TASTE IV. Refining ephemeris and orbital parameters for HAT-P-20b and WASP-1b

TL;DR

This study refines the orbital parameters of exoplanets HAT-P-20b and WASP-1b using new and re-analyzed light curves, finding no significant TTVs for WASP-1b and possible stellar activity influence on HAT-P-20b.

Contribution

The paper provides a homogeneous re-analysis of transit data, refining ephemeris and orbital parameters, and investigates transit timing variations with implications for stellar activity.

Findings

WASP-1b shows no significant TTVs at 120 s level.

HAT-P-20b exhibits deviations possibly due to stellar activity.

HAT-P-20 A's rotation period suggests a young stellar age (< 1 Gyr).

Abstract

We present four new light curves of 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 we obtained from archival data (P_rot ~ 14.5 days), combined with its optical variability and strong emission of CaII 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.