Planetary surfaces

Abstract:

Aims. Qatar-1b is a close-orbiting hot Jupiter (R_p ≃ 1.18 R_J, M_p ≃ 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^{+ 212}_-168 K. We also measured a small deviation in the central phase of the secondary eclipse of −0.0079^{+ 0.0162}_-0.0043, which leads to a value for ecosω of −0.0123^{+ 0.0252}_-0.0067. However, this last result needs to be confirmed with more data.

Abstract:

Light curves produced from color observations taken during New Horizons’ approach to the Pluto-system by its Multi-spectral Visible Imaging Camera (MVIC, part of the Ralph instrument) are analyzed. Fifty seven observations were analyzed, they were obtained between 9th April and 3rd July 2015, at a phase angle of 14.5° to 15.1°, sub-observer latitude of 51.2 °N to 51.5 °N, and a sub-solar latitude of 41.2°N. MVIC has four color channels; all are discussed for completeness but only two were found to produce reliable light curves: Blue (400–550 nm) and Red (540–700 nm). The other two channels, Near Infrared (780–975 nm) and Methane-Band (860–910 nm), were found to be potentially erroneous and too noisy respectively. The Blue and Red light curves show that Charon's surface is neutral in color, but slightly brighter on its Pluto-facing hemisphere. This is consistent with previous studies made with the Johnson B and V bands, which are at shorter wavelengths than that of the MVIC Blue and Red channel respectively.