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 ? ) planet with 29 day orbital period transiting young (age 420 140 Myr) A-type star southern continuous-viewing zone. is one hottest stars T eff 8500 150 K) to host known sub-Jovian planet. lies on boundary hot Neptune desert radius–bolometric insolation flux space, suggesting that may be experiencing mass loss. To explore this, we apply photoevaporation model incorporates high near-ultraviolet continuum emission stars. find can retain most its atmosphere over typical 1 Gyr main-sequence lifetime an if ?8 M . Our also predicts close-in planets masses <14 are susceptible total atmospheric stripping Gyr, hinting desert, which has been previously observed around FGKM-type stars, likely extends