Detection of the NLS1 galaxy Mkn 335 in its lowest UV state ever observed with the Neil Gehrels Swift observatory

ATel #15469; Dirk Grupe (Morehead State University), S. Komossa (MPIfR), Luigi Gallo (St. Mary's University)
on 24 Jun 2022; 19:30 UT
Credential Certification: Dirk Grupe (dgrupe007@gmail.com)

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We report on the detection of the lowest UV-optical state of the Narrow-Line Seyfert 1 (NLS1) galaxy Mkn 335 (RA-2000=00h06m19.5s, Dec-2000=+20d12m11s) ever observed by Swift. Mkn 335 is a highly variable AGN that was once among the X-ray brightest AGN, but was found in X-ray low-states most of the time in recent years (e.g., Grupe et al. 2012). It has been monitored by us since May 2007.

Mkn 335 recently emerged from its Swift sun-constraint on 2022 May 16 and has remained in this lowest UV-optical state since we have resumed our regular monitoring campaign on May 19. Our latest 1 ks Swift observation was performed on 2022 June 19 starting at 03:59 UT and showed the following observed (and Galactic-reddening-corrected; in parentheses) UVOT magnitudes in the Vega system: V: 14.98+/-0.05 (14.86), B: 15.49+/-0.04 (15.34), U: 14.42+/-0.04 (14.23), W1: 14.27+/-0.04 (14.03), M2: 14.35+/-0.06 (14.01), and W2: 14.40+/-0.04 (14.11). This compares to the highest W2 magnitude observed with Swift in 2012 of 12.6 mag.

The X-ray emission has remained at a very low observed flux level already since 2018, except episodes of flaring in 2020 and 2021 (Komossa et al. 2020), uncorrelated with the UV emission. During the Swift observation of 2022 June 19, we found Mkn 335 at a low 0.3-10 keV flux level of (1.4+/-0.1)e-15 W m^-2; or 1.7e-15 W m^-2 after correction for Galactic absorption). The X-ray spectral slope had an index of alpha_x=0.76+/-0.45 or a photon-index of Gamma_x=1.76+/-0.45.

We would like to thank Brad Cenko for approving all of our monitoring campaigns and the Swift team for starting the observations right away when Mkn 335 came out of the sun-constraint.