Flat-Spectrum Radio-Quasar 3C345: most powerful optical outburst since 2018 May

ATel #15244; O. I. Spiridonova, V. V. Vlasyuk, A. S. Moskvitin, O. A. Maslennikova (Special Astrophysical Observatory of the Rus. Ac. Sci.)
on 26 Feb 2022; 06:53 UT
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Credential Certification: Alexander Moskvitin (mosk@sao.ru)

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Flat-spectrum radio-quasar 3C345 (PKS 1641+399; z=0.59) is observing by SAO RAS team on a regular basis in search of possible correlation between its optical and radio activity events. Most of data were taken using by 1-m SAO RAS reflector.

We have observed 3C345 few times each month except period in November-December under convenient weather conditions in BVRI passbands. Typical accuracy of our data was about 0.02 mag. under good atmospheric transparency and seeing value (FWHM) better than 3".

Analysis of our data in R-band between 2021 January and 2022 February showed that quasar demonstrates slow increasing of brightness from 17.6 to 16.8 with some variations. But between February 11th and February 23th it's flux increased from m_R ~16.9 to m_R =16.05 (MJD=59634.1). Accuracy of our measurements was about 0.01. At February 24/25 (MJD=59635.1) we got only one it’s estimate with poor accuracy due to weather conditions - 16.37 +/- 0.07, at February 25/26 (MJD = 59636.0) averaged brightness was 16.13 +/- 0.03.

According to published data, we detected the brightest optical state of 3C345 since 2018 May (ATel #11624). Further observations of 3C345 in all ranges are highly encouraged. Resulting photometrical curve in range MJD=59240-59636 is presented on Figure https://drive.google.com/file/d/1OTm1Sum5JAl2LHNgOI-snGznEokRwJc9/view?usp=sharing