A self-consistent test of Comptonization models using a long BeppoSAX observation of NGC 5548
Abstract
We test accurate models of Comptonization spectra over the high quality data of the BeppoSAX long look at NGC 5548. The data are well represented by a plane parallel corona with an inclination angle of 30$^{\circ}$, a soft photon temperature of 5 eV and a hot plasma temperature and optical depth of $kT_{\rm e}\simeq$ 360 keV and $\tau\simeq$ 0.1, respectively. If energy balance applies, such values suggest that a more ``photon-starved'' geometry (e.g. a hemispheric region) is necessary. The spectral softening detected during a flare, appears to be associated to a decrease of the heating-to-cooling ratio, indicating a geometric and/or energetic modification of the disk plus corona system. The hot plasma temperature derived with the models above is significantly higher than that obtained fitting the same data with a power law plus high energy cut off model for the continuum. This is due to the fact that in anisotropic geometries Comptonization spectra show "intrinsic" curvature which moves the fitted high energy cut-off to higher energies.
- Publication:
-
X-ray Astronomy: Stellar Endpoints, AGN, and the Diffuse X-ray Background
- Pub Date:
- December 2001
- DOI:
- 10.1063/1.1434664
- arXiv:
- arXiv:astro-ph/0004120
- Bibcode:
- 2001AIPC..599..470P
- Keywords:
-
- 98.54.Cm;
- 98.70.Qy;
- 95.30.Cq;
- Active and peculiar galaxies and related systems;
- X-ray sources;
- X-ray bursts;
- Elementary particle processes;
- Seyfert galaxies;
- X-ray sources (astronomical);
- astrophysical plasma;
- Compton effect;
- astronomical spectra;
- astrophysical radiation mechanisms;
- data analysis;
- X-ray astronomy;
- Astrophysics
- E-Print:
- 4 pages, 2 figures, to appear in the proceedings of the conference "X-ray Astronomy '99", Bologna, Italy, September 1999