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A superburst from 4U 1254-690

J. J. M. in 't Zand·E. Kuulkers·F. Verbunt·J. Heise·R. Cornelisse
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Abstract

We report the detection with the BeppoSAX Wide Field Cameras of a superburst from 4U 1254-690. The superburst is preceded by a normal type-I X-ray burst, has a decay time that is the longest of all eight superbursts detected so far and a peak luminosity that is the lowest. Like for the other seven superbursts, the origin is a well-known type-I X-ray burster with a persistent luminosity level close to one tenth of the Eddington limit. Based on WFC data of all persistently bright X-ray bursters, the average rate of superbursts is 0.51+/-0.25 per year per persistently bright X-ray burster. Some systems may have higher superburst rates. For all superbursters, we present evidence for a pure helium layer which is burnt in an unstable as well as a stable manner.

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J. J. M. in 't Zand, E. Kuulkers, F. Verbunt, J. Heise, R. Cornelisse. 2003-10-14. A superburst from 4U 1254-690. https://doi.org/10.1051/0004-6361%3A20031586

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