The flaring blazar S4 0954+65 observed brighter than R=12.8, a new record for its optical brightness.

ATel #15380; Alessandro Marchini (Astronomical Observatory, University of Siena, Italy); Thomas J. Balonek, Riley M. Corcoran, John J. Slater, Warner S. Neal (Foggy Bottom Observatory, Colgate University, Hamilton, NY, USA); Christian Lorey, Niels Bader, Noe Boutter, Jonas Seufert, David Reinhart (Hans-Haffner Observatory, Friedrich-Koenig-Gymnasium, Würzburg, Germany); Dominik Elsaesser (Technische Universität, Dortmund, Germany); Giacomo Bonnoli (INAF - Brera Astronomical Observatory, Italy); C. M. Raiteri, M. Villata (INAF, Osservatorio Astrofisico di Torino, Italy).
on 14 May 2022; 20:10 UT
Credential Certification: Claudia M. Raiteri (raiteri@oato.inaf.it)

Tweet

The BL Lac type object S4 0954+65 (RA: 09 58 47.2452 Dec: +65 33 54.8194; ICRS J2000) has been showing strong activity in both the optical (ATel #15322; ATel #15344; ATel #15376) and gamma-ray (ATel #15375) bands in recent weeks. Some groups of the Whole Earth Blazar Telescope (WEBT) Collaboration have been more closely monitoring this object's enhanced activity during the last month since the reports in April that it was particularly bright. We observed the most extraordinary variations in optical brightness in the R band during the four day interval 2022 May 11-14. Both the large amplitude and the short time scale of brightness fluctuations are remarkable. Our data show several instances of drastic increase or drop in brightness of almost one magnitude in less than two hours. At the extremes, increases and decreases in brightness of almost half a magnitude occurred within about 15 to 30 minutes. During this interval, a new maximum brightness of R=12.72 (0.02) was observed on May 13 around 04:30 UT (JD 2459712.6873). Although S4 0954+65 has historically shown a large variability in brightness of 3 magnitudes or more in some cases, these changes normally occur within a few weeks. The variability in brightness observed by us in the last few days in such short time intervals is unusual for such an object, especially because it has occurred several times in the last few days. At this page are reported some lightcurves obtained during our intensive observations: https://www.dsfta.unisi.it/en/research/labs/astronomical-observatory/optical-follow-blazar-s4-095465-during-its-flare-may-2022 The observations were conducted with a 0.3 m telescope at the Astronomical Observatory of the University of Siena (https://www.dsfta.unisi.it/en/research/labs/astronomical-observatory), with a 0.4 m telescope at the Foggy Bottom Observatory (https://observatory.colgate.edu/) and with a 0.5 m telescope at the Hans-Haffner Observatory (https://schuelerlabor-wuerzburg.de/en/observatory/). All data was acquired with a Rc standard filter and using the photometric sequence for this source made available by the WEBT Collaboration (https://www.oato.inaf.it/blazars/webt/0954658-s4-095465/). We point out that on May 12-13, the Siena and Colgate Universities data cover 13 continuous hours, when the maximum brightness of S4 0954+65 was recorded. Therefore, we strongly encourage further multi-wavelength coverage, especially from different longitudes. Any enquiry on these observations can be addressed either to Alessandro Marchini (marchini@unisi.it) or to Thomas J. Balonek (tbalonek@colgate.edu).