TY - JOUR
T1 - Access
T2 - A featureless optical transmission spectrum for WASP-19b from Magellan/IMACS
AU - Espinoza, Néstor
AU - Rackham, Benjamin V.
AU - Jordán, Andrés
AU - Apai, Dániel
AU - López-Morales, Mercedes
AU - Osip, David J.
AU - Grimm, Simon L.
AU - Hoeijmakers, Jens
AU - Wilson, Paul A.
AU - Bixel, Alex
AU - McGruder, Chima
AU - Rodler, Florian
AU - Weaver, Ian
AU - Lewis, Nikole K.
AU - Fortney, Jonathan J.
AU - Fraine, Jonathan
N1 - Funding Information:
We would like to thank an anonymous referee for suggestions and comments that improved this manuscript. NE would like to thank J. Araya, J. Bravo, P. Jones, M. Martinez, V. Meriño, M. Navarrete, H. Nuñez, A. Pasten, and G. Prieto for numerous discussions (and subsequent experiments) done at LCO which were fundamental to better understand the many sources of systematics in the instrument, and all the staff at LCO for their invaluable support which made this work possible. NE would also like to thank R. McDonald for sharing the Na and K cross-section calculation method, and K. Heng for fruitful discussions regarding the semi-analytical formalism for transmission spectroscopy. NE would like to thank the Gruber Foundation for its generous support to this research. NE and AJ acknowledge support from the Ministry for the Economy, Development and Tourism Programa Iniciativa Científica Milenio through grant IC 120009, awarded to the Millennium Institute of Astrophysics. AJ acknowledges support by Fondecyt grant 1171208 and by CATA-Basal (PB06, CONICYT). NE acknowledges support from Finan-ciamiento Basal PFB06 and from the CONICYT-PCHA/Doctorado Nacional graduate fellowship. BR acknowledges support from the National Science Foundation Graduate Research Fellowship Program under Grant No. DGE-1143953. DA acknowledges support from the Max Planck Institute for Astronomy, Heidelberg, for a sabbatical visit. The results reported herein benefited from collaborations and/or information exchange within NASA's Nexus for Exoplanet System Science research coordination network sponsored by NASA's Science Mission Directorate. This work has made use of the Vienna Atomic Line Database (VALD), operated at Uppsala University, the Institute of Astronomy RAS in Moscow, and the University of Vienna. This paper includes data gathered with the 6.5 m Magellan Telescopes located at LCO, Chile.
Publisher Copyright:
© 2018 The Author(s) Published by Oxford University Press on behalf of the Royal Astronomical Society.
PY - 2019/1/11
Y1 - 2019/1/11
N2 - 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 0.45 to 0.9 μm 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.
AB - 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 0.45 to 0.9 μm 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.
KW - Planets and satellites: atmospheres
KW - Planets and satellites: individual: WASP-19b
KW - Stars: activit
KW - Stars: individual: WASP-19
KW - Starspots
KW - Techniques: spectroscopic
UR - http://www.scopus.com/inward/record.url?scp=85062920997&partnerID=8YFLogxK
U2 - 10.1093/mnras/sty2691
DO - 10.1093/mnras/sty2691
M3 - Article
AN - SCOPUS:85062920997
SN - 0035-8711
VL - 482
SP - 2065
EP - 2087
JO - Monthly Notices of the Royal Astronomical Society
JF - Monthly Notices of the Royal Astronomical Society
IS - 2
ER -