REMAP: Determination of the inner edge of the dust torus in AGN by
  measuring time delays
  Active galactic nuclei (AGN) are high luminosity sources powered by accretion
of matter onto SMBHs located at the centres of galaxies. The SMBH is surrounded
by a broad emission line region (BLR) and a dusty torus. It is difficult to
study the extent of the dusty torus as the central region of AGN is not
resolvable using any conventional imaging techniques available today. Though,
current IR interferometric techniques could in principle resolve the torus in
nearby AGN, it is very expensive and limited to few bright and nearby AGN. A
more feasible alternative to the interferometric technique to find the extent
of the dusty torus in AGN is the technique of reverberation mapping (RM). REMAP
(REverberation Mapping of AGN Program) is a long term photometric monitoring
program being carried out using the 2 m HCT operated by the IIA, Bangalore,
aimed at measuring the torus size in many AGN using the technique of RM. It
involves accumulation of suitably long and well sampled light curves in the
optical and near-infrared bands to measure the time delays between the light
curves in different wavebands. These delays are used to determine the radius of
the inner edge of the dust torus. REMAP was initiated in the year 2016 and
since then about one hour of observing time once every five days (weather
permitting) has been allocated at the HCT. Our initial sample carefully
selected for this program consists of a total of 8 sources observable using the
HCT. REMAP has resulted in the determination of the extent of the inner edge of
the dusty torus in one AGN namely H0507+164. Data accumulation for the second
source is completed and observations on the third source are going on. We will
outline the motivation of this observational program, the observational
strategy that is followed, the analysis procedures adopted for this work and
the results obtained from this program till now.
