Mon. Not. R. Astron. Soc., 482, 2065-2087 (2019/January-2)
ACCESS: a featureless optical transmission spectrum for WASP-19b from Magellan/IMACS.
ESPINOZA N., RACKHAM B.V., JORDAN A., APAI D., LOPEZ-MORALES M., OSIP D.J., GRIMM S.L., HOEIJMAKERS J., WILSON P.A., BIXEL A., McGRUDER C., RODLER F., WEAVER I., LEWIS N.K., FORTNEY J.J. and FRAINE J.
Abstract (from CDS):
The short-period (0.94-d) transiting exoplanet WASP-19b is an exceptional target for transmission spectroscopy studies, due to its relatively large atmospheric scale height (∼500 km) and equilibrium temperature (∼2100 K). Here, we report on six precise spectroscopic Magellan/IMACS observations, five of which target the full optical window from 0.45µm and one targeting the 0.4-0.55 µm blue-optical range. Five of these data sets are consistent with a transmission spectrum without any significant spectral features, while one shows a significant slope as a function of wavelength, which we interpret as arising from photospheric heterogeneities in the star. Coupled with HST/WFC3 infrared observations, our optical/near-infrared measurements point to the presence of high altitude clouds in WASP-19b's atmosphere in agreement with previous studies. Using a semi-analytical retrieval approach, considering both planetary and stellar spectral features, we find a water abundance consistent with solar for WASP-19b and strong evidence for sub-solar abundances for optical absorbers such as TiO and Na; no strong optical slope is detected, which suggests that if hazes are present, they are much weaker than previously suggested. In addition, two spot-crossing events are observed in our data sets and analysed, including one of the first unambiguously detected bright-spot-crossing events on an exoplanet host star.
© 2018 The Author(s) Published by Oxford University Press on behalf of the Royal Astronomical Society
techniques: spectroscopic - planets and satellites: atmospheres - planets and satellites: individual: WASP-19b - stars: activit - stars: individual: WASP-19 - starspots
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