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Spitzer Secondary Eclipses of the Dense, Modestly-irradiated, Giant Exoplanet HAT-P-20b Using Pixel-level Decorrelation

Deming, Drake and Knutson, Heather and Kammer, Joshua and Fulton, Benjamin J. and Ingalls, James and Carey, Sean and Burrows, Adam and Fortney, Jonathan J. and Todorov, Kamen and Agol, Eric and Cowan, Nicolas and Desert, Jean-Michel and Fraine, Jonathan and Langton, Jonathan and Morley, Caroline and Showman, Adam P. (2015) Spitzer Secondary Eclipses of the Dense, Modestly-irradiated, Giant Exoplanet HAT-P-20b Using Pixel-level Decorrelation. Astrophysical Journal, 805 (2). Art. No. 132. ISSN 0004-637X.

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HAT-P-20b is a giant metal-rich exoplanet orbiting a metal-rich star. We analyze two secondary eclipses of the planet in each of the 3.6 and 4.5 μm bands of Warm Spitzer. We have developed a simple, powerful, and radically different method to correct the intra-pixel effect for Warm Spitzer data, which we call pixel-level decorrelation (PLD). PLD corrects the intra-pixel effect very effectively, but without explicitly using—or even measuring—the fluctuations in the apparent position of the stellar image. We illustrate and validate PLD using synthetic and real data and comparing the results to previous analyses. PLD can significantly reduce or eliminate red noise in Spitzer secondary eclipse photometry, even for eclipses that have proven to be intractable using other methods. Our successful PLD analysis of four HAT-P-20b eclipses shows a best-fit blackbody temperature of 1134 ± 29 K, indicating inefficient longitudinal transfer of heat, but lacking evidence for strong molecular absorption. We find sufficient evidence for variability in the 4.5 μm band that the eclipses should be monitored at that wavelength by Spitzer, and this planet should be a high priority for James Webb Space Telescope spectroscopy. All four eclipses occur about 35 minutes after orbital phase 0.5, indicating a slightly eccentric orbit. A joint fit of the eclipse and transit times with extant RV data yields e cos ω = 0.01352^(+0.00054)_(-0.00057) and establishes the small eccentricity of the orbit to high statistical confidence. HAT-P-20b is another excellent candidate for orbital evolution via Kozai migration or other three-body mechanisms.

Item Type:Article
Related URLs:
URLURL TypeDescription Paper
Deming, Drake0000-0001-5727-4094
Knutson, Heather0000-0002-0822-3095
Kammer, Joshua0000-0002-3441-3757
Fulton, Benjamin J.0000-0003-3504-5316
Ingalls, James0000-0003-4714-1364
Carey, Sean0000-0002-0221-6871
Burrows, Adam0000-0002-3099-5024
Fortney, Jonathan J.0000-0002-9843-4354
Todorov, Kamen0000-0002-9276-8118
Agol, Eric0000-0002-0802-9145
Cowan, Nicolas0000-0001-6129-5699
Desert, Jean-Michel0000-0002-0875-8401
Fraine, Jonathan0000-0003-0910-5805
Morley, Caroline0000-0002-4404-0456
Additional Information:© 2015 The American Astronomical Society. Received 2014 November 30; accepted 2015 March 25; published 2015 May 28. We thank Jasmina Blecic, Patricio Cubillos, and Joseph Harrington for sending us the digital version of their results, used in Figures 5–7, and we thank Julie Moses for comments on this paper. This work is based on observations made with Spitzer, which is operated by the Jet Propulsion Laboratory, California Institute of Technology, under a contract with NASA.
Group:Infrared Processing and Analysis Center (IPAC)
Funding AgencyGrant Number
Subject Keywords:eclipses – infrared: planetary systems – planetary systems – planets and satellites: atmospheres
Issue or Number:2
Record Number:CaltechAUTHORS:20150724-140910245
Persistent URL:
Official Citation:Spitzer Secondary Eclipses of the Dense, Modestly-irradiated, Giant Exoplanet HAT-P-20b Using Pixel-level Decorrelation Drake Deming et al. 2015 ApJ 805 132
Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:59012
Deposited By: Tony Diaz
Deposited On:25 Jul 2015 02:04
Last Modified:06 Nov 2019 18:09

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