The X-ray time variability and spectrum of gamma Cassiopeiae (X 0053+604).
Abstract
A 30 h duration EXOSAT observation made in 1985 December is used to examine the X-ray time variability and spectrum of the Be star γ Cassiopeiae (X 0053+604). We find that the X-ray lightcurve is dominated by irregular energy-independent flaring on time-scales ≳ 100 s. This flaring markedly decreases the sensitivity to any periodic signals. We find no evidence for the 6000 5 oscillations reported by Frontera et al. (1987) from an earlier EXOSAT observation. We suggest that these arise from statistical fluctuations in the red noise power. The X-ray spectrum of γ Cas can either be modeled by thermal emission from an optically thin plasma with a temperature of 12 keV, or by a cut-off power-law model with a narrow iron line at an energy of 6.67 keV.
The origin of the X-ray emission in this system remains open since its spectral and temporal properties are consistent with both an acereting neutron star and a white dwarf while its high temperature argues against a coronal mechanism.- Publication:
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Astronomy and Astrophysics
- Pub Date:
- August 1993
- Bibcode:
- 1993A&A...275..227P
- Keywords:
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- stars: individual: γ Cas;
- stars: emission-line Be;
- stars: neutron;
- X-rays: stars