Follow-up Observations of the Neptune Mass Transiting Extrasolar Planet HAT-P-11b

TL;DR

This study confirms the transiting nature of HAT-P-11b, refines its orbital and physical parameters, and rules out large transit timing deviations, enhancing understanding of this Neptune-mass exoplanet.

Contribution

The paper provides follow-up observations that improve the accuracy of HAT-P-11b's orbital period and radius, and confirms the stability of its transit timing.

Findings

Transit observed with 1.7 millimag accuracy

Transit timing shows no large deviations

Planetary radius slightly larger than previous estimates

Abstract

We have confirmed the existence of the transiting super Neptune extrasolar planet HAT-P-11b. On May 1, 2009 UT the transit of HAT-P-11b was detected at the University of Arizona's 1.55m Kuiper Telescope with 1.7 millimag rms accuracy. We find a central transit time of T_c = 2454952.92534+/-0.00060 BJD; this transit occurred 80+/-73 seconds sooner than previous measurements (71 orbits in the past) would have predicted. Hence, our transit timing rules out the presence of any large (>200 s) deviations from the ephemeris of Bakos et al. (2009). We obtain a slightly more accurate period of P=4.8878045+/-0.0000043 days. We measure a slightly larger planetary radius of R_p=0.452+/-0.020 R_J (5.07+/-0.22 R_earth) compared to Bakos and co-workers' value of 0.422+/-0.014 R_J (4.73+/-0.16 R_earth). Our values confirm that HAT-P-11b is very similar to GJ 436b (the only other known transiting super Neptune) in radius and other bulk properties.