Extrasolar planets and brown dwarfs around A-F type stars. IV. A candidate brown dwarf around the A9V pulsating star HD180777

TL;DR

This study reports the detection of a candidate brown dwarf orbiting the pulsating A9V star HD180777 using radial velocity measurements, demonstrating the ability to distinguish companion signals from stellar pulsations.

Contribution

First detection of a brown dwarf around an A-F type star that separates orbital signals from stellar pulsations in radial velocity data.

Findings

Detected a 28.4-day period companion with minimum mass of 25 MJup.

Successfully disentangled companion-induced radial velocity variations from stellar pulsations.

Showed that intrinsic stellar phenomena can be distinguished from companion signals.

Abstract

We present here the detection of a brown dwarf orbiting the A9V star HD180777. The radial velocity measurements, obtained with the ELODIE echelle spectrograph at the Haute-Provence Observatory, show a main variation with a period of 28.4 days. Assuming a primary mass of 1.7 Mo, the best Keplerian fit to the data leads to a minimum mass of 25 MJup for the companion (the true mass could be significantly higher). We also show that, after substraction of the Keplerian solution from the radial velocity measurements, the residual radial velocities are related to phenomena intrinsic to the star, namely pulsations with typical periods of Gamma Dor stars. These results show that in some cases, it is possible to disentangle radial velocity variations due to a low mass companion from variations intrinsic to the observed star.