arXiv subjects

Thomas Collin-Dufresne

Publications and source records attributed to Thomas Collin-Dufresne.

2 recordsLinked to original sources

arXiv2026

Destructuring the disk of AB Aurigae: Dynamics and accretion

In this paper, we present near-IR polarized images of the AB Aur disk at three epochs spanning 3.85 years with SPHERE/IRDIS, as well as Halpha images obtained with SPHERE/ZIMPOL at a single epoch. The purpose of this study is to analyze the dynamics of the entire disk and of the various structures in near-IR polarimetry, and to identify sources of Halpha emission to derive constraints on their mass accretion rate. The dynamical study in the near-IR shows that the disk globally follows Keplerian rotation, but we observe a departure from this behavior at radii smaller than ~60au. At the smallest radius of ~25au, we measure a deviation from Keplerian rotation as large as ~12deg over 3.85 years, demonstrating sub-Keplerian rotation. The two bright spirals within the millimeter cavity have different dynamic trends, and we discuss their possible link with the identified planet candidates. We also discuss the implications of the non-Keplerian behavior, and we posit that it could be related to interactions with multiple protoplanets orbiting out of the disk plane on elliptical orbits. Furthermore, the orbital analysis of the compact sources (labeled f1, f2, and f3) suggests that their orbital planes are significantly inclined with respect to the disk plane by several tens of degrees. The variability of the shadows suggests that they are produced by optically thick regions located within ~60au. For the photometric analysis in Halpha, we derive a flux of about 8.22x10^{-15} erg/s/cm^2 for the entire feature f1, but only 6.46x10^{-16} erg/s/cm^2 at the location of AB Aur b, consistent with non-detection. If f1 were a point source and the accretion remained constant for 1Myr, it would correspond to ~5-20 Jupiter masses according to the magnetospheric accretion model or ~6-10 Jupiter masses according to the boundary layer accretion model.

astro-ph.EP↗

arXiv2025

Coexistence of coagulation and streaming instabilities in protoplanetary discs

The streaming instability is considered one of the leading candidates for the formation of planetesimals, due to its ability to overcome the bouncing and fragmentation barriers. The formation of dense dust clumps through this process, however, is possible provided it involves solids with dimensionless stopping times $\sim 0.1$ in standard discs, which typically corresponds to 1-10 cm-sized particles. This implies that dust coagulation is required for the SI to be an efficient process. Here, we employ unstratified, shearing-box simulations combined with a moment equation for solving the coagulation equation to examine the effect of dust growth on the SI. In dust-rich discs with a dust-to-gas ratio $ε\gtrsim 1$, coagulation is found to have little impact on the SI; while in dust-poor discs with $ε\sim 0.01$, we observe the formation of vertically extended filaments through the action of the coagulation instability (CI), which is triggered due to the dependence of coagulation efficiency on dust density. For moderate dust-to-gas ratios $ε\sim 0.1$ and Stokes numbers $St \lesssim 0.1$, we find onset of the SI within these filaments, with a linear growth rate significantly higher compared to standard SI. We refer to this regime as coagulation-assisted SI. The synergy between both instabilities in that case leads to isotropic turbulence and dust concentrations that are increased by a factor of $30-40$. As dust continues to grow, SI tends to overcome the effect of the CI such that the nonlinear saturation phase is similar to pure SI. Our results suggest that coagulation, by simply increasing dust size, may facilitate the formation of dense clumps through the SI; even though it has only little effect on its nonlinear evolution.

astro-ph.EP↗