CaltechAUTHORS
Published April 2020 | Version Published + Submitted
Journal Article Open

Statistical Characterization of Hot Jupiter Atmospheres using Spitzer's Secondary Eclipses

Creators

  • 1. ROR icon University of Maryland, College Park
  • 2. ROR icon Arizona State University
  • 3. ROR icon Goddard Space Flight Center
  • 4. ROR icon California Institute of Technology
  • 5. ROR icon Princeton University
  • 6. ROR icon University of California, Santa Cruz
  • 7. ROR icon Johns Hopkins University
  • 8. ROR icon University of Montreal
  • 9. ROR icon Space Telescope Science Institute
  • 10. ROR icon Jet Propulsion Lab
  • 11. ROR icon Cornell University
  • 12. ROR icon University of Cambridge
  • 13. ROR icon Johns Hopkins University Applied Physics Laboratory

Abstract

We report 78 secondary eclipse depths for a sample of 36 transiting hot Jupiters observed at 3.6 and 4.5 μm using the Spitzer Space Telescope. Our eclipse results for 27 of these planets are new, and include highly irradiated worlds such as KELT-7b, WASP-87b, WASP-76b, and WASP-64b, and important targets for James Webb Space Telescope such as WASP-62b. We find that WASP-62b has a slightly eccentric orbit (e cos ω = 0.00614±0.00064), and we confirm the eccentricity of HAT-P-13b and WASP-14b. The remainder are individually consistent with circular orbits, but we find statistical evidence for eccentricity increasing with orbital period in our range from 1 to 5 days. Our day-side brightness temperatures for the planets yield information on albedo and heat redistribution, following Cowan & Agol (2011). Planets having maximum day-side temperatures exceeding ~2200 K are consistent with having zero albedo and a distribution of stellar irradiance uniformly over the day-side hemisphere. Our most intriguing result is that we detect a systematic difference between the emergent spectra of these hot Jupiters as compared to blackbodies. The ratio of observed brightness temperatures, Tb(4.5)/Tb(3.6), increases with equilibrium temperature by 100 ± 24 parts-per-million per Kelvin, over the entire temperature range in our sample (800–2500 K). No existing model predicts this trend over such a large range of temperature. We suggest that this may be due to a structural difference in the atmospheric temperature profiles of real planetary atmospheres as compared to models.

Additional Information

© 2020 The American Astronomical Society. Received 2019 January 19; revised 2019 November 8; accepted 2020 January 15; published 2020 February 28. We thank the staff of the Spitzer Space Telescope for their help in planning and their careful scheduling and execution of the observations. We also thank an anonymous referee and the statistical editor for comments that significantly improved this paper. This work was supported by NASA ADAP grant NNX16AF34G.

Attached Files

Published - Garhart_2020_AJ_159_137.pdf

Submitted - 1901.07040.pdf

Files

1901.07040.pdf

Files (11.8 MB)

Name Size
md5:3489e77ccc3bdcf463cdbb4b88de5bc7
3.3 MB Preview Download
md5:a77f187c0f9ed9297a14c335b8949876
8.5 MB Preview Download

Additional details

Identifiers

Eprint ID
92456
Resolver ID
CaltechAUTHORS:20190124-122555938

Related works

Describes
https://arxiv.org/abs/1901.07040 (URL)

Funding

NASA
NNX16AF34G

Dates

Created
2019-01-25
Created from EPrint's datestamp field
Updated
2021-11-16
Created from EPrint's last_modified field

Caltech Custom Metadata

Caltech groups
Astronomy Department , Division of Geological and Planetary Sciences (GPS)