A Comprehensive X-Ray Spectral Analysis of the Seyfert 1.5 NGC 3227

Abstract

We present results of a 100 ks XMM-Newton observation of the Seyfert 1.5 AGN NGC 3227. Our best-fit broadband model to the EPIC pn spectrum consists of a moderately flat (photon index of 1.57) hard X-ray power-law absorbed by cold gas with a column density of 3 × 10 21 cm 2 , plus a strong soft excess, modeled as a steep power law with a photon index of 3.35, absorbed by cold gas with a column density of 9 × 10 20 cm −2 . The soft excess increases in normalization by ∼20% in ∼20 ks, independently of the hard X-ray emission component, and the UV continuum, tracked via the OM, also shows a strong increasing trend over the observation, consistent with reprocessing of soft X-ray emission. Warm absorber signatures are evident in both the EPIC and RGS spectra; we model two absorbing layers, with ionization parameters logξ = 1.2 and 2.9 erg cm s −1 , and with similar column densities (∼ 1-2 ×10 21 cm −2 ). The outflow velocities relative to systemic of the high-and low-ionization absorbers are estimated to be -(2060 +240 −170 ) km s −1 and -(420 +430 −190 ) km s −1 , respectively. The Fe Kα line FWHM width is 7000 ± 1500 km s −1 ; its inferred distance from the black hole is consistent with the BLR and with the inner radius of the dust reverberation-mapped by Suganuma et al. An emission feature near 6.0 keV is modeled equally well as a narrow redshifted Fe K line, possibly associated with a disk "hot-spot," or as the red wing to a relativistically broadened Fe line profile. Swift-BAT and archival RXTE data suggest at most a weak Compton reflection hump (R 0.5), and a high-energy cutoff near 100 keV. From RXTE monitoring, we find tentative evidence for a significant fraction of the Fe line flux to track variations in the continuum on time scales < 700 days. 11 The Hα/Hβ ratio is intrinsically 3.1, assuming case B recombination and assuming that collisional excitation is negligible, applicable for typical NLR conditions, but see warnings by Netzer 1990 regarding uncertainties in the intrinsic Balmer decrement. 12 radial emissivity per unit area is quantified as a power law, r −β 13 1 Rg ≡ GM BH /c 2

A variable-density absorption event in NGC 3227 mapped withSuzakuandSwift

“…The similar spectral shape prefers WA 2 to be partial covering in both observations. In contrast to the 2000 data, a steep soft excess is seen in 2006, which we describe by a soft power law (SXPL), consistent with the results of Markowitz et al (2009). The fit converges to a statistic of…”

“…We call these WA 2 and WA 3 in the following. Markowitz et al (2009) also detected an absorber with a small neutral column, which is similar to WA 1 seen in 2000 by Lamer et al (2003).…”

“…The high soft X-ray flux and the long exposure time allowed Markowitz et al (2009) to obtain a high S/N RGS spectrum. They constrained two layers of ionized absorption, one absorber that is moderately ionized, log ξ ∼ 1.45, and one absorber that is highly ionized, log ξ ∼ 2.93.…”

“…However, we cannot exclude the possibility of some observations capturing an additional physically distinct absorber with similar ionization level moving into the line of sight. Figure 2 shows the steps followed to find the best-fit baseline model on the 2008 Suzaku spectra motivated by Lamer et al (2003) and Markowitz et al (2009). We use observation Suz 3 in this example, which has the best combination of count rate and strong absorbing column density.…”

“…We assume that the incident hard X-ray power law (HXPL) of the ionized reflection and the continuum power law are identical. To reduce model degeneracies, we freeze the photon index to the value found by Markowitz et al (2009), who find WA 3 to be outflowing. We therefore also freeze the absolute redshift of WA 3 to the according value in our model.…”