| Abstract: | 1ES 1011+496 $(z=0.212)$ was discovered in very high energy (VHE, E >100 GeV)
$gamma$-rays with MAGIC in 2007. The absence of simultaneous data at lower
energies led to a rather incomplete characterization of the broadband spectral
energy distribution (SED). We study the source properties and the emission
mechanisms, probing whether a simple one-zone synchrotron-self-Compton (SSC)
scenario is able to explain the observed broadband spectrum. We analyzed VHE to
radio data from 2011 and 2012 collected by MAGIC, $Fermi$-LAT, $Swift$, KVA,
OVRO, and Mets"{a}hovi in addition to optical polarimetry data and radio maps
from the Liverpool Telescope and MOJAVE. The VHE spectrum was fit with a simple
power law with a photon index of $3.69pm0.22$ and a flux above 150 GeV of
$(1.46pm0.16) imes10^{-11}$ ph cm$^{-2}$ s$^{-1}$. 1ES 1011+496 was found to
be in a generally quiescent state at all observed wavelengths, showing only
moderate variability from radio to X-rays. A low degree of polarization of less
than 10\% was measured in optical, while some bright features polarized up to
60\% were observed in the radio jet. A similar trend in the rotation of the
electric vector position angle was found in optical and radio. The radio maps
indicated a superluminal motion of $1.8pm0.4,c$, which is the highest speed
statistically significantly measured so far in a high-frequency-peaked BL Lac.
For the first time, the high-energy bump in the broadband SED of 1ES 1011+496
could be fully characterized from 0.1 GeV to 1 TeV which permitted a more
reliable interpretation within the one-zone SSC scenario. The polarimetry data
suggest that at least part of the optical emission has its origin in some of
the bright radio features, while the low polarization in optical might be due
to the contribution of parts of the radio jet with different orientations of
the magnetic field to the optical emission. |
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