Rapid short-term pulse-period variations in Vela X-1 (4U 0900-40)
Abstract
Results are presented of an analysis of 83 days of 2-12 keV X-ray observations of Vela X-1 (4U 0900-40) obtained during three separate pointings with the ESA COS-B satellite. The pulsation period is shown to undergo very rapid intrinsic changes, at a rate of up to P˙/P ~ 10-1 yr-1 during intervals of a few days. The lower values of P˙/P ~ 10-3 yr-1 which were previously observed over longer intervals, appear to result from an averaging-out of these rapid changes. It is argued, that the transfer of angular momentum to the neutron star by the accreting matter is very unlikely to be sufficient to explain these pulsation-period changes. An alternative explanation is suggested.
- Publication:
-
Advances in Space Research
- Pub Date:
- 1984
- DOI:
- 10.1016/0273-1177(84)90057-7
- Bibcode:
- 1984AdSpR...3j..39V
- Keywords:
-
- Binary Stars;
- Diurnal Variations;
- Pulsars;
- Stellar Rotation;
- X Ray Sources;
- Angular Momentum;
- Cos-B Satellite;
- Phase Shift;
- Stellar Mass Accretion;
- X Ray Spectra;
- Astrophysics;
- X-ray binaries;
- X-ray pulsations;
- neutron stars;
- angular-momentum transfer;
- accretion torques;
- Vela X-1;
- 4U 0900-40