J/MNRAS/454/3094 Optical transit light curves of WASP-57 (Southworth+, 2015) ================================================================================ Larger and faster: revised properties and a shorter orbital period for the WASP-57 planetary system from a pro-am collaboration. Southworth J., Mancini L., Tregloan-Reed J., Calchi Novati S., Ciceri S., D'Ago G., Delrez L., Dominik M., Evans D.F., Gillon M., Jehin E., Jorgensen U.G., Haugbolle T., Lendl M., Arena C., Barbieri L., Barbieri M., Corfini G., Lopresti C., Marchini A., Marino G., Alsubai K.A., Bozza V., Bramich D.M., Figuera Jaimes R., Hinse T.C., Henning TH., Hundertmark M., Juncher D., Korhonen H., Popovas A., Rabus M., Rahvar S., Schmidt R.W., Skottfelt J., Snodgrass C., Starkey D., Surdej J., Wertz O. =2015MNRAS.454.3094S (SIMBAD/NED BibCode) ================================================================================ ADC_Keywords: Stars, double and multiple ; Planets ; Photometry, ugriz Keywords: stars: fundamental parameters - stars: individual: WASP-57 - planetary systems Abstract: Transits in the WASP-57 planetary system have been found to occur half an hour earlier than expected. We present 10 transit light curves from amateur telescopes, on which this discovery was based, 13 transit light curves from professional facilities which confirm and refine this finding, and high-resolution imaging which show no evidence for nearby companions. We use these data to determine a new and precise orbital ephemeris, and measure the physical properties of the system. Our revised orbital period is 4.5 s shorter than found from the discovery data alone, which explains the early occurrence of the transits. We also find both the star and planet to be larger and less massive than previously thought. The measured mass and radius of the planet are now consistent with theoretical models of gas giants containing no heavy-element core, as expected for the subsolar metallicity of the host star. Two transits were observed simultaneously in four passbands. We use the resulting light curves to measure the planet's radius as a function of wavelength, finding that our data are sufficient in principle but not in practise to constrain its atmospheric properties. We conclude with a discussion of the current and future status of transmission photometry studies for probing the atmospheres of gas-giant transiting planets. Description: Two complete transits of WASP-57 were observed using the 1.54 m Danish Telescope and DFOSC instrument at ESO La Silla, Chile (see Dominik et al. 2010AN....331..671D), on the dates 2014/05/18 and 2014/06/24. Both transits were obtained through a Bessell R filter. The transit on 2014/06/24 observed with DFOSC was also monitored using GROND (Greiner et al. 2008PASP..120..405G) mounted on the MPG 2.2 m telescope at La Silla, Chile. GROND was used to obtain light curves simultaneously in four passbands, which approximate the SDSS g, r, i and z bands. We observed WASP-57 on the night of 2012/05/10 using the BUSCA instrument on the 2.2 m telescope at Calar Alto Astronomical Observatory. BUSCA is capable of observing simultaneously in four passbands, for which we chose Gunn u, g, r and z. One transit of WASP-57 was observed on 2012/04/01 with EulerCam, using the same methods as for the EulerCam transit in Faedi et al. (2013, J/A+A/551/A73). We obtained 212 images through a Gunn r filter, without applying a defocus to the instrument. Two transits of WASP-57 were observed on 2012/03/15 and 2012/04/01 using the 0.6 m TRAPPIST robotic telescope located at La Silla (Gillon et al. 2011EPJWC..1106002G; Jehin et al. 2011Msngr.145....2J). Images were obtained with a slight defocus and through a blue-blocking filter that has a transmittance greater than 90 per cent from 500 nm to beyond 1000 nm. Objects: -------------------------------------------------------- RA (ICRS) DE Designation(s) -------------------------------------------------------- 14 55 16.82 -02 03 27.5 WASP-57 = GSC 04991-00565 -------------------------------------------------------- File Summary: -------------------------------------------------------------------------------- FileName Lrecl Records Explanations -------------------------------------------------------------------------------- ReadMe 80 . This file table3.dat 47 2189 Defocussed photometry for the transiting extrasolar planetary system WASP-57 -------------------------------------------------------------------------------- See also: J/ApJ/707/167 : Transiting planetary system WASP-18 (Southworth+, 2009) J/MNRAS/396/1023 : Transiting planetary system WASP-5 (Southworth+, 2009) J/MNRAS/399/287 : Transiting planetary system WASP-4 (Southworth+, 2009) J/MNRAS/408/1680 : Transiting planetary system WASP-2 (Southworth+, 2010) J/A+A/527/A8 : Transiting planetary system WASP-7 (Southworth+, 2011) J/MNRAS/426/1338 : Transiting planetary system WASP-17 (Southworth+, 2012) J/A+A/562/A126 : Light curves of WASP-80 transit events (Mancini+, 2014) J/A+A/568/A127 : Light curves of WASP-67 transit events (Mancini+, 2014) Byte-by-byte Description of file: table3.dat -------------------------------------------------------------------------------- Bytes Format Units Label Explanations -------------------------------------------------------------------------------- 1- 8 A8 --- Inst Instrument used for observation 10- 11 A2 --- Filter [ugriz R bb] Filter 13- 26 F14.6 d BJD Barycentric Julian Date (TDB) 28- 37 F10.7 mag Dmag Differencial magnitude in Filter 39- 47 F9.7 mag e_Dmag Uncertainty in Dmag -------------------------------------------------------------------------------- History: From electronic version of the journal ================================================================================ (End) Tiphaine Pouvreau [CDS] 19-Jan-2018