The ROSAT source RX J0630.8 - 2834 was suggested by positional coincidence to be the X-ray counterpart of the pulsar PSR B0628 - 28 .
This association , however , was regarded to be unlikely based on the computed energetics of the putative X-ray counterpart .
In this paper we report on multi-wavelength observations of PSR B0628 - 28 made with the ESO/NTT observatory in La Silla , the Lovell telescope at Jodrell Bank and XMM-Newton .
Although the optical observations do not detect any counterpart of RX J0630.8 - 2834 down to a limiting magnitude of V=26.1 mag and B=26.3 mag , XMM-Newton observations finally confirm it to be the pulsar ’ s X-ray counterpart by detecting X-ray pulses with the radio pulsar ’ s spin-period .
The X-ray pulse profile is not sinusoidal but characterized by a two component pulse profile , consisting of a broad peak with a second narrow pulse leading the main pulse by \sim 144 ^ { \circ } .
The fraction of pulsed photons is ( 39 \pm 6 ) \% with no strong energy dependence in the XMM-Newton bandpass .
The pulsar ’ s X-ray spectrum is well described by a power law with photon index \alpha = 2.63 ^ { +0.23 } _ { -0.15 } .
A composite Planckian plus power law spectral model yields an interesting alternative which formally describes the observed energy spectrum equally well .
Inferred from best fits are a blackbody temperature of \sim 1.7 \times 10 ^ { 6 } K and a projected blackbody radius of \sim 69 _ { -25 } ^ { +30 } m , yielding a thermal flux contribution of \sim 20 \% within the 0.1 - 2.4 keV band .
The pulsar ’ s spin-down to X-ray energy conversion efficiency as obtained from the single power law spectral model is \sim 16 \% , aumming the distance inferred from the radio dispersion measure .
If confirmed , PSR B0628 - 28 would be the first X-ray over-luminous rotation-powered pulsar identified among all \sim 1400 radio pulsars known today .
The emission beam geometry of PSR B0628 - 28 is estimated from radio polarization data taken at 408 MHz and 1400 MHz .
A formal best fit of the 1400 MHz data yields \alpha \sim 11 ^ { \circ } for the inclination of the magnetic axis to the rotation axis and \beta \sim - 3 ^ { \circ } for the impact angle of the line of sight .
A combination of results obtained from 408 MHz and 1400 MHz data , however , makes a nearly orthogonal solution with \alpha \sim 70 ^ { \circ } and \beta \sim - 12 ^ { \circ } the most likely one .