Exocomets of Pictoris II: Two dynamical families of exocomets simulated with REBOUND
arXiv:2603.05600
Abstract
We investigate the dynamical evolution of particles in the Pic system to determine likely formation pathways to the present-day observed exocomet populations. We aim to relate these results to similar studies recently carried out since the discovery of the inner planet Pic c. We simulate the Pic system using the non-symplectic adaptive N-body integrator IAS15 in REBOUND. We seed the system with over 100,000 mass-less test particles that evolve for 25 Myr, and adopt initial conditions and a particle distribution that closely matches similar simulations in recent literature. Using IAS15, REBOUND resolves close-encounters between test particles and the two gas giants in the system, which is crucial for understanding aspects of the dynamical evolution. Planet-disk interactions rapidly clear most of the system within 35 AU apart from a region within the orbit of Pic c, and a region between 20 and 25 AU. After 10 Myr, exocomets can be sourced continuously from these regions, as well as from the inner edge of the region beyond ~35 AU where particles are stable on longer timescales. From the region interior to Pic c, the exocomets are formed by excitation via mean-motion resonance with Pic c, obtaining a narrow distribution of radial velocities, consistent with spectroscopic observations. Particles initialized in the outer system may enter onto stargrazing orbits due to disruption by the two gas giants, causing a wider radial velocity distribution, and we propose that this population corresponds to a second dynamical family previously observed via spectroscopy. These particles typically undergo chaotic dynamical evolution for to years after passing the water sublimation limit at ~8 AU until reaching the sublimation distance of calcium near 0.4 AU, implying that the two families of exocomets may have different volatile contents.
12 pages, 10 figures, accepted for publication in A&A