The activity of FSRQ Ton 599 in 2025 --- the repeating flares
ATel #17610; V. V. Vlasyuk, O. I. Spiridonova (Special Astrophysical Observatory of the Rus. Ac. Sci.)
on 19 Jan 2026; 15:17 UT
Credential Certification: Alexander Moskvitin (mosk@sao.ru)
Subjects: Optical, Quasar
We continuing optical BVRI-monitoring of
the bright blazars sample using by our 1-meter and 0.5-meter reflectors equipped by CCD photometers.
The flat spectrum radio quasar (FSRQ) Ton 599 (4C 29.45, PKS 1156+295) demonstrated significant activity over total last year. As we noted earlier (ATel #17074), since March 1 the blazar undergone stage of exponential growth with slope about 0.2 mag per day: from R = 15.38 to R = 14.42 mag (MJD 60736.0--60745.0). Since that flare our observations revealed at least 4 events, then brightness of the Ton 599 exceeded level of R ~ 15m till the end of 2025 --- in June 20th, July 17th, September 5th, November 29th, according to our estimates.
The yearly maximum (R = 13.97 mag) was reached at June 20th (MJD 50846.80). This event appeared not far from gamma-ray and infra-red activity epochs in the first decade of June (ATel#17226, 17248). The most dimmest Ton 599 was detected in last November (Rmin ~ 16.4 mag) and December (Rmin ~ 16.6 mag). Our last observation in January 16--18th gave new flare --- from R=15.1 to 14.4 mag within 2 days.
Typical accuracy of our data was about 0.01 mag under good transparency and seeing value (FWHM) about 1.5 arcsec. Data were calibrated using by stars 1--4 from (Raiteri C.M. et al., A&AS 130, 495, 1998).
More accurate reduction is necessary. We strongly encourage further multi-wavelength observations.
