HATS-37Ab and HATS-38b: Two Transiting Hot Neptunes in the Desert*

Abstract

We report the discovery of two transiting Neptunes by the HATSouth survey. The planet HATS-37Ab has a mass of (31.5 ± 13.4 M ⊕ ) and a radius of , and is on a day orbit around a mag, star with a radius of . We also present evidence that the star HATS-37A has an unresolved stellar companion HATS-37B, with a photometrically estimated mass of . The planet HATS-38b has a mass of (23.5 ± 3.5 M ⊕ ) and a radius of , and is on a day orbit around a mag, star with a radius of . Both systems appear to be old, with isochrone-based ages of Gyr, and Gyr, respectively. Both HATS-37Ab and HATS-38b lie in the Neptune desert and are thus examples of a population with a low occurrence rate. They are also among the lowest-mass planets found from ground-based wide-field surveys to date.