MAGIC and H.E.S.S. detect VHE gamma rays from the blazar OT081 for the first time: a deep multiwavelength study


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Discussion timeslot (ZOOM-Meeting): 13. July 2021 - 18:00
ZOOM-Meeting URL:
ZOOM-Meeting ID: 98542982538
ZOOM-Meeting Passcode: ICRC2021
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'OT081 is a luminous blazar well known for its variability in many energy bands.rnThe very-high-energy (VHE, E larger 100 GeV) gamma-ray emission from the source was discovered by MAGIC and H.E.S.S. during flaring activity in July 2016, after a trigger from the LAT onboard the Fermi satellite.rnFrom the analysis of the multiwavelength (MWL) light curves and of the broadband spectral energy distribution (SED), we study the activity of the source, in particular during four identified states of activity in the window MJD 57575 to MJD 57600. The intrinsic gamma-ray spectrum can be described by a power law with spectral indices of 3.27+/- 0.44 (MAGIC) and 3.39 +/- 0.58 (H.E.S.S.) for energy ranges 60-300 GeV and 120-500 GeV, respectively.rnThe combined contemporaneous HE (E larger 100 MeV) through VHE SED shows curvature and can be described by a log-parabola shape.rnVLBI analysis of the flare reveals the ejection of a superluminal knot and its subsequent passage through a stationary feature as a possible cause of the HE gamma-ray activity.rnA simple one-zone synchrotron self-Compton (SSC) model is not sufficient to describe the broadband SED, and external Compton is required to explain the high Compton dominance displayed by the source.rnThe presence of broad emission lines in the optical spectrum of the source challenges the categorization of OT081 as a BL Lac and, together with the emission scenarios tested, points to the possibility that the source is transitional in nature between a BL Lac and a flat spectrum radio quasar (FSRQ).'

Authors: Marina Manganaro
Co-Authors: Monica Seglar Arroyo | Josefa Becerra González | David Sanchez | Matteo Cerruti | Vandad Fallah Ramazani | Fabrizio Tavecchio | Ivan Agudo | Stefano Ciprini | A Esteban-Guiterrez | A. V. Filippenko | Talvikki Hovatta | Helena Jermak | Svetlana Jorstad | Alan Marscher | E.N. Kopatskaya | Anne Laahteenmaaki | V.M. Larionov | L.V. Larionova | D.A. Morozova | Merja Tornikoski | Yu. V. Troitskaya | I. Troitsky | Francesco Verrecchia | Z. R. Weaver | H. B. Xiao | for the MAGIC, H.E.S.S. and Fermi-LAT Collaborations
Collaboration: MAGICH.E.S.S., Fermi-LAT

Indico-ID: 516
Proceeding URL:

Presenter: Marina Manganaro

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