Two Exoplanets Discovered at Keck Observatory

TL;DR

This paper reports the discovery of two exoplanets around G5 subgiant stars at Keck Observatory, detailing their orbital characteristics and discussing biases in eccentricity measurements for low-amplitude systems.

Contribution

First detection of two exoplanets around G5 subgiants with detailed orbital parameters and analysis of eccentricity measurement biases.

Findings

HD 179079 hosts a hot Neptune with a 14.48-day orbit.

HD 73534 hosts a Jupiter-like planet with a 4.85-year orbit.

Eccentricity distribution varies with velocity amplitude, K.

Abstract

We present two exoplanets detected at Keck Observatory. HD 179079 is a G5 subgiant that hosts a hot Neptune planet with Msini = 27.5 M_earth in a 14.48 d, low-eccentricity orbit. The stellar reflex velocity induced by this planet has a semiamplitude of K = 6.6 m/s. HD 73534 is a G5 subgiant with a Jupiter-like planet of Msini = 1.1 M_jup and K = 16 m/s in a nearly circular 4.85 yr orbit. Both stars are chromospherically inactive and metal-rich. We discuss a known, classical bias in measuring eccentricities for orbits with velocity semiamplitudes, K, comparable to the radial velocity uncertainties. For exoplanets with periods longer than 10 days, the observed exoplanet eccentricity distribution is nearly flat for large amplitude systems (K > 80 m/s), but rises linearly toward low eccentricity for lower amplitude systems (K > 20 m/s).