The brightness of blazar B2 1308+326 is at 3-year maximae

ATel #17185; V. V. Vlasyuk, O. I. Spiridonova (Special Astrophysical Observatory of the Rus. Ac. Sci.)
on 15 May 2025; 17:59 UT
Credential Certification: Alexander Moskvitin (mosk@sao.ru)

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We continuing optical BVRI-monitoring of the bright blazars sample using by our 1-meter and 0.5-meter reflectors equipped by CCD photometers.

As it was noted earlier (ATels #16963, #16972, #16979, #17005) the flat spectrum radio quasar B2 1308+326 is undergoing extended activity phase in optical range after powerful flares in gamma-rays in December and January.

The last flare of B2 1308+326 (OP 313) in gamma-ray emission was detected on May 4, with a daily averaged gamma-ray flux about 70 times higher than the average flux from 4FGL catalogue, the highest LAT daily flux ever observed for it (ATel #17167).

According to the last optical data (ATel #17173) the blazar brightness in R-band increased by 0.6 magnitudes between May 3 and May 6 and reached value R=13.82 at May 6/7 night.

Our last estimate of the B2 1308+326 brightness was made at May 14/15 night and gave value R=13.04 +/- 0.02 (MJD 60809.84) in comparison with previous one R=14.20 +/- 0.01 (MJD 60798.90). We detected higher level of the blazar flux with R=12.60 only during its flare in 2022 July, so the current flare is amongst historically most powerful outbursts of B2 1308+326.

As a comparison star the object F from Smith et al (1985, AJ, 90, 1184) with adopted value as R=14.00.

The monitoring of blazar is in progress; the most of data were taken under good weather condition (seeing (FWHM) < 1.5 arcsec and normal transparency) and have typical accuracy about 0.01 mags. We strongly encourage further multi-wavelength studies.