WARMSPITZERPHOTOMETRY OF THE TRANSITING EXOPLANETS CoRoT-1 AND CoRoT-2 AT SECONDARY ECLIPSE

Abstract

We measure secondary eclipses of the hot giant exoplanets CoRoT-1 at 3.6 and 4.5 μm, and CoRoT-2 at 3.6 μm, both using Warm Spitzer. We find that the Warm Spitzer mission is working very well for exoplanet science. For consistency of our analysis we also re-analyze archival cryogenic Spitzer data for secondary eclipses of CoRoT-2 at 4.5 and 8 μm. We compare the total data for both planets, including optical eclipse measurements by the CoRoT mission, and ground-based eclipse measurements at 2 μm, to existing models. Both planets exhibit stronger eclipses at 4.5 than at 3.6 μm, which is often indicative of an atmospheric temperature inversion. The spectrum of CoRoT-1 is best reproduced by a 2460 K blackbody, due either to a high altitude layer that strongly absorbs stellar irradiance, or an isothermal region in the planetary atmosphere. The spectrum of CoRoT-2 is unusual because the 8 μm contrast is anomalously low. Non-inverted atmospheres could potentially produce the CoRoT-2 spectrum if the planet exhibits line emission from CO at 4.5 μm, caused by tidal-induced mass loss. However, the viability of that hypothesis is questionable because the emitting region cannot be more than about 30% larger than the planet's transit radius, based on the ingress and egress times at eclipse. An alternative possibility to account for the spectrum of CoRoT-2 is an additional opacity source that acts strongly at wavelengths less than 5 μm, heating the upper atmosphere while allowing the deeper atmosphere seen at 8 μm to remain cooler. We obtain a similar result as Gillon et al. for the phase of the secondary eclipse of CoRoT-2, implying an eccentric orbit with e cos(ω) = −0.0030 ± 0.0004.

WASP-50 b: a hot Jupiter transiting a moderately active solar-type star

“…With a size larger than Jupiter's, a high irradiation, and a relatively small and infrared-bright (K = 10) host star, WASP-50 b is a good target for near-IR thermal emission measurements with the occultation photometry technique, using Warm Spitzer at 3.6 and 4.5 μm (e.g. Deming et al 2011) or ground-based instruments at shorter wavelengths (e.g. Gillon et al 2009b).…”

Ground-based near-UV observations of 15 transiting exoplanets: constraints on their atmospheres and no evidence for asymmetrical transits

“…Several follow-up primary transit photometry studies of the system find no signs of a changing period (Bean 2009;Gillon et al 2009;Csizmadia et al 2010;Rauer et al 2010;Southworth 2011;Sada et al 2012;Ranjan et al 2014). CoRoT-1b's atmosphere may have a temperature inversion (Alonso et al 2009;Gillon et al 2009;Rogers et al 2009;Snellen, de Mooij & Albrecht 2009;Zhao et al 2012) or an isothermal profile (Deming et al 2011). Infrared transmission spectroscopy observations by Schlawin et al (2014) disfavour a TiO/VO-rich spectrum for CoRoT-1b, suggesting the temperature inversion is caused by another absorber in the atmosphere or that flat spectrum is due to clouds or a haze layer.…”

SPITZERSECONDARY ECLIPSES OF THE DENSE, MODESTLY-IRRADIATED, GIANT EXOPLANET HAT-P-$20{\rm b}$ USING PIXEL-LEVEL DECORRELATION

“…We used a quadratic polynomial for Figure 2 because that order is commonly used in real Spitzer decorrelations (e.g., Deming et al 2011;Todorov et al 2012Todorov et al , 2013. However, that is arguably an unfair comparison because the quadratic decorrelation has only four position-dependent parameters, versus nine for PLD.…”

“…Irrespective of this debate, there are already multiple examples in the literature where the emergent day-side spectra of hot Jupiters are consistent with that of a blackbody. For example, CoRot-1b (Deming et al 2011), WASP-48b, and HAT-P-23b (O'Rourke et al 2014) resemble blackbodies. However, there are also planets whose emergent spectrum is clearly not a blackbody, WASP-43b being the most recent example (Kreidberg et al 2014).…”