* Astronomy

Title: WASP-54b, WASP-56b and WASP-57b: Three new sub-Jupiter mass planets from SuperWASP
Authors: F. Faedi (Warwick), D. Pollacco (Warwick), S. C. C. Barros, D. Brown, A. Collier Cameron, A. P. Doyle, M. Gillon, Y. Gomez Maqueo Chew (Warwick, Vanderbilt), G. Hebrard, M. Lendl, C. Liebig, B. Smalley, A. H. M. J. Triaud, R. G. West, P. J. Wheatley, K. A. Alsubai, D. R. Anderson, D. J. Armstrong (Warwick), J. Bento, J. Bochinski, F. Bouchy, R. Busuttil, L. Fossati, A. Fumel, C. A. Haswell, C. Hellier, S. Holmes, E. Jehin, U. Kolb, J. McCormac (ING, Warwick), G. R. M. Miller, C. Moutou, A. J. Norton, N. Parley, D. Queloz, I. Skillen, A. M. S. Smith, S. Udry, C. Watson

We present three newly discovered sub-Jupiter mass planets from the SuperWASP survey: WASP-54b is a heavily bloated planet of mass 0.636^{+0.025}_{-0.024} Jupiter masses and radius 1.653^{+0.090}_{-0.083} Jupiter radii. It orbits a F9 star, evolving off the main sequence, every 3.69 days. Our MCMC fit of the system yields a slightly eccentric orbit (e=0.067^{+0.033}_{-0.025}) for WASP-54b. We investigated further the veracity of our detection of the eccentric orbit for WASP-54b, and we find that it could be real. However, given the brightness of WASP-54 V=10.42 magnitudes, we encourage observations of a secondary eclipse to draw robust conclusions on both the orbital eccentricity and the thermal structure of the planet. WASP-56b and WASP-57b have masses of 0.571^{+0.034}_{-0.035} Jupiter masses and 0.672^{+0.049}_{-0.046} Jupiter masses, respectively; and radii of 1.092^{+0.035}_{-0.033} Jupiter radii for WASP-56b and 0.916^{+0.017}_{-0.014} Jupiter radii for WASP-57b. They orbit main sequence stars of spectral type G6 every 4.67 and 2.84 days, respectively. WASP-56b and WASP-57b show no radius anomaly and a high density possibly implying a large core of heavy elements; possibly as high as \sim 50 earth masses in the case of WASP-57b. However, the composition of the deep interior of exoplanets remain still undetermined. Thus, more exoplanet discoveries such as the ones presented in this paper, are needed to understand and constrain giant planets' physical properties.

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