EXOSAT observations of 4U1705-44: Type 1 bursts and persistent emission
Abstract
Observations of the bright galactic X-ray source 4U1705-44 by EXOSAT showed that persistent emission varied from 1.3 to 10.7 times 10 to the minus 9th power ergs/sq cm/sec in the 1 to 20 keV energy band. During low intensity observations 23 type-1 X-ray bursts were detected. Three of the bursts were observed within only 5 to 18 min after a preceeding burst. Burst activity is anticorrelated with source intensity. At minimum flux 4U1705-44 is bursting at a nearly constant frequency of 0.5/hr. In a medium intensity state the burst rate decreases. No burst was detected in the maximum intensity state. Average burst flux is 15 times 10 to the minus 9th power ergs/sq cm/sec, comparable to the maximum observed flux to the persistent emission. The spectrum during maximum is best fitted by a two component model, a blackbody together with a Boltzman-Wien law and an additional iron K emission line. At minimum intensity the spectrum becomes drastically harder and is best represented by a power-law with an indication of an iron absorption edge at 8 keV.
- Publication:
-
NASA STI/Recon Technical Report N
- Pub Date:
- November 1986
- Bibcode:
- 1986STIN...8725266L
- Keywords:
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- Bursts;
- Emission Spectra;
- Stellar Radiation;
- X Ray Sources;
- Exosat Satellite;
- Stellar Activity;
- Stellar Spectra;
- Space Radiation