High Energy Astrophysics and Gravitational Wave Sources: New Results from Magnetars and Short Gamma Ray Bursts

Luigi Stella
INAF - Osservatorio Astronomico di Roma

ABSTRACT: Over the last decade considerable evidence has been found for the existence of magnetars, neutron stars whose electromagnetic emission is powered by the decay of their extremely high magnetic field. A new perspective in this field was brought about by the 2004 December 27 giant flare from the magnetar in the soft gamma-ray source SGR 1806-20. The enormous energy liberated in this event points to an internal magnetic field strength of >1016 Gauss. For such a field the gravitational wave signal in the first few days after formation of a fast spinning magnetar is expected to be so strong that it can be detected with Advanced LIGO/Virgo class interferometers up to the distance of the Virgo cluster, where ~1 magnetar per year is born. There is now (indirect) evidence that short Gamma Ray Bursts originate in the merging of binary systems containing two neutron stars, or a neutron star and a black hole. Coalescing binaries are considered among the most promising GW sources. Recent results on short Gamma Ray Bursts indicate that a sizeable fraction of these events take place at low redshift and in globular clusters of stars, where they can be more easily detected by gravitational wave interferometers.