APOSTLE: 11 TRANSIT OBSERVATIONS OF TrES-3b

Abstract

The Apache Point Survey of Transit Lightcurves of Exoplanets (APOSTLE) observed eleven transits of TrES-3b over two years in order to constrain system parameters and look for transit timing and depth variations. We describe an updated analysis protocol for APOSTLE data, including the reduction pipeline, transit model and Markov Chain Monte Carlo analyzer. Our estimates of the system parameters for TrES-3b are consistent with previous estimates to within the 2σ confidence level. We improved the errors (by 10-30%) on system parameters like the orbital inclination (i orb ), impact parameter (b) and stellar density (ρ ⋆ ) compared to previous measurements. The near-grazing nature of the system, and incomplete sampling of some transits, limited our ability to place reliable uncertainties on individual transit depths and hence we do not report strong evidence for variability. Our analysis of the transit timing data show no evidence for transit timing variations and our timing measurements are able to rule out Super-Earth and Gas Giant companions in low order mean motion resonance with TrES-3b.

Observations of the Wasp-2 System by the Apostle Program

“…The large aperture of the system and frametransfer capabilities of Agile allow us to obtain high-precision (500 ppm rms) relative photometry between R = 10.8 th and R = 10.8 th magnitude stars (XO-2; Kundurthy et al 2013a), decreasing to 700 ppm at R = 12.2 versus R = 12.9 (TrES-3; Kundurthy et al 2013b), and 1000 ppm at R = 13.8 versus R = 13.6 (GJ 1214; Kundurthy et al 2011). Importantly, these observations happen at 100% duty cycle due to Agile's frametransfer capabilities.…”

“…Importantly, these observations happen at 100% duty cycle due to Agile's frametransfer capabilities. We make use of the MultiTransitQuick modeling program described in Kundurthy et al (2013b), which uses a Markov Chain Monte Carlo (MCMC) analyzer alongside a light-curve parameterization that minimizes degeneracies between fitted parameters, ensuring that the MCMC proceeds efficiently and faithfully samples parameter space.…”

“…The APOSTLE data reduction pipeline is described in prior publications, including our observational techniques, details of photometric extraction, detrending of the light curves, and parameterization of the transit model (Kundurthy et al 2013b). Specifically to the WASP-2 system, we acquired seven Cousins I-band and three r-band transit sequences between 2007 July and 2010 October.…”

“…Specifically to the WASP-2 system, we acquired seven Cousins I-band and three r-band transit sequences between 2007 July and 2010 October. The I-band images were fringe-corrected using the techniques described in Kundurthy et al (2013a). Observations were taken with a variety of instrumental settings, staring with 0.5 s observations on the nights of 2007 July 24 and 2007 July 26, and moving to longer defocussed exposures starting in 2010.…”

“…Reduced light curves were detrended and modeled using the MultiTransitQuick (MTQ) package (Kundurthy et al 2013b). We used MTQ in two modes: to fit for similar transit depths for data taken in a given filter ( As outlined in Kundurthy et al (2013aKundurthy et al ( , 2013b, we did not fit for the limb-darkening coefficients as they result in poorly converged Markov chains.…”