Detection of a Third Planet in the HD 74156 System Using the Hobby-Eberly Telescope

TL;DR

This paper reports the discovery of a third planet orbiting HD 74156 using high-precision radial velocity measurements from the Hobby-Eberly Telescope, revealing a complex multi-planet system with significant eccentricities.

Contribution

The study presents the first detection of a third planet in the HD 74156 system, expanding the known planetary system architecture and providing data for understanding planet formation.

Findings

Discovery of a third planet with a 347-day orbit and 0.4 M_Jup mass.

Revised orbital periods and masses for the two previously known planets.

Indication that the three-planet system is dynamically stable despite high eccentricities.

Abstract

We report the discovery of a third planetary mass companion to the G0 star HD 74156. High precision radial velocity measurements made with the Hobby-Eberly Telescope aided the detection of this object. The best fit triple Keplerian model to all the available velocity data yields an orbital period of 347 days and minimum mass of 0.4 M_Jup for the new planet. We determine revised orbital periods of 51.7 and 2477 days, and minimum masses of 1.9 and 8.0 M_Jup respectively for the previously known planets. Preliminary calculations indicate that the derived orbits are stable, although all three planets have significant orbital eccentricities (e = 0.64, 0.43, and 0.25). With our detection, HD 74156 becomes the eighth normal star known to host three or more planets. Further study of this system's dynamical characteristics will likely give important insight to planet formation and evolutionary processes.