Deep optical observations at the position of PSR1706-44 with the VLT-UT1
  We present optical data gathered by the VLT Test Camera in the V-band at the radio (interferometric) position of PSR1706-44. We find no optical counterpart to the pulsar in the VLT image. At a distance of 2.7 arcsec from a nearby bright star, the 3-sigma upper limit to the pulsar magnitude above the background is V = 25.5. Within an error circle of 1.0 arcsec the upper limit is degraded in the direction towards the star. At a distance < 2 arcsec from the star we can with confidence only claim an upper limit of V = 24.5. This is still several magnitudes fainter than previous estimates. The implications of the optical upper limit taken together with the high energy pulsed gamma-ray radiation for theoretical models of pulsar emission are discussed. 
Peter Lundqvist, Jesper Sollerman, Alak Ray, Bruno Leibundgut, Firoza   Sutaria