A millisecond pulsar in an eclipsing binary

摘要: We have discovered a remarkable pulsar with period 1.6 ms, moving in nearly circular 9.17-h orbit around low-mass companion star. At an observing frequency of 430 MHz, the pulsar, PSR1957 + 20, is eclipsed once each for about 50 minutes. For few minutes before eclipse becomes complete, and more than 20 after signal reappears, pulses are delayed by as much several hundred microseconds—presumably result propagation through plasma surrounding companion. The pulsar's system barycentre has radius 0.089 light seconds projected on to line sight. observed orbital size, together fact that eclipses occur, imply surprisingly low mass, only per cent mass Sun.