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29 March 2024
 
  » arxiv » astro-ph/0103171

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The X-ray Spectrum of the Vela Pulsar Resolved with Chandra
G.G. Pavlov ; V.E Zavlin ; D. Sanwal ; V. Burwitz ; G. Garmire ;
Date 12 Mar 2001
Subject astro-ph
AffiliationPSU), V.E Zavlin (MPE), D. Sanwal (PSU), V. Burwitz (MPE) and G. Garmire (PSU
AbstractWe report the results of the spectral analysis of two observations of the Vela pulsar with the Chandra X-ray observatory. The spectrum of the pulsar does not show statistically significant spectral lines in the observed 0.25-8.0 keV band. Similar to middle-aged pulsars with detected thermal emission, the spectrum consists of two distinct components. The softer component can be modeled as a magnetic hydrogen atmosphere spectrum - for the pulsar magnetic field $B=3 imes 10^{12}$ G and neutron star mass $M=1.4 M_odot$ and radius $R^infty =13$ km, we obtain $ ef^infty =0.68pm 0.03$ MK, $L_{ m bol}^infty = (2.6pm 0.2) imes 10^{32}$ erg s$^{-1}$, $d=210pm 20$ pc (the effective temperature, bolometric luminosity, and radius are as measured by a distant observer). The effective temperature is lower than that predicted by standard neutron star cooling models. A standard blackbody fit gives $T^infty =1.49pm 0.04$ MK, $L_{ m bol}^infty=(1.5pm 0.4) imes 10^{32} d_{250}^2$ erg s$^{-1}$ ($d_{250}$ is the distance in units of 250 pc); the blackbody temperature corresponds to a radius, $R^infty =(2.1pm 0.2) d_{250}$ km, much smaller than realistic neutron star radii. The harder component can be modeled as a power-law spectrum, with parameters depending on the model adopted for the soft component - $gamma=1.5pm 0.3$, $L_x=(1.5pm 0.4) imes 10^{31} d_{250}^2$ erg s$^{-1}$ and $gamma=2.7pm 0.4$, $L_x=(4.2pm 0.6) imes 10^{31} d_{250}^2$ erg s$^{-1}$ for the hydrogen atmosphere and blackbody soft component, respectively ($gamma$ is the photon index, $L_x$ is the luminosity in the 0.2--8 keV band). The extrapolation of the power-law component of the former fit towards lower energies matches the optical flux at $gammasimeq 1.35$--1.45.
Source arXiv, astro-ph/0103171
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