Abstract
We present photometry of the extrasolar planet WASP-5b in the 3.6 and 4.5 micron bands taken with the Spitzer Space Telescope's Infrared Array Camera as part of the extended warm mission. By examining the depth of the planet's secondary eclipse at these two wavelengths, we can place joint constraints on the planet's atmospheric pressure-temperature profile and chemistry. We measure secondary eclipse depths of 0.197% +/- 0.028% and 0.227% +/- 0.025% in the 3.6 micron and 4.5 micron bands, respectively. Our observations are best matched by models showing a hot dayside and, depending on our choice of model, a weak thermal inversion or no inversion at all. We measure a mean offset from the predicted center of eclipse of 0.078 +/- 0.032 hours, translating to ecos(omega) = 0.0031 +/- 0.0013 and consistent with a circular orbit. We see no evidence for any eclipse timing variations comparable to those reported in a previous transit study.
Highlights
Hot Jupiters are a class of extrasolar planet that, as the name suggests, are similar in size and composition to Jupiter but orbit very close to their parent star and have correspondingly high effective temperatures, ranging from 1000 K to over 3000 K
We began by extracting photometry from calibrated images in the 3.6 μm and 4.5 μm bands from the Spitzer Space Telescope following the methods described in Knutson et al (2012) and Lewis et al (2013)
We observed secondary eclipses of the extrasolar planet WASP-5b in the 3.6 and 4.5 μm bands, and compared our measurements with atmospheric models generated according to the methodology of Burrows et al (2008) and Fortney et al (2008)
Summary
Hot Jupiters are a class of extrasolar planet that, as the name suggests, are similar in size and composition to Jupiter but orbit very close to their parent star and have correspondingly high effective temperatures, ranging from 1000 K to over 3000 K. The resulting studies indicate that hot Jupiters can be differentiated by the presence or absence of a strong thermal inversion in the planet’s upper atmosphere (Burrows et al 2008; Fortney et al 2008; Barman 2008; Madhusudhan & Seager 2009). We present observations of the transiting hot Jupiter WASP-5b This planet is very dense compared to other planets in its class, suggesting the presence of a large, metalrich core (Anderson et al 2008; Southworth et al 2009; Madhusudhan & Seager 2009; Gillon et al 2009; Dragomir et al 2011; Fukui et al 2011; Pont et al 2011; Hoyer et al 2012).
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