1999/05/19 by Alan Owens, A. Owens, Owens, A. +11
Physics and Astronomy · #Astronomy #Astrophysical Phenomena and Observations #Astrophysics #Astrophysics (astro-ph) #Astrophysics and Star Formation Studies #Black-body radiation #FOS: Physical sciences #Galaxy #Luminosity #Observatory #Optics #Physics #ROSAT #Stars #Stellar, planetary, and galactic studies #White dwarf #astro-ph
paper · pdf · doi:10.48550/arxiv.astro-ph/9905245
5 pages. Accepted for publication in A&A
arxiv created 1999/05/19 · openalex publication_date 1999/05/19 · arxiv updated 2009/12/01 · openalex created_date 2025/10/10 · openalex updated_date 2026/07/28
We report broad-band X-ray measurements of the Be star Gamma Cassiopeiae by the BeppoSAX X-ray astronomy satellite. The observations took place on 1998 July, 18-23. The 0.1-200 keV X-ray spectrum is reasonably well fit by an optically thin thermal plasma model of temperature 12.5 +/- 0.6 keV with significant residuals around 0.3 keV and 1 keV. The former is interpreted as the variable soft component reported by ROSAT, although there is no evidence for variability at the 5 % level. For a blackbody interpretation, the fitted temperature is 100 +320 -13 eV, in agreement with the ROSAT value of 200 +/- 10 eV. However, a MEKAL interpretation gives a significantly lower temperature of (48 +/- 11 eV). The fitted abundances are about half solar values, in agreement with previous measurements. At higher energies, the spectrum does not require non-thermal components and the observation of a line at 6.8 keV supports the ASCA interpretation of the source as an accreting white dwarf. Assuming a source distance of 188 pc, the bolometric luminosity in the 2-10 keV band is 6 1032 erg/s. Simultaneous optical measurements by the Wendelstein Observatory near Munich, indicate that the source continues to be in a late but rather normal Be phase, with no obvious signs of a transition to the Be-shell phase. The measured magnitudes at B, V and R wavelengths of 2.18 +/- 0.06, 2.23 +/- 0.02 and 2.36 + /- 0.03, respectively, confirm this.