The Black Widow Pulsar
The so-called "Black Widow" pulsar
was discovered in 1988 by Fruchter
et al. The pulsar has a pulse period of 1.6 milliseconds and is
in an eclipsing orbit with a companion.
The signal from the pulsar is
delayed, causing the period to lengthen, a few minutes before eclipse
and for about 20 minutes after the pulsar reappears. This time delay
arises because the signal must travel through the ionized plasma
surrounding the companion. It is believed that most of the companion's
material lies well beyond its Roche Lobe,
and that this outer material is being blown off the companion by
the neutron star. Calculations suggest that the "black widow" will
evaporate away its companion in about a billion years.
Suggested readings:
Fruchter, A.S., Stinebring, D.R. and Taylor, J.H. 1988,
Nature 333, 237.
