Showing papers by "Laura Brenneman published in 2004"

Iron line spectroscopy of NGC 4593 with XMM–Newton: where is the black hole accretion disc?

Abstract: We present an analysis of the 2-10 keV XMM-Newton/EPIC-pn spectrum of the Seyfert-1 galaxy NGC 4593. Apart from the presence of two narrow emission lines corresponding to the Ka lines of cold and hydrogen-like iron, this spectrum possesses a power-law form to within ∼3-5 per cent. There is a marked lack of spectral features from the relativistic regions of the black hole accretion disc. We show that the data are, however, consistent with the presence of a radiatively efficient accretion disc extending right down to the radius of marginal stability if it possesses low iron abundance, an appropriately ionized surface, a very high inclination, or a very centrally concentrated emission pattern (as has been observed during the deep minimum state of the Seyfert galaxy MCG-6-30-15). Deeper observations of this source are required in order to validate or reject these models.

Iron Line Spectroscopy of NGC4593 with XMM-Newton: Where is the Black Hole Accretion Disk?

Abstract: We present an analysis of the 2-10keV XMM-Newton/EPIC-pn spectrum of the Seyfert-1 galaxy NGC4593. Apart from the presence of two narrow emission lines corresponding to the Kalpha lines of cold and hydrogen-like iron, this spectrum possesses a power-law form to within 3-5%. There is a marked lack of spectral features from the relativistic regions of the black hole accretion disk. We show that the data are, however, consistent with the presence of a radiatively-efficient accretion disk extending right down to the radius of marginal stability if it possesses low iron abundance, an appropriately ionized surface, a very high inclination, or a very centrally concentrated emission pattern (as has been observed during the Deep Minimum State of the Seyfert galaxy MCG-6-30-15). Deeper observations of this source are required in order to validate or reject these models.

The Interaction of 3C401 with the Surrounding Intracluster Medium

Abstract: We present an observation of the radio-galaxy 3C401 and the surrounding intracluster medium (ICM) of its host galaxy cluster by the Chandra X-ray Observatory. This luminous radio-galaxy is notable in that it has characteristics intermediate between the FRI and FRII morphologies. We clearly detect point-like emission coincident with the radio-core of 3C401, although the spatial resolution of even Chandra is only 2kpc at the distance of 3C401 (z=0.201) and so the possibility remains that this is a dense (and rapidly cooling) thermal gaseous core in the center of the ICM atmosphere. Strong departures from spherical symmetry in the central 10-20kpc of the ICM clearly suggest interaction between the ICM and the radio-lobes of 3C401. A central X-ray bar probably results from the evacuation of two ICM cavities by the expanding radio lobes. Beyond these central regions, the cluster possesses a flatter profile than many clusters of comparable mass suggesting the importance of ICM heating and entropy injection by 3C401. We detect an interesting cross-like structure in the ICM on 100kpc scales. We speculate that this could be a radio-galaxy induced disturbance corresponding to a time when 3C401 was substantially more powerful. A particularly exciting possibility is that this cross-like structure corresponds to a large scale global g-mode oscillation excited by a past outburst of 3C401.