New activity period of FSRQ Ton 599 after 70 days low-state interval
ATel #17074; V. V. Vlasyuk, O. I. Spiridonova (Special Astrophysical Observatory of the Rus. Ac. Sci.)
on 11 Mar 2025; 11:04 UT
Credential Certification: Alexander Moskvitin (mosk@sao.ru)
Subjects: Optical, Blazar, Quasar
The flat spectrum radio quasar (FSRQ) Ton 599 (4C 29.45, PKS 1156+295) begun new activity period through last few days.
After completing of last activity phase in 2024 September its brightness varied below 16.5 mag. (R-band) from November to first decade of January. Unlike the previous low-activity state of Ton 599 in 2023, which spanned over 250 days, the current one became as short as 70 days only. After completing of first increase from R = 17 to R = 15.2 mag. between December 14 and January 10 the brightness of blazar varied below R = 15.5 till end of February.
Since March 1 the blazar undergone stage of exponential growth: from from R = 15.38 (MJD 60735.9) to R = 14.42 (MJD 60745.0). The light curve between these epochs can be well approximated by linear law with a slope about 0.2 mag. per day. This value is close to slope of Ton599 light curve (about 0.25 mag. per day) at last January epoch. According to our estimates brightness of the blazar reached levels of powerful outburst, which was detected in 2024 February-March.
Typical accuracy of our data was about 0.005 mag. under good transparency and seeing value (FWHM) about 1".5. Data were calibrated using 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.
