Retired A Stars and Their Companions II: Jovian planets orbiting kappa Coronae Borealis and HD167042

TL;DR

This study reports the discovery of Jovian planets orbiting two evolved intermediate-mass stars, using precise Doppler measurements, revealing their orbital parameters and contributing to understanding planet formation around such stars.

Contribution

First detection of Jovian planets around evolved A-type stars with detailed orbital parameters, expanding knowledge of planetary systems around intermediate-mass subgiants.

Findings

Planets have minimum masses around 1.7-1.8 Mjup.

Orbits have periods of 412.6 and 1208 days.

One planet has a nearly circular orbit, similar to Solar System giants.

Abstract

We report precise Doppler measurements of two evolved stars, kappa CrB (HD142091) and HD 167042, obtained at Lick Observatory as part of our search for planets orbiting intermediate-mass subgiants. Periodic variations in the radial velocities of both stars reveal the presence of substellar orbital companions. These two stars are notably massive with stellar masses of 1.80 Msun and 1.64 Msun, indicating that they are former A-type dwarfs that have evolved off of the main sequence and are now K-type subgiants. The planet orbiting kappa CrB has a minimum mass Msini = 1.8 Mjup, eccentricity e = 0.146 and a 1208 day period, corresponding to a semimajor axis of 2.7 AU. The planet around HD167042 has a minimum mass Msini = 1.7 Mjup and a 412.6 day orbit, corresponding to a semimajor axis of 1.3 AU. The eccentricity of HD167042b is consistent with circular (e = 0.027+/-0.04), adding to the rare class of known exoplanets in long-period, circular orbits similar to the Solar System gas giants. Like all of the planets previously discovered around evolved A stars, kappa CrBb and HD167042b orbit beyond 0.8 AU.