2023/07/18 by González, Jorge Pérez, Greklek-McKeon, Michael, Vissapragada, Shreyas +4 · 2 citations
#Earth and Planetary Astrophysics (astro-ph.EP) #FOS: Physical sciences
paper · doi:10.48550/arxiv.2307.09515
Photoevaporative mass-loss rates are expected to be highest when planets are young and the host star is more active, but to date there have been relatively few measurements of mass-loss rates for young gas giant exoplanets. In this study we measure the present-day atmospheric mass-loss rate of TOI-1268b, a young (110 - 380 Myr) and low density (0.71+0.17-0.13~g~cm-3) hot Saturn located near the upper edge of the Neptune desert. We use Palomar/WIRC to search for excess absorption in the 1083~nm helium triplet during two transits of TOI-1268b. We find that it has a larger transit depth (0.285-0.050+0.048% excess) in the helium bandpass than in the TESS observations, and convert this excess absorption into a mass-loss rate by modeling the outflow as a Parker wind. Our results indicate that this planet is losing mass at a rate of log M = 10.2 ± 0.3~g~s-1 and has a thermosphere temperature of 6900+1800-1200~K. This corresponds to a predicted atmospheric lifetime much larger than 10 Gyr. Our result suggests that photoevaporation is weak in gas giant exoplanets even at early ages.