| Abstract : | Since MSPs (Milli-second pulsars having spin period ≤ 30 ms) are intrinsically faint sources combined with lack of availability of sensitive wide-band observing facilities until about last decade (before upgraded GMRT, UWL receiver for Parkes, LOFAR came online), simultaneous multi-frequency study of spectra (as well as other properties) for MSPs is still in its infancy as compared to normal pulsars. Due to the observed diversity of spectral properties of MSPs, and in absence of systematic flux measurements for a large sample of MSPs, it is not
possible to draw a firm conclusion from the comparison of the spectra of MSPs and ordinary pulsars. The sensitivity of the GMRT aided with wide band width observing facility makes it the premier instrument for investigation of MSPs in the southern sky. We will present the investigation of spectral index variation for some of the MSPs discovered by the GMRT. We investigated temporal variation of the spectral index for the folded profile and pulse phase resolved spectral index variations for some of the MSPs discovered by the GMRT that were monitored regularly over last few years. For example for PSR J2144-5237, discovered with
the GMRT, we investigated the spectra for multiple observing epochs (in band-3, band-4 and band-5) and found huge variations observed in the spectra for J2144-5237 at different epochs (e.g. ranging from -4 to -2 in band-5). Also we note that J2144-5237 has several profile components, and each have different spectral index. In addition, we will present single pulse study of spectral properties for some of the brightest MSPs using the uGMRT. These observations was taken simultaneously on band-3 (300-500 MHz, in coherent dedispersed mode) and on band-4 (550-750 MHz, in phased array mode). We will also explore the constraints that this study can put on MSP emission physics. |
