A Detection of the Secondary Eclipse of hot Jupiter Qatar-1b

A detection of the secondary eclipse of Qatar-1b in the Ks-band

Authors:

Cruz et al

Abstract:

Qatar-1b is a close-orbiting hot-Jupiter (Rp≃1.18 RJ, Mp≃1.33 MJ) around a metal-rich K-dwarf, with orbital separation and period of 0.023 AU and 1.42 days, respectively. 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. 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 in order to model the correlated systematics and fit for the secondary eclipse of Qatar-1b using the occultation model by Mandel & Agol (2002). 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 should be confirmed with more data. This work highlights that ground-based secondary eclipse observations are capable of providing useful constraints on the orbital configuration of bright, giant planets that can be used to probe the architecture and multiplicity in hot Jupiter systems.

Detecting Exoplanet Rotation Rate and Obliquity Through Secondary Eclipses

Radial velocity eclipse mapping of exoplanets

Authors:

Nikolov et al

Abstract:

Planetary rotation rates and obliquities provide information regarding the history of planet formation, but have not yet been measured for evolved extrasolar planets. Here we investigate the theoretical and observational perspective of the Rossiter-McLauglin effect during secondary eclipse (RMse) ingress and egress for transiting exoplanets. Near secondary eclipse, when the planet passes behind the parent star, the star sequentially obscures light from the approaching and receding parts of the rotating planetary surface. The temporal block of light emerging from the approaching (blue-shifted) or receding (red-shifted) parts of the planet causes a temporal distortion in the planet's spectral line profiles resulting in an anomaly in the planet's radial velocity curve. We demonstrate that the shape and the ratio of the ingress-to-egress radial velocity amplitudes depends on the planetary rotational rate, axial tilt and impact factor (i.e. sky-projected planet spin-orbital alignment). In addition, line asymmetries originating from different layers in the atmosphere of the planet could provide information regarding zonal atmospheric winds and constraints on the hot spot shape for giant irradiated exoplanets. The effect is expected to be most-pronounced at near-infrared wavelengths, where the planet-to-star contrasts are large. We create synthetic near-infrared, high-dispersion spectroscopic data and demonstrate how the sky-projected spin axis orientation and equatorial velocity of the planet can be estimated. We conclude that the RMse effect could be a powerful method to measure exoplanet spins.

Hot Jupiter WASP-10b Orbit Refined

Detection of the secondary eclipse of WASP-10b in the Ks-band

Authors:

Cruz et al

Abstract:

WASP-10b, a non-inflated hot Jupiter, was discovered around a K-dwarf in a near circular orbit (∼0.06). Since its discovery in 2009, different published parameters for this system have led to a discussion about the size, density, and eccentricity of this exoplanet. In order to test the hypothesis of a circular orbit for WASP-10b, we have observed its secondary eclipse in the Ks-band, where the contribution of planetary light is high enough to be detected from the ground. Observations were performed with the OMEGA2000 instrument at the 3.5-meter telescope at Calar Alto (Almer\'ia, Spain), in staring mode during 5.4 continuous hours, with the telescope defocused, monitoring the target during the expected secondary eclipse. A relative light curve was generated and corrected from systematic effects, using the Principal Component Analysis (PCA) technique. The final light curve was fitted using a transit model to find the eclipse depth and a possible phase shift. The best model obtained from the Markov Chain Monte Carlo analysis resulted in an eclipse depth of ΔF of 0.137%+0.013%−0.019% and a phase offset of Δϕ of −0.0028+0.0005−0.0004. The eclipse phase offset derived from our modeling has systematic errors that were not taken into account and should not be considered as evidence of an eccentric orbit. The offset in phase obtained leads to a value for |ecosω| of 0.0044. The derived eccentricity is too small to be of any significance.