Strong multi-wavelength flaring activity from FSRQ OP 313 from optical to gamma rays
ATel #16979; Jorge Otero-Santos (INFN-Padova), Giacomo Bonnoli (INAF), Jose A. Acosta-Pulido (IAC), Axel Arbet-Engels (MPI-Physics), Mireia Nievas Rosillo (IAC), Fabio Acero (FSLAC, CNRS/IAC), Ivan Agudo (IAA-CSIC), Juan Escudero Pedrosa (CfA Harvard), Daniel Morcuende (IAA-CSIC), Victor Casanova (IAA-CSIC), Alfredo Sota (IAA-CSIC), Francisco J. Aceituno (IAA-CSIC), S. Leonini (Montarrenti Observatory, Sovicille (Siena, Italy)), M. Conti (Montarrenti Observatory, Sovicille (Siena, Italy)), P. Rosi (Montarrenti Observatory, Sovicille (Siena, Italy)), L. M. Tinjaca Ramirez (Montarrenti Observatory, Sovicille (Siena, Italy)), Alessandro Marchini (Astronomical Observatory, University of Siena, Italy), Leonardo Stiaccini, (Department of Physical Sciences, Earth and Environment (DSFTA), University of Siena, Italy), Gaia Verna (Department of Physical Sciences, Earth and Environment (DSFTA), University of Siena, Italy), Ivo Peretto (MarSEC, Marana di Crespadoro, Vicenza, Italy), Giovanni Furlato (MarSEC, Marana di Crespadoro, Vicenza, Italy), Stefano Lora (MarSEC, Marana di Crespadoro, Vicenza, Italy), Elina Lindfors (University of Turku), Pasi Nurmi (University of Turku)
on 15 Jan 2025; 16:25 UT
Credential Certification: Jorge Otero-Santos (jorge.otero@pd.infn.it)
Subjects: Optical, X-ray, Gamma Ray, >GeV, AGN, Blazar, Quasar
Following the bright very-high-energy gamma-ray activity reported by the MAGIC Collaboration (ATel #16977) for the flat spectrum radio quasar (FSRQ) OP 313 (also known as B2 1308+32), with coordinates R.A. = 197.619 deg, Dec. = +32.345 deg (J2000; Johnston et al., 1995) and located at redshift z = 0.997 (Schneider et al., 2010), we report enhanced activity in its multi-wavelength emission from optical to gamma rays.
All-sky Fermi-LAT observations from the public light curve repository (Abdollahi et al., 2023) show a sudden increase in the measured energy flux starting from December 1, 2024, reaching a historical maximum around January 6, 2025 (ATel #16970). At a peak energy flux of ~5e-9 erg/cm2/s with a photon index of ~1.6, it is the second most luminous flare from an AGN ever recorded by Fermi-LAT to date.
The X-ray follow-up was performed by Swift-XRT, revealing enhanced activity in the 0.3 to 10 keV band. The preliminary analysis suggests an energy flux of around 1.5-2.0 e-11 erg/cm2/s, with a de-absorbed index of 2.3-2.5 (January 5 to 12, 2025). This suggests that Swift-XRT is, at least partly, seeing the synchrotron component of OP 313.
Optical observations were also coordinated starting from January 9, showing the second brightest optical emission ever detected from OP 313, at the same level of a flare occurring in February 2024 and only after another high emission state in 2022. A preliminary evaluation of the optical spectrum yields a photon index of ~1.9. The measured magnitude values for each night are reported below. We report the average magnitudes over each night. Errors refer to statistical uncertainties only.
Date [MJD] - U (dU) - B (dB) - V (dV) - R (dR) - I (dI) - Instrument
60684.27 -- (--) 14.26 (0.05) -- (--) 13.50 (0.02) 13.03 (0.01) IAC80
60685.15 -- (--) -- (--) -- (--) 13.56 (0.09) -- (--) T90
60686.11 -- (--) -- (--) -- (--) 13.64 (0.06) -- (--) LCO-TFN0.4m
60687.12 13.50 (0.10) 14.10 (0.07) 13.71 (0.06) 13.29 (0.09) 12.88 (0.06) T90
60687.13 -- (--) -- (--) 13.70 (0.01) 13.36 (0.01) -- (--) Siena
60687.95 -- (--) -- (--) -- (--) 13.37 (0.01) -- (--) MarSEC
60688.12 -- (--) -- (--) 13.65 (0.01) 13.32 (0.01) -- (--) Siena
60688.17 -- (--) 14.12 (0.01) 13.64 (0.01) 13.31 (0.01) 12.82 (0.01) Montarrenti
60688.18 13.48 (0.11) 14.04 (0.08) 13.66 (0.06) 13.26 (0.08) 12.83 (0.05) T90
60688.21 -- (--) -- (--) -- (--) 13.29 (0.01) -- (--) Siena
Date [MJD] - u (du) - g (dg) - r (dr) - i (di) - z (dz) - Instrument
60688.17 14.10 (0.20) 13.83 (0.04) 13.50 (0.01) 13.28 (0.01) 13.13 (0.02) LT
60689.10 14.08 (0.20) 13.77 (0.04) 13.46 (0.01) 13.23 (0.01) 13.08 (0.02) LT
Optical observations were performed with the 90-cm T90 telescope at Sierra Nevada Observatory (SNO, Granada, Spain), the 80-cm IAC80 telescope at Teide Observatory (Tenerife, Spain), the Liverpool Telescope (LT) and Nordic Optical Telescope (NOT) at Roque de Los Muchachos Observatory (La Palma, Spain), the worldwide robotic telescope network of Las Cumbres Observatory (LCO), the 30-cm telescope at Siena Observatory, the 53-cm telescope at Montarrenti Observatory (Siena, Italy), and the 36-cm telescope at the Marana Space Explorer Center (MarSEC, Vicenza, Italy).
Finally, the optical observations performed at SNO and NOT also included polarimetric coverage, showing a large polarization degree reaching ~19%. Polarization variability down to the scale of hours has also been clearly detected. Reported values correspond to nightly averages.
Date[MJD] - P (dP) - EVPA (dEVPA) - Instrument
60685.17 10.56 (0.52) 157.4 (1.4) T90
60687.18 5.34 (0.52) 150.4 (1.9) T90
60687.28 7.99 (0.08) 151.3 (0.3) NOT
60688.10 17.37 (0.57) 150.9 (0.9) T90
Follow-up observations are encouraged during this high multi-wavelength activity period.
