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CCD image
Binary star visible
Binary star invisible

Details of two 200-second unguided V band CCD frames taken on 23 June 1988, UT 01:51 (top) and UT 04:34 (bottom), at orbital phases 0.92 and 0.22, respectively. The weakening of the optical counterpart of PSR1957+20 near the radio eclipse (V > 23, phase 0.25) is clearly visible. The field shown measures about 16 × 16 arcsec. The pulsar is 0.7 arcsec from a contaminating star.

We are not seeing the pulsar itself but the strongly heated face of the companion star which is irradiated by the enormously high energy flux from the radio pulsar. This flux is responsible for the apparent evaporation of material from the companion star (seen during the radio eclipses) which will eventually destroy it completely. The pulsar was spun up to its present high rotation rate by the accretion of material from the companion. Once the accretion stopped (due to the evolution of the companion star) the pulsar turned on and became the system we see now. [ TIFF ]

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Last modified: 13 December 2010