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Optical to near-infrared transmission spectrum of the warm sub-Saturn HAT-P-12b

Wong, Ian and Benneke, Björn and Gao, Peter and Knutson, Heather A. and Chachan, Yayaati and Henry, Gregory W. and Deming, Drake and Kataria, Tiffany and Lee, Graham K. H. and Nikolov, Nikolay and Sing, David K. and Ballester, Gilda E. and Baskin, Nathaniel J. and Wakeford, Hannah R. and Williamson, Michael H. (2020) Optical to near-infrared transmission spectrum of the warm sub-Saturn HAT-P-12b. Astronomical Journal, 159 (5). Art. No. 234. ISSN 1538-3881. doi:10.3847/1538-3881/ab880d.

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We present the transmission spectrum of HAT-P-12b through a joint analysis of data obtained from the Hubble Space Telescope Space Telescope Imaging Spectrograph and Wide Field Camera 3 and Spitzer, covering the wavelength range 0.3–5.0 μm. We detect a muted water vapor absorption feature at 1.4 μm attenuated by clouds, as well as a Rayleigh scattering slope in the optical indicative of small particles. We interpret the transmission spectrum using both the state-of-the-art atmospheric retrieval code SCARLET and the aerosol microphysics model CARMA. These models indicate that the atmosphere of HAT-P-12b is consistent with a broad range of metallicities between several tens to a few hundred times solar, a roughly solar C/O ratio, and moderately efficient vertical mixing. Cloud models that include condensate clouds do not readily generate the submicron particles necessary to reproduce the observed Rayleigh scattering slope, while models that incorporate photochemical hazes composed of soot or tholins are able to match the full transmission spectrum. From a complementary analysis of secondary eclipses by Spitzer, we obtain measured depths of 0.042% ± 0.013% and 0.045% ± 0.018% at 3.6 and 4.5 μm, respectively, which are consistent with a blackbody temperature of 890⁺⁶⁰₋₇₀ K and indicate efficient day–night heat recirculation. HAT-P-12b joins the growing number of well-characterized warm planets that underscore the importance of clouds and hazes in our understanding of exoplanet atmospheres.

Item Type:Article
Related URLs:
URLURL TypeDescription Paper
Wong, Ian0000-0001-9665-8429
Benneke, Björn0000-0001-5578-1498
Gao, Peter0000-0002-8518-9601
Knutson, Heather A.0000-0002-0822-3095
Chachan, Yayaati0000-0003-1728-8269
Henry, Gregory W.0000-0003-4155-8513
Deming, Drake0000-0001-5727-4094
Kataria, Tiffany0000-0003-3759-9080
Lee, Graham K. H.0000-0002-3052-7116
Nikolov, Nikolay0000-0002-6500-3574
Sing, David K.0000-0001-6050-7645
Ballester, Gilda E.0000-0002-3891-7645
Wakeford, Hannah R.0000-0003-4328-3867
Additional Information:© 2020 The American Astronomical Society. Received 2019 May 17; revised 2020 February 7; accepted 2020 April 7; published 2020 April 23. This work is based on observations with the NASA/ESA Hubble Space Telescope obtained at the Space Telescope Science Institute (STScI) operated by AURA, Inc. This work is also based in part on observations made with the Spitzer Space Telescope, which is operated by the Jet Propulsion Laboratory, California Institute of Technology, under a contract with NASA. The research leading to these results has received funding from the European Research Council under the European Union's Seventh Framework Program (FP7/2007-2013)/ERC grant agreement No. 336792. Support for this work was also provided by NASA/STScI through grants linked to the HST-GO-12473 and HST-GO-14767 programs. I.W. and P.G. are supported by Heising-Simons Foundation 51 Pegasi b postdoctoral fellowships. H.A.K. acknowledges support from the Sloan Foundation.
Group:Astronomy Department
Funding AgencyGrant Number
European Research Council (ERC)336792
Heising-Simons Foundation51 Pegasi b Fellowship
Alfred P. Sloan FoundationUNSPECIFIED
Subject Keywords:Exoplanet atmospheres ; Exoplanet astronomy
Issue or Number:5
Classification Code:Unified Astronomy Thesaurus concepts: Exoplanet atmospheres (487); Exoplanet astronomy (486)
Record Number:CaltechAUTHORS:20200420-101335006
Persistent URL:
Official Citation:Ian Wong et al 2020 AJ 159 234
Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:102647
Deposited By: Tony Diaz
Deposited On:20 Apr 2020 17:26
Last Modified:16 Nov 2021 18:14

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