Refined physical properties andg′,r′,i′,z′,J, H, Ktransmission spectrum of WASP-23b from the ground

Abstract

Context. Multi-band observations of planetary transits using the telescope defocus technique may yield high-quality light curves suitable for refining the physical properties of exoplanets even with small or medium size telescopes. Such observations can be used to construct a broad-band transmission spectrum of transiting planets and search for the presence of strong absorbers. Aims. We have thoroughly characterised the orbital ephemeris and physical properties of the transiting planet and host star in the WASP-23b system, constructed a broad-band transmission spectrum of WASP-23 b and performed a comparative analysis with theoretical models of hot Jupiters. Methods. We observed a complete transit of WASP-23 b in seven passbands simultaneously, using the GROND instrument on the MPG/ESO 2.2 m telescope at La Silla Observatory and telescope defocussing. The optical data were taken in the Sloan g , r , i and z passbands. The resulting light curves are of high quality, with a root-mean-square scatter of the residual as low as 330 parts per million (ppm) in the z -band, with a cadence of 90 s. Near-infrared data were obtained in the JHK passbands. We performed a MCMC analysis of our photometry plus existing radial velocity data to refine measurements of the ephemeris and physical properties of the WASP-23 system. We constructed a broad-band transmission spectrum of WASP-23 b and compared it with a theoretical transmission spectrum of a hot Jupiter. Results. We measured the central transit time with a precision ∼8 s. From this and earlier observations we obtain an orbital period of P = 2.9444300 ± 0.0000011 d. Our analysis also yielded a larger radius and mass for the planet (R p = 1.067 +0.045 −0.038 R Jup and M p = 0.917 +0.040 −0.039 M Jup ) compared to previous estimates (R p = 0.962 +0.047 −0.056 R Jup and M p = 0.884 +0.088 −0.094 M Jup ). The derived transmission spectrum is marginally flat, which is not surprising given the limited precision of the measurements for the planetary radius and the poor spectral resolution of the data.

HST hot-Jupiter transmission spectral survey: haze in the atmosphere of WASP-6b

“…Due to the relatively long STIS integration time (i.e. 287 s), the data contains large number of cosmic ray events, which were identified and removed following the procedures described in Nikolov et al (2013). It was found that the total number of pixels affected by cosmic ray events comprise ∼ 4 % of the total number of pixels of each 2D spectrum.…”

“…clear/hazy/cloudy, delve into the presence/lack of TiO/alkali and other molecular features, probe the diversities between possible subclasses and perform comparative exoplanetology. Initial results from four exoplanets have been presented so far in Huitson et al (2013) for WASP-19b, Wakeford et al (2013) and Nikolov et al (2013) for HAT-P-1b and Sing et al (2013) for WASP-12b and Sing et al (2014) for WASP-31b. Already a wide diversity among exoplanet atmospheres is observed.…”

Erratum: Physical properties, star-spot activity, orbital obliquity and transmission spectrum of the Qatar-2 planetary system from multicolour photometry

“…Simultaneous multiband observations of planetary transits have been obtained for several TEP systems using the instruments BUSCA (Southworth et al 2012b;Mancini et al 2013c), GROND (de Mooij et al 2012;Bayliss et al 2013;Mancini et al 2013a,b;Mohler-Fischer et al 2013;Nikolov et al 2013;Penev et al 2013;Southworth et al 2013), ULTRACAM (Bento et al 2013;Copperwheat et al 2013) and SIRIUS (Narita et al 2013). Table 1.…”

Physical properties of the HAT-P-23 and WASP-48 planetary systems from multi-colour photometry

“…Southworth et al 2012b;Copperwheat et al 2013;Nikolov et al 2013;Mancini et al 2013c;Narita et al 2013;Chen et al 2014). We used our multi-band data to investigate possible variations of the radius of HAT-P-23 b and WASP-48 b in different optical passbands.…”