A Kinematic History of Stellar Encounters with Beta Pictoris

Abstract

Beta Pictoris is an A-type star hosting a complex planetary system with two massive gas giants and a prominent debris disk. Variable absorption lines in its stellar spectrum have been interpreted as signatures of exocomets (comet-like bodies transiting the star). Stellar flybys can gravitationally perturb objects in the outer comet reservoir, altering their orbits and potentially injecting them into the inner system, thereby triggering exocomet showers. We aim to assess the contribution of stellar flybys to the observed exocomet activity by reconstructing the stellar encounter history of beta Pictoris in the past and future. We used Gaia DR3 data, supplemented with radial velocities from complementary spectroscopic surveys, to compile a catalogue of stars currently within 80 pc of beta Pictoris. Their orbits were integrated backward and forward in time in an axisymmetric Galactic potential (Gala package) to identify encounters within 2 pc of the system. We identified 99 416 stars within 80 pc of beta Pictoris at present with resolved kinematics. Among these, 49 stars (including the eight components of five binaries) encounter beta Pictoris within 2 pc between -1.5 Myr and +2 Myr. For four of the binaries, the centre-of-mass trajectories also pass within 2 pc. We estimate the sample to be more than 60 % complete within 0.5 Myr of the present. Despite beta Pictoris being the eponym of its famous moving group, none of the identified encounters involved its moving group members; all are unrelated field stars. We find no encounter capable of shaping observed disc structures, although stellar flybys may contribute to the long-term evolution of a potential Oort Cloud. Our catalogue constitutes the most complete reconstruction of the beta Pictoris encounter history to date and provides a robust foundation for future dynamical simulations.

13 pages, 6 figures, accepted for publication in Astronomy & Astrophysics

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