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Optical Pulse-Phased Observations of Faint Pulsars with a Phase-Binning CCD Camera


Kern, Brian Daniel (2002) Optical Pulse-Phased Observations of Faint Pulsars with a Phase-Binning CCD Camera. Dissertation (Ph.D.), California Institute of Technology. doi:10.7907/XP9W-WM62.


We have constructed a phase-binning CCD camera optimized for optical observations of faint pulsars. The phase-binning CCD camera combines the high quantum efficiency of a CCD with a pulse-phased time resolution capable of observing pulsars as fast as 10 ms, with no read noise penalty. The phase-binning CCD can also operate as a two-channel imaging polarimeter, obtaining pulse-phased linear photopolarimetric observations. We have used this phase-binning CCD to make the first measurements of optical pulsations from an anomalous X-ray pulsar. We measured the optical pulse profile of 4U 0142+61, finding a pulsed fraction of 27%, many times larger than the pulsed fraction in X-rays. From this observation, we concluded that 4U 0142+61 must be a magnetar, an ultramagnetized neutron star (B > 10^14 G). The optical pulse is double-peaked, similar to the soft X-ray pulse profile. We also used the phase-binning CCD to obtain the photometric and polarimetric pulse profiles of PSR B0656+14, a middle-aged isolated rotation-powered pulsar. The optical pulse profile we measured significantly disagrees with the low signal-to-noise profile previously published for this pulsar. Our results show that the optical flux is entirely pulsed, with optical peaks at phases 0.2 and 0.8 with respect to the radio peak, and a bridge of emission between the peaks. The significance of the detection of pulsed polarized flux is low, but the position angles match the extrapolation of the radio polarization profile. The optical data, both photometric and polarimetric, are consistent with the polar cap model of pulsar magnetospheric emission. The fit of the optical data with the competing emission model, the outer gap model, has not yet been determined. We have developed a number of statistical tools, both to estimate the errors in our measurements and to identify systematic errors present in the pulse profiles. The statistical tools, when applied to the data presented here, show that the systematic errors are negligible, bolstering the claims of significance of these results.

Item Type:Thesis (Dissertation (Ph.D.))
Subject Keywords:instrumentation; magnetars; outer gap; polar cap; polarization; pulsars
Degree Grantor:California Institute of Technology
Division:Physics, Mathematics and Astronomy
Major Option:Astronomy
Thesis Availability:Public (worldwide access)
Research Advisor(s):
  • Martin, D. Christopher (advisor)
  • Djorgovski, George (co-advisor)
Group:Astronomy Department
Thesis Committee:
  • Goldreich, Peter Martin (chair)
  • Steidel, Charles C.
  • Martin, D. Christopher
  • Harrison, Fiona A.
  • Kulkarni, Shrinivas R.
  • Djorgovski, George
Defense Date:29 May 2002
Record Number:CaltechETD:etd-06042002-125011
Persistent URL:
Default Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:2430
Deposited By: Imported from ETD-db
Deposited On:06 Jun 2002
Last Modified:05 Nov 2021 20:41

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