skip to main content
OSTI.GOV title logo U.S. Department of Energy
Office of Scientific and Technical Information

Title: The softest Einstein AGN (active galactic nuclei)

Abstract

We have undertaken a coarse spectral study to find the softest sources detected with the Imaging Proportional Counter (IPC) on the Einstein Observatory. Of the nearly 7700 IPC sources, 226 have color ratios that make them candidate ultrasoft'' sources; of these, 83 have small enough errors that we can say with confidence that they have a spectral component similar to those of the white dwarfs Sirius and HZ 43, nearby stars such as {alpha} Cen and Procyon, and typical polar'' cataclysmic variables. By means of catalog searches and ground-based optical and radio observations we have thus far identified 96 of the 226 candidate soft sources; 37 of them are active galactic nuclei (AGN). In the more selective subset of 83 sources, 47 have been identified, 12 of them with AGN. The list of 47 identifications is given in Cordova et al. For one QSO in our sample, E0132.8--411, we are able to fit the pulse-height data to a power-law model and obtain a best fit for the energy spectral index of 2. 2{sub {minus}0.4}{sup +0.6}. For the remainder of the AGN in the higher confidence sample we are able to infer on the basis of their x-ray colors that theymore » have a similar spectral component. Two-thirds of the AGN are detected below 0.5 keV only, while the remainder evidence a flatter spectral component in addition to the ultra-soft component. 14 refs., 5 figs.« less

Authors:
; ; ;  [1];  [2];  [3]
  1. (Los Alamos National Lab., NM (USA)
  2. (USA)
  3. (UK). Mullard Space Science Lab.)
Publication Date:
Research Org.:
Los Alamos National Lab., NM (USA)
Sponsoring Org.:
DOE/DP; National Aeronautic and Space Administration (NASA)
OSTI Identifier:
5469894
Report Number(s):
LA-UR-89-863; CONF-891127-1
ON: DE89009389
DOE Contract Number:
W-7405-ENG-36
Resource Type:
Conference
Resource Relation:
Conference: Einstein to AXAF conference, Cambridge, MA (USA), Nov 1989
Country of Publication:
United States
Language:
English
Subject:
71 CLASSICAL AND QUANTUM MECHANICS, GENERAL PHYSICS; GALAXY NUCLEI; DETECTION; COSMIC X-RAY SOURCES; PROPORTIONAL COUNTERS; QUASARS; SIGNAL-TO-NOISE RATIO; COSMIC RADIO SOURCES; COSMIC RAY SOURCES; MEASURING INSTRUMENTS; RADIATION DETECTORS; 640105* - Astrophysics & Cosmology- Galaxies; 640102 - Astrophysics & Cosmology- Stars & Quasi-Stellar, Radio & X-Ray Sources

Citation Formats

Cordova, F.A., Kartje, J., Mason, K.O., Mittaz, J.P.D., Chicago Univ., IL, and University Coll., London. The softest Einstein AGN (active galactic nuclei). United States: N. p., 1989. Web.
Cordova, F.A., Kartje, J., Mason, K.O., Mittaz, J.P.D., Chicago Univ., IL, & University Coll., London. The softest Einstein AGN (active galactic nuclei). United States.
Cordova, F.A., Kartje, J., Mason, K.O., Mittaz, J.P.D., Chicago Univ., IL, and University Coll., London. 1989. "The softest Einstein AGN (active galactic nuclei)". United States. doi:. https://www.osti.gov/servlets/purl/5469894.
@article{osti_5469894,
title = {The softest Einstein AGN (active galactic nuclei)},
author = {Cordova, F.A. and Kartje, J. and Mason, K.O. and Mittaz, J.P.D. and Chicago Univ., IL and University Coll., London},
abstractNote = {We have undertaken a coarse spectral study to find the softest sources detected with the Imaging Proportional Counter (IPC) on the Einstein Observatory. Of the nearly 7700 IPC sources, 226 have color ratios that make them candidate ultrasoft'' sources; of these, 83 have small enough errors that we can say with confidence that they have a spectral component similar to those of the white dwarfs Sirius and HZ 43, nearby stars such as {alpha} Cen and Procyon, and typical polar'' cataclysmic variables. By means of catalog searches and ground-based optical and radio observations we have thus far identified 96 of the 226 candidate soft sources; 37 of them are active galactic nuclei (AGN). In the more selective subset of 83 sources, 47 have been identified, 12 of them with AGN. The list of 47 identifications is given in Cordova et al. For one QSO in our sample, E0132.8--411, we are able to fit the pulse-height data to a power-law model and obtain a best fit for the energy spectral index of 2. 2{sub {minus}0.4}{sup +0.6}. For the remainder of the AGN in the higher confidence sample we are able to infer on the basis of their x-ray colors that they have a similar spectral component. Two-thirds of the AGN are detected below 0.5 keV only, while the remainder evidence a flatter spectral component in addition to the ultra-soft component. 14 refs., 5 figs.},
doi = {},
journal = {},
number = ,
volume = ,
place = {United States},
year = 1989,
month = 1
}

