EC 11481−2303: A Peculiar Hot High‐Gravity Pre–White Dwarf

• Published in: Publications of the Astronomical Society of the Pacific 2000-03, Vol.112 (769), p.354-358
• Main Authors: Stys, D., Slevinsky, R., Sion, E. M., Saffer, R., Holberg, J. B., O’Donoghue, Darragh, Kilkenny, D., Stobie, R. S., Koen, C.
• Format: Article
• Language: English
• Subjects: Apparent magnitude; Astronomical objects; Line spectra; Photospheres; Spectroscopy; Stellar evolution; Subdwarf stars; Visible spectrum; Wavelengths; White dwarfs
• ISSN: 0004-6280; 1538-3873
• DOI: 10.1086/316525

We report the discovery of a peculiar new hot high‐gravity predegenerate star, EC 11481−2303 from the Edinburgh‐Cape Blue Object Survey, based upon the analysis of far‐UVInternational Ultraviolet Explorer(IUE) echelle and low‐resolution spectra and an optical spectrum. TheIUEspectra reveal the presence of far‐UV photospheric/circumstellar high‐ionization absorption features due to Nvλλ1238, 1242, Siivλλ1393, 1402, Civλλ1548, 1550, and Heiiλ1640. The mean velocity of these features is −17.5 km s−1. In addition, there is low‐ionization interstellar absorption at an average velocity of −5.6 km s−1. The interstellar lines are strong and imply a distance of more than 500 pc. The optical spectrum is dominated by Stark‐broadened Balmer absorption, a sharp Heiiλ4686 feature, and the absence of Balmer members higher than H8. A best‐fit model atmosphere to the optical data yields \documentclass{aastex} \usepackage{amsbsy} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{bm} \usepackage{mathrsfs} \usepackage{pifont} \usepackage{stmaryrd} \usepackage{textcomp} \usepackage{portland,xspace} \usepackage{amsmath,amsxtra} \usepackage[OT2,OT1]{fontenc} \newcommand\cyr{ \renewcommand\rmdefault{wncyr} \renewcommand\sfdefault{wncyss} \renewcommand\encodingdefault{OT2} \normalfont \selectfont} \DeclareTextFontCommand{\textcyr}{\cyr} \pagestyle{empty} \DeclareMathSizes{10}{9}{7}{6} \begin{document} \landscape $T_{\mathrm{eff}\,}=41,790$ \end{document} K and \documentclass{aastex} \usepackage{amsbsy} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{bm} \usepackage{mathrsfs} \usepackage{pifont} \usepackage{stmaryrd} \usepackage{textcomp} \usepackage{portland,xspace} \usepackage{amsmath,amsxtra} \usepackage[OT2,OT1]{fontenc} \newcommand\cyr{ \renewcommand\rmdefault{wncyr} \renewcommand\sfdefault{wncyss} \renewcommand\encodingdefault{OT2} \normalfont \selectfont} \DeclareTextFontCommand{\textcyr}{\cyr} \pagestyle{empty} \DeclareMathSizes{10}{9}{7}{6} \begin{document} \landscape $\mathrm{log}\,g=5.84$ \end{document} , suggesting an extended horizontal branch sdOB subdwarf. However, synthetic spectral fits to the far‐UV spectrum do not provide a consistent fit to both the Lyα region and the far‐UV continuum of EC 11481−2303. It is possible that EC 11481−2303 is an unresolved binary. Follow‐up ground‐based and far‐UV studies are encouraged to discern the possible nature of any binary companion.