VERITAS Observations of the BL Lac Object TXS 0506+056
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.
- Publication:
-
The Astrophysical Journal
- Pub Date:
- July 2018
- DOI:
- 10.3847/2041-8213/aad053
- arXiv:
- arXiv:1807.04607
- Bibcode:
- 2018ApJ...861L..20A
- Keywords:
-
- astroparticle physics;
- BL Lacertae objects: individual: TXS 0506+056;
- VER J0509+057;
- gamma rays: galaxies;
- quasars: general;
- neutrinos;
- Astrophysics - High Energy Astrophysical Phenomena
- E-Print:
- ApJL 2018