Paper: astro-ph/0604318
Date: Thu, 13 Apr 2006 20:36:17 GMT (94kb)

Title: Chandra X-Ray Observations of Nineteen Millisecond Pulsars in the
Globular Cluster 47 Tucanae

Authors: Slavko Bogdanov, Jonathan E. Grindlay, Craig O. Heinke, Fernando
Camilo, Paulo C. C. Freire, Werner Becker

Comments: 13 pages, 6 figures, accepted for publication in the Astrophysical
Journal
\\
We present spectral and long-timescale variability analyses of
\textit{Chandra} ACIS-S observations of the 19 millisecond pulsars (MSPs) with
precisely known positions in the globular cluster 47 Tucanae. The X-ray
emission of the majority of these MSPs is well described by a thermal
(blackbody or neutron star hydrogen atmosphere) spectrum with a temperature
$T_{\rm eff}\sim(1-3)\times10^6$ K, emission radius $R_{\rm eff}\sim0.1-3$ km,
and luminosity $L_{X}\sim10^{30-31}$ ergs s$^{-1}$. For several MSPs, there is
indication that a second thermal component is required, similar to what is seen
in some nearby field MSPs. The radio-eclipsing binary MSPs 47 Tuc J, O, and W
show a significant non-thermal component, with photon index $\Gamma\sim 1-1.5$,
which may originate in an shock formed due to interaction between the
relativistic pulsar wind and matter from the stellar companion. We re-examine
the X-ray--spindown luminosity relation ($L_{X}-\dot{E}$) and find that due to
the large uncertainties in both parameters the result is consistent with both
the linear $L_{X}-\dot{E}$ relation and the flatter $L_X\propto\dot{E}^{0.5}$
predicted by polar cap heating models. In terms of X-ray properties, we find no
clear systematic differences between MSPs in globular clusters and in the field
of the Galaxy.

\\ ( http://arXiv.org/abs/astro-ph/0604318 , 94kb)