The NASA-UC Eta-Earth Program: III. A Super-Earth orbiting HD 97658 and a Neptune-mass planet orbiting Gl 785

TL;DR

This paper reports the discovery of a super-Earth and a Neptune-mass planet orbiting two nearby K dwarf stars, using radial velocity measurements and photometric observations to confirm their planetary nature.

Contribution

First detection of planets around HD 97658 and Gl 785 using Keplerian modeling of radial velocities in the NASA-UC Eta-Earth Survey.

Findings

HD 97658 b is a super-Earth with 8.2 Earth masses and a 9.5-day orbit.

Gl 785 b is a Neptune-mass planet with 21.6 Earth masses and a 74.4-day orbit.

Photometry confirms the planetary signals by showing stellar stability at the radial velocity periods.

Abstract

We report the discovery of planets orbiting two bright, nearby early K dwarf stars, HD 97658 and Gl 785. These planets were detected by Keplerian modelling of radial velocities measured with Keck-HIRES for the NASA-UC Eta-Earth Survey. HD 97658 b is a close-in super-Earth with minimum mass Msini = 8.2 +/- 1.2 M_Earth, orbital period P = 9.494 +/- 0.005 d, and an orbit that is consistent with circular. Gl 785 b is a Neptune-mass planet with Msini = 21.6 +/- 2.0 M_Earth, P = 74.39 +/- 0.12 d, and orbital eccentricity 0.30 +/- 0.09. Photometric observations with the T12 0.8 m automatic photometric telescope at Fairborn Observatory show that HD 97658 is photometrically constant at the radial velocity period to 0.09 mmag, supporting the existence of the planet.