[Previous] | [Session 34] | [Next]
S. Kaspi, W.N. Brandt (PSU), H. Netzer (Tel-Aviv University, Israel), R. Sambruna, G. Chartas, G.P. Garmire, J.A Nousek (PSU)
We present the first grating-resolution X-ray spectra of the Seyfert 1 galaxy NGC 3783, obtained with the High Energy Transmission Grating Spectrometer on the Chandra X-ray Observatory. These spectra reveal many narrow absorption lines from the H-like and He-like ions of O, Ne, Mg, Si, S and Ar, as well as FeXVII--FeXXI L-shell lines. We have also identified several weak emission lines, mainly from O and Ne. The absorption lines are blueshifted by a mean velocity of a few hundred km/s and are not resolved, indicating a velocity dispersion within the absorbing gas of a few hundred km/s or less. We measure the lines' equivalent widths and compare them with the predictions of photoionization models. The best-fitting model has a microturbulence velocity of 150 km/s and a hydrogen column density of 1.3\times 1022 cm-2. The measured blueshifts and inferred velocity dispersions of the X-ray absorption lines are consistent with those of the strongest UV absorption lines observed in this object. However, simple models that propose to strictly unify the X-ray and UV absorbers have difficulty explaining simultaneously the X-ray and UV absorption line strengths.
This work was partially supported through NASA grant NAS 8-38252 and NASA LTSA grant NAG 5-8107.