Abstract

We report on deep VLT observations of the fields of two nearby, isolated millisecond pulsars, PSR J1744-1134 and PSR J1024-0719. Both objects are old neutron stars with characteristic age ? ?109 yr and have relatively high spin-down flux. They have been detected earlier as X-ray sources by ROSAT HRI observations and were considered good candidates for non-thermal emission in the optical bands. Our observations set an upper limit of B = 26.9, V = 26.3 and R = 26.0 for PSR J1744-1134. In the case of PSR J1024-0719, we find two faint objects near the radio position of the pulsar. Using multiband photometry from the VLT and spectroscopy carried out with the Magellan I telescope, we discuss the nature of the brighter object and the possibility of the fainter one being the optical counterpart of PSR J1024-0719. We consider the implications of our findings for both pulsars in the context of theoretical models of high-energy emission from old pulsars.