Stairs, I HManchester, Richard NLyne, A JKaspi, VCamilo, FBell, Jon FD'Amico, NKramer, MCrawford, FMorris, DPossenti, AMcKay, N P FLumsden, StuartTacconi-Garman, LCannon, RussellHambly, N.Wood, Peter R2015-12-130035-8711http://hdl.handle.net/1885/89433We report on the discovery of a binary pulsar, PSR J1740-3052, during the Parkes multibeam survey. Timing observations of the 570-ms pulsar at Jodrell Bank and Parkes show that it is young, with a characteristic age of 350 kyr, and is in a 231-d, highly eccentric orbit with a companion whose mass exceeds 11M⊙. An accurate position for the pulsar was obtained using the Australia Telescope Compact Array. Near-infrared 2.2-μm observations made with the telescopes at the Siding Spring observatory reveal a late-type star coincident with the pulsar position. However, we do not believe that this star is the companion of the pulsar, because a typical star of this spectral type and required mass would extend beyond the orbit of the pulsar. Furthermore, the measured advance of periastron of the pulsar suggests a more compact companion, for example, a main-sequence star with radius only a few times that of the Sun. Such a companion is also more consistent with the small dispersion measure variations seen near periastron. Although we cannot conclusively rule out a black hole companion, we believe that the companion is probably an early B star, making the system similar to the binary PSR J0045-7319.Keywords: Binaries: general; Pulsars: general; Pulsars: individual: PSR J1740-3052; Stars: late-type; Stars: mass-loss; X-rays: stars200110.1046/j.1365-8711.2001.04447.x2015-12-12