Astronomy and Astrophysics – Astronomy
Scientific paper
Oct 1997
adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=1997apj...488..413r&link_type=abstract
Astrophysical Journal v.488, p.413
Astronomy and Astrophysics
Astronomy
8
Stars: Pulsars: Individual Alphanumeric: 4U 1538-52, Stars: Neutron, Stars: Rotation, X-Rays: Stars
Scientific paper
The high-mass X-ray pulsar 4U 1538-52 has been continually monitored by the BATSE (Burst and Transient Source Experiment) on Compton Gamma-Ray Observatory. These observations permit the construction of long-term pulse frequency and intensity histories. The frequency history reveals that a reversal of the long-term trend in the accretion torque, from spinning down to spinning up, has occurred, probably in 1988. This is the first time a long-term change is known to have occurred for this source. The magnitude of the average | nu dot / nu |~10^{-11} s-1 over an interval of ~5 yr is similar during spin-down and spin-up. Shorter term pulse frequency variations of either sign are also observed. The power density spectrum of fluctuations in angular acceleration is consistent with white noise on timescales from 16 to 1600 days. It can be well fit with a power law with a power-law index of 0.10 +/- 0.21 and white noise strength of (7.6 +/- 1.6) x 10-21(Hz s-1)2 Hz-1. These observations are also used to set 95% confidence level lower and upper limits on the rate of orbital period change, -3.9
Finger Mark H.
Rubin Bradley C.
Scott Mathew D.
Wilson Robert B.
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