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High-Energy Gamma-Ray Observations of Active Galaxies

Published online by Cambridge University Press:  12 April 2016

Carl E. Fichtel
Carl E. Fichtel*
Affiliation:
NASA/Goddard Space Flight Center, Greenbelt, MD 20771

Abstract

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During the period from 1992 May to early 1992 November, the Energetic Gamma-Ray Experiment Telescope (EGRET) on board the Compton Gamma Ray Observatory obtained high-energy gamma-ray data for most of the sky. A total of 18 active galaxies have been seen with high certainty, and it is expected that more will be found in the data when a more thorough analysis is complete. All of those that have been seen are radio-loud quasars or BL Lacertae objects; most have already been identified as blazars. No Seyfert galaxies have been found thus far. If the spectra are represented as a power law in energy, spectral slopes ranging from approximately −1.7 to −2.4 are found. A wide range of z-values exists in the observed sample, eight having values in excess of 1.0. Time variations have been seen, with the timescale for a significant change being as short as days in at least one case. These results imply the existence of very large numbers of relativistic particles, probably close to the central object. Although a large extrapolation is required, their existence also suggests that these active galactic nuclei may be the source of the extragalactic cosmic rays.

Subject headings: acceleration of particles — galaxies: active — gamma rays: observations — quasars: general

Type
Active Galaxies and Quasi-Stellar Objects
Information
International Astronomical Union Colloquium , Volume 142: Particle Acceleration Phenomena in Astrophysical Plasmas , 1994 , pp. 917 - 922
Copyright
Copyright © The American Astronomical Society 1994

References

Bertsch, D.L., et al. 1993, ApJ, 405, L21 CrossRefGoogle Scholar
Blandford, R.D., & Königl, A. 1979, ApJ, 232, 34 CrossRefGoogle Scholar
Blandford, R.D., & Rees, M.J. 1978, in Pittsburgh Conf. on BL Lac Objects, ed. Wolfe, A.M. (Pittsburgh: Univ. Pittsburgh Press), 328 Google Scholar
Blandford, R.D., & Znajek, R. 1977, MNRAS, 179, 433 CrossRefGoogle Scholar
Bloom, S., & Marscher, A. 1992, in Proc. Compton Observatory ScienceWorkshop (NASA CP-3137), 578 Google Scholar
Cameron, R.A., et al. 1993, in AIP Conf. Proc., Compton Gamma Ray Observatory, ed. Friedlander, M., Gehrels, N., & MacComb, D. J. (New York: AIP), 478 Google Scholar
Colgate, S. 1990, paper presented at AAS Meeting, 1990 June 10-14, paper 51.01Google Scholar
Dingus, B.L., et al. 1993, IAU Circ., No. 5690 Google Scholar
Fichtel, C.E., et al. 1993a, in AIP Conf. Proc., Compton Gamma Ray Observatory, ed. Friedlander, M., Gehrels, N., & MacComb, D. J. (New York: AIP), 1194 Google ScholarPubMed
Fichtel, C.E., et al. 1993b, in AIP Conf. Proc., Compton Gamma Ray Observatory, ed. Friedlander, M., Gehrels, N., & MacComb, D. J. (New York: AIP), 461 Google ScholarPubMed
Ghisellini, G., Maraschi, L., & Treves, A. 1985, A&A, 146, 204 Google Scholar
Goldreich, P., & Julian, W.H. 1969, ApJ, 157, 869 CrossRefGoogle Scholar
Gould, R.J. 1979, A&A, 76, 306 Google Scholar
Impey, C.D. 1992, in Variability of Blazars, ed. Valtaoja, E. & Valtonen, M. (Cambridge: Cambridge Univ. Press), 55 Google Scholar
Jones, T.W., O’Dell, S.L., & Stein, W.A. 1974, ApJ, 188, 353 CrossRefGoogle Scholar
Kanbach, G., et al. 1988, Space Sci. Rev., 46, 69 Google Scholar
Kazanas, D., & Ellison, D.C. 1986, Nature, 319, 380 CrossRefGoogle Scholar
Kniffen, D.A., et al. 1993, ApJ, 411, 133 CrossRefGoogle Scholar
Lin, Y.C., et al. 1993a, ApJ, 416, L53 CrossRefGoogle Scholar
Lin, Y.C., et al. 1993b, ApJ, submittedGoogle Scholar
Lovelace, R.V.E. 1976, Nature, 262, 649 CrossRefGoogle Scholar
MacDonald, D., & Thorne, K.S. 1982, MNRAS, 198, 345 CrossRefGoogle Scholar
MacDonald, D.A., Thorne, K.S., Price, R.H., & Zhang, X-H. 1986, in Black Holes: The Membrane Paradigm, ed. Thorne, K. P. S., Richard H., Price, & Douglas A., MacDonald (New Haven: Yale Univ. Press), chap. 4Google Scholar
Maraschi, I., Ghisellini, G., & Celotti, A. 1992, in AIP Conf. Proc 254, Testing the AGN Paradigm, ed., Holt, S., Neff, S.G., & Urry, C.M. (New York: AIP), 439 Google Scholar
Osterbrock, D.E. 1991, Rep. Progr. Phys., 54, 579 CrossRefGoogle Scholar
Punch, M., et al. 1992, Nature, 358, 477 CrossRefGoogle Scholar
Swanenburg, B.N., et al. 1978, Nature, 275, 298 CrossRefGoogle Scholar
Thompson, D.J., et al. 1993a, ApJS, 86, 629 CrossRefGoogle Scholar
Thompson, D.J., et al. 1993b, BAAS, Vol. 24, paper 21.04Google Scholar
Valtaoja, E., Terasranta, H., Lainela, M., & Teerikorpi, P. 1992, in Variability of Blazars, ed. Valtaoja, E. & Valtonen, M. (Cambridge: Cambridge Univ. Press), 70 Google Scholar