Atmospheric Mass Loss from TOI-1259 A b, a Gas Giant Planet With a White Dwarf Companion

Atmospheric Mass Loss from TOI-1259 A b, a Gas Giant Planet With a White Dwarf Companion
Morgan Saidel, Shreyas Vissapragada, Jessica Spake, Heather A. Knutson, Dion Linssen, Michael Zhang, Michael Greklek-McKeon, Jorge P’erez Gonz’alez, Antonija Oklopv{c}i’c
arXiv:2404.08736v1 Announce Type: new
Abstract: The lack of close-in Neptune-mass exoplanets evident in transit surveys has largely been attributed either to photoevaporative mass loss or high-eccentricity migration. To distinguish between these two possibilities, we investigate the origins of TOI-1259 A b, a Saturn-mass (0.4 M$_J$, 1.0 R$_J$) exoplanet lying along the upper edge of the Neptune desert. TOI-1259 A b’s close-in ($P$ = 3.48 days) orbit and low bulk density make the planet particularly vulnerable to photoevaporation. Using transits observed in the 1083 nm metastable helium line, we probe the upper atmosphere of TOI-1259 A b with the Hale Telescope at Palomar Observatory and the Near-Infrared Spectrograph on Keck II. We report an excess absorption of $0.395pm{0.072}%$ with Palomar and a blueshifted absorption of $2.4pm0.52%$ with Keck, consistent with an extended escaping atmosphere. Fitting this signal with a Parker wind model, we determine a corresponding atmospheric mass loss rate of log($dot{M}$) = $10.33pm 0.13$ g/s for a thermosphere temperature of $8400^{+1200}_{-1000}$ K based on the Palomar absorption and log($dot{M}$) = $10.0pm 0.1$ g/s for a thermosphere temperature of $8200^{+1000}_{-900}$ K based on the Keck absorption. This relatively low rate suggests that this planet would not have been significantly altered by mass loss even if it formed in-situ. However, the presence of a white dwarf companion, TOI-1259 B, hints that this planet may not have formed close-in, but rather migrated inward relatively late. Given the estimated parameters of the proto-white dwarf companion, we find that high-eccentricity migration is possible for the system.arXiv:2404.08736v1 Announce Type: new
Abstract: The lack of close-in Neptune-mass exoplanets evident in transit surveys has largely been attributed either to photoevaporative mass loss or high-eccentricity migration. To distinguish between these two possibilities, we investigate the origins of TOI-1259 A b, a Saturn-mass (0.4 M$_J$, 1.0 R$_J$) exoplanet lying along the upper edge of the Neptune desert. TOI-1259 A b’s close-in ($P$ = 3.48 days) orbit and low bulk density make the planet particularly vulnerable to photoevaporation. Using transits observed in the 1083 nm metastable helium line, we probe the upper atmosphere of TOI-1259 A b with the Hale Telescope at Palomar Observatory and the Near-Infrared Spectrograph on Keck II. We report an excess absorption of $0.395pm{0.072}%$ with Palomar and a blueshifted absorption of $2.4pm0.52%$ with Keck, consistent with an extended escaping atmosphere. Fitting this signal with a Parker wind model, we determine a corresponding atmospheric mass loss rate of log($dot{M}$) = $10.33pm 0.13$ g/s for a thermosphere temperature of $8400^{+1200}_{-1000}$ K based on the Palomar absorption and log($dot{M}$) = $10.0pm 0.1$ g/s for a thermosphere temperature of $8200^{+1000}_{-900}$ K based on the Keck absorption. This relatively low rate suggests that this planet would not have been significantly altered by mass loss even if it formed in-situ. However, the presence of a white dwarf companion, TOI-1259 B, hints that this planet may not have formed close-in, but rather migrated inward relatively late. Given the estimated parameters of the proto-white dwarf companion, we find that high-eccentricity migration is possible for the system.