Mrk 279 reaches historic brightness maximum

ATel #17308; FiV. L. Oknyansky (SAI MSU & University of Haifa), A. S. Dodin (SAI MSU), A. M. Tatarnikov, V. G. Metlov, M. A. Burlak, N. P. Ikonnikova, D. Chelouche (University of Haifa), C. Sobrino Figaredo, S. Harikesh, S. Kaspi (Wise, Tel Aviv University), C. Fian (University of Valencia) rstname1 Lastname1 (Affil1), Firstname2 Lastname2 (Affil2)...
on 25 Jul 2025; 12:14 UT
Credential Certification: Victor Oknyansky (oknyan@mail.ru)

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Mrk 279 is a typical Seyfert 1 galaxy, which has exhibited significant, >10% intraday (a few times monthly) non-monotonic X-ray flux variability, and has been the target of several NIR, optical, UV and X-ray observing campaigns. We explore the data to see if Mrk 279 can be considered as a potential Changing Look (CL) AGN. Mrk279 is being continuously monitored from the ground (SAI MSU, Wise, and some other observatories) and with the Neil Gehrels Swift Observatory (XRT and UVOT telescopes). A historical minimum was observed in Sep. 2023 and a high-state on 2024 Jun 14 followed by another minimum. From the Swift observations we found that the UV level decreased similarly with optical bands, but the X-ray reached its maximum on 2024 Jul 3 with X-ray flux of 8.7 e-11 ergs/cm^2/s (0.5-10keV), before moving down again. Our findings reveal that high X-ray/UV correlation with a few days time delay of UV predominantly occurs during periods of moderate to low luminosity. Conversely, during high flux periods it exhibit either anti-correlation or low correlation. During December 2024 to July 2025 our ground-based and Swift photometry shows very significant and fast increase in optical bands with a historical maximum on 2025 July 14 ( B= 14.09 +/-0.03 , Swift). The X-ray flux and UV brightness reached the highest levels on 2025 July 19, since the Swift monitoring began (May 2008) with X-ray flux of 1.07 +/-0.05 e-10 ergs/cm^2/s, UVW1=12.56+/-0.02 , and UVW2=12.50+/-0.02 (Swift). We thank the Neil Gehrels Swift observatory staff for accepting and performing this target of opportunity observation. We acknowledge the service by the UK Swift Science Data Centre at the University of Leicester for data reduction (Evans et al. 2009, MNRAS, 397, 1177).