摘要：We report the detection of millimeter-wavelength intraday variability in polarized
emission from S5 0716+714 based on multifrequency polarization observations using the
Korean VLBI Network (KVN) radio telescopes. The observations were conducted on November 7,
2013 at 22, 43, and 86 GHz in dual polarization using two 21 m radio telescopes belonging
to KVN Yonsei and Ulsan. We found significant variations in the degree of linear
polarization at 86 GHz and in polarization angle at 43 and 86 GHz during ~10 h. We measured mean flux densities
of 2.8 Jy, 2.8 Jy, and 2.7 Jy at 22, 43, and 86 GHz, respectively, with a flux modulation
index ranging from 1.5% to
7.2% at the frequencies. The
spectrum of the source is quite flat with spectral indices of −0.07 to 0.07 at 22−43 GHz and −0.23 to 0.04 at 43−86 GHz. The measured degree of the linear
polarization ranges from 2.3%
to 3.3% at 22 GHz from
0.9% to 2.2% at 43 GHz and from 0.4% to 4.0% at 86 GHz, yielding prominent variations
at 86 GHz over 4−5 h. The
linear polarization angle is in the range of 4° to 12°
at 22 GHz, −39° to 81° at 43 GHz, and 66° to 119° at 86 GHz with a maximum rotation of
110° at 43 GHz over
~4 h. We estimated the
Faraday rotation measures (RM) ranging from −9200 to 6300 rad m-2 between 22 and 43 GHz, and from −71 000 to 7300 rad m-2 between 43 and 86 GHz,
respectively. The frequency dependency of RM was investigated, yielding a mean power-law
index, a, of
2.0. This implies that the polarized emission from S5 0716+714 at 22−86 GHz moves through a Faraday screen in or
near the jet of the source.
