Journal Article

High-precision transit observations of the exoplanet WASP-13b with the RISE instrument

S. C. C. Barros, D. L. Pollacco, N. P. Gibson, F. P. Keenan, I. Skillen and I. A. Steele

in Monthly Notices of the Royal Astronomical Society

Published on behalf of The Royal Astronomical Society

Volume 419, issue 2, pages 1248-1253
Published in print January 2012 | ISSN: 0035-8711
Published online December 2011 | e-ISSN: 1365-2966 | DOI: http://dx.doi.org/10.1111/j.1365-2966.2011.19784.x
High-precision transit observations of the exoplanet WASP-13b with the RISE instrument

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WASP-13b is a sub-Jupiter mass exoplanet orbiting a G1V type star with a period of 4.35 d. The current uncertainty in its impact parameter (0 < b < 0.46) results in poorly defined stellar and planetary radii. To better constrain the impact parameter, we have obtained high-precision transit observations with the rapid imager to search for exoplanets (RISE) instrument mounted on 2.0-m Liverpool Telescope. We present four new transits which are fitted with a Markov chain Monte Carlo routine to derive accurate system parameters. We found an orbital inclination of 85°.2 ± 0°.3 resulting in stellar and planetary radii of 1.56 ± 0.04 R and 1.39 ± 0.05RJup, respectively. This suggests that the host star has evolved off the main sequence and is in the hydrogen-shell-burning phase. We also discuss how the limb darkening affects the derived system parameters. With a density of 0.17ρJ, WASP-13b joins the group of low-density planets whose radii are too large to be explained by standard irradiation models. We derive a new ephemeris for the system, T0= 245 5575.5136 ± 0.0016 (HJD) and P= 4.353 011 ± 0.000 013 d. The planet equilibrium temperature (Tequ= 1500 K) and the bright host star (V= 10.4 mag) make it a good candidate for follow-up atmospheric studies.

Keywords: methods: data analysis; methods: observational; techniques: photometric; stars: individual: WASP-13; planetary systems

Journal Article.  4434 words.  Illustrated.

Subjects: Astronomy and Astrophysics

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