Efficient Dust Radial Drift Around Young Intermediate-mass Stars

Abstract

The radial velocities and direct imaging observations of exoplanets have suggested that the frequency of giant planets may decrease for intermediate-mass stars (2.5 − 8 M ). The key mechanism that could hinder their formation remains unclear. From a theoretical point of view, planet formation around intermediate-mass stars may take place on longer timescales, which -coupled with fast migration and efficient photoevaporation -may prevent planetary formation in these environments. In this letter, we investigate the temporal evolution of the radial drift for dust particles in disks when stellar evolution is taken into account. We demonstrate that the particle drift velocity around intermediate-mass stars sharply increases after 1−2 Myr, potentially forming a difficult barrier to overcome in the first steps of planet formation. This high radial drift could explain the lack of disk detections around intermediate-mass stars older than 3−4 Myr, as opposed to low-mass stars (< 2.5 M ), where the drift may not be the most impactful factor for the disk evolution. Future high-resolution images of these disks can help us to explain why planets around intermediate-mass stars may be rare. In addition, we can explore whether the role of efficient dust radial drift does in fact hinder planet formation around intermediate-mass stars -or otherwise.

First steps of planet formation around very low mass stars and brown dwarfs

“…It has been demonstrated that these radial drift velocities are higher for disks around BDs and VLMS [32,63]. This is because the radial drift velocities of dust particles depend on the stellar mass and luminosity as v drift ∝ L 1/4 / √ M , where the dependency with stellar mass dominates for the low mass regime, while the stellar luminosity dominates for intermediate-mass stars M > 2.5M [65]. Figure 4 shows the stellar evolution up to 30 Myr of 0.1-1 M stars in the H-R diagram (left panel) and the absolute value of the maximum drift velocity as a function of time of dust particles around a 0.1 M and 1 M .…”