A magnetic explanation for the rapid burster

The observations of X-ray Type II bursts from the low-mass X-ray binary MXB 1730-335 can be explained by a particular form of magnetic gating in the presence of steady external accretion. The requirements are a strong magnetic field of the neutron star (7×10¹¹–2×10¹² gauss at the surface), rotational symmetry and alignment of the field axis with the axis of a steadily accreting disk to within 6°.     

An EXOSAT observation of the morphology of the coronal X-ray emission from algol

The X-ray emission from Algol is thought to originate in a corona associated with the K star in this system. We report the results of a 35 hr continuous EXOSAT observation through secondary optical eclipse that was designed to measure the structure of the corona. No obvious X-ray eclipse was seen. The spectrum measured by the ME gives a temperature of 2.5 × 10⁷ K, consistent with the hard component previously seen by the Einstein SSS. The soft component previously reported by the SSS would only contribute at most 25% to the count rate seen in the LE (used with Al/P). The lack of a hard X-ray eclipse indicates the dimensions of the higher temperature emission region to be comparable to or greater than the size of the K star. An X-ray flare was detected with a peak luminosity of 1.4 × 10³¹ erg s^-1 and a total duration of 8 hours. The peak temperature was 5.0 keV with an emission measure of 9.4 × 10⁵³ cm^-3. The thermal nature of the flare is confirmed by the detection of an iron line with an EW of 2 keV. By equating the observed decay time of the flare to a known cooling law gives a dimension for the flaring loop of 0.3 stellar radii. This is much smaller than the dimensions of the hard component inferred from the lack of an eclipse. It seems probable that the flare occurred in one of the loops responsible for the lower temperature component seen by the SSS.     

Pair creation in double layers

Pair creation in relativistic double layers in shown to have consequences for the charge density in the double layer and the current flowing through it.