2011A&A...531A.105M

Optical-ultraviolet (UV) observations of >100Myr pulsars are crucial to understand the long-term evolution of neutron stars, including the late stages of the neutron star cooling. The 166Myr old pulsar PSR J0108-1431 is one of the best targets since it is the oldest non-recycled pulsar with a candidate counterpart, detected with the Very Large Telescope (VLT). Aim of our observations is to obtain a firm detection of its candidate counterpart, only detected with marginal significance and to measure anew its flux in the U and B bands, for which we obtained only uncertain values. We observed the PSR J0108-1431 field with the FOcal Reducer/low dispersion Spectrograph (FORS2) at the VLT, exploiting the updated pulsar radio coordinates obtained from recent VLBI observations. Due to non-optimal seeing conditions, we only reached 3σ detection limits of U∼26.5 and B∼27.2, i.e. not incompatible with the fluxes of the candidate counterpart