Observations of NGC 4151 at 2 keV to 2 MeV from HEAO 1

W. A. Baity, D. M. Worrall, R. E. Rothschild, R. F. Mushotzky, A. F. Tennant, F. A. Primini

Research output: Contribution to journalArticle (Academic Journal)peer-review


Broad-range X-ray and gamma-ray spectra of the Seyfert galaxy NGC 4151 obtained by the UCSD/MIT and GSFC/CIT detectors of HEAO 1 are presented. For two out of the three observational epochs the best-fit model is a power law with photon index 1.6 + or - 0.1 in the 2 keV-2 MeV spectral range. The third observation, in June, 1978, when the intensity was a factor of 2 higher, requires a change above 50 keV from a similar power law to a steeper power law or an exponential. Through comparisons with previous observations, a weak correlation is found between the high-energy spectral index and the flux level. Comparison of these data and other X-ray and gamma-ray observations with the spectra expected from several possible emission mechanisms supports a synchrotron-self-Compton model using infrared target photons or a Compton-scattering process involving X-rays of less than 10 keV energies.
Original languageEnglish
Pages (from-to)555-562
JournalAstrophysical Journal
Publication statusPublished - 1 Apr 1984


  • Gamma Ray Astronomy
  • Seyfert Galaxies
  • Spaceborne Astronomy
  • X Ray Spectra
  • Black Holes (Astronomy)
  • Energy Spectra
  • Galactic Nuclei
  • Gamma Ray Spectra
  • Heao 1
  • Power Spectra
  • Synchrotron Radiation


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