The Soft X-Ray Properties of the Polar Ek-Ursae
Abstract
We present the first extensive soft X-ray observation of the polar EK UMa (1E 1048.5+5241). The complete orbital light curve obtained from this ROSAT observation shows a single bright phase of width Δφ=0.63. EK UMa is not detected outside this phase interval. During the bright phase a number of deep dips in the flux are seen. These dips can be caused by an additional absorption of 8 × 1018 < ΔNH < 3 × 1020 atom cm-2. The soft X-ray spectrum has an unusually high temperature of 50 < kTBB < 62 eV. No hard X-ray flux is detected, and EK UMa is shown to have a large soft X-ray excess, with a soft-to-hard X-ray luminosity ratio of 7.7-12.2.
- Publication:
-
Monthly Notices of the Royal Astronomical Society
- Pub Date:
- May 1994
- DOI:
- 10.1093/mnras/268.1.229
- Bibcode:
- 1994MNRAS.268..229C
- Keywords:
-
- binaries: close - stars: individual: EK UMa - stars: magnetic fields - novae;
- cataclysmic variables - stars: rotation - X-rays: stars