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A lower mass for the exoplanet WASP-21b

Barros, SCC, Pollacco, DL, Gibson, NP, Howarth, ID, Keenan, FP, Simpson, EK, Skillen, I and Steele, IA (2011) A lower mass for the exoplanet WASP-21b. Monthly Notices of the Royal Astronomical Society, 416 (4). pp. 2593-2599. ISSN 0035-8711

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We present high-precision transit observations of the exoplanet WASP-21b, obtained with the Rapid Imager to Search for Exoplanets instrument mounted on the 2.0-m Liverpool Telescope. A transit model is fitted, coupled with a Markov chain Monte Carlo routine, to derive accurate system parameters. The two new high-precision transits allow us to estimate the stellar density directly from the light curve. Our analysis suggests that WASP-21 is evolving off the main sequence which led to a previous overestimation of the stellar density. Using isochrone interpolation, we find a stellar mass of 0.86 ± 0.04 M⊙, which is significantly lower than previously reported (1.01 ± 0.03 M⊙). Consequently, we find a lower planetary mass of 0.27 ± 0.01 MJup. A lower inclination (87°.4 ± 0°.3) is also found for the system than previously reported, resulting in a slightly larger stellar (R*= 1.10 ± 0.03 R⊙) and planetary radius (Rp= 1.14 ± 0.04 RJup). The planet radius suggests a hydrogen/helium composition with no core which strengthens the correlation between planetary density and host star metallicity. A new ephemeris is determined for the system, i.e. T0= 245 5084.519 74 ± 0.000 20 (HJD) and P= 4.322 5060 ± 0.000 0031 d. We found no transit timing variations in WASP-21b.

Item Type: Article
Additional Information: This article has been accepted for publication in Monthly Notices of the Royal Astronomical Society ©: 2011 The Authors Published by Oxford University Press on behalf of the Royal Astronomical Society. All rights reserved.
Uncontrolled Keywords: 0201 Astronomical And Space Sciences
Subjects: Q Science > QB Astronomy
Q Science > QC Physics
Divisions: Astrophysics Research Institute
Publisher: Oxford University Press
Related URLs:
Date Deposited: 19 Jan 2017 09:31
Last Modified: 20 Apr 2022 09:50
DOI or ID number: 10.1111/j.1365-2966.2011.19210.x
URI: https://researchonline.ljmu.ac.uk/id/eprint/5290
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