HATS-15 b and HATS-16 b: Two massive planets transiting old G dwarf stars

TL;DR

This paper reports the discovery of two massive hot Jupiters, HATS-15 b and HATS-16 b, orbiting old G dwarf stars, highlighting their physical properties and possible star-planet tidal interactions.

Contribution

First discovery of two massive hot Jupiters orbiting old G dwarf stars with detailed characterization and analysis of their stellar activity and rotation.

Findings

HATS-15 b has a mass of 2.17 M_J and orbits in 1.7 days.

HATS-16 b has a mass of 3.27 M_J and orbits in 2.7 days.

HATS-16 shows a rapid rotation period of 12 days, possibly due to tidal interactions.

Abstract

We report the discovery of HATS-15 b and HATS-16 b, two massive transiting extrasolar planets orbiting evolved ($\sim 10$ Gyr) main-sequence stars. The planet HATS-15 b, which is hosted by a G9V star ($V=14.8$ mag), is a hot Jupiter with mass of $2.17\pm0.15\, M_{\mathrm{J}}$ and radius of $1.105\pm0.0.040\, R_{\mathrm{J}}$, and completes its orbit in nearly 1.7 days. HATS-16 b is a very massive hot Jupiter with mass of $3.27\pm0.19\, M_{\mathrm{J}}$ and radius of $1.30\pm0.15\, R_{\mathrm{J}}$; it orbits around its G3 V parent star ($V=13.8$ mag) in $\sim2.7$ days. HATS-16 is slightly active and shows a periodic photometric modulation, implying a rotational period of 12 days which is unexpectedly short given its isochronal age. This fast rotation might be the result of the tidal interaction between the star and its planet.