HAT-P-24b: An Inflated Hot Jupiter on a 3.36 Day Period Transiting a Hot, Metal-poor Star

Creators: Kipping, D. M.; Bakos, G. Á.; Hartman, J.; Torres, G.; Shporer, A.; Latham, D. W.; Kovács, Géza; Noyes, R. W.; Howard, A. W.; Fischer, D. A.; Johnson, J. A.; Marcy, G. W.; Béky, B.; Perumpilly, G.; Esquerdo, G. A.; Sasselov, D. D.; Stefanik, R. P.; Lázár, J.; Papp, I.; Sári, P.

Abstract

We report the discovery of HAT-P-24b, a transiting extrasolar planet orbiting the moderately bright V = 11.818 F8 dwarf star GSC 0774−01441, with a period P = 3.3552464 ± 0.0000071 days, transit epoch T_c = 2455216.97669 ± 0.00024 (BJD)11, and transit duration 3.653 ± 0.025 hr. The host star has a mass of 1.191 ± 0.042M_⊙, radius of 1.317 ± 0.068R_⊙, effective temperature 6373 ± 80 K, and a low metallicity of [Fe/H] = −0.16 ± 0.08. The planetary companion has a mass of 0.681 ± 0.031 M_J and radius of 1.243 ± 0.072 R_J yielding a mean density of 0.439 ± 0.069 g cm^(−3). By repeating our global fits with different parameter sets, we have performed a critical investigation of the fitting techniques used for previous Hungarian-made Automated Telescope planetary discoveries. We find that the system properties are robust against the choice of priors. The effects of fixed versus fitted limb darkening are also examined. HAT-P-24b probably maintains a small eccentricity of e = 0.052^(+0.022)_(−0.017), which is accepted over the circular orbit model with false alarm probability 5.8%. In the absence of eccentricity pumping, this result suggests that HAT-P-24b experiences less tidal dissipation than Jupiter. Due to relatively rapid stellar rotation, we estimate that HAT-P-24b should exhibit one of the largest known Rossiter–McLaughlin effect amplitudes for an exoplanet (ΔV_(RM) ≃ 95 m s^(−1)) and thus a precise measurement of the sky-projected spin–orbit alignment should be possible.

Additional Information

© 2010 American Astronomical Society. Received 2010 August 1, accepted 2010 October 11. Published 2010 December 3. Based in part on observations obtained at the W. M. Keck Observatory, which is operated by the University of California and the California Institute of Technology. Keck time has been granted by NOAO and NASA. HATNet operations have been funded by NASA grants NNG04GN74G, NNX08AF23G and SAO IR&D grants. DK was supported by STFC and as an SAO Predoctoral Fellow. Work of G. Á. B. and J. Johnson were supported by the Postdoctoral Fellowship of the NSF Astronomy and Astrophysics Program (AST-0702843 and AST-0702821, respectively). GT acknowledges partial support from NASA grant NNX09AF59G. We acknowledge partial support also from the Kepler Mission under NASA Cooperative Agreement NCC2-1390 (D.W.L., PI). G.K. thanks the Hungarian Scientific Research Foundation (OTKA) for support through grant K-81373. This research has made use of Keck telescope time granted through NOAO and NASA. This paper uses observations obtained with facilities of the Las Cumbres Observatory Global Telescope.

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