SIMBAD references

We present spectral and long-timescale variability analyses of Chandra X-Ray Observatory 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_eff~(1-3)x10⁶ K, emission radius R_eff∼0.1-3 km, and luminosity L_X∼10³⁰-10³¹ ergs.s^–1. For several MSPs, there are indications that a second thermal component is required, similar to what is seen in some nearby field MSPs. The observed radiation most likely originates from the heated magnetic polar caps of the MSPs. The small apparent scatter in L_X is consistent with thermal emission from the polar caps of a global dipole field, although the small emission areas may imply either a more complex small-scale magnetic field configuration near the neutron star surface or nonuniform polar cap heating. The radio eclipsing binary MSPs 47 Tuc J, O, and W show a significant nonthermal (power-law) component, with spectral photon index Γ∼1-1.5, which most likely originates in an intrabinary shock formed due to interaction between the relativistic pulsar wind and matter from the stellar companion. We reexamine the X-ray-spin-down luminosity relation (L_X-E{dot} relation) and find that for the MSPs with thermal spectra L_X∝E{dot}^β, where β∼0.2±1.1. Due to the large uncertainties in both parameters, the result is consistent with both the linear L_X-E{dot} relation and the flatter L_X∝E{dot}^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. We discuss the implications of these results on the present understanding of the X-ray emission properties of MSPs.