HAT-P-32b and HAT-P-33b: Two Highly Inflated Hot Jupiters Transiting High-Jitter Stars

TL;DR

This paper reports the discovery and characterization of two highly inflated hot Jupiters transiting stars with high stellar jitter, providing new insights into their physical parameters and orbital dynamics.

Contribution

The study presents the first detailed analysis of two inflated hot Jupiters orbiting high-jitter stars, including their masses, radii, and eccentricities, with methods to mitigate stellar jitter effects.

Findings

Both planets are among the largest transiting exoplanets discovered.

The planets have high inflation levels with radii exceeding 1.7 Jupiter radii.

Orbital eccentricities are constrained to be around 0.16 and consistent with Roche lobe filling.

Abstract

We report the discovery of two exoplanets transiting high-jitter stars. HAT-P-32b orbits the bright V=11.289 star GSC 3281-00800, with a period P = 2.150008 d. The stellar and planetary masses and radii depend on the eccentricity of the system, which is poorly constrained due to the high velocity jitter (~80m/s). Assuming a circular orbit, the star has a mass of 1.16+-0.04 M_sun, and radius of 1.22+-0.02 R_sun, while the planet has a mass of 0.860+-0.164 MJ, and a radius of 1.789+-0.025 RJ. When the eccentricity is allowed to vary, the best-fit model results in a planet which is close to filling its Roche Lobe. Including the constraint that the planet cannot exceed its Roche Lobe results in the following best-fit parameters: e = 0.163+-0.061, Mp = 0.94+-0.17 MJ, Rp = 2.04+-0.10 RJ, Ms = 1.18+0.04-0.07 M_sun and Rs = 1.39+-0.07 R_sun. The second planet, HAT-P-33b, orbits the bright V=11.188 star GSC 2461-00988, with a period P = 3.474474 d. As for HAT-P-32, the stellar and planetary masses and radii of HAT-P-33 depend on the eccentricity, which is poorly constrained due to the high jitter (~50m/s). In this case spectral line bisector spans are significantly anti-correlated with the radial velocity residuals, and we use this correlation to reduce the residual rms to ~35m/s. We find the star has a mass of either 1.38+-0.04 M_sun or 1.40+-0.10 M_sun, and a radius of either 1.64+-0.03 R_sun or 1.78+-0.28 R_sun, while the planet has a mass of either 0.762+-0.101 MJ or 0.763+-0.117 MJ, and a radius of either 1.686+-0.045 RJ or 1.827+-0.290 RJ, for an assumed circular orbit or for the best-fit eccentric orbit respectively. Due to the large bisector span variations exhibited by both stars we rely on detailed modeling of the photometric light curves to rule out blend scenarios. Both planets are among the largest radii transiting planets discovered to date.