Radial Velocities of Galactic O-Type Stars. II. Single-lined Spectroscopic Binaries

TL;DR

This study reports new radial velocity data and orbital solutions for several Galactic O-type stars suspected to be single-lined spectroscopic binaries, aiming to understand their binary fraction and characteristics.

Contribution

It provides the first orbital parameters for five O-type stars, enhancing knowledge of their binary nature and properties.

Findings

Orbits for five O-type stars are determined.

No photometric variations detected in these systems.

Companions are likely faint with small Doppler shifts.

Abstract

We report on new radial velocity measurements of massive stars that are either suspected binaries or lacking prior observations. This is part of a survey to identify and characterize spectroscopic binaries among O-type stars with the goal of comparing the binary fraction of field and runaway stars with those in clusters and associations. We present orbits for HDE 308813, HD 152147, HD 164536, BD-16 4826 and HDE 229232, Galactic O-type stars exhibiting single-lined spectroscopic variation. By fitting model spectra to our observed spectra we obtain estimates for effective temperature, surface gravity, and rotational velocity. We compute orbital periods and velocity semiamplitudes for each system and note the lack of photometric variation for any system. These binaries probably appear single-lined because the companions are faint and because their orbital Doppler shifts are small compared to the width of the rotationally broadened lines of the primary.