Open AccessOn the accretion geometry of Cyg X‐1 in the low/hard state
Author(s) -
Barrio F. Eugenio,
Done Chris,
Nayakshin Sergei
Publication year - 2003
Publication title -
monthly notices of the royal astronomical society
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 2.058
H-Index - 383
eISSN - 1365-2966
pISSN - 0035-8711
DOI - 10.1046/j.1365-8711.2003.06555.x
Subject(s) - physics , astrophysics , flare , spectral line , ionization , reflection (computer programming) , accretion disc , accretion (finance) , astronomy , ion , quantum mechanics , computer science , programming language
We fit the broad‐band RXTE PCA and HEXTE spectrum of Cyg X‐1 from 3–200 keV with reflection models which calculate the vertical ionization structure of an X‐ray illuminated disc. We consider two geometries corresponding to a truncated disc/inner hot flow and magnetic flares above an untruncated disc. Both models are able to fit the PCA 3–20 keV data, but with very different spectral components. In the magnetic flare models the 3–20 keV PCA spectrum contains a large amount of highly ionized reflection, while in the truncated disc models the amount of reflection is rather small. The Compton downscattering rollover in reflected emission means that the magnetic flare models predict a break in the spectrum at the high energies covered by the HEXTE bandpass which is not seen. By contrast, the weakly illuminated truncated disc models can easily fit the 3–200 keV spectra.