Astron. Astrophys. 363, 617-628 (2000)

High speed phase-resolved 2-d UBV photometry of the Crab pulsar ^*

A. Golden ¹, A. Shearer ¹, R.M. Redfern ¹, G.M. Beskin ², S.I. Neizvestny ², V.V. Neustroev ², V.L. Plokhotnichenko ² and M. Cullum <sup>3

1</sup> National University of Ireland, Galway, Ireland
² Special Astrophysical Observatory, Nizhnij Arhyz, Karachai-Cherkessia, Russia
³ European Southern Observatory, Garching-bei-München, Germany

Received 11 May 2000 / Accepted 28 September 2000

Abstract

We report a phase-resolved photometric and morphological analysis of UBV data of the Crab pulsar obtained with the 2-d TRIFFID high speed optical photometer mounted on the Russian 6m telescope. By being able to accurately isolate the pulsar from the nebular background at an unprecedented temporal resolution (1 µs), the various light curve components were accurately fluxed via phase-resolved photometry. Within the UBV range, our datasets are consistent with the existing trends reported elsewhere in the literature. In terms of flux and phase duration, both the peak Full Width Half Maxima and Half Width Half Maxima decrease as a function of photon energy. This is similarly the case for the flux associated with the bridge of emission. Power-law fits to the various light curve components are as follows; = 0.07 0.19 (peak 1), = -0.06 0.19 (peak 2) and = -0.44 0.19 (bridge) - the uncertainty here being dominated by the integrated CCD photometry used to independently reference the TRIFFID data. Temporally, the main peaks are coincident to 10 µs although an accurate phase lag with respect to the radio main peak is compromised by radio timing uncertainties. The plateau on the Crab's main peak was definitively determined to be 55 µs in extent and may decrease as a function of photon energy. There is no evidence for non-stochastic activity over the light curves or within various phase regions, nor is there evidence of anything akin to the giant pulses noted in the radio. Finally, there is no evidence to support the existence of a reported 60 second modulation suggested to be as a consequence of free precession.

Key words: radiation mechanisms: non-thermal instrumentation: photometers stars: neutron stars: pulsars: individual: PSR B0531+12

* Based on observations taken at SAO, Karachai-Cherkessia, Russia

Send offprint requests to: A. Golden (agolden@itc.nuigalway.ie)

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Contents

• 1. Introduction
• 2. Review
• 3. Precession issues
• 4. January 1996 BTA run - observations in UBV & data preparation
• 5. Analysis - temporal issues
• 6. Analyses - phase resolved photometry
  • 6.1. Phase averaged/integrated colour photometry
  • 6.2. Phase resolved colour spectra - the peaks & bridge
  • 6.3. Phase resolved colour spectra - leading & trailing peak edges
• 7. Analyses - morphological characteristics
  • 7.1. Peak 1 position & peak-to-peak phase difference
  • 7.2. Full width half maximum differences
  • 7.3. Half width half maximum differences
  • 7.4. Plateau on the main peak
• 8. Discussion
  • 8.1. Resolution of the unpulsed component of emission
  • 8.2. The temporal extent of the main peak's cusp
  • 8.3. Phase difference between radio & UBV main peak arrival
• 9. Conclusion
• Acknowledgements
• References

© European Southern Observatory (ESO) 2000

Online publication: December 11, 2000
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