This publication makes use of data from the Indian astronomy mission AstroSat;
archived at the Indian Space Science Data Centre (ISSDC). The CZT Imager instrument was built by a TIFR-led consortium of institutes across India;
including VSSC;
ISAC;
IUCAA;
SAC;
and PRL. The Indian Space Research Organisation funded;
managed and facilitated the project. We thank the staff of the Ooty Radio Telescope and the Giant Meterwave Radio Telescope for taking observations over such a large number of epochs. Both these telescopes are operated by National Centre for Radio Astrophysics of Tata Institute of Fundamental Research. PONDER backend;
used in this work;
was built with TIFR XII plan grants 12P0714 and 12P0716. We would like to thank the anominous referee for his/her useful comments and suggestions. AB would like to thank Alessandro Ridolfi for exposing to various techniques of PSRCHIVE package and Surajit Mondal for various fruitful discussions related to computational issues. We also thank Yogesh Maan for his valuable suggestions. BCJ;
PKM and MAK acknowledges support for this work from DSTSERB grant EMR/2015/000515.was built with TIFR XII plan grants 12P0714 and 12P0716. We would like to thank the anominous referee for his/her useful comments and suggestions. AB would like to thank Alessandro Ridolfi for exposing to various techniques of PSRCHIVE package and Surajit Mondal for various fruitful discussions related to computational issues. We also thank Yogesh Maan for his valuable suggestions. BCJ;
PKM and MAK acknowledges support for this work from DST-SERB grant EMR/2015/000515;