VERITAS Observations of the BL Lac Object TXS 0506+056

July 2018 • 2018ApJ...861L..20A

Authors • Abeysekara, A. U. • Archer, A. • Benbow, W. • Bird, R. • Brill, A. • Brose, R. • Buckley, J. H. • Christiansen, J. L. • Chromey, A. J. • Daniel, M. K. • Falcone, A. • Feng, Q. • Finley, J. P. • Fortson, L. • Furniss, A. • Gillanders, G. H. • Gueta, O. • Hanna, D. • Hervet, O. • Holder, J. • Hughes, G. • Humensky, T. B. • Johnson, C. A. • Kaaret, P. • Kar, P. • Kelley-Hoskins, N. • Kertzman, M. • Kieda, D. • Krause, M. • Krennrich, F. • Lang, M. J. • Moriarty, P. • Mukherjee, R. • O'Brien, S. • Ong, R. A. • Otte, A. N. • Park, N. • Petrashyk, A. • Pohl, M. • Pueschel, E. • Quinn, J. • Ragan, K. • Reynolds, P. T. • Richards, G. T. • Roache, E. • Rulten, C. • Sadeh, I. • Santander, M. • Scott, S. S. • Sembroski, G. H. • Shahinyan, K. • Tyler, J. • Wakely, S. P. • Weinstein, A. • Wells, R. M. • Wilcox, P. • Wilhelm, A. • Williams, D. A. • Williamson, T. J. • Zitzer, B. • VERITAS Collaboration • Kaur, A.

Abstract • 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 (σ) in the full 35 hr data set. The average photon flux of the source during this period was (8.9 ± 1.6) × 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.

Links

• SIMBAD http://simbad.u-strasbg.fr/simbo.pl?bibcode=2018ApJ...861L..20A
• PDF https://iopscience.iop.org/article/10.3847/2041-8213/aad053/pdf
• PDF https://stacks.iop.org/2041-8205/861/L20/pdf
• NED https://ned.ipac.caltech.edu/uri/NED::InRefcode/2018ApJ...861L..20A
• PREPRINT http://arxiv.org/abs/1807.04607
• ELECTR https://doi.org/10.3847%2F2041-8213%2Faad053