The ACCESS Transiting Exoplanets Spectroscopy Survey - Methodology, Results to date, Future Prospects

One of the most exciting possibilities enabled by transiting exoplanets is to measure their atmospheric properties through the technique of transmission spectroscopy. The optical window, in particular, is rich in atmospheric information which is capable of disentangling several degeneracies in atmospheric modelling. Initiated in 2014, ACCESS is a multi-institutional collaboration aimed at responding to this opportunity by generating the first uniform observational set of ~ 0.35 – 1.0 μm transmission spectra of a meaningful sample (~20) exoplanet atmospheres, spanning those from hot Jupiters to super-Earths. In this talk, we present the survey methodology and lessons learned to date following over 40 transits observed using the IMACS multi-object spectrograph on the 6.5-m Magellan Baade Telescope at Las Campanas Observatory.  ACCESS minimizes systematics caused by different instruments and data analysis techniques allowing us to discuss approaches to correct for instrumental and astrophysical systematics to improve the diagnostic power of transit spectroscopy. We will present a brief overview of the survey and highlight results on multiple targets, including hot Jupiters and the sub-Neptune GJ 1214b.  Of particular interest are recent results obtained from a series of 6 observed transits of WASP-19b which show transmission spectra that are in striking contrast with published VLT/FORS2 results for which claims of TiO and a strong blue-optical slope were postulated.  Finally, we will elucidate where we see the brightest future prospects in the era of space missions such as TESS and JWST. 

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