ASCA Observations of Fe K$\alpha$ Line Profiles in Seyfert Galaxies

Previous abstract Next abstract

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

[108.03] ASCA Observations of Fe K$\alpha$ Line Profiles in Seyfert Galaxies

K. A. Weaver, J. Nousek (Penn State), T. Yaqoob (NASA/GSFC)

We present new X-ray spectral data for Fe K$\alpha$ lines in five Seyfert galaxies observed recently with the ASCA satellite. NGC 4151, MCG$-$2-58-22, and IC 4329A were observed during the performance verification phase of the mission; NGC 2992 and MCG$-$5-23-16 were observed during the AO-1 guest observer phase. We find that all of the Fe K$\alpha$ line energies are consistent with fluorescence of neutral or weakly ionized Fe. The other Fe K$\alpha$ line properties such as intrinsic line width and equivalent width (EW) have a range of values, suggesting that there is not a ubiquitous origin for Fe K$\alpha$ lines in Seyfert galaxies.

The inferred Fe K$\alpha$ widths can be strongly affected by uncertainties in the assumed 2--10 keV continuum in cases where ASCA can resolve the emission line. In particular, the widths can change depending on whether and how much Compton reflection is present. For MCG$-$2-58-22, assuming no reflection, the line is resolved with a FWHM of 33,000($-$20,000,+32,000) km s$^{-1}$. This is consistent with the line arising from some portion of the broad line region, but an accretion disk origin is possible. The EW of $\sim$340~eV is larger than expected for an accretion disk, but would be allowed if the disk were at least weakly ionized. In NGC 2992, the line is unresolved (FWHM $<$5,000~km s$^{-1}$). The large EW of $\sim$500~eV suggests that this line arises from an extended reprocessing region. For IC 4329A we prefer a reflection model and find the Fe~K$\alpha$ line is resolved with a FWHM of $\sim$17,000 km s$^{-1}$ and an EW of $\sim$100~eV, consistent with originating in a neutral accretion disk. The line profile appears asymmetric with a possible red wing. Finally, in MCG$-$5-23-16 and NGC 4151, the Fe K$\alpha$ lines are complex, with both narrow and broad components, although the ``broad'' component in NGC 4151 is more likely the result of continuum complexity between 5 and 10 keV.

Thursday program listing