Preparing high-precision PTA data sets for nano-Hertz GW Astronomy

Maturing Pulsar Timing Arrays (PTAs) are expected to expedite the detection of nano-Hertz gravitational waves (GWs) under the auspices of the International PTA (IPTA) consortium. This consortium plans to combine data from around 80 milli-second pulsars (MSPs) and resources from different PTA experiments for its Data Release 3 (IPTA DR3) to begin the low-frequency GW Astronomy era. Indian PTA (InPTA), the latest entrant to the IPTA consortium, has made the first official data release (DR1) of 14 MSPs, observed simultaneously in 300-500 MHz (Band 3) and 1260-1460 MHz (Band 5) frequency bands using TIFR's uGMRT to contribute to various IPTA efforts. The next crucial milestone for the InPTA collaboration is its second data release (DR2) of five-year long GMRT data set for 29 MSPs. I will present my contributions towards the InPTA DR1 and ongoing efforts for InPTA DR2, particularly, in estimating a series of pulsar Time of Arrival (ToA) and Dispersion measures (DM). I will also present Multiband extensions of the standard Wideband timing technique, where two novel independent methods are developed to combine simultaneous multi-band pulsar data incorporating profile evolution over a larger frequency span to estimate DMs and ToAs with enhanced precision. This technique is expected to be a pathfinder for combining (quasi) simultaneously observed MSP data sets of two telescopes. Thereafter, I will discuss my contributions to the ongoing IPTA activities; specifically, preparing its early data release (EDR3) by combining data sets of various PTAs. I will also present our ongoing pilot effort to observe MSPs quasi-simultaneously using the uGMRT and MeerKAT telescopes, together covering a large frequency range from 300 MHz to 1700MHz. Our pilot study would provide directions for combining the data from distinct arrays for the SKA era using the low and high-frequency observations.