0635000

AO-6 Key Programme 6: Virgo ClusterSoft Gamma Repeaters (SGRs) likely contain magnetars neutron stars whose emission is powered by the decay of their exceptionally high magnetic field. These sources emit short duration soft gamma ray bursts with a wide range of fluences the highest being those of the 3 giant flares detected so far. A new perspective in this field was brought about by the 2004 Dec 27 giant flare from SGR 1806-20. The energy liberated in this event was enormous (>> 5?10^46 erg) and indicates that the internal field of magnetars is > 10^16 G i.e. a decade higher than previously thought. Amongst the potentially important consequences of this finding are: (a) newborn fast-spinning magnetars can be powerful sources of gravitational radiation (b) a sizeable fraction of the short Gamma Ray Burst population might originate in very powerful giant flares in the local universe (c) the earth atmosphere damage that a powerful giant flare from a nearby SGR can produce is much higher than previously estimated. INTEGRAL/IBIS is presently the best suited instrument to extend the search for giant flares to a large number of galaxies. We propose here a 2 Ms INTEGRAL observation of the Virgo Cluster during which 7-13 giant flares are expected to go off. This study should at least double the number of known giant flares thus yielding much needed information on the recurrence rate and distribution of total emitted energy of these paroxysmal events.The Virgo cluster field has already been shown to be rich in detectable sources and offers an excellent opportunity for further detailed studies. A deep INTEGRAL observation such as that proposed here will afford the study of the high energy emission of 7 known sources and likely lead to the detection of few serendipitous background AGNs. [truncated! Please see actual data for full text]