HAT-P-15b: A 10.9-day Extrasolar Planet Transiting a Solar-type Star

TL;DR

HAT-P-15b is a newly discovered transiting exoplanet with a 10.86-day orbit around a G-type star, notable for its position in the period valley and potential for atmospheric studies.

Contribution

This paper reports the discovery and detailed characterization of HAT-P-15b, including its orbital, physical, and atmospheric properties, filling a gap in the period distribution of known exoplanets.

Findings

HAT-P-15b has a mass of 1.946 Jupiter masses and a radius of 1.072 Jupiter radii.

The planet orbits its star every 10.86 days with a transit duration of 0.2285 days.

It is a potential target for atmospheric spectroscopy due to its moderate temperature.

Abstract

We report the discovery of HAT-P-15b, a transiting extrasolar planet in the `period valley', a relatively sparsely-populated period regime of the known extrasolar planets. The host star, GSC 2883-01687, is a G5 dwarf with V=12.16. It has a mass of 1.01+/-0.04 M(Sun), radius of 1.08+/-0.04 R(Sun), effective temperature 5568+/-90 K, and metallicity [Fe/H] = +0.22+/-0.08. The planetary companion orbits the star with a period 10.863502+/-0.000027 days, transit epoch Tc = 2454638.56019+/-0.00048 (BJD), and transit duration 0.2285+/-0.0015 days. It has a mass of 1.946+/-0.066 M(Jup), and radius of 1.072+/-0.043 R(Jup) yielding a mean density of 1.96+/-0.22 g/cm3. At an age of 6.8+/-2.1 Gyr, the planet is H/He-dominated and theoretical models require about 2% (10 M(Earth)) worth of heavy elements to reproduce its measured radius. With an estimated equilibrium temperature of 820 K during transit, and 1000 K at occultation, HAT-P-15b is a potential candidate to study moderately cool planetary atmospheres by transmission and occultation spectroscopy.