TASTE IV: Refining ephemeris and orbital parameters for HAT‐P‐20b and WASP‐1b

Abstract

We present four new light curves of the transiting exoplanets WASP-1b and HAT-P-20b, observed within the TASTE (The Asiago Search for Transit timing variations of Exoplanets) project. We re-analyzed light curves from the literature in a homogeneous way, calculating a refined ephemeris and orbital-physical parameters for both objects. WASP-1b does not show any significant Transit Timing Variation signal at the 120 s level. As for HAT-P-20b, we detected a deviation from our re-estimated linear ephemeris that could be ascribed to the presence of a perturber or, more probably, to a previously unnoticed high level of stellar activity. The rotational period of HAT-P-20 A that we obtained from archival data (P rot 14.5 d), combined with its optical variability and strong emission of Ca ii H & K lines, is consistent with a young stellar age (< 1 Gyr) and support the hypothesis that stellar activity may be responsible of the measured deviations of the transit times.

Refined System Parameters and TTV Study of Transiting Exoplanetary System Hat-P-20

“…We find that optically variable modulation exists in both survey data which is probably due to photospheric spots which persisted at fixed longitudes of HAT-P-20 for a long time, which is consistent with strong chromospheric Ca II H & K emission and X-ray emission (Bakos et al 2011;Granata et al 2014;Salz et al 2015), and both peak powers overlay quite well in the GLS periodogram (e.g., =  P 14.66 0.03 day; rot see Figure 7). …”

“…Besides our own light curves, we also collect two Sloan iband light curves from Bakos et al (2011), three R-band light curves from Granata et al (2014), and one R-band light curve from Baştürk et al (2015). Meanwhile, we have obtained raw photometric images of three transit events sent to ETD 12 by Paul Benni, Alberto Villa, and Mark Salisbury, and then reduced these data with our standard procedure.…”

“…In addition, we have obtained five light curves at Observatori Ca I'Ou (hereafter, OCIO) since 2013. Here, we present our results of the transiting system HAT-P-20, based on our new photometric observations, available light curves, and radial velocity curve from the literature (Bakos et al 2011;Granata et al 2014;Baştürk et al 2015). In Section 2, we describe our observations and data reduction techniques.…”

“…It is a massive hot Jupiter with a mass of  M 7.246 0.03 Jup and a radius of  R 0.867 0.033 Jup . Its host star is a K3 main-sequence star, and it has a relatively strong magnetic activity (Bakos et al 2011;Shkolnik 2013;Granata et al 2014;Salz et al 2015). HAT-P-20 has a red companion (2MASS07273963+2420171, -= J K 0.92) with a   6.…”

“…925 0.012 separation, which is fainter than HAT-P-20 by  =  i 2.01 0.08 mag (Bakos et al 2011;Wöllert & Brandner 2015). Granata et al (2014) obtained three light curves of HAT-P-20 by utilizing the Asiago 1.82 m Copernico telescope on 2011 February 5, November 28, and December 22, respectively, and studied the TTV of HAT-P-20 based on their new observations and available data in the literature. Later Baştürk et al (2015) recalculated the transit parameters of HAT-P-20 relying on their newly obtained transit light curve with the 1 m Turkish telescope T100 at TUBİTAK National Observatory.…”