2022ApJ...936...86S

Modeling of frequency-dependent effects, contributed by the turbulence in the free electron density of interstellar plasma, is required to enable the detection of the expected imprints from the stochastic gravitational-wave (GW) background in pulsar timing data. In this work, we present an investigation of temporal variations of interstellar medium for a set of millisecond pulsars (MSPs) with the upgraded Giant Metrewave Radio Telescope (GMRT) aided by large fractional bandwidth at lower observing frequencies. Contrary to the conventional narrowband analysis using a frequency-invariant template profile, we applied PulsePortraiture-based wide-band timing analysis while correcting for the evolution of the pulsar profile with frequency. Implementation of the PulsePortraiture-based wide-band timing method for the GMRT-discovered MSPs to probe the dispersion measure (DM) variations resulted in a DM precision of 10^–4 pc cm^–3. In general, we achieve similar DM and timing precision from wide-band timing compared to the narrowband timing with matching temporal variations of DMs. This wide-band timing study of newly discovered MSPs over a wide frequency range highlights the effectiveness of profile modeling at low frequencies and probes the potential of using them in a pulsar timing array.