The Transit Light Curve Project. VII. The Not-So-Bloated Exoplanet HAT-P-1b

TL;DR

This study refines the physical parameters of exoplanet HAT-P-1b through transit photometry, revealing it is slightly larger and less dense than Jupiter, consistent with models of irradiated, coreless giant planets.

Contribution

The paper provides precise measurements of HAT-P-1b's size and gravity, confirming its properties align with existing models of irradiated giant exoplanets.

Findings

HAT-P-1b is 1.20 times larger than Jupiter.

Its surface gravity is 2.7 times weaker than Jupiter's.

Transit times are consistent with a constant orbital period.

Abstract

We present photometry of the G0 star HAT-P-1 during six transits of its close-in giant planet, and we refine the estimates of the system parameters. Relative to Jupiter's properties, HAT-P-1b is 1.20 +/- 0.05 times larger and its surface gravity is 2.7 +/- 0.2 times weaker. Although it remains the case that HAT-P-1b is among the least dense of the known sample of transiting exoplanets, its properties are in accord with previously published models of strongly irradiated, coreless, solar-composition giant planets. The times of the transits have a typical accuracy of 1 min and do not depart significantly from a constant period.