Multiwavelength observations of the blazar BL Lacertae: A new fast TeV γ-ray flare

VERITAS Collaboration

Research output: Contribution to journalConference articlepeer-review


Observations of fast TeV γ-ray flares from blazars reveal the extreme compactness of emitting regions in blazar jets. Combined with very-long-baseline radio interferometry measurements, they probe the structure and emission mechanism of the jet. We report on a fast TeV γ-ray flare from BL Lacertae observed by VERITAS, with a rise time of about 2.3 hours and a decay time of about 36 minutes. The peak flux at >200 GeV measured with the 4-minute binned light curve is (4.2 ±0.6) × 10-6 photons m-2 s-1, or ∼180% the Crab Nebula flux. Variability in GeV γ-ray, X-ray, and optical flux, as well as in optical and radio polarization was observed around the time of the TeV γ-ray flare. A possible superluminal knot was identified in the VLBA observations at 43 GHz. The flare constrains the size of the emitting region, and is consistent with several theoretical models with stationary shocks.

Original languageEnglish (US)
JournalProceedings of Science
StatePublished - 2017
Event35th International Cosmic Ray Conference, ICRC 2017 - Bexco, Busan, Korea, Republic of
Duration: Jul 10 2017Jul 20 2017

ASJC Scopus subject areas

  • General


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