2009ApJ...703.1557B

We present deep XMM-Newton European Photon Imaging Camera spectroscopic and timing X-ray observations of the nearby solitary radio millisecond pulsar, PSR J0030+0451. Its emission spectrum in the 0.1-10 keV range is found to be remarkably similar to that of the nearest and best-studied millisecond pulsar, PSR J0437-4715, being well described by a predominantly thermal two-temperature model plus a faint hard tail evident above ∼2 keV. The pulsed emission in the 0.3-2 keV band is characterized by two broad pulses with pulsed fraction ∼60%-70%, consistent with a mostly thermal origin of the X-rays only if the surface polar cap radiation is from a light-element atmosphere. Modeling of the thermal pulses permits us to place constraints on the neutron star radius of R > 10.7 (95% confidence) and R > 10.4 km (at 99.9% confidence) for M = 1.4 M_☉.