The HD 192263 system: planetary orbital period and stellar variability disentangled

TL;DR

This study refines the orbital parameters of the HD 192263 planetary system, analyzes stellar variability over 10 years, and rules out transits for the known planet, distinguishing stellar activity from planetary signals.

Contribution

It provides improved orbital data, characterizes stellar activity, and constrains transit possibilities for HD 192263b using extensive photometry and radial velocity measurements.

Findings

Refined orbital period of 24.3587 days for HD 192263b.

Detected stellar rotation period near 23.4 days with variable spot activity.

Ruled out transits for planets with radii down to 0.79 RJ.

Abstract

As part of the Transit Ephemeris Refinement and Monitoring Survey (TERMS), we present new radial velocities and photometry of the HD 192263 system. Our analysis of the already available Keck-HIRES and CORALIE radial velocity measurements together with the five new Keck measurements we report in this paper results in improved orbital parameters for the system. We derive constraints on the size and phase location of the transit window for HD 192263b, a Jupiter-mass planet with a period of 24.3587 \pm 0.0022 days. We use 10 years of Automated Photoelectric Telescope (APT) photometry to analyze the stellar variability and search for planetary transits. We find continuing evidence of spot activity with periods near 23.4 days. The shape of the corresponding photometric variations changes over time, giving rise to not one but several Fourier peaks near this value. However, none of these frequencies coincides with the planet's orbital period and thus we find no evidence of star-planet interactions in the system. We attribute the ~23-day variability to stellar rotation. There are also indications of spot variations on longer (8 years) timescales. Finally, we use the photometric data to exclude transits for a planet with the predicted radius of 1.09 RJ, and as small as 0.79 RJ.