The blazar S5 1044+71: maximum brightness over 2026

ATel #18052; V. V. Vlasyuk, O. I. Spiridonova (Special Astrophysical Observatory of the Rus. Ac. Sci.)
on 17 Sep 2026; 12:13 UT
Credential Certification: Alexander Moskvitin (mosk@sao.ru)

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The flat-spectrum radio quasar S5 1044+71 demonstrate continuing optical activity over whole last year. As was reported in ATel #17715, this source reached an R band magnitude of 16.25 +/- 0.01 in the early March. Later, in August 20/21 night, brightness of S5 1044+71 became as high as 15.882 +/- 0.012 in the R band (ATel #17999).

SAO RAS team also carried out observations of S5 1044+71 as part of the WEBT collaboration (https://www.oato.inaf.it/blazars/webt) after Claudia Raiteri proposal using our 1-meter and 0.5- meter optical reflectors. Our results are in a good agreement with published estimates within internal uncertainties. More dense estimates of S5 1044+71 over its flare in August allow us to refine parameters of flare: R = 15.67 +/- 0.03, maximum epoch MJD= 61272.05 (August 19/20). The shape of this flare was almost triangular in stellar magnitudes scale --- the growing wing was linear with a slope -0.1 mag/day in the interval MJD 61260--61272, the dimming of the blazar was even faster --- about 0.4 mag/day till MJD 61274.

After official completing of the WEBT campaign we continued observing of blazar. Over the past month, the brightness of S5 1044+71 has fluctuated roughly between 16.5 and 15.9 mag in the R band. Last re-brightening phase for blazar started since value R = 16.21 +/- 0.01 mag at September 10/11 night. After 3 days of brightness growth with slope -0.18 mag/day S5 1044+71 reached an absolute maximum for last year --- 15.63 +/- 0.01 in the R band (MJD 61297.0).

More accurate data reduction is necessary. We strongly encourage further multi-wavelength observations.

All estimates for the S5 1044+71 3C 138 re-brightening phase were provided with 0.5-meter SAO RAS optical reflector equipped by EM CCD Andor 512x512 pixels camera. The recommended by WEBT reference stars NN3 and 4 were used as standards.