Type II X-ray Bursts
Click on the picture to watch a cool movie of an X-ray burster:
Type II X-ray bursts are believed to be due to sudden increases in the accretion rate of gas from the companion star, caused by such factors as changes in the viscous properties of the accretion disk or the influence of the neutron star's magnetic field.
The profiles of Type II bursts also vary greatly, but are generally characterized by
- rapid successions of bursts a few minutes apart
- sudden drops in flux without a gradual decay from peak values
- no spectral softening in decay
- sustained peak values of flux seen in longer bursts (resembling a flat top on the graph of photon count rate vs. time)
Notably, Type II bursts have been observed in only two sources:
- MXB 1730-335 (the Rapid Burster)
- GRO J1744-28 (the Bursting Pulsar).
The following figure shows a Type II X-ray burst from the Rapid Burster:
Figure from Lewin, W.H.G., van Paradijs, J. & Taam, R.E., 1993, Sp Sci Rev, 62, 223.