Coherently dedispersed gated imaging of millisecond pulsars

Abstract

Motivated by the need for rapid localisation of newly discovered faint millisecond pulsars (MSPs) we have developed a coherently dedispersed gating correlator. This gating correlator accounts for the orbital motions of MSPs in binaries while folding the visibilities with best-fit topocentric rotational model derived from periodicity search in simultaneously generated beamformer output. Unique applications of the gating correlator for sensitive interferometric studies of MSPs are illustrated using the Giant Metrewave Radio Telescope (GMRT) interferometric array. We could unambiguously localise five newly discovered Fermi MSPs in the on-off gated image plane with an accuracy of +-1". Immediate knowledge of such precise position allows the use of sensitive coherent beams of array telescopes for follow-up timing observations, which substantially reduces the use of telescope time (~ 20X for the GMRT). In addition, precise a-priori astrometric position reduces the effect of large covariances in timing fit (with discovery position, pulsar period derivative and unknown binary model), which in-turn accelerates the convergence to initial timing model. For example, while fitting with precise a-priori position (+-1"), timing model converges in about 100 days, accounting the effect of covariance between position and pulsar period derivative. Moreover, such accurate positions allows for rapid identification of pulsar counterpart at other wave-bands. We also report a new methodology of in-beam phase calibration using the on-off gated image of the target pulsar, which provides the optimal sensitivity of the coherent array removing the possible temporal and spacial decoherences.

14 pages, 3 figures, accepted for publication in ApJ Letters

References in corpus (3)

• Precision Southern Hemisphere pulsar VLBI astrometry: techniques and results for PSR J1559-4438
• A multi-pixel beamformer using an interferometric array and its application towards localisations of newly discovered pulsars
• On the nature of Off-pulse emission from pulsars

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• The MeerTime Pulsar Timing Array -- A Census of Emission Properties and Timing Potential
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• Inferring the composition of super-Jupiter mass companions of pulsars with radio line spectroscopy
• The GMRT High Resolution Southern Sky Survey for pulsars and transients -II. New discoveries, timing and polarization properties
• Discovery and timing of three millisecond pulsars in radio and gamma-rays with the GMRT and Fermi-LAT
• A 350-MHz Green Bank Telescope Survey of Unassociated Fermi LAT Sources: Discovery and Timing of Ten Millisecond Pulsars
• Search for pulsars and transients with the GMRT