Chandra LETGS spectroscopy of the Quasar MR2251-178 and its warm absorber - AstrophysicsReport as inadecuate

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Abstract: We present an analysis of our Chandra Low Energy Transmission GratingSpectrometer LETGS observation of the quasar MR2251-178. The warm absorber ofMR2251-178 is well described by a hydrogen column density, N H~2x10^21 cm^-2,and an ionization parameter logxi~0.6. We find in the spectrum weak evidencefor narrow absorption lines from Carbon and Nitrogen which indicate that theionized material is in outflow. We note changes in time of the absorptionstructure in the band 0.6-1 keV around the UTAs plus the OVII and OVIIIK-edges at different periods of the observation. We measure a 0.1-2 keV fluxof 2.58x10^-11 ergs cm^-2 s^-1. This flux implies that the nuclear source ofMR2251-178 is in a relatively low state. No significant variability is seen inthe light curve. We do not find evidence for an extra cold material in the lineof sight, and set an upper limit of N H~1.2x10^20 cm^-2. The X-ray spectrumdoes not appear to show evidence for dusty material, though an upper limit inthe neutral carbon and oxygen column densities can only be set to N CI~2x10^19cm^-2 and N OI~9x10^19 cm^-2, respectively.

Author: J.M. Ramírez 1, S. Komossa 1, V. Burwitz 1, S. Mathur 2 1 Max-Planck-Institut für extraterrestriche Physik, Garching, Germany,


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