Radial Velocity Confirmation of a Binary Detected from Pulse Timings

TL;DR

This study confirms a binary companion to the hot subdwarf B star CS 1246 using radial velocity measurements, validating pulse timing as an effective method for detecting binary systems.

Contribution

First direct spectroscopic confirmation of a binary companion to a pulsating hot subdwarf B star via pulse timing method.

Findings

Radial velocity variations match pulse timing predictions.

Binary companion confirmed with orbital parameters.

Pulse timing is effective for binary detection.

Abstract

A periodic variation in the pulse timings of the pulsating hot subdwarf B star CS 1246 was recently discovered via the O-C diagram and suggests the presence of a binary companion with an orbital period of two weeks. Fits to this phase variation, when interpreted as orbital reflex motion, imply CS 1246 orbits a barycenter 11 light-seconds away with a velocity of 16.6 km/s. Using the Goodman spectrograph on the SOAR telescope, we decided to confirm this hypothesis by obtaining radial velocity measurements of the system over several months. Our spectra reveal a velocity variation with amplitude, period, and phase in accordance with the O-C diagram predictions. This corroboration demonstrates that the rapid pulsations of hot subdwarf B stars can be adequate clocks for the discovery of binary companions via the pulse timing method.