A FEROS Survey of Hot Subdwarf Stars

TL;DR

This survey of 22 ultraviolet-selected hot subdwarfs using FEROS identified new binary systems, determined their orbital parameters, and analyzed their chemical abundances, providing insights into their evolution.

Contribution

The paper presents the first comprehensive spectroscopic survey of hot subdwarfs with new binary detections and detailed chemical abundance analysis.

Findings

Discovered three new short-period binary systems.

Determined orbital parameters of a long-period sdO+G III system.

Found nitrogen and argon abundance excesses in some subdwarfs.

Abstract

We have completed a survey of twenty-two ultraviolet-selected hot subdwarfs using the Fiber-fed Extended Range Optical Spectrograph (FEROS) and the 2.2-m telescope at La Silla. The sample includes apparently single objects as well as hot subdwarfs paired with a bright, unresolved companion. The sample was extracted from our GALEX catalogue of hot subdwarf stars. We identified three new short-period systems (P=3.5 hours to 5 days) and determined the orbital parameters of a long-period (P=62.66 d) sdO plus G III system. This particular system should evolve into a close double degenerate system following a second common envelope phase. We also conducted a chemical abundance study of the subdwarfs: Some objects show nitrogen and argon abundance excess with respect to oxygen. We present key results of this programme.