PG 1553+113 optically brighter than during the last 1.5 years
ATel #16882; K. Schoch, S. Duerr, O. Koppitz, T. Apell, M. M. Brown, O. Domann, R. Goldbach, M. Heidemann, F. Hemrich, S. Huesam, D. Kuberek, G. Manhalter, D. Paulini, F. Pfeuffer, G. Rinke, T. Scheller, N. Zottmann, R. Steineke, M. Feige, D. Reinhart, C. Lorey (all Hans-Haffner-Sternwarte, Friedrich-Koenig-Gymnasium, Wuerzburg, Germany) F. Eppel, J. Hessdoerfer, M. Kadler, K. Mannheim, F. Roesch (all University of Wurzburg, Germany) D. Elsaesser (TU Dortmund, Germany)
on 29 Oct 2024; 16:10 UT
Credential Certification: Dominik Elsaesser (dominik.elsaesser@tu-dortmund.de)
Subjects: Optical, AGN, Blazar
The BL Lac-type AGN PG 1553+113 (RA: 15 55 43.0440 Dec: +11 11 24.3656; ICRS J2000; z approx. 0.4; cf. Danforth et al. 2010, ApJ 720, 976) reached its highest brightness in the optical range over the last 1.5 years during the recent few nights.
This blazar has been proposed to harbour a binary system of two supermassive black holes (cf. M. Tavani et al 2018 ApJ 854 11), for which a periodicity of about 2.2 years has been assumed both in the optical (cf. A. Agarwal et al. 2022 JApA 43,9) and in the gamma-ray range (cf. M. Ackermann et al. 2015, ApJL 813, L41).
The last major increases in brightness occurred with a shorter periodicity of about 2 years and slightly below: Maxima in April 2019 (ATel # 12695, ATel # 12649 -optical- ATel # 12645 -NIR- # 12641 -gamma-ray) and in April 2021 (ATel # 14520 - gamma-ray), followed by a maximum in February 2023 (ATel # 15915; ATel #15944 - optical).
After the last major increase in activity of this object in February 2023, an increase in activity would therefore not have been expected again until early to mid-2025.
Until the end of 2023, the optical brightness of the object initially also decreased continuously (with fluctuations) by about one magnitude to 14.2 mag (14.225 ± 0.034 JD 2460260.2052), but has since increased again just as continuously, also with smaller fluctuations, and reached in the night from 27. to 28. October the highest R-band brightness we have been able to measure in the last one and a half years.
Here, we report the following preliminary R-band magnitudes:
2460568.2786 13,814 ± 0.005
2460574.2745 13,825 ± 0.006
2460575.2592 13,873 ± 0.011
2460582.2932 13,704 ± 0.003
2460589.2672 13,591 ± 0.004
2460595.3108 13,496 ± 0.006
2460607.2262 13,437 ± 0.006
2460609.2294 13,382 ± 0.006
2460609.2505 13,376 ± 0.006
2460610.2412 13,386 ± 0.008
2460611.2285 13,373 ± 0.005
2460612.2251 13,433 ± 0.007
2460612.2542 13,437 ± 0.005
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 University. The optical data were acquired through a Bessel R filter (Chroma) with the 0.5m CDK-astrograph (PlaneWave Instruments) 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
