Detection of the secondary eclipse of Qatar-1b in the Ks band

Cruz, Patricia;Barrado, David;Lillo-Box, Jorge;Diaz, Marcos;Birkby, Jayne;López-Morales, Mercedes;Fortney, Jonathan J. 2016. Detection of the secondary eclipse of Qatar-1b in the Ks band. Astronomy and Astrophysics 595, DOI: 10.1051/0004-6361/201526333

Qatar-1b is a close-orbiting hot Jupiter (R-p similar or equal to 1.18 RJ, M-p similar or equal to 1.33 M-J) around a metal-rich K-dwarf, with orbital separation and period of 0.023 AU and 1.42 days. We have observed the secondary eclipse of this exoplanet in the Ks band with the objective of deriving a brightness temperature for the planet and providing further constraints to the orbital configuration of the system.

Methods. We obtained near-infrared photometric data from the ground by using the OMEGA2000 instrument at the 3.5 m telescope at Calar Alto (Spain) in staring mode, with the telescope defocused. We have used principal component analysis (PCA) to identify correlated systematic trends in the data. A Markov chain Monte Carlo analysis was performed to model the correlated systematics and fit for the secondary eclipse of Qatar-1b using a previously developed occultation model. We adopted the prayer bead method to assess the effect of red noise on the derived parameters.

Results. We measured a secondary eclipse depth of 0.196% (+0.071%)(-0.051%),which indicates a brightness temperature in the Ks band for the planet of 1885(-168)(+212) K. We also measured a small deviation in the central phase of the secondary eclipse of -0.0079(-0.0043)(+0.0162), which leads to a value for e cos omega of 0.012(-0.0067)(+0.0252). However, this last result needs to be confirmed with more data.

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