The GMRT High Resolution Southern Sky Survey for pulsars and transients -- V: Localisation of two millisecond pulsars

TL;DR

This paper reports the precise localization of two millisecond pulsars discovered by the GMRT survey using an upgraded correlator, enabling detailed timing and profile studies crucial for gravitational wave detection efforts.

Contribution

The paper introduces an upgraded 33 MHz correlator for the GMRT, achieving arc-second localization of MSPs, and demonstrates improved timing precision and profile analysis across multiple frequencies.

Findings

Achieved arc-second localization of two MSPs.

Obtained sub-microsecond timing precision.

Analyzed profile evolution over 300-1460 MHz.

Abstract

The timing follow-up of newly discovered millisecond pulsars (MSPs) is hindered by the larger positional uncertainty (a few tens of arc-minutes) associated with the discovery. In this paper, we present the localization of two MSPs, discovered by the GMRT High Resolution Southern Sky (GHRSS) survey, up to arc-second accuracy using a 33~MHz offline coherently dedispersed gated correlator. This gated correlator is an upgraded version of the earlier 16~MHz design. This new development with a factor of two enhancement in the observing bandwidth offers better sensitivity in the image domain, leading to more precise localization. Aided by the precise position, we followed up these two MSPs with sensitive phased-array (PA) beams of upgraded GMRT from 300 to 1460 MHz. More sensitive observations in the PA mode for these two MSPs yield precise ($\sim$ sub-$\mu s$) time-of-arrivals, with DM uncertainties in the range of $10^{-4}-10^{-5}$ $pc\,cm^{-3}$. We also report the profile evolution of the two MSPs over 300$-$1460 MHz. Finally, we discuss the suitability of these MSPs for the pulsar timing array experiments aimed to detect low-frequency gravitational waves.