2020 MWA Virtual Project Meeting

Dispersion measure investigation towards millisecond pulsars with the MWA

17 Jul 2020, 14:00

20m

VCS Science

Speaker

Dilpreet Kaur (Curtin University-ICRAR)

Description

With the ability to reconstruct high-time resolution voltage time series at microsecond ($\sim 0.78\mu$s) time resolution and perform phase-coherent de-dispersion, it has become possible to obtain high-fidelity detections of millisecond pulsars (MSPs) with the MWA. In combination with the large frequency lever arm provided by the MWA this allows measuring pulsar dispersion measures (DMs) at very high precision – almost an order of magnitude better than those currently achievable at conventional timing frequencies ($\sim 1-2$ GHz) for pulsar timing array (PTA) experiments. A particularly interesting target is PSR J$2241$-$5236$, a short period ($2.18$ ms) MSP in a $3.5$-hour, almost circular orbit with a low-mass ($\sim 0.01$ M${}_{\odot }$), white dwarf companion. In this talk, I will present results from our recent measurements from the MWA observations that span the full orbit, and analysis of DM variations to investigate any likely orbital modulations of DM that may be caused by the companion’s winds. I will also present new results from our recent multi-telescope observing campaign undertaken with the MWA, GMRT, and Parkes telescopes to investigate recently theorised chromaticity (frequency dependence) in pulsar DM, which is thought to arise as a consequence of multi-path propagation effects. Much of this analysis is focused on data for MSPs J$2241$-$5236$ and J$2145$-$0750$. These analyses and results also showcase the importance of low-frequency observations in the larger context of global PTA efforts.