Open AccessThe broad‐band X‐ray spectrum of Mrk 3
Author(s) -
Griffiths R. G.,
Warwick R. S.,
Georgantopoulos I.,
Done C.,
Smith D. A.
Publication year - 1998
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.1365-8711.1998.01750.x
Subject(s) - physics , astrophysics , spectral line , scattering , galaxy , spectral shape analysis , power law , spectral index , emission spectrum , radiation , astronomy , optics , statistics , mathematics
We use non‐simultaneous Ginga ASCA ROSAT observations to investigate the complex X‐ray spectrum of the Seyfert 2 galaxy Mrk 3. We find that the composite spectrum can be well described in terms of a heavily cut‐off hard X‐ray continuum, iron Kα emission and a soft X‐ray excess, with spectral variability confined to changes in the continuum normalization and the flux in the iron line. Previous studies have suggested that the power‐law continuum in Mrk 3 is unusually hard. We obtain a canonical value for the energy index of the continuum (i.e., α ≈ 0.7) when a warm absorber (responsible for an absorption edge observed near 8 keV) is included in the spectral model. Alternatively, the inclusion of a reflection component yields a comparable power‐law index. The soft‐excess flux cannot be modelled solely in terms of pure electron scattering of the underlying power‐law continuum. However, a better fit to the spectral data is obtained if we include the effects of both emission and absorption in a partially photoionized scattering medium. In particular, the spectral feature prominent at ∼ 0.9 keV could represent O VIII recombination radiation produced in a hot photoionized medium. We discuss our results in the context of other recent studies of the soft X‐ray spectra of Seyfert 2 galaxies.