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Warm Spitzer Occultation Photometry of WASP-26b at 3.6{\mu}m and 4.5{\mu}m

Mahtani, D. P.; Mahtani, D. P.; Maxted, P. F. L.; Anderson, D. R.; Smith, A. M. S.; Smalley, B.; Tregloan-Reed, J.; Southworth, J.; Madhusudhan, N.; Collier Cameron, A.; Gillon, M.; Harrington, J.; Hellier, C.; Pollacco, D.; Queloz, D.; Triaud, A. H. M. J.; West, R. G.

Authors

D. P. Mahtani

D. P. Mahtani

D. R. Anderson

A. M. S. Smith

J. Tregloan-Reed

N. Madhusudhan

A. Collier Cameron

M. Gillon

J. Harrington

D. Pollacco

D. Queloz

A. H. M. J. Triaud

R. G. West



Abstract

We present new warm Spitzer occultation photometry of WASP-26 at 3.6{\mu}m and 4.5{\mu}m along with new transit photometry taken in the g,r and i bands. We report the first detection of the occultation of WASP-26b, with occultation depths at 3.6{\mu}m and 4.5{\mu}m of 0.00126 +/- 0.00013 and 0.00149 +/- 0.00016 corresponding to brightness temperatures of 1825+/-80K and 1725+/-89K, respectively. We find that the eccentricity of the orbit is consistent with a circular orbit at the 1{\sigma} level with a 3{\sigma} upper limit of e < 0.04. According to the activity-inversion relation of Knutson et al. (2010), WASP-26b is predicted to host a thermal inversion. The brightness temperatures deduced from the eclipse depths are consistent with an isothermal atmosphere, although it is within the uncertainties that the planet may host a weak thermal inversion. The data are equally well fit by atmospheric models with or without a thermal inversion. We find that variation in activity of solar-like stars does not change enough over the time-scales of months or years to change the interpretation of the Knutson et al. (2010) activity-inversion relation, provided that the measured activity level is averaged over several nights. Further data are required to fully constrain the thermal structure of the atmosphere because the planet lies very close to the boundary between atmospheres with and without a thermal inversion.

Citation

Mahtani, D. P., Mahtani, D. P., Maxted, P. F. L., Anderson, D. R., Smith, A. M. S., Smalley, B., …West, R. G. (2013). Warm Spitzer Occultation Photometry of WASP-26b at 3.6{\mu}m and 4.5{\mu}m. Monthly Notices of the Royal Astronomical Society, 432(1), 693-701. https://doi.org/10.1093/mnras/stt505

Journal Article Type Article
Acceptance Date Mar 19, 2013
Online Publication Date Apr 17, 2013
Publication Date Jun 11, 2013
Deposit Date Jun 16, 2023
Journal Monthly Notices of the Royal Astronomical Society
Print ISSN 0035-8711
Electronic ISSN 0035-8711
Publisher Oxford University Press
Peer Reviewed Peer Reviewed
Volume 432
Issue 1
Pages 693-701
DOI https://doi.org/10.1093/mnras/stt505
Keywords Earth and Planetary Astrophysics