GALEX J184559.8-413827: a new extreme helium star identified using SALT

Abstract

A high-resolution spectrum of the helium-rich `hot subdwarf' GALEX J184559.8-413827 (J1845-4138) obtained with SALT HRS demonstrates it to be the first extreme helium (EHe) star to be discovered in nearly 40 years. A quantitative analysis demonstrates it to have an atmosphere described by Teff = 26 170 +/- 750 K, log g /(cm s^-2) = 4.22 +/- 0.10, and a surface chemistry characterised by CNO-processed helium, a 1% contamination of hydrogen (by number), and a metallicity 0.4 dex subsolar. Its distance and position are consistent with membership of the Galactic bulge. Its sharp absorption lines place strong constraints on both the rotation and microturbulent velocities. Spectroscopically, J1845-4138 closely resembles the pulsating EHe star V652 Her, generally considered to be the product of a double helium white dwarf merger evolving to become a helium-rich sdO star.

MNRAS, in press, 10 pages, 6 figures

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Cited by in corpus (10)

• Evolutionary models for R Coronae Borealis stars
• The SALT survey of helium-rich hot subdwarfs: methods, classification, and coarse analysis
• A search for heavy-metal stars: abundance analyses of hot subdwarfs with Subaru
• Non-Local Thermodynamic Equilibrium abundance analyses of the extreme helium stars: V652 Her and HD 144941
• Revised surface abundances of R Coronae Borealis stars
• Spectroscopic analysis of BPS CS 22940-0009: connecting evolved helium stars
• The distribution, kinematics and luminosities of extreme helium stars as probes of their origin and evolution
• Abundance analysis of a nitrogen-rich extreme-helium hot subdwarf from the SALT survey
• Detection of Enhanced Germanium in a New Cool Extreme Helium Star A 980: Insights and Implications
• Merged white dwarfs and nucleosynthesis