MAGIC long-term study of the distant TeV blazar PKS 1424+240 in a
  multiwavelength context
  We present a study of the very high energy (VHE; E > 100 GeV) gamma-ray
emission of the blazar PKS 1424+240 observed with the MAGIC telescopes. The
primary aim of this paper is the multiwavelength spectral characterization and
modeling of this blazar, which is made particularly interesting by the recent
discovery of a lower limit of its redshift of z > 0.6 and makes it a promising
candidate to be the most distant VHE source. The source has been observed with
the MAGIC telescopes in VHE gamma rays for a total observation time of ~33.6 h
from 2009 to 2011. The source was marginally detected in VHE gamma rays during
2009 and 2010, and later, the detection was confirmed during an optical
outburst in 2011. The combined significance of the stacked sample is ~7.2
sigma. The differential spectra measured during the different campaigns can be
described by steep power laws with the indices ranging from 3.5 +/- 1.2 to 5.0
+/- 1.7. The MAGIC spectra corrected for the absorption due to the
extragalactic background light connect smoothly, within systematic errors, with
the mean spectrum in 2009-2011 observed at lower energies by the Fermi-LAT. The
absorption-corrected MAGIC spectrum is flat with no apparent turn down up to
400 GeV. The multiwavelength light curve shows increasing flux in radio and
optical bands that could point to a common origin from the same region of the
jet. The large separation between the two peaks of the constructed
non-simultaneous spectral energy distribution also requires an extremely high
Doppler factor if an one zone synchrotron self-Compton model is applied. We
find that a two-component synchrotron self-Compton model describes the spectral
energy distribution of the source well, if the source is located at z~0.6.
