One of the major challenges for pulsar timing array ( PTA ) experiments is the mitigation of the effects of the turbulent interstellar medium ( ISM ) from timing data .
These can potentially lead to measurable delays and/or distortions in the pulse profiles and scale strongly with the inverse of the radio frequency .
Low-frequency observations are therefore highly appealing for characterizing them .
However , in order to achieve the necessary time resolution to resolve profile features of short-period millisecond pulsars , phase-coherent de-dispersion is essential , especially at frequencies below 300 MHz .
We present the lowest-frequency ( 80 - 220 MHz ) , coherently de-dispersed detections of one of the most promising pulsars for current and future PTAs , PSR J2241 - 5236 , using our new beam-former software for the MWA ’ s voltage capture system ( VCS ) , which reconstructs the time series at a much higher time resolution of \sim 1 \mu s by re-synthesizing the recorded voltage data at 10 -kHz/ 100 - \mu s native resolutions .
Our data reveal a dual-precursor type feature in the pulse profile that is either faint or absent in high-frequency observations from Parkes .
The resultant high-fidelity detections have enabled dispersion measure ( DM ) determinations with very high precision , of the order of ( 2 - 6 ) \times 10 ^ { -6 } pc cm ^ { -3 } , owing to the microsecond level timing achievable for this pulsar at the MWA ’ s low frequencies .
This underscores the usefulness of low-frequency observations for probing the ISM toward PTA pulsars and informing optimal observing strategies for PTA experiments .