Enhanced optical activity of the flat-spectrum radio quasar 4C 10.45

ATel #17916; D. Reinhart, R. Steineke, C. Lorey, S. Ankara, E. Bommert, S. Duerr, O. Domann, M. Feige, R. Goldbach, M. Grischy, M. Heidemann, D. Kuberek, S. Krauth, L. Lehmann, J. Meiler, N. Mildner, L. Neisser, F. Pfeuffer, K. Warmuth, N. Zottmann (all Hans-Haffner-Sternwarte, Friedrich-Koenig-Gymnasium, Wuerzburg, Germany) K. Mannheim (University of Wurzburg, Germany) D. Elsaesser (TU Dortmund, Germany)
on 21 Jul 2026; 09:17 UT
Credential Certification: Dominik Elsaesser (dominik.elsaesser@tu-dortmund.de)

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The Blazar 4C 10.45 (PKS 1606+106) at ICRS J2000 coordinates R.A.: 16 08 46.203 Dec.: +10 29 07.776 and redshift z(spectroscopic)=1.23248 (data from the Simbad astronomical database), has been remarkably bright in the optical spectral range over the past few nights and reached a magnitude of 15.853 in the R-Band, which is a considerable brightness for this object.
The object has been classified as a flat-spectrum radio quasar (see Fichtel, C. E., 1994, ApJS 90, 917).
Increased gamma-ray activity from 4C 10.45 was detected both at the end of 2024 and in early summer 2025 by the Large Area Telescope on the Fermi Gamma-ray Space Telescope (Fermi LAT) (ATel #16889, ATel #17206). In both cases, subsequent optical measurements showed slightly increased activity (ATel #16892, ATel #17213). At that time, the blazar reached R-band magnitudes of 17.3 (2024) and 16.26 (2025).
From the beginning of this year, the R-band magnitude of 4C 10.45 has fluctuated between 18.16 and 17.3 mag. Since early July, the R-band brightness has increased by 1.5 mag from 17.377 (JD 2461228.4871) to 15.853 (JD 2461241.5269).

We report the following preliminary R-band magnitudes:

JD 2461228.4871 17.377 ± 0.026
JD 2461237.4837 16.014 ± 0.015
JD 2461237.5327 15.991 ± 0.013
JD 2461241.3736 16.094 ± 0.008
JD 2461241.4526 15.890 ± 0.007
JD 2461241.5269 15.853 ± 0.011
JD 2461242.3695 16.008 ± 0.008
JD 2461242.4719 16.063 ± 0.007

Our measurements are carried out as part of the long-term AGN monitoring program of the Naturwissenschaftliches Labor fuer Schueler am Friedrich-Koenig-Gymnasium (FKG), the Universitaet Wuerzburg, and TU Dortmund University.
Comparison stars and their magnitudes were taken from the APASS DR9 catalogue (Henden et al., 2016). The Sloan magnitudes were transformed to the Johnson-Cousins system with the equations by Lupton (2005).
The optical data were acquired through a Bessel R filter (Chroma) with a 0.5m CDK-astrograph (PlaneWave) and a Moravian C4-16000EC camera at the school and university observatory Hans-Haffner-Sternwarte in 97265 Hettstadt, Germany (https://schuelerlabor-wuerzburg.de/en/observatory/).

Hans-Haffner-Sternwarte