| ESA PRESS RELEASE
We have recently
discovered a new kind of high mass X-ray binaries
which may represent a major subclass. These objects are characterised
by the occurrence of very fast X-ray outbursts. Most of the time, they
are not detected as X-ray sources or only detected as a waek source.
Occasionally, they flare up and, for a very brief period of time, emit
strong hard X-ray radiation. Because of the brevity of the outbursts,
these X-ray sources had been dubbed fast X-ray transients. Our recent
work has shown that, at least a significant fraction of them, are
associated with supergiant stars, huge stars that represent the final
phase in the life of stars much more massive than the Sun. The
connection between supergiant stars and fast transients was rather
unexpected. We have called these objects Supergiant Fast X-ray
to celestial X-ray sources, check out the X-ray
Some X-ray sources are not normally detected, or are normally observed as very weak sources, but occasionally display 'outbursts', that is, short periods of activity during which X-ray emission is much stronger. Scientists call these sources transient. Thanks to the capabilities of ESA's gamma-ray observatory INTEGRAL, combined with other space-born X-ray observatories and ground telescopes, a new kind of transients, known as "Supergiant Fast X-ray Transients" has been discovered.