COHERENTLY DEDISPERSED GATED IMAGING OF MILLISECOND PULSARS

Journal Article · Sun Mar 10 04:00:00 EDT 2013 · Astrophysical Journal Letters

DOI:https://doi.org/10.1088/2041-8205/765/2/L45· OSTI ID:22130821

Roy, Jayanta; Bhattacharyya, Bhaswati ^[1]

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1. National Centre for Radio Astrophysics, Pune 411007 (India)

Motivated by the need for rapid localization 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 a best-fit topocentric rotational model derived from a periodicity search in a 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 localize five newly discovered Fermi MSPs in the on-off gated image plane with an accuracy of {+-}1''. Immediate knowledge of such a precise position enables the use of sensitive coherent beams of array telescopes for follow-up timing observations which substantially reduces the use of telescope time ({approx}20 Multiplication-Sign for the GMRT). In addition, a precise a priori astrometric position reduces the effect of large covariances in the timing fit (with discovery position, pulsar period derivative, and an unknown binary model), which in-turn accelerates the convergence to the initial timing model. For example, while fitting with the precise a priori position ({+-}1''), the timing model converges in about 100 days, accounting for the effect of covariance between the position and pulsar period derivative. Moreover, such accurate positions allow for rapid identification of pulsar counterparts 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 optimal sensitivity of the coherent array removing possible temporal and spacial decoherences.

• OSTI ID: 22130821
• Journal Information: Astrophysical Journal Letters, Journal Name: Astrophysical Journal Letters Journal Issue: 2 Vol. 765; ISSN 2041-8205
• Country of Publication: United States
• Language: English

Related Subjects

46 INSTRUMENTATION RELATED TO NUCLEAR SCIENCE AND TECHNOLOGY
79 ASTRONOMY AND ASTROPHYSICS
ACCOUNTING
ACCURACY
BEAMS
CALIBRATION
CONVERGENCE
IMAGES
PERIODICITY
PULSARS
QUANTUM DECOHERENCE
RADIO TELESCOPES
SENSITIVITY