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Title:
New X-ray spectral observations of NGC 4151 with ASCA
Authors:
Weaver, K. A.; Yaqoob, T.; Holt, S. S.; Mushotzky, R. F.; Matsuoka, M.; Yamauchi, M.
Affiliation:
AA(Pennsylvania State University, University Park, PA, US), AB(Pennsylvania State University, University Park, PA, US), AC(NASA. Goddard Space Flight Center, Greenbelt, MD, US), AD(NASA. Goddard Space Flight Center, Greenbelt, MD, US), AE(The Institute of Physical and Chemical Research, Saitama, Japan), AF(The Institute of Physical and Chemical Research, Saitama, Japan)
Publication:
Astrophysical Journal, Part 2 - Letters (ISSN 0004-637X), vol. 436, no. 1, p. L27-L30 (ApJL Homepage)
Publication Date:
11/1994
Category:
Astrophysics
Origin:
STI
NASA/STI Keywords:
Galactic Nuclei, Seyfert Galaxies, X Ray Astronomy, X Ray Spectra, Light Curve, Stellar Models, X Ray Telescopes
DOI:
10.1086/187625
Bibliographic Code:
1994ApJ...436L..27W

Abstract

We present new X-ray spectral data for the well-studied Seyfert galaxy NGC 4151, which was observed twice for about 20 ks each during the ASCA performance verification phase, once on 1993 May 25 and again on 1993 November 5. The source underwent complex spectral variability, and the observed 2-10 keV flux increased by a factor of 2 while the intrinsic 2-10 keV flux increased by no more than 20%. The data can be modeled with either a dual cold absorber plus a soft X-ray excess consisting of scattered continuum flux and an additional 'ultrasoft' X-ray excess component, or a warm absorber plus scattered continuum flux. There is evidence for variability at less than 1 keV energies that is unrelated to the 2-10 keV continuum. For an ionized-absorber description of NGC 4151, changes in the ionization state of the absorber appear to be unrelated to changes in the ionizing continuum.

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