A remarkable long-term light curve and deep, low-state spectroscopy: Swift and XMM-Newton monitoring of the NLS1 galaxy Mkn 335

Abstract

The narrow-line Seyfert 1 galaxy (NLS1) Mkn 335 is remarkable because it has repeatedly shown deep, long X-ray low states that show pronounced spectral structure. It has become one of the prototype active galactic nuclei (AGNs) in deep minimum X-ray states. Here we report on the continuation of our ongoing monitoring campaign with Swift and the examination of the low-state X-ray spectra based on a 200 ks triggered observation with XMM-Newton in 2009 June. Swift has continuously monitored Mkn 335 since 2007 May typically on a monthly basis. This is one of the longest simultaneous UV/X-ray light curves so far obtained for an AGN. Mkn 335 has shown strong X-ray variability even on timescales of hours. In the UV, it turns out to be one of the most variable among NLS1s. Long-term Swift monitoring allows us to examine correlations between the UV, X-rays, and X-ray hardness ratios. We find no significant correlation or lag between the UV and X-ray variability; however, we do find distinct trends in the behavior of the hardness ratio variability. The hardness ratio and count rate are correlated in the low-flux state, but no correlation is seen in the high state. The X-ray low-state spectra of the 2007 and 2009 XMM-Newton observations display significant spectral variability. We fit the X-ray spectra with a suite of phenomenological models in order to characterize the data. The broadband CCD spectrum can be fitted equally well with partial absorption and blurred reflection models. These more complicated models are explored in further detail in upcoming work.