The optical fluxes of blazars S4 0954+658 and B2 1308+326 at gamma-ray flaring epoch in 2025 January
ATel #17005; V. V. Vlasyuk, O. I. Spiridonova (Special Astrophysical Observatory of the Rus. Ac. Sci.)
on 30 Jan 2025; 22:17 UT
Credential Certification: Alexander Moskvitin (mosk@sao.ru)
Subjects: Optical, Blazar, 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 blazar S4 0954+658 shows an increase in the optical spectral range after 1 year of rather quiet behavior. The previous epoch of its optical activity was denoted on 2024 January (ATel #16491), when R-magnitude exceeded value of 14.0. Between February and October its brightness was changed between 15.5 and 16.5 magnitudes mostly with only a few sub-flares above 15 magnitude.
Since the October of 2024, the brightness of blazar has increased again and now reached a brightness of R = 14.46 +/- 0.01 on the 2025 January 20/21 and 21/22 (MJD 60695.90 and 60696.98 respectively). According to our data the higher level R = 14.24 was detected only on the 2024 January 23/24 night (MJD 60332.90). We did not observe S4 0954+658 close to moment of gamma-ray flaring on January 24 (ATel #16994), but within last three nights it became fainter --- from R = 14.61 (MJD 60701.91) to 14.66 (MJD 60703.93). So we can only suspect the possible link between gamma-flare and local maximum in optical light curve.
As it was noted earlier (ATel #16963, #16972, #16979) the flat spectrum radio quasar B2 1308+326 is undergoing extended activity phase in optical range after two powerful flares in gamma-rays in December and January.
Activity of the blazar in very-high-energy gamma-rays (VHE; E > 100 GeV) was detected on January 26 and 27 by some experiments: VERITAS (ATel #16993), MAGIC (ATel #17000), MACE (ATel #17003). As it is followed from our data, optical activity epoch (R-band) agrees well with these results: the maximal value R = 13.26 was taken on January 26 (MJD 60701.97). After the B2 1308+326 became fainter --- our measurements for January 29 gave value of R = 13.52.
The monitoring of these blazars 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.