VERITAS Observations of the BL Lac Object TXS 0506+056

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IOP Publishing

On 2017 September 22, the IceCube Neutrino Observatory reported the detection of the high-energy neutrino event IC 170922A, of potential astrophysical origin. It was soon determined that the neutrino direction was consistent with the location of the gamma-ray blazar TXS 0506+056. (3FGL J0509.4+ 0541), which was in an elevated gamma-ray emission state as measured by the Fermi satellite. Very Energetic Radiation Imaging Telescope Array System (VERITAS) observations of the neutrino/blazar region started on 2017 September 23 in response to the neutrino alert and continued through 2018 February 6. While no significant very-high-energy (VHE; E > 100 GeV) emission was observed from the blazar by VERITAS in the two-week period immediately following the IceCube alert, TXS 0506+ 056 was detected by VERITAS with a significance of 5.8 standard deviations (sigma) in the full 35 hr data set. The average photon flux of the source during this period was (8.9 +/- 1.6). x. 10(-12) cm(-2) s(-1), or 1.6% of the Crab Nebula flux, above an energy threshold of 110 GeV, with a soft spectral index of 4.8. +/-. 1.3.

astroparticle physics, BL Lacertae objects: individual (TXS 0506+056, VER J0509+057), gamma rays: galaxies, quasars: general, neutrinos, RADIATION, I., Astronomy & Astrophysics
Abeysekara, A.U., et al. (2018): VERITAS Observations of the BL Lac Object TXS 0506+056. The Astrophysical Journal Letters, 861(2). DOI: