HIGH-RESOLUTION SPECTROSCOPY OF FEIGE 24 IN THE EXTREME-ULTRAVIOLET

Journal Article · Fri Apr 01 04:00:00 EDT 2011 · Astrophysical Journal

DOI:https://doi.org/10.1088/0004-637X/730/2/115· OSTI ID:21574612

Kowalski, M P; Wood, K S; Yentis, D J; Berendse, F B; Cruddace, R G ^[1]; Barstow, M A; Lapington, J S ^[2]; Fritz, G G ^[3]; Barbee, Jr, T W ^[4]

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1. Naval Research Laboratory, Code 7655, 4555 Overlook Avenue, SW, Washington, DC 20375 (United States)
2. Department of Physics and Astronomy, University of Leicester, Leicester LE1 7RH (United Kingdom)
3. PRAXIS, Inc., 5845 Richmond Hwy, Suite 700, Alexandria, VA 22303 (United States)
4. Lawrence Livermore National Laboratory, MS L-353, 7000 East Avenue, P.O. Box 808, Livermore, CA 94550 (United States)

We report the first high-resolution (R = 4000) spectroscopic observation of the binary DA white dwarf Feige 24 in the extreme-ultraviolet band 220-250 A. A stellar atmosphere model assuming a homogeneous element distribution yields a best fit to the data that excludes a significant abundance of photospheric helium. The upper limit on the photospheric helium abundance is 2.5 x 10{sup -6} (90% confidence), equivalent to a lower limit of 1.2 x 10{sup -13} M{sub sun} on the overlying layer of hydrogen. An ionized interstellar He component (3.9 x 10{sup 17} cm{sup -2}) is clearly present along the line of sight, which implies an He ionization fraction of 0.72, considerably higher than is typical of the local interstellar medium. However, some of this material may be associated with circumstellar gas, which has been detected by analysis of the C IV absorption line doublet in a Hubble Space Telescope/Space Telescope Imaging Spectrograph spectrum.

• OSTI ID: 21574612
• Journal Information: Astrophysical Journal, Journal Name: Astrophysical Journal Journal Issue: 2 Vol. 730; ISSN ASJOAB; ISSN 0004-637X
• Country of Publication: United States
• Language: English

Related Subjects

79 ASTRONOMY AND ASTROPHYSICS
ABUNDANCE
ATMOSPHERES
BINARY STARS
DWARF STARS
ELECTROMAGNETIC RADIATION
ELEMENT ABUNDANCE
ELEMENTS
EXTREME ULTRAVIOLET RADIATION
FLUIDS
GASES
HELIUM
IONIZATION
NONMETALS
RADIATIONS
RARE GASES
SPECTROSCOPY
STARS
STELLAR ATMOSPHERES
ULTRAVIOLET RADIATION
WHITE DWARF STARS