Discovery of the Narrow-Line Seyfert 1 galaxy Mkn 335 in an historical low X-ray flux state

TL;DR

This paper reports the discovery of Mkn 335 in an unprecedented low X-ray flux state, revealing insights into its extreme variability and possible absorption mechanisms, and discusses its relation to other NLS1 galaxies and quasars.

Contribution

The study provides the first detailed analysis of Mkn 335's extreme low X-ray flux state and models it with partial covering absorption, offering new understanding of NLS1 galaxy variability.

Findings

Mkn 335's X-ray flux decreased by over 30 times compared to previous observations.

The spectrum is extremely hard above 2 keV, consistent with partial covering absorption.

UV variability is around 0.2 magnitudes, indicating multi-wavelength activity.

Abstract

We report the discovery of the Narrow-Line Seyfert 1 galaxy Mkn 335 in an extremely low X-ray state. A comparison of Swift observations obtained in May and June/July 2007 with all previous X-ray observations between 1971 to 2006 show the AGN to have diminished in flux by a factor of more than 30, the lowest X-ray flux Mkn 335 has ever been observed in. The Swift observations show an extremely hard X-ray spectrum at energies above 2 keV. Possible interpretations include partial covering absorption or X-ray reflection from the disk. In this letter we consider the partial covering interpretation. The Swift observations can be well fit by a strong partial covering absorber with varying absorption column density N_H= 1-4 x 10^{23} cm-2 and a covering fraction f_c=0.9 - 1. When corrected for intrinsic absorption, the X-ray flux of Mkn 335 varies by only factors of 4-6. In the UV Mkn 335 shows variability in the order of 0.2 mag. We discuss the similarity of Mkn 335 with the highly variable NLS1 WPVS007, and speculate about a possible link between NLS1 galaxies and broad-absorption line quasars.