Broadband Spectrum of Cygnus X‐1 in Two Spectral States withBeppoSAX
| Autor: | A. A. Zdziarski, Andrea Santangelo, A. N. Parmar, S. Del Sordo, Mauro Orlandini, G. Cusumano, G. C. Perola, L. Piro, F. Frontera, Francesco Haardt, D. Dal Fiume, A. Segreto, Aldo Treves, L. Chiappetti, M. Trifoglio, E. Palazzi |
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| Rok vydání: | 2001 |
| Předmět: |
Physics
Accretion Photon accretion disks Astrophysics::High Energy Astrophysical Phenomena Astrophysics (astro-ph) Bolometer FOS: Physical sciences Broad band X-rays: stars Astronomy and Astrophysics Astrophysics Plasma Black hole physics law.invention Accretion accretion disks Binaries: general Stars: individual (Cygnus X-1) Soft state Space and Planetary Science law Thermal Black-body radiation Plasma cloud |
| Zdroj: | The Astrophysical Journal. 546:1027-1037 |
| ISSN: | 1538-4357 0004-637X |
| Popis: | We report on the 0.5--200 keV spectral properties of Cyg X-1 observed at different epochs with the Narrow Field Instruments of the BeppoSAX satellite. The source was in its soft state during the first observation of 1996 June. In the second observation of 1996 September, the source had parameters characteristic to its hard state. A soft X-ray excess, a broad Fe K$\alpha$ line and Compton reflection are clearly detected in both states. The soft-state broad-band continuum is well modeled by a disk blackbody (accounting for the soft excess) and Compton upscattering of the disk photons by a hybrid, thermal/non-thermal, plasma, probably forming a corona above the disk (also giving rise to the Compton-reflection component). In the hard state, the primary hard X-ray spectrum can be well modeled by Compton upscattering of a weak blackbody emission by a thermal plasma at a temperature of $\sim 60$ keV. The soft excess is then explained by thermal Comptonization of the same blackbody emission by another hot plasma cloud characterized by a low value of its Compton parameter. Finally, we find the characteristic ratio of the bolometric flux in the soft state to that in the hard state to be about 3. This value is much more compatible with theories of state transitions than the previously reported (and likely underestimated) value of 1.5. Comment: 15 pages, 5 figures. Accepted for publication in ApJ |
| Databáze: | OpenAIRE |
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