| Abstract : | Due to the observed diversity of the spectral properties of millisecond pulsars (MSPs), and in the absence of systematic flux density measurements for large samples of MSPs, spectral studies of MSPs is still in its infancy. The recent development of wide bandwidth observing capability of telescopes (e.g. upgraded GMRT, Parkes UWL receiver etc) provides increased sensitivity which opens up opportunities to investigate spectra MSPs, possibly due its fainter nature. The sensitivity of the GMRT aided with wide bandwidth observing facility makes it a suitable instrument for investigation of MSPs. I will present the investigation of spectral index variation for 9 MSPs discovered by the GMRT spanning from 2018 to 2023, observed with the uGMRT in band 3 (300 - 500 MHz), band 4 (550 - 750 MHz). With the wider observing bandwidth, steep spectra are more prone to inaccurate estimation of band averaged flux density. Thus in case of wide band telescopes, the full band is divided into multiple subbands, and subband averaged flux density is calculated. My work is mainly devoted to extracting and quantifying the variation of flux density with the subband's central frequency. Scintillation plays an important role in the flux density variations. Hence, the broad enough subbands are chosen such that the diffractive scintillation gets averaged out for each subband. The in-band spectra will also help in modeling the companion’s environment of the binary systems along the line of sight. I observed huge temporal variations in the spectral indices and indication of turn-over in the observed spectra(which is not reported for MSPs as of now). However, the estimated flux densities will be modulated by scintillation, the quantification of scintillation on the in-band spectra will help us to disentangle the properties intrinsic to the pulsar emission mechanism to those contributed by ISM. |
