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 crosscorrelation 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 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 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 τ-M V plane indicates that our results are in excellent agreement with the now known lag-luminosity scaling relationship for dust in AGN.

Narrow line Seyfert 1 galaxies (NLS1s) are believed to be powered by accretion of matter onto low mass black holes (BHs) in spiral host galaxies with BH masses M BH ∼ 10 6 -10 8 M . However, the broad band spectral energy distribution of the γ-ray emitting NLS1s are found to be similar to flat spectrum radio quasars. This challenges our current notion of NLS1s having low M BH . To resolve this tension of low M BH values in NLS1s, we fitted the observed optical spectrum of a sample of radio-loud NLS1s (RL-NLS1s), radio-quiet NLS1s (RQ-NLS1s) and radio-quiet broad line Seyfert 1 galaxies (RQ-BLS1s) of ∼500 each with the standard Shakura-Sunyaev accretion disk (AD) model. For RL-NLS1s we found a mean log(M AD BH /M ) of 7.98±0.54. For RQ-NLS1s and RQ-BLS1s we found mean log(M AD BH /M ) of 8.00±0.43 and 7.90±0.57, respectively. While the derived M AD BH values of RQ-BLS1s are similar to their virial masses, for NLS1s the derived M AD BH values are about an order of magnitude larger than their virial estimates. Our analysis thus indicates that NLS1s have M BH similar to RQ-BLS1s and their available virial M BH values are underestimated influenced by their observed relatively small emission line widths. Considering Eddington ratio as an estimation of the accretion rate and using M AD BH , we found the mean accretion rate of our RQ-NLS1s, RL-NLS1s and RQ-BLS1s as 0.06 +0.16 −0.05 , 0.05 +0.18 −0.04 and 0.05 +0.15 −0.04 , respectively. Our results therefore suggest that NLS1s have BH masses and accretion rates similar to BLS1s.