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 K _ { s } 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 K _ { s } 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 } \mathrm { days } ( V vs . J ) , 30.4 ^ { +13.9 } _ { -12.0 } \mathrm { days } ( V vs . H ) and 34.6 ^ { +12.1 } _ { -9.6 } \mathrm { days } ( V vs . K _ { s } ) .
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 - M _ { V } plane indicates that our results are in excellent agreement with the now known lag-luminosity scaling relationship for dust in AGN .