Deep BVR Imaging of the Field of the Millisecond Pulsar PSR J0030+0451   with the VLT
  We report on deep BVR-imaging of the field of the nearby millisecond pulsar PSR J0030+0451 obtained with the ESO/VLT/FORS2. We do not detect any optical counterpart down to B>27.3, V>27.0 and R>27.0 in the immediate vicinity of the radio pulsar position. The closest detected sources are offset by >3'', and they are excluded as counterpart candidates by our astrometry. Using our upper limits in the optical, and including recent XMM-Newton X-ray data we show that any nonthermal power-law spectral component of neutron star magnetospheric origin, as suggested by the interpretation of X-ray data, must be suppressed by at least a factor of ~500 in the optical range. This either rules out the nonthermal interpretation or suggests a dramatic spectral break in the 0.003-0.1 keV range of the power-law spectrum. Such a situation has never been observed in the optical/X-ray spectral region of ordinary pulsars, and the origin of such a break is unclear. An alternative interpretation with a purely thermal X-ray spectrum is consistent with our optical upper limits. In this case the X-ray emission is dominated by hot polar caps of the pulsar. 
A. B. Koptsevich (1), P. Lundqvist (2), N. I. Serafimovich (1 and 2),   Yu. A. Shibanov (1), and J. Sollerman (2) ((1) Ioffe...