Marginally Resolved, 5 au Disk around LkCa 15 Identified via Near-infrared Sparse Aperture Masking Interferometry

“…To test the robustness of the direct image result, we followed a similar approach to that used by Sanchez-Bermudez et al (2021) and directly reconstructed an image using simulated data from the best-fit 2PG+IG model instead of the observations themselves. For this test we obtain a very similar image to that discussed in the previous paragraph.…”

The Inner Disk Rim of HD 163296: Linking Radiative Hydrostatic Models with Infrared Interferometry

“…We use the radiative hydrostatic approach of Flock et al (2016Flock et al ( , 2019 to calculate the distribution of the disk gas density ρ, dust density ρ d , and temperature T. Our implementation was done in the FARGO3D code (Benítez-Llambay & Masset 2016), extending the work of Chrenko & Nesvorný (2020). The model relies on a decoupling between the timescales of thermal relaxation (driven mostly by the radiation reprocessing), vertical hydrostatic relaxation (driven by the propagation of sound waves), and disk accretion (driven by the redistribution of the angular momentum).…”

“…Sub-au regions of protoplanetary disks represent the environment that has shaped precursors of terrestrial planets as well as the numerous populations of short-period exoplanets (e.g., Mulders et al 2018;Petigura et al 2018) during their early evolution. For instance, the transition between the outer dead zone and the inner zone of active magnetorotational (MRI) turbulence (at ≈900 K) is considered a sweet spot for accumulation of dust grains (e.g., Varnière & Tagger 2006;Dzyurkevich et al 2010;Ueda et al 2019;Jankovic et al 2022) as well as a migration trap for planets (e.g., Masset et al 2006;Flock et al 2019), although the local suppression of the dust drift and planet migration seems to strongly depend on disk properties (e.g., Schobert et al 2019;Jankovic et al 2021;Chrenko et al 2022).…”

“…The question remains unsettled mostly because the recently used parametric fits (Lazareff et al 2017;GRAVITY Collaboration et al 2021;Varga et al 2021) employ only a handful of parameters to avoid degeneracy and they are also difficult to link directly to physical models. With this in mind, the strategy of our paper is to start from a physical model of the inner rim alone (following the framework developed by Flock et al 2016Flock et al , 2019 and see how it compares to the visibility profiles in multiple NIR and MIR bands, to the half-light radii determined in earlier works, and to previously reported fractional disk fluxes. Our objective is to answer what it takes to modify the physical model in order to push some of the synthetic observables closer to the real data.…”

Optical interferometry imaging contest IX

“…The simulation of this young-stellar object was created following the model described in. 4 The ring is elongated with the semimajor axis at a position angle of 50 • East of North. The inclination angle of the ring is also at 50 • .…”