Optical identification of binary system millisecond pulsar J1045−4509 with the VLT

We analyse archival optical data on the binary companion to the millisecond pulsar J1045-4509 obtained with the Very Large Telescope. A possible optical counterpart candidate is found at the pulsar position. Its magnitudes are V > 26.4, R = 25.7(2) and I = 25.4(2). The data are compared with white dwarf evolutionary models. Depending on still poorly known distance to the pulsar, two alternative interpretations are possible. For the radio timing parallax distance, the candidate can be a very cool and old white dwarf with the hydrogen atmosphere and the temperature of 5 Gyr. The dispersion measure distance suggests a younger (~ 2 Gyr) and hotter (~ 6000 K) white dwarf, whose atmosphere composition remains unknown.