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.
- Publication:
-
The Astrophysical Journal
- Pub Date:
- August 2022
- DOI:
- 10.3847/2041-8213/ac80f4
- arXiv:
- arXiv:2208.06396
- Bibcode:
- 2022ApJ...935L..10G
- Keywords:
-
- Exoplanet astronomy;
- Exoplanet systems;
- Exoplanet evolution;
- Transits;
- 486;
- 484;
- 491;
- 1711;
- Astrophysics - Earth and Planetary Astrophysics
- E-Print:
- 12 pages, 4 figures, 1 table