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.

WASP-12b and Qatar-1b do NOT Appear to be in Multi Exoplanetary Systems

Transit Timing Variation Measurements of WASP-12b and Qatar-1b: No Evidence for Additional Planets

Authors:

Collins et al

Abstract:

WASP-12b and Qatar-1b are transiting Hot Jupiters for which previous works have suggested the presence of transit timing variations (TTVs) indicative of additional bodies in these systems---an Earth-mass planet in WASP-12 and a brown-dwarf mass object in Qatar-1. Here, we present 23 new WASP-12b and 18 new Qatar-1b complete (or nearly complete) transit observations. We perform global system fits to all of our lights curves for each system, plus RV and stellar spectroscopic parameters from the literature. The global fits provide refined system parameters and uncertainties for each system, including precise transit center times for each transit. The transit model residuals of the combined and five minute binned light curves have a RMS of 183 and 255 parts per million (ppm) for WASP-12b and Qatar-1b, respectively. Most WASP-12b system parameter values from this work are consistent with values from previous studies, but have ~40-50% smaller uncertainties. Most of the Qatar-1b system parameter values and uncertainties from this work are consistent with values recently reported in the literature. We find no convincing evidence for sinusoidal TTVs with a semi-amplitude of more than ~ 35 s and ~ 25 s in the WASP-12b and Qatar-1b systems, respectively. On the other hand, the data are sparsely sampled and it may be possible that short period, low level, or non-sinusoidal TTV signals are lurking in the data.

Hot Jupiters Qatar-1b and TrES-5b Revisited

High-precision multi-band time-series photometry of exoplanets Qatar-1b and TrES-5b

Authors:

Mislis et al

Abstract:

We present an analysis of the Qatar-1 and TrES-5 transiting exoplanetary systems, which contain Jupiter-like planets on short-period orbits around K-dwarf stars. Our data comprise a total of 20 transit light curves obtained using five medium-class telescopes, operated using the defocussing technique. The average precision we reach in all our data is RMSQ=1.1 mmag for Qatar-1 (V=12.8) and RMST=1.0 mmag for TrES-5 (V=13.7). We use these data to refine the orbital ephemeris, photometric parameters, and measured physical properties of the two systems. One transit event for each object was observed simultaneously in three passbands (gri) using the BUSCA imager. The QES survey light curve of Qatar-1 has a clear sinusoidal variation on a period of P⋆=23.697±0.123\,d, implying significant starspot activity. We searched for starspot crossing events in our light curves, but did not find clear evidence in any of the new datasets. The planet in the Qatar-1 system did not transit the active latitudes on the surfaces of its host star. Under the assumption that P⋆ corresponds to the rotation period of Qatar-1\,A, the rotational velocity of this star is very close to the vsini⋆ value found from observations of the Rossiter-McLaughlin effect. The low projected orbital obliquity found in this system thus implies a low absolute orbital obliquity, which is also a necessary condition for the transit chord of the planet to avoid active latitudes on the stellar surface.