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Author (up) McGruder, C.D.; Lopez-Morales, M.; Espinoza, N.; Rackham, B.V.; Apai, D.; Jordan, A.; Osip, D.J.; Alam, M.K.; Bixel, A.; Fortney, J.J.; Henry, G.W.; Kirk, J.; Lewis, N.K.; Rodler, F.; Weaver, I.C. doi  openurl
  Title ACCESS: Confirmation of No Potassium in the Atmosphere of WASP-31b Type
  Year 2020 Publication Astronomical Journal Abbreviated Journal Astron. J.  
  Volume 160 Issue 5 Pages 22 pp  
  Abstract We present a new optical (400-950 nm) transmission spectrum of the hot Jupiter WASP-31b (M = 0.48 M-J; R = 1.54 R-J; P = 3.41 days), obtained by combining four transit observations. These transits were observed with IMACS on the Magellan Baade Telescope at Las Campanas Observatory as part of the ACCESS project. We investigate the presence of clouds/hazes in the upper atmosphere of this planet, as well as the contribution of stellar activity on the observed features. In addition, we search for absorption features of the alkali elements Na i and K i, with particular focus on K i, for which there have been two previously published disagreeing results. Observations with Hubble Space Telescope (HST)/STIS detected K i, whereas ground-based low- and high-resolution observations did not. We use equilibrium and nonequilibrium chemistry retrievals to explore the planetary and stellar parameter space of the system with our optical data combined with existing near-IR observations. Our best-fit model is that with a scattering slope consistent with a Rayleigh slope (alpha = 5(-3.1)(+2.9)), high-altitude clouds at a log cloud top pressure of -3.6(-2.1)(+2.7) bars, and possible muted H2O features. We find that our observations support other ground-based claims of no K I. Clouds are likely why signals like H2O are extremely muted and Na or K cannot be detected. We then juxtapose our Magellan/IMACS transmission spectrum with existing VLT/FORS2, HST/WFC3, HST/STIS, and Spitzer observations to further constrain the optical-to-infrared atmospheric features of the planet. We find that a steeper scattering slope (alpha = 8.3 +/- 1.5) is anchored by STIS wavelengths blueward of 400 nm and only the original STIS observations show significant potassium signal.  
  Address [McGruder, Chima D.; Lopez-Morales, Mercedes; Alam, Munazza K.; Kirk, James; Weaver, Ian C.] Harvard & Smithsonian, Ctr Astrophys, 60 Garden St, Cambridge, MA 02138 USA, Email:  
  Corporate Author Thesis  
  Publisher Iop Publishing Ltd Place of Publication Editor  
  Language English Summary Language Original Title  
  Series Editor Series Title Abbreviated Series Title  
  Series Volume Series Issue Edition  
  ISSN 0004-6256 ISBN Medium  
  Area Expedition Conference  
  Notes WOS:000584919200001 Approved  
  Call Number UAI @ alexi.delcanto @ Serial 1262  
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