Wide-Angle Quasar Feedback

We present results from the detection of relativistic winds launched near the innermost stable circular orbits of supermassive black holes. A recent detection of a powerful wind in the X-ray-bright narrow absorption line (NAL) z=1.51 quasar HS 0810+2554 strengthens the case that quasars play a significant role in feedback. In both deep Chandra and XMM-Newton observations of HS 0810 we detected blueshifted absorption lines implying outflowing velocities ranging from 0.1c and 0.4c. The presence of both an emission line at 6.8 keV and an absorption line at 7.8 keV in the spectral line profile of HS 0810 is a characteristic feature of a P-Cygni profile supporting the presence of an expanding outflowing highly ionized Fe absorber. A hard excess component is detected in the XMM-Newton observation of HS 0810 possibly originating from reflection off the disk. Modelling of the XMM-Newton spectrum constrains the inclination angle to be < 35° (68% confidence). The presence of relativistic winds in both low inclination angle NAL quasars as well as in high inclination angle BAL quasars implies that the solid angle of quasar winds may be quite large. The larger solid angle of quasar winds would also indicate that their contribution to the regulation of the host galaxy may be more important than previously thought.

A Model of the Broad-Band Continuum of NGC 5548

We discuss a model of the central source in Seyfert 1 galaxy NGC 5548. The model assumes a three phase disk structure consisting of a cold outer disk, a hot central disk constituting a Comptonizing X/γ source, and an intermediate unstable and complex phase emitting a soft excess component. The model qualitatively explains broad-band spectrum and variability behavior assuming that the soft excess contributes significantly to the continuum emission and drives variability by geometrical changes of the intermediate disk zone.

ASCA Sky Survey Observations and the Cosmic X-Ray Background in 2-10 KeV

The X-ray background in the energy range above 2 keV is highly uniform except for an excess component along the Galactic plane. The excess along the plane is considered to be associated with our Galaxy, whereas the rest of the emission is believed to be of extragalactic origin. In this paper, the X-ray background at high Galactic latitude is discussed and is designated as the CXB (cosmic X-ray background) to distinguish it from the Galactic origin.

Soft X-rays of AGN: Emission from Accretion Disks?

Soft X-ray spectra of many Active Galactic Nuclei (AGN) show structure which suggests excess emission at low energies, mostly below 1 keV. This was confirmed by the ROSAT spectra (0.1–2.4 keV) AGN in our samples which generally have steeper power law spectra than the canonical index of 0.7. The soft excess component may be the high energy tail of the big blue bump which in turn may be due to the integrated emission from an accretion disk around the central black hole.We discuss results of our spectral analysis of two different samples of AGN: 1) QSO/Seyfert-I from the ROSAT All Sky Survey (RASS) and 2) radio-quiet QSO from ROSAT Pointed Observations. The ROSAT data are combined with UV Data from IUE and hard X-ray data from various hard X-ray missions.

Some properties of flash-evaporated Ga1−xAsx films

a-Ga1−xAsx films containing small GaAs crystallites were prepared by flash evaporation onto low-temperature glass substrates. The As content in the films was varied from 41 to 69 at.%. Thermoelectric power measurements indicate that Ga-rich films are n-type and As-rich films are p-type, but the Seebeck coefficients for samples near the stoichiometric ratio were too small to measure. The optical gaps vary with As content in a way that is consistent with the suggestion that the material appears to be an alloy of a-GaAs and the excess component. High-temperature activation energies place the Fermi level near midgap in all samples and this is in line with the suggestion that this class of materials tend to self compensate as the film grows.

A study of high-purity CdxSe1−x vacuum-deposited thin films

Pure CdSe films were vacuum deposited onto liquid-nitrogen-cooled substrates using a doubly baffled source in an attempt to prepare and study amorphous CdSe. The deposition of stable stoichiometric amorphous pure films was not verified since the films were always polycrystalline when analyzed at room temperature. CdSe appears to be different from some other II– VI compounds that can be prepared as pure stoichiometric amorphous materials and can be studied at a temperature up to 400 K. Pure nonstoichiometric films were also prepared using a second source to supply the excess component. Amorphous Se-rich films could only be produced for samples with at least 59 at.% Se. For Cd-rich films, the excess Cd agglomerates and the CdSe crystallite sizes are smaller than those observed in stoichiometric films. The electrical and optical properties scale as a function of the Cd content and the films become metallike as the Cd content increases through 60 at.%. The electrical transport properties are very different for polycrystalline films, depending on whether the CdSe is deposited on a hot substrate, or on a cold substrate and annealed to the same high temperature. We show that impure amorphous films of CdSe can be deposited if the system's background pressure is high.