Conference:
Other availability
Please see Document Availability for additional information on obtaining the full-text document. Library patrons may search WorldCat to identify libraries that hold this conference proceeding.

Save / Share:
  • The physical processes that operate in Active Galactic Nuclei (AGN) and the aspects connected with the generation of supersonic and relativistic ordered bulk motions and with the acceleration of highly relativistic particles are discussed. The nonthermal spectra of AGN indicate the presence of high temperature plasmas, kT greater than 100 MeV, with large photon densities which are responsible for comptonized synchrotron emission. Models based on accretion disks which provide the conditions for generating both relativistic particles and flows are discussed. The most efficient processes for accelerating particles inside AGN are plasma turbulence and shocks. Extended radio sources are discussed asmore » a typical environment where ultra-high-energy cosmic rays may be produced, either by mechanisms based on ordered fields or by stochastic acceleration processes. It is concluded that AGN inject a large amount of energetic particles into the metagalactic space, but are not likely to be the prime generators of the nuclear component of cosmic rays above 10 to the 18th eV. 48 references.« less
  • Barring relativistic bulk motions, the continuum emitted by AGN's implies very compact sources. It is found that the compactness parameter k = Lc/R cannot, especially in the X-ray band, exceed a level interestingly close to the current data. In sources driven by high energy electrons, the main limitation is associated with pair production by heavily absorbed, inverse-Compton ..gamma..-rays. 13 references.
  • An analysis of the variability timescale against bolometric luminosity for Active Galactic Nuclei shows that a number of sources violate the Eddington limit. The average ratio (L/LE) is found to change according to group classification. Whilst Seyfert Galaxies have luminosities well within the Eddington limit, Quasars and BL Lac object tend to approach and exceed this limit. Furthermore, BL Lac objects may be further subdivided on the basis of their (L/LE) ratio. The data on luminosity and variability timescale indicate the existence of two types of active galaxies, one having highly anisotropic emission, probably collimated into jets with pointing anglesmore » within few degrees to the line of sight, and the other relating to isotropic emission of photons from the nuclear region. The results are discussed in the light of the high gamma-ray luminosity suggested by recent observations of active galaxies. 9 references.« less
  • The kinematics of gas clouds in broad-line region of active galactic nuclei and quasars is considered. The motion of the clouds is governed by three forces - gravitational influence from the central supermassive body, radiational pressure from the continuum radiation, and resistance of the intercloud medium. Clouds move radial but only outward motion gives a velocity field, which is in accordance with the observational data. The profiles of the permitted lines are obtained in some simplified assumptions for the emissive capacity of the gas in clouds, and are in good agreement with the observational data. In the framework of themore » model under consideration there is a possibility to estimate some physical parameters of the nuclei such as mass of the central body and density of the intercloud medium. 7 references.« less
  • Recent observational and theoretical investigations of AGN are reviewed. The basic AGN characteristics (broad emission lines of abundant ions, X-ray emission, and a sharp starlike appearance) are summarized, and particular attention is given to the spectral classification of Seyfert galaxies, the AGN velocity fields and their measurement, low-ionization narrow-emission-line regions (LINERs), observations supporting a torus model of Seyfert AGN, extended gas and ionization, and the black-hole/accretion-disk model of the AGN energy source. It is suggested that no one model can explain the physical processes in all types of AGN. 43 refs.