From dense hot Jupiter to low-density Neptune: The discovery of WASP-127b, WASP-136b and WASP-138b
astro-ph.EP
/ Authors
K. W. F. Lam, F. Faedi, D. J. A. Brown, D. R. Anderson, L. Delrez, M. Gillon, G. Hébrard, M. Lendl, L. Mancini, J. Southworth
and 31 more authors
B. Smalley, A. H. M. Triaud, O. D. Turner, K. L. Hay, D. J. Armstrong, S. C. C. Barros, A. S. Bonomo, F. Bouchy, P. Boumis, A. Collier Cameron, A. P. Doyle, C. Hellier, T. Henning, E. Jehin, G. King, J. Kirk, T. Louden, P. F. L. Maxted, J. J. McCormac, H. P. Osborn, E. Palle, F. Pepe, D. Pollacco, J. Prieto-Arranz
/ Abstract
We report three newly discovered exoplanets from the SuperWASP survey. WASP-127b is a heavily inflated super-Neptune of mass 0.18 +/- 0.02 M_J and radius 1.37 +/- 0.04 R_J. This is one of the least massive planets discovered by the WASP project. It orbits a bright host star (Vmag = 10.16) of spectral type G5 with a period of 4.17 days. WASP-127b is a low-density planet that has an extended atmosphere with a scale height of 2500 +/- 400 km, making it an ideal candidate for transmission spectroscopy. WASP-136b and WASP-138b are both hot Jupiters with mass and radii of 1.51 +/- 0.08 M_J and 1.38 +/- 0.16 R_J, and 1.22 +/- 0.08 M_J and 1.09 +/- 0.05 R_J, respectively. WASP-136b is in a 5.22-day orbit around an F9 subgiant star with a mass of 1.41 +/- 0.07 M_sun and a radius of 2.21 +/- 0.22 R_sun. The discovery of WASP-136b could help constrain the characteristics of the giant planet population around evolved stars. WASP-138b orbits an F7 star with a period of 3.63 days. Its radius agrees with theoretical values from standard models, suggesting the presence of a heavy element core with a mass of ~10 M_earth. The discovery of these new planets helps in exploring the diverse compositional range of short-period planets, and will aid our understanding of the physical characteristics of both gas giants and low-density planets.