An alternative scheme to estimate AstroSat/LAXPC background for faint sources

An alternative scheme is described to estimate the layer 1 LAXPC 20 background for faint sources where source contribution 50-80 keV count rate less than 0.25 counts/sec (15 milli-crabs or $6 \times 10^{-11}$ ergs/s/cm$^2$). We consider 12 blank sky observations and based on their in 100 second time-bins, generate four template spectra which are then used spectrum lightcurve a given observation. The variance of estimated subtracted taken as energy dependent systematic uncertainty will dominate over statistical one exposures longer 5 ksecs. time bin 4-20 band with 3\% error matches ones. can be constrained flux $\gtrapprox 1$ milli-crab. Fractional r.m.s variability 10\% determined $\sim 5$ milli-crab binned at seconds. To illustrate scheme, lightcurves, three different observations, AGN (Mrk 0926, Mrk 110, NGC 4593), LMC X-1 shown.