Search Publications
Self-Consistent Models of the AGN and Black Hole Populations: Duty Cycles, Accretion Rates, and the Mean Radiative Efficiency
Miralda-Escudé, Jordi; Weinberg, David H.; Shankar, Francesco
We construct evolutionary models of the populations of active galactic nuclei (AGNs) and supermassive black holes, in which the black hole mass function grows at the rate implied by the observed luminosity function, given assumptions about the radiative efficiency and the luminosity in Eddington units. We draw on a variety of recent X-ray and opti…
The Space Density of Compton-Thick Active Galactic Nucleus and the X-Ray Background
Treister, E.; Urry, C. Megan; Virani, Shanil
We constrain the number density and evolution of Compton-thick (CT) active galactic nuclei (AGNs). In the local universe, we use the wide-area surveys from the Swift and INTEGRAL satellites, while for high redshifts we explore candidate selections based on a combination of X-ray and mid-infrared (mid-IR) parameters. We find a significantly lower s…
Variable Polarization Measured in the Prompt Emission of GRB 041219A Using IBIS on Board INTEGRAL
Götz, Diego; Laurent, Philippe; Lebrun, François +2 more
Polarization measurements provide a direct insight into the nature of astrophysical processes. Unfortunately, only a few instruments are available for this kind of measurement at γ-ray energies, and the sources need to be very bright. Gamma-ray bursts (GRBs) are ideal candidates due to their large flux over limited time intervals, maximizing the a…
The First Swift Ultraviolet/Optical Telescope GRB Afterglow Catalog
Cucchiara, A.; Brown, P. J.; Page, M. J. +21 more
We present the first Swift Ultraviolet/Optical Telescope (UVOT) gamma-ray burst (GRB) afterglow catalog. The catalog contains data from over 64,000 independent UVOT image observations of 229 GRBs first detected by Swift, the High Energy Transient Explorer 2 (HETE2), the International Gamma-Ray Astrophysics Laboratory (INTEGRAL), and the Interplane…
Simultaneous Multi-Wavelength Observations of Sgr A* During 2007 April 1-11
Grosso, N.; Dowell, C. D.; Porquet, D. +18 more
We report the detection of variable emission from Sgr A* in almost all wavelength bands (i.e., centimeter, millimeter, submillimeter, near-IR, and X-rays) during a multi-wavelength observing campaign. Three new moderate flares are detected simultaneously in both near-IR and X-ray bands. The ratio of X-ray to near-IR flux in the flares is consisten…
Detection of Gamma-Ray Emission from the Eta-Carinae Region
Antonelli, L. A.; Pian, E.; Costa, E. +63 more
We present the results of extensive observations by the gamma-ray AGILE satellite of the Galactic region hosting the Carina nebula and the remarkable colliding wind binary Eta Carinae (η Car) during the period 2007 July-2009 January. We detect a gamma-ray source (1AGL J1043-5931) consistent with the position of η Car. If 1AGL J1043-5931 is associa…
The Implications of a High Cosmic-Ray Ionization Rate in Diffuse Interstellar Clouds
Indriolo, Nick; Fields, Brian D.; McCall, Benjamin J.
Diffuse interstellar clouds show large abundances of H+ 3 which can only be maintained by a high ionization rate of H2. Cosmic rays are the dominant ionization mechanism in this environment, so the large ionization rate implies a high cosmic-ray flux, and a large amount of energy residing in cosmic rays. In this pa…
The Galactic Positron Annihilation Radiation and the Propagation of Positrons in the Interstellar Medium
Rothschild, R. E.; Higdon, J. C.; Lingenfelter, R. E.
The ratio of the luminosity of diffuse 511 keV positron annihilation radiation, measured by INTEGRAL in its four years, from a Galactic "positron bulge" (<1.5 kpc) compared to that of the disk is ~1.4. This ratio is roughly 4 times larger than that expected simply from the stellar bulge-to-disk ratio of ~0.33 of the Galactic supernovae (SNe), w…
Galaxy Clusters in the Swift/Burst Alert Telescope Era: Hard X-rays in the Intracluster Medium
Böhringer, H.; Greiner, J.; Moretti, A. +6 more
We report the detection of 10 clusters of galaxies in the ongoing Swift/Burst Alert Telescope (BAT) all-sky survey. This sample, which mostly comprises merging clusters, was serendipitously detected in the 15-55 keV band. We use the BAT sample to investigate the presence of excess hard X-rays above the thermal emission. The BAT clusters do not sho…
Calibration Of [O IV] 26 µm as a Measure of Intrinsic Active Galactic Nucleus Luminosity
Rigby, J. R.; Aniano, G.; Diamond-Stanic, A. M.
We compare [O IV] 25.89 µm emission line luminosities with very hard (10-200 keV) X-rays from Swift, INTEGRAL, and BeppoSAX for a complete sample of 89 Seyferts from the Revised Shapley-Ames sample. Using Seyfert 1s, we calibrate [O IV] as a measure of active galactic nucleus (AGN) intrinsic luminosity, for particular use in high-obscuration…