Multiwavelength Observations of the Blazar VER J0521+211 During an
  Elevated TeV Gamma-Ray State
  We report on a long-lasting, elevated gamma-ray flux state from VER J0521+211
observed by VERITAS, MAGIC, and Fermi-LAT in 2013 and 2014. The peak integral
flux above 200 GeV measured with the nightly-binned light curve is $(8.8 \pm
0.4) \times 10^{-7} \;\text{ph}\;\text{m}^{-2}\; \text{s}^{-1}$, or ~37% of the
Crab Nebula flux. Multiwavelength observations from X-ray, UV, and optical
instruments are also presented. A moderate correlation between the X-ray and
TeV gamma-ray fluxes was observed, and the X-ray spectrum appeared harder when
the flux was higher. Using the gamma-ray spectrum and four models of the
extragalactic background light (EBL), a conservative 95% confidence upper limit
on the redshift of the source was found to be z<=0.31. Unlike the gamma-ray and
X-ray bands, the optical flux did not increase significantly during the studied
period compared to the archival low-state flux. The spectral variability from
optical to X-ray bands suggests that the synchrotron peak of the spectral
energy distribution (SED) may become broader during flaring states, which can
be adequately described with a one-zone synchrotron self-Compton model varying
the high-energy end of the underlying particle spectrum. The synchrotron peak
frequency of the SED, as well as the radio morphology of the jet from the
MOJAVE program, are consistent with the source being an
intermediate-frequency-peaked BL Lac object.
