HD 17156b: a transiting planet with a 21.2-day period and an eccentric orbit

Free access article

Issue		A&A Volume 476, Number 2, December III 2007


Page(s)		L13 - L16
Section		Letters
DOI		http://dx.doi.org/10.1051/0004-6361:20078787

A&A 476, L13-L16 (2007)
DOI: 10.1051/0004-6361:20078787

Letter

HD 17156b: a transiting planet with a 21.2-day period and an eccentric orbit

M. Barbieri¹, R. Alonso¹, G. Laughlin², J. M. Almenara³, R. Bissinger⁴, D. Davies⁵, D. Gasparri⁶, E. Guido⁷, C. Lopresti⁸, F. Manzini⁹, and G. Sostero⁷

¹ LAM, Traverse du Siphon, BP 8, Les Trois Lucs, 13376 Marseille Cedex 12, France
e-mail: [mauro.barbieri;roi.alonso]@oamp.fr
² University of California Observatories, University of California at Santa Cruz Santa Cruz, CA 95064, USA
e-mail: laugh@ucolick.org
³ Instituto de Astrofísica de Canarias, C/Vía Láctea s/n, 38200 La Laguna, Spain
⁴ Racoon Run Observatory, Pleasanton, CA, USA
⁵ 23819 Ladeene Avenue, Torrance, CA 90505, USA
⁶ Università di Bologna, Dipartimento di Astronomia, via Ranzani 1, 40127 Bologna, Italy
⁷ Associazione Friulana di Astronomia e Meteorologia, Piazza Miani nr. 2, 33047 Remanzacco, Italy
⁸ Istituto Spezzino Ricerche Astronomiche, via Castellazzo 8/d, 19123 La Spezia, Italy
⁹ Stazione Astronomica di Sozzago, 28060 Sozzago, Italy

(Received 4 October 2007 / Accepted 24 October 2007)

Abstract
We report the detection of transits by the $3.1~M_{\rm Jup}$ companion to the V=8.17 G0V star HD 17156 . The transit was observed by three independant observers on Sep. 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 might be expected to occur. Analyses of the 7.9 $\sigma$ data set indicates a transit depth d=0.0062 $\pm$ 0.0004 and a transit duration t=186 $\pm$ 5 min. These values are consistent with the transit of a Jupiter-sized planet with an impact parameter $b=a \cos{i}/R_{\star} \sim 0.8$ . 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 ( $P=21.2~{\rm d}$ ). The planet receives a 26-fold variation in insolation during the course of its orbit, which will make it a useful object for characterizing exoplanetary atmospheric dynamics.

Key words: binaries: eclipsing -- planetary systems -- stars: individual: HD 17156 -- techniques: photometric

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