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Revisiting the Short-term X-ray Spectral Variability of NGC 4151 with Chandra

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Abstract

  • We present new X-ray spectral data for the Seyfert 1 nucleus in NGC 4151 observed with Chandra for ~200 ks. A significant ACIS pileup is present, resulting in a nonlinear count rate variation during the observation. With pileup corrected spectral fitting, we are able to recover the spectral parameters and find consistency with those derived from unpiled events in the ACIS readout streak and outer region from the bright nucleus. The absorption corrected 2-10 keV flux of the nucleus varied between 6 × 10-11 erg s-1 cm-2 and 10-10 erg s-1 cm-2 (L 2-10 keV ~ 1.3-2.1 × 1042 erg s-1). Similar to earlier Chandra studies of NGC 4151 at a historical low state, the photon indices derived from the same absorbed power-law model are ? ~ 0.7-0.9. However, we show that ? is highly dependent on the adopted spectral models. Fitting the power-law continuum with a Compton reflection component gives ? ~ 1.1. By including passage

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  • 2010

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