Continuous Monitoring of NGC4151 with CGRO/BATSE

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Session 108 -- Seyfert Galaxies
Display presentation, Thursday, 12, 1995, 9:20am - 6:30pm

[108.01] Continuous Monitoring of NGC4151 with CGRO/BATSE

A. Parsons, N. Gehrels (NASA/GSFC), W. Paciesas (U. of Alabama), A. Harmon, G. Fishman, C. Wilson (NASA/MSFC)

We will present the results of BATSE (15-200 keV) occultation measurements of the nearby Seyfert galaxy NGC 4151. This AGN is variable on time scales of a few days, but long-term daily monitoring has never been possible in X-rays or gamma-rays prior to BATSE. Earlier balloon experiments measured large variations in both intensity and spectral shape, while OSSE observations have reported only a 15% flux variation with no variation in spectral shape in the last few years. Long term monitoring is thus quite important. The standard occultation analysis allows detection of NGC4151 on few-day time scales and spectral measurements on week time scales. NGC4151 is well suited for this study because it is fairly isolated in the X-ray sky and is often observed by OSSE. We will present a time history of both the flux and the spectrum of the source over a fraction of the CGRO mission. The ultimate goal of this work is to compile a 3+ year time history of flux and spectral variations. Future work will be focused on the study of the occultation method to determine the systematic errors that may be present.

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