Binary Pulsar PSR J1518+4904: Orbital Precession and Mass Estimates
Session 48 -- Degenerate Stars and Pulsars
Display presentation, Thursday, June 15, 1995, 9:20am - 4:00pm

## [48.03] Binary Pulsar PSR J1518+4904: Orbital Precession and Mass Estimates

D. J. Nice (NRAO), R. W. Sayer, J. H. Taylor (Princeton)

We have made timing observations of newly discovered binary pulsar PSR J1518+4904 over a span of five months using the 140ft telescope of NRAO/Green Bank at frequencies between 320 and 800 MHz. Typical precision of a pulse time of arrival is 15 $\mu$s in a 1 hour integration (using a 40 MHz passband at 370 or 575 MHz). The timing data were reduced using standard techniques, and they fit well to a standard model of neutron star and orbital behavior. The pulse period is 40.934 ms, and the period derivative is at most $10^{-18}$, implying an age of at least 600 Myr and a surface magnetic field no stronger than $6\times10^9$~ Gauss.

The pulsar is in an 8.6 day, eccentric (e=0.249) orbit, with semi-major axis 0.040 AU. Orbital precession of $0.0110\pm0.0008$ deg/yr ($2\sigma$ uncertainty) has been detected. This implies a total system mass of $2.6\pm0.3$~M$_\odot$. The masses of the pulsar and companion (quite possibly another neutron star) cannot be fully separated. However, the system mass, combined with other orbital parameters, implies a pulsar mass of at most 1.9~M$_\odot$ and a companion mass of at least 0.9~M$_\odot$.

Precision of the precession measurement increases at least linearly with the length of the data series, so further observations of this system will provide a better measure of the total system mass. It is unlikely that the estimates of the individual component masses will improve.