A white dwarf companion to the relativistic pulsar PSRJ1141-6545

Pulsars with compact companions in close eccentric orbits are unique laboratories for testing general relativity and alternative theories of gravity. Moreover, they are excellent targets for future gravitational wave experiments like LISA and they are also highly important for understanding the equation of state of superdense matter and the evolution of massive binaries. Here we report on optical observations of the 1.02M⊙ companion to the pulsar PSRJ1141-6545. We detect an optical counterpart with apparent magnitudes V= 25.08(11) and R= 24.38(14), consistent with the timing position of the pulsar. We demonstrate that our results are in agreement with a white dwarf companion. However the latter is redder than expected and the inferred values are not consistent with the theoretical cooling tracks, preventing us from deriving the exact age. Our results confirm the importance of the PSRJ1141-6545 system for gravitational experiments. © 2011 The Authors Monthly Notices of the Royal Astronomical Society © 2011 RAS.