HD 17156b: A Transiting Planet with a 21.2 Day Period and an Eccentric Orbit

TL;DR

This paper reports the discovery of a transiting exoplanet, HD 17156b, with a long 21.2-day period and high orbital eccentricity, observed through multiple independent detections, providing a unique case for atmospheric studies.

Contribution

First detection of a transiting planet with a long period and high eccentricity, expanding the known diversity of transiting exoplanets.

Findings

Transit depth of 0.0062±0.0004 confirmed

Orbital eccentricity of 0.67 measured

Planet receives 26-fold insolation variation

Abstract

We report the detection of transits by the 3.1 M_Jup companion to the V=8.17 G0V star HD 17156. The transit was observed by three independant observers on Sept. 9/10, 2007 (two in central Italy and one in the Canary Islands), who obtained detections at confidence levels of 3.0 sigma, 5.3 sigma, and 7.9 sigma, respectively. The observations were carried out under the auspices of the Transitsearch.org network, which organizes follow-up photometric transit searches of known planet-bearing stars during the time intervals when transits are expected to possibly occur. Analyses of the 7.9 sigma data set indicates a transit depth d=0.0062+/-0.0004, and a transit duration t=186+/-5 min. These values are consistent with the transit of a Jupiter-sized planet with an impact parameter b=a*cos(i)/R_star ~ 0.8. This planet occupies a unique regime among known transiting extrasolar planets, both as a result of its large orbital eccentricity (e=0.67) and long orbital period (P=21.2 d). The planet receives a 26-fold variation in insolation during the course of its orbit, which will make it a useful object for characterization of exoplanetary atmospheric dynamics.