Deep Chandra Survey of the Small Magellanic Cloud. II. Timing Analysis of X-ray Pulsars

May 26, 2017
26 pages
Published in:
  • Astrophys.J. 847 (2017) 1, 26
  • Published: Sep 20, 2017
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Abstract: (IOP)
We report the timing analysis results of X-ray pulsars from a recent deep Chandra survey of the Small Magellanic Cloud (SMC). We analyzed a total exposure of 1.4 Ms from 31 observations over a 1.2 deg(2) region in the SMC under a Chandra X-ray Visionary Program. Using the Lomb–Scargle and epoch-folding techniques, we detected periodic modulations from 20 pulsars and a new candidate pulsar. The survey also covered 11 other pulsars with no clear sign of periodic modulation. The 0.5–8 keV X-ray luminosity (L ( )X( )) of the pulsars ranges from 10(34) to 10(37) erg s(−)(1) at 60 kpc. All of the Chandra sources with L ( )X( ) ≳ 4 × 10(35) erg s(−)(1) exhibit X-ray pulsations. The X-ray spectra of the SMC pulsars (and high-mass X-ray binaries) are in general harder than those of the SMC field population. All but SXP 8.02 can be fitted by an absorbed power-law model with a photon index of Γ ≲ 1.5. The X-ray spectrum of the known magnetar SXP 8.02 is better fitted with a two-temperature blackbody model. Newly measured pulsation periods of SXP 51.0, SXP 214, and SXP 701, are significantly different from the previous XMM-Newton and RXTE measurements. This survey provides a rich data set for energy-dependent pulse profile modeling. Six pulsars show an almost eclipse-like dip in the pulse profile. Phase-resolved spectral analysis reveals diverse spectral variations during pulsation cycles: e.g., for an absorbed power-law model, some exhibit an (anti)-correlation between absorption and X-ray flux, while others show more intrinsic spectral variation (i.e., changes in photon indices).
Note:
  • 24 pages, 19 figures, 11 tables, submitted to ApJ
  • Magellanic Clouds
  • pulsars: general
  • stars: neutron
  • X-rays: binaries