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

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jats:titleAbstract</jats:title> jats:pWe report the discovery in TESS data and validation of HD 56414 b (a.k.a. TOI-1228 b), a Neptune-size (jats:italicR</jats:italic> jats:subp</jats:sub> = 3.71 ± 0.20 jats:italicR</jats:italic> jats:sub⊕</jats:sub>) 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 (jats:italicT</jats:italic> jats:subeff</jats:sub> = 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 jats:italicM</jats:italic> jats:sub⊕</jats:sub>. Our model also predicts that close-in Neptune-size planets with masses <14 jats:italicM</jats:italic> jats:sub⊕</jats:sub> 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.</jats:p>



5109 Space Sciences, 51 Physical Sciences, 5101 Astronomical Sciences

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Astrophysical Journal Letters

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American Astronomical Society
NASA ∣ Science Mission Directorate (SMD) (80NSSC20K1549)