VERITAS discovery of very high energy gamma-ray emission from S3 1227+25 and multiwavelength observations
Creators: name: Acharyya, A.
name: Adams, C. B.
name: Archer, A.
name: Bangale, P.
name: Benbow, W.
name: Brill, A.
name: Christiansen, J. L.
name: Chromey, A. J.
name: Errando, M.
name: Falcone, A.
name: Feng, Q.
name: Finley, J. P.
name: Foote, G. M.
name: Fortson, L.
name: Furniss, A.
name: Gallagher, G.
name: Hanlon, W.
name: Hanna, D.
name: Hervet, O.
name: Hinrichs, C. E.
name: Hoang, J.
name: Holder, J.
name: Jin, W.
name: Johnson, M. N.
name: Kaaret, P.
name: Kertzman, M.
name: Kieda, D.
name: Kleiner, T. K.
name: Korzoun, N.
name: Krennrich, F.
name: Lang, M. J.
name: Lundy, M.
name: Maier, G.
name: McGrath, C. E.
name: Millard, M. J.
name: Millis, J.
name: Mooney, C. L.
name: Moriarty, P.
name: Mukherjee, R.
name: O'Brien, S.
name: Ong, R. A.
name: Pohl, M.
name: Pueschel, E.
name: Quinn, J.
name: Ragan, K.
name: Reynolds, P. T.
name: Ribeiro, D.
name: Roache, E.
name: Sadeh, I.
name: Sadun, A. C.
name: Saha, L.
name: Santander, M.
name: Sembroski, G. H.
name: Shang, R.
name: Splettstoesser, M.
name: Talluri, A. Kaushik
name: Tucci, J. V.
name: Vassiliev, V. V.
name: Williams, D. A.
name: Wong, S. L.
name: Hovatta, Talvikki
name: Jorstad, Svetlana G.
name: Kiehlmann, Sebastian
name: Lähteenmäki, Anne
name: Liodakis, Ioannis
name: Marscher, Alan P.
name: Max-Moerbeck, Walter
name: Readhead, Anthony C. S.
name: Reeves, Rodrigo
name: Smith, Paul S.
name: Tornikoski, Merja
name: VERITAS Collaboration
Publisher: name: Deutsches Elektronen-Synchrotron, DESY, Hamburg
Year: 2023
Subjects: gamma ray: VHE
gamma ray: emission
gamma ray: flux
emission: model
detector: imaging
polarization: monitoring
VERITAS
GeV
optical
correlation
spectral
variability
power spectrum
blazar
photon
spectral energy distribution
GLAST
synchrotron

description: We report the detection of very high energy gamma-ray emission from the blazar S3 1227+25 (VER J1230+253) with the Very Energetic Radiation Imaging Telescope Array System (VERITAS). VERITAS observations of the source were triggered by the detection of a hard-spectrum GeV flare on May 15, 2015 with the Fermi-Large Area Telescope (LAT). A combined five-hour VERITAS exposure on May 16th and May 18th resulted in a strong 13$\sigma$ detection with a differential photon spectral index, $\Gamma$ = 3.8 $\pm$ 0.4, and a flux level at 9% of the Crab Nebula above 120 GeV. This also triggered target of opportunity observations with Swift, optical photometry, polarimetry and radio measurements, also presented in this work, in addition to the VERITAS and Fermi-LAT data. A temporal analysis of the gamma-ray flux during this period finds evidence of a shortest variability timescale of $\tau_{obs}$ = 6.2 $\pm$ 0.9 hours, indicating emission from compact regions within the jet, and the combined gamma-ray spectrum shows no strong evidence of a spectral cut-off. An investigation into correlations between the multiwavelength observations found evidence of optical and gamma-ray correlations, suggesting a single-zone model of emission. Finally, the multiwavelength spectral energy distribution is well described by a simple one-zone leptonic synchrotron self-Compton radiation model.