Determination of the size of the dust torus in H0507+164 through optical
  and infrared monitoring
  The time delay between flux variations in different wavelength bands can be
used to probe the inner regions of active galactic nuclei (AGN). Here, we
present the first measurements of the time delay between optical and
near-infrared (NIR) flux variations in H0507+164, a nearby Seyfert 1.5 galaxy
at z = 0.018. The observations in the optical V -band and NIR J, H and Ks bands
carried over 35 epochs during the period October 2016 to April 2017 were used
to estimate the inner radius of the dusty torus. From a careful reduction and
analysis of the data using cross-correlation techniques, we found delayed
responses of the J, H and Ks light curves to the V -band light curve. In the
rest frame of the source, the lags between optical and NIR bands are found to
be $27.1^{+13.5}_{-12.0}$ days (V vs. J), $30.4^{+13.9}_{-12.0}$ days (V vs. H)
and $34.6^{+12.1}_{-9.6}$ days (V vs. K ). The lags between the optical and
different NIR bands are thus consistent with each other. The measured lags
indicate that the inner edge of dust torus is located at a distance of 0.029 pc
from the central UV/optical AGN continuum. This is larger than the radius of
the broad line region of this object determined from spectroscopic monitoring
observations thereby supporting the unification model of AGN. The location of
H0507+164 in the {\tau} - MV plane indicates that our results are in excellent
agreement with the now known lag-luminosity scaling relationship for dust in
AGN.
