\newcommand{\Msun}{{\rm M}_\odot}
The Orbital Period Derivative of PSR~B1957+20
Session 69 -- Cataclysmic Variables and Pulsars
Oral presentation, Thursday, 10:30-12:00, Dwinelle 155 Room

## [69.04] The Orbital Period Derivative of PSR~B1957+20

Andrew S. Fruchter (UC Berkeley), Zaven Arzoumian, Joseph H. Taylor (Princeton University)

The eclipsing pulsar B1957+20 is part of an extraordinary binary system. The spin-down radiation of this 1.6 ms pulsar heats its $0.02\, \Msun$ companion to optical temperatures, and an ionized evaporated wind off of the secondary's surface delays and absorbs the pulsar's radio signal. Timing observations undertaken between 1988 and 1991 revealed a large orbital period derivative, corresponding to an orbital lifetime of only $3\times10^7$ yrs, which is far less than is suggested by the tenuousness of the observed evaporate. However, compact binaries occasionally display non-secular orbital period derivatives over timescales of years. Here we report the results of an intensive timing program designed to determine whether the pulsar is indeed destroying its companion at this astounding rate.