The flaring blazar S5 1044+71 shows a significant increase in its optical brightness
ATel #17715; Alessandro Marchini (Astronomical Observatory, DSFTA, University of Siena - Italy); Leonardo Stiaccini, Gaia Verna (Department of Physical Sciences, Earth and Environment (DSFTA), University of Siena - Italy); Giacomo Bonnoli (INAF - Brera Astronomical Observatory, Milan - Italy); Ivo Peretto, Giovanni Furlato, Stefano Lora, William Rivato (MarSEC, Marana di Crespadoro, Vicenza - Italy); Alessandro Nastasi, Sabrina Masiero, Alessio Squilloni (GAL Hassin - Centro Internazionale per le Scienze Astronomiche, Isnello, Palermo - Italy)
on 9 Mar 2026; 22:19 UT
Credential Certification: Gaia Verna (gaia.verna@unisi.it)
Subjects: Optical, AGN, Blazar, Transient
In the last nights, we recorded an optical flare of the flat-spectrum radio quasar S5 1044+71 (R.A. = 10 48 27.62, Dec. = +71 43 35.94; J2000; Charlot et al. 2020, A&A, 644A, 159) at redshift z = 1.150 (Snellen et al. 2002, MNRAS, 329, 700). In the last few years, we regularly monitored this blazar as part of the Whole Earth Blazar Telescope (WEBT) collaboration.
We report the brightness recorded in the R band of the Johnson-Cousins photometric systems in the last few months:
Civil date (UT) Mag(R)(dMag) - Observatory
2025 Dec. 27.189 17.86 (0.08) - Siena
2026 Jan. 02.355 17.81 (0.06) - MarSEC
2026 Jan. 11.846 17.89 (0.04) - MarSEC
2026 Jan. 13.918 17.90 (0.14) - Gal Hassin
2026 Jan. 18.215 17.72 (0.11) - Siena
2026 Jan. 20.869 17.69 (0.07) - MarSEC
2026 Jan. 22.200 17.49 (0.08) - Siena
2026 Jan. 31.928 17.37 (0.07) - Siena
2026 Feb. 01.933 17.48 (0.11) - Siena
2026 Feb. 17.897 17.38 (0.05) - MarSEC
2026 Feb. 20.787 17.57 (0.09) - Siena
2026 Feb. 21.781 17.48 (0.09) - Siena
2026 Mar. 07.899 16.25 (0.01) - MarSEC
2026 Mar 09.893 16.56 (0.04) - Siena
Reported uncertainty is statistical only.
As a reference, the most recent measurements are approximately 1 mag brighter than those recorded just two weeks ago, but fainter than the record R-band magnitude of 14.96 observed in March 2023.
Observations were conducted from the 0.30 m telescope of the Astronomical Observatory of the University of Siena (Siena, Italy - IAU MPC observatory code K54), the 0.36 m telescope of the Marana Space Explorer Centre (MarSEC, Vicenza, Italy) and the 0.40 m telescope of the GAL Hassin - Centro Internazionale per le Scienze Astronomiche (Isnello, Palermo, Italy - L34).
Any inquiry on these observations can be addressed either to Alessandro Marchini (marchini@unisi.it) or to Gaia Verna (gaia.verna@unisi.it). We will continue monitoring the source in the following nights. Multi-wavelength follow-up is strongly encouraged.
Brief descriptions of the instrumental setups used for the reported observations are available at the official webpage of the
Astronomical Observatory of the University of Siena, on the website of the
MarSEC - Marana Space Explorer Center and on the page of the
GAL Hassin - Centro Internazionale per le Scienze Astronomiche.
Astronomical Observatory of the University of Siena - Official Webpage
