The GTC exoplanet transit spectroscopy survey

Abstract

Context. Transiting planets offer an excellent opportunity for characterizing the atmospheres of extrasolar planets under very different conditions from those found in our solar system. Aims. We are currently carrying out a ground-based survey to obtain the transmission spectra of several extrasolar planets using the 10 m Gran Telescopio Canarias. In this paper we investigate the extrasolar planet WASP-48b, a hot Jupiter orbiting around an F-type star with a period of 2.14 days. Methods. We obtained long-slit optical spectroscopy of one transit of WASP-48b with the Optical System for Imaging and lowIntermediate-Resolution Integrated Spectroscopy (OSIRIS) spectrograph. We integrated the spectrum of WASP-48 and one reference star in several channels with different wavelength ranges, creating numerous color light curves of the transit. We fit analytic transit curves to the data taking into account the systematic effects present in the time series in an effort to measure the change of the planetto-star radius ratio (R p /R s ) across wavelength. The change in transit depth can be compared with atmosphere models to infer the presence of particular atomic or molecular compounds in the atmosphere of WASP-48b. Results. After removing the transit model and systematic trends to the curves we reached precisions between 261 ppm and 455-755 ppm for the white and spectroscopic light curves, respectively. We obtained R p /R s uncertainty values between 0.8 × 10 −3 and 1.5 × 10 −3 for all the curves analyzed in this work. The measured transit depth for the curves made by integrating the wavelength range between 530 nm and 905 nm is in agreement with previous studies. We report a relatively flat transmission spectrum for WASP-48b with no statistical significant detection of atmospheric species, although the theoretical models that fit the data more closely include TiO and VO.

LBT transmission spectroscopy of HAT-P-12b

“…Ground-based observations have also proved to be successful in correcting for the telluric effects by applying the differential spectrophotometry method. These observations are mostly carried out with multi-object spectrographs mounted on large telescopes, for example, FORS2 on the Very Large Telescope (VLT; Lendl et al 2016;Nikolov et al 2016;Sedaghati et al 2016), OSIRIS on the Gran Telescopio Canarias (Chen et al 2017a;Murgas et al 2017), GMOS on the Gemini telescope (Gibson et al 2013;Todorov et al 2019), IMACS on the Magellan telescope (Rackham et al 2017;Espinoza et al 2019), and MODS on the Large Binocular Telescope (LBT; Mallonn & Strassmeier 2016). These ground-based observations provide transmission spectra in the optical wavelength range that cover features such as Na/K (Sing et al 2012;Lendl et al 2017;Chen et al 2018;Nikolov et al 2018;Pearson et al 2019), TiO/VO (Sedaghati et al 2017), and the Rayleigh-scattering slopes (Nikolov et al 2015;Parviainen et al 2016;Kirk et al 2017;Chen et al 2017b).…”

High-resolution Transmission Spectroscopy of Four Hot Inflated Gas Giant Exoplanets

“…If sodium, and in some cases, potassium measurements based on low-resolution spectra were reported (e.g., for some of the most recent ones, Sedaghati et al 2016;Chen et al 2017;Pallé et al 2017;Murgas et al 2017;Lendl et al 2017;Chen et al 2018;Pearson et al 2019), only a few studies detected sodium using highresolution transmission spectroscopy: Wyttenbach et al (2017) registered strong absorption signal in WASP-49b. Using HARPS-N mounted on the TNG, Casasayas- Barris et al (2017) andCasasayas-Barris et al (2018) concluded to the presence of sodium in the atmospheres of WASP-69b and MASCARA-2b.…”

MOPSS. I. Flat Optical Spectra for the Hot Jupiters WASP-4 b and WASP-52b

“…More recently, Tsiaras et al (2017) did a reanalysis of the Hubble observations for 30 exoplanets in order to provide a uniformly reduced and analyzed sample of planets. At optical wavelengths, numerous ground-based observatories are working on surveys; including the ACCESS group, also at the Magellan telescopes at Las Campanas, with results for GJ 1214 b (Rackham et al 2017); and the Gran Telescopio Canarias exoplanet transit spectroscopy survey, currently with results for numerous planets (see Sing et al 2012;Murgas et al 2014;Parviainen et al 2016;Pallé et al 2016;Nortmann et al 2016;Chen et al 2017a,b;Murgas et al 2017;Parviainen et al 2017). Because telescope time is limited, it is important to make use of all resources available to us to study the atmospheres of new planets, as well as ensure reproducibility of results across telescopes, instruments, and reduction methods.…”