Exocomet Orbital Distribution Around Beta Pictoris
The 23 Myr young star β Pictoris is a laboratory for planet formation studies given its observed debris disk, its two directly imaged super-Jovian planets, and the evidence of transiting extrasolar comets.
The most recent evidence of exocometary transits around β Pic came from the TESS space mission. Previous analyses of these transits constrained the orbital distribution of the underlying exocomet population to range between about 0.03 and 1.3 AU assuming a fixed transit impact parameter. Here we examine the distribution of the observed transit durations (Δt) to infer the orbital surface density distribution (δ) of the underlying exocomet sample.
We show that a narrow belt of exocomets around β Pic, in which the transit impact parameters are randomized but the orbital semimajor axes are equal, results in a pile-up of long transit durations. This is contrary to observations, which reveal a pile-up of short transit durations (Δt≈0.1 d) and a tail of only a few transits with Δt>0.4 d. A flat density distribution of exocomets between about 0.03 and 2.5 AU results in a better match between the resulting Δt distribution and the observations but the slope of the predicted Δt histogram is not sufficiently steep.
An even better match to the observations can be produced with a δ∝aβ power law. Our modeling reveals a best fit between the observed and predicted Δt distribution for β=−0.15+0.05−0.10. A more reasonable scenario in which the exocometary trajectories are modeled as hyperbolic orbits can also reproduce the observed Δt distribution to some extent. Our results imply that cometary material exists on highly eccentric orbits with a more extended range of semimajor axes than suggested by previous spectroscopic observations.
René Heller (Max Planck Institute for Solar System Research, Göttingen, Germany)
Comments: accepted in Astronomy & Astrophysics, 6 pages, 7 Figures (6 col., 1 b/w)
Subjects: Earth and Planetary Astrophysics (astro-ph.EP)
Cite as: arXiv:2407.20829 [astro-ph.EP] (or arXiv:2407.20829v1 [astro-ph.EP] for this version)
Submission history
From: René Heller
[v1] Tue, 30 Jul 2024 13:55:40 UTC (1,212 KB)
https://arxiv.org/abs/2407.20829
Astrobiology, Exoplanet,
