Diego Altamirano: "Millihertz quasi-periodic oscillations and their relation with Type-I X-ray Bursts: an intimate relation?"

Diego discussed whether there is a strong link between the mHz QPOs seen in some LMXBs and the occurence of Type I X-ray bursts. Until now we haven't been able to predict X-ray bursts, the recurrence time of which depend on a lot of unknown parameters. However, mHz QPOs, sometimes drifting in frequency, disapear just before an X-ray burst. This is the first time that something in the persistent emission seems to predict an X-ray burst (though mHz QPOs are not always seen before a burst). It appears that one won't see a burst unless the frequency of the mHz QPO drops below some threshold (9mHz appears to be the "magic number" in e.g. 4U1636-53). How do we interpret this? It could possibly be due to marginally stable burning.

Are mHz QPOs a new way to study X-ray bursts and changes in spectral states? Why is 9mHz the "magic number" and why there is frequency drift remains unknown.

Anna Watts: "Type I bursts and burst oscillations"

Anna reviewed the X-ray bursts which are observed from roughly half the known NS LMXBs. There is a rich variety of phenomena observed in these bursts, and new types of bursts are still emerging (e.g. burst triplets). These new types of bursts are revealing new burning regimes. However, there is still no satisfactory explanation for the burst oscillations, which are confidently observed in 12 sources. These burst oscillations show great variety in behaviour from source to source, which makes it difficult to provide a singular explanation.