Spectroscopy of NGC 3783 with the XMM-RGS

1. Spectroscopy of NGC 3783 with the XMM-RGS J Blustin1*, G Branduardi-Raymont1, E Behar2 & J Kaastra3 1 MSSL, Holmbury St. Mary, Dorking, Surrey RH5 6NT, England 2 Columbia University, New York, NY 10027, USA 3 SRON, Sorbonnelaan 2, 3584 CA Utrecht, Netherlands * jeb1@mssl.ucl.ac.uk O VIII Mg, Si O VII triplet Fe-L, Ne O IV-VII, N VI-VII Fe-M C, S, Si, Ar We present the RGS spectrum of NGC 3783 from a 40 ksec exposure. This Seyfert 1 galaxy has a deep warm absorber, with blueshifted narrow absorption and emission lines indicating both warm and cold phases to the gas. In order to model the line and continuum absorption self-consistently, we used the xabs model in SPEX 2.0, incorporating new atomic data. This model applies both line and continuum absorption from a column of photoionised gas to the spectral continuum, which was modelled as a power-law obtained from the PN spectrum (top right). There is a rich absorption structure from various states of iron, including both L-shell and a prominent Unresolved Transition Array (UTA) feature from cooler M-shell iron, which enabled us to derive the ionisation parameters of the two temperature regimes. We then fitted equivalent hydrogen columns and elemental abundances for the two phases, using absorption lines from the various elements present. A summary of the properties of the hotter and cooler phases of the warm absorber is given (left). Hot phase: - log ionisation parameter x = 2.38 - equivalent hydrogen column 2.8 x 1022 cm-2 - blueshift ~1000 km/s - abundances probably close to solar - characteristic spectral features: narrow line and continuum absorption by L-shell iron, O VIII and N VII Power-law best fit to the 3.5-5.5 and 7.5-10 keV ranges of the PN spectrum of NGC 3783: G = 1.66, norm = 0.0195 photons keV-1 cm-2 s-1 at 1 keV and a fixed NHgal = 8.7 x 1020 cm-2. The two iron lines in the PN spectrum. These are (left) an iron Ka lineand (right) a much fainter line, which is probably either Fe Kb or from a more highly ionised state of iron. The two-phase warm absorber of NGC 3783 Fluxed RGS spectrum of NGC 3783 with model overlaid Cool phase: - log ionisation parameter x = 0.4 - equivalent hydrogen column 1.0 x 1021 cm-2 - blueshift ~1000 km/s - iron apparently several times more abundant than oxygen - characteristic spectral features: a deep Unresolved Transition Array (UTA) of M-shell iron, and narrow absorption lines from O IV, O V and O VI