"Sodium detected in the upper atmosphere of WASP-74b"

MICULÁN, ROMINA G.; VON ESSEN, C.; TORRES, ANDREA F.

La Serena

Congreso; Second Binational Meeting AAA-SOCHIAS; 2018

Primary transits offer a unique opportunity to investigate the atmospheres of planets. The lightthat emerges from the center of the star interacts first with the stellar atmosphere and then with the transitingplanet. This last interaction produces an excess of absorption that is printed in the absorption lines of the stellarspectrum. It is evident that this excess is given for some particular atomic and molecular elements that must bepresent not only in the atmosphere of the star but also in the outer layers of the exoplanet atmosphere. Thanks tothe precision of the data acquired today with state-of-the-art telescopes, we can analyze this interaction in greatdetail, revealing the chemistry of the atmospheres that surround these new worlds. We have recently observedthe exoplanet WASP-74b during a primary transit in high resolution, using the ?Ultraviolet and Visual EchelleSpectrograph? mounted on the Very Large Telescope, ESO. We obtained 65 spectra well spread during, beforeand after the transit, which have high signal-to-noise ratio around sodium lines. Analyzing these data we detectedfor the first time sodium in the upper atmosphere of this exoplanet. In this work, we characterize the effect ofthe changing radial velocity and Doppler shifts of the planetary sodium lines during the transit. We also estimatethe shape of the sodium absorption lines produced in the exo-atmosphere and their equivalent widths and derivethe number density of sodium, as well as other relevant atmospheric parameters.