Another brightness peak of the BL Lac object S2 0109+22
ATel #17025; S. Duerr, D. Schneider, M. Heemskerk, G. Rinke, D. Paulini, O. Domann, R. Goldbach, M. Heidemann, O. Koppitz, D. Kuberek, B. Lehmann, L. Lehmann, N. Zottmann, K. Schoch, M. Feige, D. Reinhart R. Steineke, 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 11 Feb 2025; 04:24 UT
Credential Certification: Dominik Elsaesser (dominik.elsaesser@tu-dortmund.de)
Subjects: Optical, AGN, Blazar
The BL Lacertae object S2 0109+22, also known as QSO B0109+224, QSO HB89 0109+224, or GC 0109+224; ICRS coordinates (ep=J2000) RA 01 12 05.825 and Dec +22 44 38.786 (optical), z(emission) = 0.265 (Data from SIMBAD (http://simbad.u-strasbg.fr/simbad/) during the last weeks showed a noticeable increase in optical brightness.
Since the beginning of this year, the object has undergone an increase in optical brightness by one magnitude in the R band, and reached a brightness peak of 13.561 mag on the night of 4th to 5th of February 2025 (JD = 2460711.3628). The brightness then slowly decreased again in the following nights.
This significant increase in brightness is similar to the one the object reached in June 2023 (ATel #16093), and slightly higher than the one it reached in August 2024 (ATel # 16783).
Since August last year, the optical brightness of S2 0109 initially decreased rapidly and then fluctuated around a value of about 14.5 mag (R-band) with a fluctuation range of about 0.2 mag until the end of 2024. Since then, the brightness has been steadily increasing.
We report the following preliminary R-band magnitudes:
JD 2460672.2121 14.562 ± 0.007
JD 2460680.2937 14.598 ± 0.010
JD 2460686.3546 14.501 ± 0.007
JD 2460688.3168 14.438 ± 0.006
JD 2460692.3686 13.947 ± 0.004
JD 2460694.3563 13.821 ± 0.003
JD 2460695.3040 13.847 ± 0.003
JD 2460696.2432 13.821 ± 0.007
JD 2460707.3503 13.778 ± 0.004
JD 2460708.3465 13.713 ± 0.003
JD 2460709.4214 13.667 ± 0.004
JD 2460711.3320 13.562 ± 0.010
JD 2460711.3628 13.561 ± 0.013
JD 2460714.2494 13.588 ± 0.010
JD 2460714.3549 13.614 ± 0.008
JD 2460715.2237 13.724 ± 0.009
JD 2460715.3403 13.758 ± 0.006
Comparison stars and their magnitudes were taken from S. Ciprini et al.: âOptical variability of the BL Lacertae object GC 0109+224â; A&A 400, 487-498 (2003).
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. 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 Hettstadt
