Abstract
view Abstract Citations (20) References (28) Co-Reads Similar Papers Volume Content Graphics Metrics Export Citation NASA/ADS The atmosphere of Sirius B. II. Extreme-ultraviolet observations. Shipman, H. L. ; Margon, B. ; Bowyer, S. ; Lampton, M. ; Paresce, F. ; Stern, R. Abstract The letter reports an observation of Sirius in the extreme-ultraviolet (100-1000 A) band, using a grazing-incidence telescope flown aboard the Apollo-Soyuz mission. No positive flux is detected; under the arbitrary assumption of flat incident spectrum, an upper limit to the flux in the 170-620 A band is 5 billion erg/sq cm per sec. A detailed model-atmosphere analysis, when combined with the EUV limits, places severe constraints on models which attribute the previously reported soft X-ray (44-60 A) flux to thermal radiation from deep layers of the atmosphere of the white dwarf Sirius B. EUV radiation should be detectable from Sirius B just below the sensitivity threshold of the current data, or a thermal origin for the X-ray flux is untenable. If the X-ray flux is thermal, the present results provide extremely sensitive constraints on the temperature and helium abundance of Sirius B: the white dwarf has an effective temperature of 32,000 K to 32,500 K and a helium abundance (relative to hydrogen) of 0.0001 to 0.0002. Publication: The Astrophysical Journal Pub Date: April 1977 DOI: 10.1086/182402 Bibcode: 1977ApJ...213L..25S Keywords: Far Ultraviolet Radiation; Spaceborne Telescopes; Stellar Atmospheres; White Dwarf Stars; X Ray Sources; Apollo Soyuz Test Project; Atmospheric Models; Grazing Incidence Telescopes; Spectrum Analysis; Stellar Models; Stellar Temperature; Astrophysics full text sources ADS |
Sign-in/Register to access full text options 
Free) 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a call
