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 0.099 +- 0.042 MJ (31.5 +- 13.4 M) and a radius of 0.606 +- 0.016 RJ, and is on a P = 4.3315 day orbit around a V = 12.266 +- 0.030 mag, 0.843-+0.0120.017 M☉ star with a radius of 0.877-+0.0120.019 R☉. We also present evidence that the star HATS-37A has an unresolved stellar companion HATS-37B, with a photometrically estimated mass of 0.654 +- 0.033 M☉. The planet HATS-38b has a mass of 0.074 +- 0.011 MJ (23.5 +- 3.5 M) and a radius of 0.614 +- 0.017 RJ, and is on a P = 4.3750 day orbit around a V = 12.411 +- 0.030 mag, 0.890-+0.0120.016 M☉ star with a radius of 1.105 +- 0.016 R☉. Both systems appear to be old, with isochrone-based ages of 11.46-+1.450.79 Gyr, and 11.89 +- 0.60 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. Show more