News From The Gamma Cephei Planetary System

TL;DR

This paper confirms the presence of a giant planet in the Gamma Cephei system with updated orbital parameters, discusses stellar pulsations, and explores the potential for additional planets based on eight more years of radial velocity data.

Contribution

It provides an extended dataset and refined orbital solution for the Gamma Cephei planet, and investigates stellar pulsations affecting RV measurements.

Findings

Confirmed the planetary companion with a more circular orbit.

Detected Gamma Cep A as a multi-periodic pulsator.

Extended the observational baseline by eight years.

Abstract

The Gamma Cephei planetary system is one of the most interesting systems due to several reasons: 1.) it is the first planet candidate detected by precise radial velocity (RV) measurements that was discussed in the literature (Campbell et al. 1988); 2.) it is a tight binary system with a ~ 20AU; and 3.) the planet host star is an evolved K-type star. In Hatzes et al. (2003) we confirmed the presence of the planetary companion with a minimum mass of 1.7 M_Jup at 2 AU. In this paper we present additional eight years of precise RV data from the Harlan J. Smith 2.7 m Telescope and its Tull Coude spectrograph at McDonald Observatory. The 900 d signal, that is interpreted as the presence of the giant planetary companion, is strongly confirmed by adding the new data. We present an updated orbital solution for the planet, which shows that the planet is slightly more massive and the orbit more circular than previous results have suggested. An intensive high-cadence week of RV observations in 2007 revealed that Gamma Cep A is a multi-periodic pulsator. We discuss this issue within the context of searching for additional planets in this system.