The Narrow-line Seyfert 1 galaxy Mkn 335 in its brighest X-ray state in more than a decade
ATel #18044; Dirk Grupe (Northern Kentucky University), S. Komossa (MPIfR), L. Gallo (St. Mary's University), Jon M. Miller (U Michigan)
on 15 Sep 2026; 17:37 UT
Credential Certification: Dirk Grupe (dgrupe007@gmail.com)
Subjects: Optical, Ultra-Violet, X-ray, AGN, Quasar
We report on the discovery of the Narrow-Line Seyfert 1 (NLS1) galaxy Mkn 335
in its brightest X-ray state in more than a decade. The NASA Neil Gehrels
Swift mission observed Mkn 335 on 2026 September 11 as part of a GI program
(PI J.M. Miller) and found it at an observed count rate in the XRT of
1.000+/-0.055 counts/s, which is the highest count rate seen since
2014 September 18. Over the last two decades, and in the course of our
dedicated long-term monitoring program (PI D. Grupe), Mkn 335 was mostly
found in low X-ray flux states (e.g., Grupe et al. 2007, 2008, 2012, Gallo et
al. 2018, Parker et al. 2019, Komossa et al. 2020, Komossa & Grupe 2024), but
has started to show enhanced activity in recent years (Komossa et al. 2025,
ATEL #17547).
Swift observed Mkn 335 on 2026 September 11 at 13:50-14:05 UT. At that epoch,
we measured an XRT X-ray count rate of 1.00 counts/s, a hardness ratio
HR = -0.18+/-0.05, an absorbed X-ray flux in the 0.3-10 keV band of
f = (2.37+/-0.10) e-14 W/m^2, and a powerlaw photon index of
Gamma_x = 2.22+/-0.14. That spectral fit is based on the assumption of a
single powerlaw model with absorption fixed at the Galactic value
(chi^2/dof = 39/25), but Mkn 335 is better fit by a partial covering absorber
model with NH = (8.3+1.9-3.8) e22 cm^-2, a covering fraction of
fc = 0.70+0.11-0.20 and a photon index Gamma = 2.49+/-0.20 (chi^2/dof = 26/23).
The high observed X-ray flux makes Mkn 335 an ideal target for spectroscopic
missions like XRISM, and for optical spectroscopic follow-ups to follow the
response (or lack thereof; Komossa et al. 2020) in HeII 4686A.
On the same date, we measured with the UVOT the following magnitudes in the
VEGA system (where values in brackets are corrected for Galactic extinction):
V = 15.01 +- 0.05 (14.89 ), B = 15.19 +/- 0.04 (15.19), U = 14.28 +/- 0.04
(14.09), W1 = 14.02 +/- 0.04 (13.78), M2 = 14.13 +/- 0.04 (13.79), and W2 =
14.08 +/- 0.04 (13.79).
We would like to acknowledge the use of the Build an XRT Product page at the
University of Leicester (https://www.swift.ac.uk/user_objects/).
That service has been instrumental for our research.
