LMC X-4: GINGA Observations and Search for Orbital Period Changes
Abstract
We report on the results of a 2.4 day observation of the binary X-ray pulsar LMC X-4 with the Ginga satellite. A high-quality X-ray spectrum which includes an Fe emission line with an equivalent width of 0.18 keV is presented. Timing analyses of the 13.5 s X-ray pulsations yield a Doppler delay curve, which, in turn, provides the most accurate determination of the LMC X-4 orbital parameters available to date. The phase of the 1.4 day orbit is determined with an accuracy of ~ 60 s. This phase is combined with four Previous determinations of the orbital phase to yield an estimate of the rate of change in the orbital period: P_orb_/P_orb_ = (1.1+/- 0.8) x 10^-6^ yr^-1^. An interpretation of this measurement and the known decay rate for the orbit of Cen X-3 is made in the context of tidal evolution. During the observation two very large flares were observed with a duration of ~30 minutes; the source luminosity, at times, exceeded ~5 Eddington luminosities. The flares are described and discussed in some detail.
- Publication:
-
The Astrophysical Journal
- Pub Date:
- November 1991
- DOI:
- 10.1086/170632
- Bibcode:
- 1991ApJ...381..101L
- Keywords:
-
- Ginga Satellite;
- Magellanic Clouds;
- Pulsars;
- X Ray Binaries;
- Astronomical Satellites;
- Orbital Elements;
- Spaceborne Astronomy;
- Astrophysics;
- GALAXIES: MAGELLANIC CLOUDS;
- PULSARS;
- X-RAYS: BINARIES