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The North American Nanohertz Observatory for Gravitational Waves (NANOGrav)project has the primary goal of detecting and characterizing low-frequencygravitational waves through high-precision pulsar timing. The mitigation ofinterstellar effects is crucial to achieve the necessary precision forgravitational wave detection. Effects like dispersion and scattering are moreinfluential at lower observing frequencies, with the variation of thesequantities over week-month timescales requiring high-cadence multi-frequencyobservations for pulsar timing projects. In this work, we utilize thedual-frequency observing capability of the Giant Metrewave Radio Telescope(GMRT) and evaluate the potential decrease in dispersion measure (DM)uncertainties when combined with existing pulsar timing array data. We presentthe timing analysis for four millisecond pulsars observed with the GMRTsimultaneously at 322 and 607 MHz, and compare the DM measurements with thoseobtained through NANOGrav observations with the Green Bank Telescope (GBT) andArecibo Observatory at 1400 to 2300 MHz frequencies. Measured DM values withthe GMRT and NANOGrav program show significant offsets for some pulsars, whichcould be caused by pulse profile evolution in the two frequency bands. Incomparison to the predicted DM uncertainties when incorporating theselow-frequency data into the NANOGrav dataset, we find that higher-precisionGMRT data is necessary to provide improved DM measurements. Through thedetection and analysis of pulse profile baseline ripple in data on test pulsarB1929+10, we find that, while not important for this data, it may be relevantfor other timing datasets. We discuss the possible advantages and challenges ofincorporating GMRT data into NANOGrav and International Pulsar Timing Arraydatasets.

Evaluating Low-Frequency Pulsar Observations to Monitor Dispersion with the Giant Metrewave Radio Telescope