X-ray observations of black widow pulsars

P. A. Gentile, M. S.E. Roberts, M. A. McLaughlin, F. Camilo, J. W.T. Hessels, M. Kerr, S. M. Ransom, P. S. Ray, I. H. Stairs

Research output: Contribution to journalArticle

Abstract

We describe the first X-ray observations of five short orbital period (PB < 1 day), γ-ray emitting, binary millisecond pulsars (MSPs). Four of these - PSRs J0023+0923, J1124-3653, J1810+1744, and J2256-1024 - are "black-widow" pulsars, with degenerate companions of mass ≪0.1 M , three of which exhibit radio eclipses. The fifth source, PSR J2215+5135, is an eclipsing "redback" with a near Roche-lobe filling 0.2 solar mass non-degenerate companion. Data were taken using the Chandra X-Ray Observatory and covered a full binary orbit for each pulsar. Two pulsars, PSRs J2215+5135 and J2256-1024, show significant orbital variability while PSR J1124-3653 shows marginal orbital variability. The lightcurves for these three pulsars have X-ray flux minima coinciding with the phases of the radio eclipses. This phenomenon is consistent with an intrabinary shock emission interpretation for the X-rays. The other two pulsars, PSRs J0023+0923 and J1810+1744, are fainter and do not demonstrate variability at a level we can detect in these data. All five spectra are fit with three separate models: a power-law model, a blackbody model, and a combined model with both power-law and blackbody components. The preferred spectral fits yield power-law indices that range from 1.3 to 3.2 and blackbody temperatures in the hundreds of eV. The spectrum for PSR J2215+5135 shows a significant hard X-ray component, with a large number of counts above 2 keV, which is additional evidence for the presence of intrabinary shock emission. This is similar to what has been detected in the low-mass X-ray binary to MSP transition object PSR J1023+0038.

Original languageEnglish (US)
Article number69
JournalAstrophysical Journal
Volume783
Issue number2
DOIs
StatePublished - Mar 10 2014

Keywords

  • X-rays: binaries
  • pulsars: general

ASJC Scopus subject areas

  • Astronomy and Astrophysics
  • Space and Planetary Science

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