Open AccessAn X‐ray Baldwin effect for the narrow Fe Kα lines observed in active galactic nuclei
Author(s) -
Page K. L.,
O'Brien P. T.,
Reeves J. N.,
Turner M. J. L.
Publication year - 2004
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 - 10.1111/j.1365-2966.2004.07203.x
Subject(s) - physics , active galactic nucleus , torus , astrophysics , luminosity , line (geometry) , x ray , equivalent width , emission spectrum , astronomy , spectral line , galaxy , optics , geometry , mathematics
The majority of active galactic nuclei (AGN) observed by XMM–Newton reveal narrow Fe Kα lines at ∼6.4 keV, due to emission from cold (neutral) material. There is an X‐ray Baldwin effect in type I AGN, in that the equivalent width (EW) of the line decreases with increasing luminosity, with weighted linear regression giving EW∝ L −0.17±0.08 (Spearman Rank probability of >99.9 per cent). With current instrumental capabilities it is not possible to determine the precise origin for the narrow line, with both the broad‐line region and putative molecular torus being possibilities. A possible explanation for the X‐ray Baldwin effect is a decrease in the covering factor of the material forming the fluorescence line.