A 4.1 keV spectral feature in a type 1 X-ray burst from EXO 1747-214.
Abstract
We present the results of a spectral analysis of two type 1 bursts from EXO 1747-214 detected during 9.4 h of observing with EXOSAT. The spectrum, during the rise of the strongest burst, shows a spectral feature, which can be well represented by an absorption line at 4.05 +/- 0.1 keV; the line has an equivalent width of 570 +/- 87 eV; the upper limit to the line width is 800 eV. At all other times during the burst, the spectrum is well represented by that of a single blackbody. The line energy coincides remarkably with those of the absorption lines observed by Waki et al. in four (of 13) bursts from 1636-53 (4.1 +/- 0.1 keV), and by Nakamura, Inoue & Tomaka in three (of 17) bursts from 1608-52 (4.07 +/- 0.07 keV). Therefore, these lines have almost certainly the same origin. We discuss possible origins and show that serious problems arise from an interpretation of the lines in terms of gravitationally redshifted atomic lines. We show that the interpretation proposed by Fujimoto, in which the line shift is partly attributed to transverse Doppler effects of fast rotating accreting material, can probably be excluded.
- Publication:
-
Monthly Notices of the Royal Astronomical Society
- Pub Date:
- April 1989
- DOI:
- 10.1093/mnras/237.3.729
- Bibcode:
- 1989MNRAS.237..729M
- Keywords:
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- Absorption Spectra;
- X Ray Sources;
- X Ray Spectra;
- Bursts;
- Exosat Satellite;
- Red Shift;
- Astrophysics