A new lamppost reflection model and its application to NGC 4151 and Cyg X-1
Abstract
We study the X-ray emission in the lamppost geometry, which has become a popular model for both X-ray binaries and AGNs. We point out the importance of the reduction of the observed luminosity due to photon trapping, time dilation and gravitational redshift, which effects have been neglected in most of lamppost studies. We also point out a major effect overlooked so far, namely that of the emission of the bottom lamp being gravitationally focused toward an observer on the top side of the accretion disc. These effects, with several other improvements in modeling the observed spectra of thermal Comptonization and its reflection, are implemented in our new xspec model for the lamppost geometry. We apply the model to the Suzaku/NuSTAR observations of NGC 4151 and Cyg X-1 in its hard state and we find that in both cases it favors truncation of an optically thick disc above 10 gravitational radii.
- Publication:
-
42nd COSPAR Scientific Assembly
- Pub Date:
- July 2018
- Bibcode:
- 2018cosp...42E2448N