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Title: Deciphering the atmospheric composition of WASP-12b: A comprehensive analysis of its dayside emission

WASP-12b was the first planet reported to have a carbon-to-oxygen ratio (C/O) greater than one in its dayside atmosphere. However, recent work to further characterize its atmosphere and confirm its composition has led to incompatible measurements and divergent conclusions. Additionally, the recent discovery of stellar binary companions ∼1'' from WASP-12 further complicates the analyses and subsequent interpretations. We present a uniform analysis of all available Hubble and Spitzer Space Telescope secondary-eclipse data, including previously unpublished Spitzer measurements at 3.6 and 4.5 μm. The primary controversy in the literature has centered on the value and interpretation of the eclipse depth at 4.5 μm. Our new measurements and analyses confirm the shallow eclipse depth in this channel, as first reported by Campo and collaborators and used by Madhusudhan and collaborators to infer a carbon-rich composition. To explain WASP-12b's observed dayside emission spectrum, we implemented several recent retrieval approaches. We find that when we exclude absorption due to C{sub 2}H{sub 2} and HCN, which are not universally considered in the literature, our models require implausibly large atmospheric CO{sub 2} abundances, regardless of the C/O. By including C{sub 2}H{sub 2} and HCN in our models, we find that a physically plausible carbon-rich solution achievesmore » the best fit to the available photometric and spectroscopic data. In comparison, the best-fit oxygen-rich models have abundances that are inconsistent with the chemical equilibrium expectations for hydrogen-dominated atmospheres and are 670 times less probable. Our best-fit solution is also 7.3 × 10{sup 6} times more probable than an isothermal blackbody model.« less
Authors:
;  [1] ;  [2] ;  [3]
  1. Department of Astronomy and Astrophysics, University of Chicago, 5640 South Ellis Avenue, Chicago, IL 60637 (United States)
  2. Institute of Astronomy, University of Cambridge, Madingley Road, Cambridge CB3 0HA (United Kingdom)
  3. Planetary Sciences Group, Department of Physics, University of Central Florida, Orlando, FL 32816-2385 (United States)
Publication Date:
OSTI Identifier:
22365383
Resource Type:
Journal Article
Resource Relation:
Journal Name: Astrophysical Journal; Journal Volume: 791; Journal Issue: 1; Other Information: Country of input: International Atomic Energy Agency (IAEA)
Country of Publication:
United States
Language:
English
Subject:
79 ASTROPHYSICS, COSMOLOGY AND ASTRONOMY; ABSORPTION; ABUNDANCE; ATMOSPHERES; CARBON; CARBON DIOXIDE; COMPARATIVE EVALUATIONS; ECLIPSE; EMISSION; EMISSION SPECTRA; EQUILIBRIUM; HYDROCYANIC ACID; HYDROGEN; MATHEMATICAL SOLUTIONS; OXYGEN; PLANETS; STARS; TELESCOPES