ChandraX‐Ray Observations of 19 Millisecond Pulsars in the Globular Cluster 47 Tucanae

We present spectral and long-timescale variability analyses of\textit{Chandra} ACIS-S observations of the 19 millisecond pulsars (MSPs) withprecisely known positions in the globular cluster 47 Tucanae. The X-rayemission 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 isindication that a second thermal component is required, similar to what is seenin some nearby field MSPs. The radio-eclipsing binary MSPs 47 Tuc J, O, and Wshow a significant non-thermal component, with photon index $\Gamma\sim 1-1.5$,which may originate in an shock formed due to interaction between therelativistic pulsar wind and matter from the stellar companion. We re-examinethe X-ray--spindown luminosity relation ($L_{X}-\dot{E}$) and find that due tothe large uncertainties in both parameters the result is consistent with boththe 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 noclear systematic differences between MSPs in globular clusters and in the fieldof the Galaxy.Comment: 13 pages, 6 figures, accepted for publication in the Astrophysical Journa