| Autor: |
M. P. Kowalski, M. A. Barstow, K. S. Wood, D. J. Yentis, G. G. Fritz, J. S. Lapington, T. W. Barbee, R. G. Cruddace, Klaus Werner, T. Rauch |
| Rok vydání: |
2010 |
| Předmět: |
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| Zdroj: |
AIP Conference Proceedings. |
| ISSN: |
0094-243X |
| DOI: |
10.1063/1.3527881 |
| Popis: |
We report the first high‐resolution (R = 4000) spectroscopic observation of the binary DA white dwarf Feige 24 in the extreme‐ultraviolet band 220–250A. A stellar atmosphere model assuming a homogeneous element distribution yields a best fit to the data that excludes a significant abundance of photospheric helium, a surprising result contrary to predictions by common envelope evolution theory. The upper limit on the photospheric helium abundance is 2.5×10−6 (90% confidence), and the lower limit on the overlying layer of hydrogen is 1.2×10−13 M⊙. An ionized He component (3.9×1017 cm−2) is clearly present along the line‐of‐sight, which if completely interstellar implies a He ionization fraction of 0.7, considerably higher than is typical of the local interstellar medium. |
| Databáze: |
OpenAIRE |
| Externí odkaz: |
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