Rapid increase in the optical brightness of the blazar AO 0235+164

ATel #16403; C. Lorey, D. Reinhart, R. Steineke, M. Feige, N. Zottmann, S. Huesam, B. Horst, F. Kaplan, J. Ludwig, (all Friedrich-Koenig-Gymnasium / Hans-Haffner-Sternwarte) A. Scherbantin, K. Mannheim (Universitaet Wuerzburg), D. Elsaesser (TU Dortmund)
on 12 Jan 2024; 10:15 UT
Credential Certification: Dominik Elsaesser (dominik.elsaesser@tu-dortmund.de)

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The Blazar AO 0235+164; ICRS coords. (ep=J2000): RA 02 38 38.930 Dec +16 36 59.275 z=0.94 showed a very strong increase in brightness of over 2 magnitudes in the R-band within the last three nights.
At the beginning of 2023, AO 0235+164 showed a brightness in the R band in the range of 19 to 17.5 mag. From April to June, we were unable to monitor the object due to the geographical location of the Hans Haffner Observatory. In summer, the optical brightness then rose to a range of 17.5 to 16.5 mag, reaching a brightness peak of a good 15.3 mag in the R-band at the end of August. Various groups have reported this increase: ATel #16190, ATel #16199, ATel #16204, ATel #16253.
After this phase of strong activity, the R-band brightness of this blazar dropped again from the end of September to a range between 19 and 18 mag, where it remained until the end of 2023 (see also: ATel #16320, ATel #16346).
Since January 8, we have been able to observe a very strong increase in R-band brightness at the Hans Haffner Observatory, which has become more and more pronounced and reached a peak value of 15.717 mag in the R-band last night. It is possible that a plateau phase in the brightness development has been reached, as the pace of the increase in brightness has decreased significantly. However, we cannot make a definite statement about this, as the object then set.


Here we report the following preliminary R-band magnitudes:
JD 2460282.225: 19.157 ± 0.338
JD 2460295.360: 18.464 ± 0.093
JD 2460297.339: 18.731 ± 0.137
JD 2460297.450: 18.827 ± 0.137
JD 2460309.233: 16.781 ± 0.072
JD 2460309.353: 16.860 ± 0.049
JD 2460314.220: 17.491 ± 0.064

JD 2460318.329: 17.987 ± 0.069
JD 2460319.285: 17.550 ± 0.048
JD 2460320.249: 17.458 ± 0.051
JD 2460320.529: 17.178 ± 0.096

JD 2460321.227: 16.159 ± 0.015
JD 2460321.380: 15.844 ± 0.010
JD 2460321.457: 15.764 ± 0.011
JD 2460321.492: 15.752 ± 0.013
JD 2460321.499: 15.722 ± 0.014
JD 2460321.507: 15.732 ± 0.015
JD 2460321.514: 15.717 ± 0.016
JD 2460321.521: 15.718 ± 0.018
JD 2460321.529: 15.750 ± 0.020
JD 2460321.536: 15.756 ± 0.024
JD 2460321.543: 15.807 ± 0.032


The data were acquired through a Bessel R filter and conducted in the framework provided by the WEBT Collaboration (https://www.oato.inaf.it/blazars/webt). The photometric sequence of WEBT for this source can be found under: https://www.oato.inaf.it/blazars/webt/ao-023516/.
These 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 with the 0.5m CDK-astrograph at the school and university observatory Hans-Haffner-Sternwarte in D-97265 Hettstadt-Germany (https://schuelerlabor-wuerzburg.de/en/observatory/).

Hans-Haffner-Sternwarte