Recent Transits of the Super-Earth Exoplanet GJ 1214b

TL;DR

This paper presents new ground-based photometric observations of the super-Earth GJ 1214b across optical and infrared wavelengths, refining its radius and orbital parameters with high precision.

Contribution

It provides the first high-precision J-band transit measurement of GJ 1214b, confirming the planetary radius and improving the transit ephemeris.

Findings

Planet radius: 2.61 (+0.30, -0.11) Earth radii

Orbital period: 1.5804043 days

Transit ephemeris improved

Abstract

We report recent ground-based photometry of the transiting super-Earth exoplanet GJ1214b at several wavelengths, including the infrared near 1.25 microns (J-band). We observed a J-band transit with the FLAMINGOS infrared imager and the 2.1-meter telescope on Kitt Peak, and we observed several optical transits using a 0.5-meter telescope on Kitt Peak and the 0.36-meter Universidad de Monterrey Observatory telescope. Our high-precision J-band observations exploit the brightness of the M-dwarf host star at this infrared wavelength as compared to the optical, as well as being significantly less affected by stellar activity and limb darkening. We fit the J-band transit to obtain an independent determination of the planetary and stellar radii. Our radius for the planet (2.61^+0.30_-0.11 Earth radii) is in excellent agreement with the discovery value reported by Charbonneau et al. based on optical data. We demonstrate that the planetary radius is insensitive to degeneracies in the fitting process. We use all of our observations to improve the transit ephemeris, finding P=1.5804043 +/- 0.0000005 days, and T0=2454964.94390 +/- 0.00006 BJD.