WTS-1 b
b"The end of the twentieth century saw a revolution in our knowledge of planetary systems. The detection of the first extrasolar planet in 1992 marked the beginning of a modern era and changed our idea of planets and planetary systems. The discoveries continue rapidly and reveal an extraordinary diversity of planetary systems and physical properties of the exoplanets, raising new questions in the field of planetary science. So far, more than 800 extrasolar planets have been detected, spanning a wide range of masses from a few Earth masses to a few tens of Jupiter masses.\\nThis Ph.D. Thesis is devoted to the confirmation via radial velocity follow-up of the candidate planets detected by the WFCAM Transit Survey (WTS), which is an on-going photometric monitoring campaign using the Wide Field Camera on the United Kingdom Infrared Telescope at Mauna Kea (Hawaii, USA). The WTS and the present work were supported by the RoPACS (Rocky Planets Around Cool Stars) group, a Marie Curie Initial\\nTraining Network funded by the Seventh Framework Programme of the European Commission.\\nSince the WTS was primarily designed to find planets transiting M-dwarf stars, the observations are obtained in the J-band (1.25 micron). This wavelength is near to the peak of the spectral energy distribution of a typical M-dwarf. Simulations show that operating\\nin the J-band reduces the effects of stellar variability, which became important at optical\\nwavelengths in cool stars. The J-band light curves that show a periodic drop and pass all\\nthe selection criteria, progress to the candidate confirmation phase. After a transit depth consistency check performed with i'-band observations, intermediate resolution spectra\\nenable to rule out false-positive eclipsing binaries scenarios. Finally, high-resolution spectroscopic follow-up is performed to confirm, by the radial velocity method, the planetary nature of the stellar companion detected by the WTS. The spectra employed in this phase were observed with the High Resolution Spectrograph (HRS) housed in the basement of the 9.2-m Hobby-Eberly Telescope (HET) in Texas, USA. \\nThe pipeline for the reduction and analysis of the HET spectra has been created. Debug, optimization and test of the whole procedure were performed observing several target stars with different apparent magnitude and spectral type. These observations allowed to estimate the precision on the velocity measures for different targets. Errorbars of 10 m/s are expected for solar type stars of magnitude up to mV=10 and SNR of the\\nobserved spectra >150. Spectra with a SNR of 30 can be measured for faint (mV=14) M stars, leading to a final radial velocity uncertainty of about 60 m/s. Furthermore, a technical problem occurring under given instrumental configurations could be identified and fixed, removing a possible source of systematic from any later observation. Finally, the zero-point offset with respect to the HARPS data was computed allowing the comparison of the HET measures with those related to any other instruments involved in radial velocity follow-up.\\nThe radial velocities computed from the HET high-resolution spectra allowed to confirm\\nthe detection of the first two extrasolar planet performed by the WTS. WTS1 b is a 4 MJ\\nplanet orbiting in 3.35 days a late F-star with possibly slightly sub-solar metallicity. With a\\nradius of 1.49 RJ, it is the third largest planet of the known extrasolar planets in the mass\\nrange 3-5 MJ. Its unusual large radius can not be explained within the standard evolution models, even considering the strong radiation that the planet receives from the parent star. Ohmic heating could be a possible mechanism able to bring energy in the deeper layers of WTS1 b and hence explaining its radius anomaly. WTS2 b is instead a 1 MJ planet orbiting an early K-star in about 1 day only. The measure of its secondary eclipses in the Ks-band will allow to study a highly irradiated planet around a cool star, cooler than many of the currently known very hot-Jupiters host star. This will provide an insight to the effect of the stellar spectrum on the composition and structure of hot-Jupiter atmospheres. \\nBeyond the RoPACS program, the pipeline has been employed in the radial velocity follow-up of the white dwarf NLTT 5306, confirming the presence of a brown dwarf companion of 56 MJ orbiting its host star in 102 minutes, the shortest period ever observed in such systems.\\nThe discoveries of WTS1 b and WTS2 b demonstrate the capability of WTS to find planets, even if it operates in a back-up mode during dead time on a queue-schedule telescope and despite of the somewhat randomised observing strategy. Moreover, the two new discovered planets are hot-Jupiters orbiting an F-star and a K-star. Both are hotter than an M-dwarf, the main target sample of the WTS. As described in Kovacs et al. (2012, MNRAS submitted), no planets around M-dwarf stars monitored by the WTS (mV<17) with period shorter than 10 days have been found. According to these results, the upper limit of the very hot-Jupiter planetary occurrence around M-stars can be estimated. The resulting value of 0.017 is a stricter constraint than the one derived for the Kepler M-dwarfs sample (0.04)."