Lecture 25 - Recycled Pulsars

The Astrophysics group of Raman Research Institute (Bangalore) played an important role in Neutron Star research in the 1980 - '90s under the leadership of Prof. G. Srinivasan. In particular his pioneering ideas about `pulsar recycling' have been (and remain) some of the truly major milestones in the area of Neutron Star Astrophysics.

Although the Hulse-Taylor binary discussed in the previous lecture has two neutron stars, only one of them was detectable through its pulsed radio emission. This pulsar was not only the first pulsar to be discovered in a binary, it was also the most peculiar. Its very rapid spin rate suggested that it might be a ``very young pulsar". And yet, its anomalously low magnetic field suggested that it must be a very old pulsar. This intriguing puzzle was solved by the novel idea of ``reincarnation of a dead pulsar". Neutron stars eventually stop functioning as `pulsars' when their period of rotation lengthens and their dynamo weakens. If the `dead pulsar' is in a binary system, then it can be spun back up to short periods by accreting angular momentum from the binary companion. This lecture is devoted to this ``Recycling scenario".