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Post Info TOPIC: WASP-50b


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Posts: 131433
Date:
WASP-50
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Title: An extremely high photometric precision in ground-based observations of two transits in the WASP-50 planetary system
Authors: Jeremy Tregloan-Reed, John Southworth

We present photometric observations of two transits in the WASP-50 planetary system, obtained using the ESO New Technology Telescope and the defocussed-photometry technique. The rms scatters for the two datasets are 258 and 211 ppm, setting a new record for ground-based photometric observations of a point source. The data were modelled and fitted using the PRISM and GEMC codes, and the physical properties of the system calculated. We find the mass and radius of the hot star to be 0.861 0.057 solar masses and 0.855 0.019 solar radii, respectively. For the planet we find a mass of 1.437 0.068 Jupiter masses, a radius of 1.138 0.026 Jupiter radii and a density of 0.911 0.033 pjup. These values are consistent with but more precise than those found in the literature. We also obtain a new orbital ephemeris for the system: T_0 = HJD/TDB 2,455,558.61237(20) + 1.9550938(13) x E.

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Posts: 131433
Date:
WASP-50b
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Title: WASP-50b: a hot Jupiter transiting a moderately active solar-type star
Authors: M. Gillon, A. P. Doyle, M. Lendl, P. F. L. Maxted, A. H. M. J. Triaud, D. R. Anderson, S. C. C. Barros, J. Bento, A. Collier-Cameron, B. Enoch, F. Faedi, C. Hellier, E. Jehin, P. Magain, J. Montalban, F. Pepe, D. Pollacco, D. Queloz, B. Smalley, D. Segransan, A. M. S. Smith, J. Southworth, S. Udry, R. G. West, P. J. Wheatley

We report the discovery by the WASP transit survey of a giant planet in a close orbit (0.02950.0009 AU) around a moderately bright (V=11.6, K=10) G9 dwarf (0.890.08 M_sun, 0.840.03 R_sun) in the Southern constellation Eridanus. Thanks to high-precision follow-up photometry and spectroscopy obtained by the telescopes TRAPPIST and Euler, the mass and size of this planet, WASP-50b, are well constrained to 1.470.09 M_jup and 1.150.05 R_jup, respectively. The transit ephemeris is 2455558.6120 (0.0002) + N x 1.955096 (0.000005) HJD_UTC. The size of the planet is consistent with basic models of irradiated giant planets. The chromospheric activity (log R'_HK = -4.67) and rotational period (P_rot = 16.30.5 days) of the host star suggest an age of 0.80.4 Gy that is discrepant with a stellar-evolution estimate based on the measured stellar parameters (rho_star = 1.480.10 rho_sun, Teff = 5400100 K, [Fe/H]= -0.120.08) which favours an age of 73.5 Gy. This discrepancy could be explained by the tidal and magnetic influence of the planet on the star, in good agreement with the observations that stars hosting hot Jupiters tend to show faster rotation and magnetic activity (Pont 2009; Hartman 2010). We measure a stellar inclination of 84 (-31,+6) deg, disfavouring a high stellar obliquity. Thanks to its large irradiation and the relatively small size of its host star, WASP-50b is a good target for occultation spectrophotometry, making it able to constrain the relationship between hot Jupiters' atmospheric thermal profiles and the chromospheric activity of their host stars proposed by Knutson et al. (2010).

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