A resonant absorption line in the ASCA spectrum of NGC 985?

F. Nicastro, F. Fiore, N. Brandt, C. S. Reynolds

Research output: Contribution to journalArticlepeer-review

1 Scopus citations

Abstract

We present timing and spectral analyses of the ASCA observation of the Seyfert 1 galaxy NGC 985. The 0.6-10 keV spectrum of this source is complex: large residuals are evident below 1 keV when fitting the spectrum with a power-law model. Fitting a warm absorber model to the 0.6-2.5 keV spectrum gives α = 1.12 ± 0.04, LogNW AH = 21.97 ± 0.08 and LogU= 0.06 ± 0.09, but the residuals continue to show a deficit of counts between 0.9 and 1 keV. Adding an absorption line improves the fit, and the energy of the line is consistent with that of Kα NeIX-X resonant absorption lines. Hence, we confirm the presence of an ionized absorber along the line of sight to this source and interpret the further 1 keV spectral feature as the first detection of a strong resonant absorption line associated with this system. The extrapolation of this model above 2.5 keV produces large positive residuals above 3-4 keV. Fitting the data with a broken power law plus warm absorber model gives an acceptable χ2 and Δα ∼ 0.5. A narrow iron line at 6.4 keV (quasar frame) of equivalent width 138+64-110 eV is also present in the ASCA data.

Original languageEnglish (US)
Pages (from-to)501-504
Number of pages4
JournalNuclear Physics B - Proceedings Supplements
Volume69
Issue number1-3
DOIs
StatePublished - Jan 1999

All Science Journal Classification (ASJC) codes

  • Atomic and Molecular Physics, and Optics
  • Nuclear and High Energy Physics

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