We report the discovery of the binary millisecond pulsar J0514 - 4002A , which is the first known pulsar in the globular cluster NGC 1851 and the first pulsar discovered using the Giant Metrewave Radio Telescope ( GMRT ) .
The pulsar has a rotational period of 4.99 ms , an orbital period of 18.8 days , and the most eccentric pulsar orbit yet measured ( e = 0.89 ) .
The companion has a minimum mass of 0.9 M _ { \odot } and its nature is presently unclear .
After accreting matter from a low-mass companion star which spun it up to a ( few ) millisecond spin period , the pulsar eventually exchanged the low-mass star for its more massive present companion .
This is exactly the same process that could form a system containing a millisecond pulsar and a black hole ; the discovery of NGC 1851A demonstrates that such systems might exist in the Universe , provided that stellar mass black holes exist in globular clusters .