A LONG-PERIOD GLOBULAR-CLUSTER PULSAR IN AN ECLIPSING BINARY-SYSTEM

PULSARS that are members of binary systems in globular clusters are all rapidly rotating, and it is assumed that they have been spun up by accretion from binary companions. Here we report an exception: PSR1718-19, in the globular cluster NGC6342, is in a 6.2-hour eclipsing binary system, but has the relatively long period of 1 s. Its magnetic field is strong, approximately 10(12) G, and its spin-down age is small, approximately 10 Myr. Furthermore, the mass of its companion is only 0.1-0.2 solar masses (M.). The eclipses show that the binary system is embedded in a cloud of material which must have been ejected from the companion star, although calculations suggest that the companion is well inside its Roche lobe. The pulsar's radiation may be causing expulsion of material beyond the Roche lobe, as in the ablating binary systems containing PSR-1744 - 24A and PSR1957 + 20, even though the incident flux at the companion is orders of magnitude smaller than in these cases. Pulsars may therefore have a much greater influence on their companions than has been supposed.