Oral Presentation
The localisation of pulsars with the GMRT
Presenter: Shyam Sunder (Academia Sinica Institute of Astronomy and Astrophysics/ASIAA)
We present the deployment of a 33 MHz offline gated imaging correlator for the GMRT, as well
as its use in localizing newly discovered pulsars. This gated correlator is an upgrade of the
previous 16 MHz design.
The GMRT High-Resolution Southern Sky (GHRSS) survey has discovered ~30 pulsars so far.
We can only determine the rotational and astrometric properties of these newly discovered
pulsars after their follow-up studies, which require precise localization within a few arcseconds.
However, the positional uncertainties achieved at the time of pulsar discovery are within tens of
arc minutes for the GHRSS survey at 400 MHz. Pulsar timing follow-up can yield precise
positions, but it takes more than a year to minimize the covariance between astrometric and
other timing parameters. However, in pulsar gating, where the visibilities are folded with pulsar
timing ephemeris binning over the pulse longitudes, we can localize pulsars in a few arcseconds
with gated imaging in a single observation. We use the off-pulse subtracted gated image to
eliminate all other continuum sources, resulting in unambiguous pulsed emission localization.
Using this upgraded correlator, we recently located four pulsars, including two-millisecond
pulsars, one mildly recycled pulsar, and one long-period pulsar. The pulsars have been localized
within one arcsec using gated imaging and multiple PA beam formation techniques.
We also discuss the future aspects of enhancing the bandwidth of the offline-gated correlator
from 33 MHz to 200 MHz to localize even fainter pulsars and Fast Radio Bursts.
asiaa.sinica.edu.tw