About/Disclaimer

Catalogue version: 1.0b



The main goal of the Catalog is to present X-ray properties of pulsars and pulsar-wind nebulae observed with Chandra ACIS detector. This is the first beta version of the Catalog. The Catalog is currently being rigorously tested and searched for different kinds of discrepancies and typos. Some of the interface features may not work properly yet.

 

The presented catalog has its limitations. There is no unique and accepted by everybody recipe on X-ray data reduction. For instance, the best-fit parameters of a spectral model can depend on the choice/size of the source region (e.g., PWN spectrum varies with distance from the pulsar), the choice of the subtracted background, whether hydrogen column is fitted or fixed at some value, the spectral binning and statistic (in the case of small number of counts), the energy range used. Therefore, the results presented in this Catalog may differ from those published in the papers (is some cases the differences can exceed the statistical uncertainties). We urge the user to evaluate the differences carefully and understand their origin before deciding which numbers should be used in each individual case. If you believe that some parameter value(s) in this catalog is seriously wrong we will be very grateful for pointing this out and letting us know. Please, send your comments through the Feedback form.

 

For these catalog we attempted to reduce the data as uniformly as possible, for instance:

 

  • When fitting the pulsar spectrum we fix hydrogen column at the best-fit value obtained from the PL fit to the PWN spectrum whenever possible. If PWN is faint or absent then the hydrogen column is calculated from the pulsars dispersion measure assuming 10% ISM ionization.
  • If the number of source counts is less than 100 (or 20 per spectral bin) we use C-statistic in our spectral fits.
  • Wheever possible the best-fit parameter uncertainties are determined from the 1σ confidence contour contour for one interestig parameter.
  • The spectral fits are carried out in the two energy bands (0.3-8 and 2-8 keV) whenever possible. If the sorce spectrum is soft or has few counts only 0.3-8 band is used.
  • The extraction regions used for PWN spectral fits are shown is the corresponding figures.
  • For pulsars with bright PWNe we used local background (from the annulus around the pulsar), to account for contamination by the PWN emission, whenever this caused substantial (beyond statistical uncertainties) differences in best-fit parmeters compare to the case when external (outside the PWN) background is used. The choice of the local background region (annulus) for the PSR spectrum is not always shown in the figures although the local background may be used in the spectral fits. In some figures the point source extraction region intentionally enlarged to make it visible. A smaller point source region may be used during the actual spectral extraction.
  • For the analysis we used: Chandra Interactive Analysis of Observations (CIAO) software (ver. 3.2.1; CALDB ver. 3.0.3) and XSPEC (v. 11.3).

 

We gratefully askbowledge the use of ATNF Pulsar Catalog templates for the database and HTML interface. The positional and radio parameters for most of the pulsars are also taken from the ATNF Pulsar Catalog.

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