WISE view of Narrow-Line Seyfert 1 galaxies: mid-infrared color and
  variability
  We present the color and flux variability analysis at 3.4 {\mu}m (W1-band)
and 4.6 {\mu}m (W 2-band) of 492 narrow-line Seyfert 1 (NLSy1) galaxies using
archival data from the Wide-field Infrared Survey Explorer (WISE). In the WISE
color-color, (W1 - W2) versus (W2 - W3) diagram, ~58% of the NLSy1 galaxies of
our sample lie in the region occupied by the blazar category of active galactic
nuclei (AGN). The mean W1 - W2 color of candidate variable NLSy1 galaxies is
$0.99 \pm 0.18$ mag. The average amplitude of variability is $0.11 \pm 0.07$
mag in long-term (multi-year) with no difference in variability between W1 and
W2-bands. The W1 - W2 color of NLSy1 galaxies is anti-correlated with the
relative strength of [O III] to H{\beta}, strongly correlated with continuum
luminosity, black hole mass, and Eddington ratio. The long-term amplitude of
variability shows weak anti-correlation with the Fe II strength, continuum
luminosity and Eddington ratio. A positive correlation between color as well as
the amplitude of variability with the radio power at 1.4 GHz was found for the
radio-detected NLSy1 galaxies. This suggests non-thermal synchrotron
contribution to the mid-infrared color and flux variability in radio-detected
NLSy1 galaxies.
