The Complex X-ray Spectrum of the Sefyert 1.5 Source NGC 6860

Abstract

The X-ray spectrum of the Seyfert 1.5 source NGC 6860 is among the most complex of the sources detected in the Swift Burst Alert Telescope all-sky survey. A short XMM-Newton follow-up observation of the source revealed a flat spectrum both above and below 2 keV. To uncover the complexity of the source, in this paper we analyze both a 40 ks Suzaku and a 100 ks XMM-Newton observation of NGC 6860. While the spectral state of the source changed between the newer observations presented here and the earlier short XMM-Newton spectrum—showing a higher flux and a steeper power-law component—the spectrum of NGC 6860 is still complex with clearly detected warm absorption signatures. We find that a two-component warm ionized absorber is present in the soft spectrum, with column densities of about 10²⁰ and 10²¹ cm^-2, ionization parameters of ξ = 180 and 45 erg s^-1, and outflow velocities for each component in the range of ≈0-300 km s^-1. Additionally, in the hard spectrum we find a broad (≈11, 000 km s^-1) Fe Kα emission line, redshifted by ≈2800 km s^-1.