Abundance analysis of a nitrogen-rich extreme-helium hot subdwarf from the SALT survey

Abstract

We have performed a detailed spectral analysis of the helium-rich hot subdwarf EC 20187-4939 using data obtained in the SALT survey of helium-rich hot subdwarfs. We have measured its effective temperature, surface gravity and chemical abundances from the spectrum. Its radius has also been determined by fitting the spectral energy distribution using photometric data, from which a mass of 0.44 Msun has been inferred using the measurement of surface gravity. This star is particularly abundant in helium and nitrogen, whilst being both carbon and oxygen-weak. The surface abundances and mass have been found to be consistent with a helium white dwarf merger product. The abundance effects of alpha captures on nitrogen during the merger process and possible connections between EC 20187-4939 and other carbon-weak related objects are discussed.

arXiv comment10 pages, 5 figures, 5 tables, accepted for publication in MNRAS

References in corpus (26)

• The chemical composition of the Sun
• MESA Isochrones and Stellar Tracks (MIST). I: Solar-Scaled Models
• The Eleventh and Twelfth Data Releases of the Sloan Digital Sky Survey: Final Data from SDSS-III
• The Origin of Subdwarf B Star (I): the Formation Channels
• The origin of sdB stars (II)
• The unWISE Catalog: Two Billion Infrared Sources from Five Years of WISE Imaging
• Hot subluminous stars
• The Dark Energy Survey Data Release 2
• SkyMapper Southern Survey: Second Data Release (DR2)
• The VISTA Science Archive
• Flash Mixing on the White Dwarf Cooling Curve: Understanding Hot Horizontal Branch Anomalies in NGC 2808
• Double degenerate mergers as progenitors of high-field magnetic white dwarfs
• Hot subdwarfs from the ESO Supernova Ia Progenitor Survey: II. Atmospheric parameters of subdwarf O stars
• Modeling He-rich subdwarfs through the hot-flasher Scenario
• Double white dwarf mergers and elemental surface abundances in extreme helium and R Coronae Borealis stars
• A brief introductory guide to TLUSTY and SYNSPEC
• Hot subdwarf stars in close-up view - III. Metal abundances of subdwarf B stars
• Discovery of a variable lead-rich hot subdwarf: UVO 0825+15
• Abundance analyses of helium-rich subluminous B stars
• Hot subdwarfs formed from the merger of two He white dwarfs
• A proto-helium white dwarf stripped by a substellar companion via common-envelope ejection -- Uncovering the true nature of a candidate hypervelocity B-type star
• The SALT survey of helium-rich hot subdwarfs: methods, classification, and coarse analysis
• On the angular momentum evolution of merged white dwarfs
• GALEX J184559.8-413827: a new extreme helium star identified using SALT
• A search for heavy-metal stars: abundance analyses of hot subdwarfs with Subaru
• TLUSTY and SYNSPEC Users's Guide IV: Upgraded Versions 208 and 54