Effects of inclined star-disk encounter on protoplanetary disk size

Abstract

Most, if not all, young stars are initially surrounded by protoplanetary disks. Owing to the preferential formation of stars in stellar clusters, the protoplanetary disks around these stars may potentially be affected by the cluster environment. Various works have investigated the influence of stellar fly-bys on disks, although many of them consider only the effects due to parabolic, coplanar encounters often for equal-mass stars, which is only a very special case. We perform numerical simulations to study the fate of protoplanetary disks after the impact of parabolic star-disk encounter for the less investigated case of inclined up to coplanar, retrograde encounters, which is a much more common case. Here, we concentrate on the disk size after such encounters because this limits the size of the potentially forming planetary systems. In addition, with the possibilities that ALMA offers, now a direct comparison to observations is possible. Covering a wide range of periastron distances and mass ratios between the mass of the perturber and central star, we find that despite the prograde, coplanar encounters having the strongest effect on the disk size, inclined and even the least destructive retrograde encounters mostly also have a considerable effect, especially for close periastron passages. Interestingly, we find a nearly linear dependence of the disk size on the orbital inclination for the prograde encounters, but not for the retrograde case. We also determine the final orbital parameters of the particles in the disk such as eccentricities, inclinations, and semi-major axes. Using this information the presented study can be used to describe the fate of disks and also that of planetary systems after inclined encounters.

External photoevaporation of circumstellar discs constrains the time-scale for planet formation

“…Regarding dynamical effects, close encounters on a single Nbody disk of test particles have been investigated in several studies (e.g. Breslau et al 2014;Jílková et al 2016;Bhandare et al 2016;Pfalzner et al 2018). Winter et al (2018a,b) use a ring of test particles around a star to obtain linearized expressions of the effect that a stellar encounter can have on the mass and morphology of the disk, and then use them to simulate the disk using a smoothed particles hydrodynamics (SPH) code.…”

Did a stellar fly-by shape the planetary system around Pr 0211 in the cluster M44?

“…Then the effect on the disc size is less and it would have needed to be even closer to result in r d < 6 AU. Bhandare et al(2016) and Vincke & Pfalzner (2017) give two different approximation for an inclination angleaveraged disc size after a fly-by. Here we use the formula given by Vincke & Pfalzner (2017), which leads to the following for- Fig.…”

DESTINY: Database for the Effects of STellar encounters on dIsks and plaNetary sYstems

“…We note that this is purely a technical paper on how to use the database. Further details of the numerical method and a discussion on the applicability of these approximations can be found in [31,33].…”

“…Many of the simulations mentioned above do not give quantitative results of the effect of fly-bys on disks. Some provide either fit formulae or tabulated values of specific disk properties after fly-bys [30,31,33,36,50,51]. Although this is valuable information for some studies, it limits the user to the properties that have already been fitted or tabulated, like disk mass, disk size etc.…”

“…In most fly-by simulations the initial disk-mass distribution is simulated by assigning each pseudo-particle the same mass [50,51,[60][61][62]. In contrast, here a fixed test-particle distribution is used initially and the particles are assigned a mass according to the desired density distribution in the disk during post processing [31,33]. This has two advantages, first, such a flexible numerical scheme allows using one suite of simulations for any initial disk mass distribution and second, this method helps achieve a higher resolution particularly in the outer disk/planetary system areas.…”