Possible Magnetic Activity in the Low Mass X-ray Binary EXO 0748-676

Abstract

We report evidence of magnetic activity associated with the secondary star in the EXO 0748-676 low mass X-ray binary system. An analysis of a sequence of five consecutive X-ray eclipses observed during December 2003 with the RXTE satellite brings out a feature occurring during ingress we interpret as the X-ray photoelectric absorption shadow, as seen by an observer at Earth, of a plasma structure suspended above the surface of the secondary star. The light curve feature consists of an initial drop in count rate to near zero (the absorption shadow) with a very short rebound to a significant fraction of the pre-ingress count rate and then a final plunge to totality over a total time scale of ~25 s. The ingress feature persists for at least 5 consecutive orbital periods (a total of ~19 hr), and possibly up to 5 days in our data. Our data also show significant post-egress dipping during this eclipse sequence, unusual for this source, indicating possible secondary star mass ejection during this episode.

Accepted by Astrophysical Journal Letters; 11 Pages including 3 figures and 1 table

References in corpus (3)

• Calibration of the Rossi X-ray Timing Explorer Proportional Counter Array
• Multiwavelength Observations of EXO 0748--676 -- II. Emission Line Behavior
• The broad-band X-ray spectrum of the dipping Low Mass X-ray Binary EXO0748--676

Cited by in corpus (7)

• Eclipse Timings of the Transient Low Mass X-ray Binary EXO0748-676. IV. The Rossi X-Ray Timing Explorer Eclipses
• The puzzling orbital period evolution of the low mass X-ray binary AX J1745.6-2901
• A possible solution of the puzzling variation of the orbital period of MXB 1659-298
• Dips and eclipses in the X-ray binary Swift J1858.6-0814 observed with NICER
• Measuring the orbital periods of low mass X-ray binaries in the X-ray band
• The $\text{False Widow}$ Link Between Neutron Star X-ray Binaries and Spider Pulsars
• The puzzling orbital residuals of XTE J1710-281: is a Jovian planet orbiting around the binary system?