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HD 56414 b: A Warm Neptune Transiting an A-type Star

Abstract : We report the discovery in TESS data and validation of HD 56414 b (a.k.a. TOI-1228 b), a Neptune-size (R p = 3.71 ± 0.20 R ) planet with a 29 day orbital period transiting a young (age = 420 ± 140 Myr) A-type star in the TESS southern continuous-viewing zone. HD 56414 is one of the hottest stars (T eff = 8500 ± 150 K) to host a known sub-Jovian planet. HD 56414 b lies on the boundary of the hot Neptune desert in the planet radius-bolometric insolation flux space, suggesting that the planet may be experiencing mass loss. To explore this, we apply a photoevaporation model that incorporates the high near-ultraviolet continuum emission of A-type stars. We find that the planet can retain most of its atmosphere over the typical 1 Gyr main-sequence lifetime of an A-type star if its mass is ≥8 M . Our model also predicts that close-in Neptune-size planets with masses <14 M are susceptible to total atmospheric stripping over 1 Gyr, hinting that the hot Neptune desert, which has been previously observed around FGKM-type stars, likely extends to A-type stars.
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Contributor : Nathalie POTHIER Connect in order to contact the contributor
Submitted on : Thursday, November 10, 2022 - 1:17:07 PM
Last modification on : Saturday, November 12, 2022 - 3:27:03 AM


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Steven Giacalone, Courtney D. Dressing, A. García Muñoz, Matthew J. Hooton, Keivan G. Stassun, et al.. HD 56414 b: A Warm Neptune Transiting an A-type Star. The Astrophysical journal letters, 2022, 935, ⟨10.3847/2041-8213/ac80f4⟩. ⟨insu-03846754⟩



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