Group members: Andrea De Luca, Patrizia Caraveo, Paolo Esposito, Martino Marelli, Sandro Mereghetti, Ruben Salvaterra, Lara Sidoli, Andrea Tiengo
The Swift Observatory is a NASA medium explorer (MIDEX) mission, developed by an international collaboration, with an important contribution from Italy. It was launched on November 20, 2004 into a low-Earth orbit.
Swift carries onboard three instruments, designed to detect GRBs and to perform multiwavelength follow-up observations of their afterglows with a unique, fast autonomous repointing capability.
The Burst Alert Telescope (BAT) is a sensitive coded mask telescope with a large field of view (about 2 sr). It computes positions of GRBs with 2-3 arcmin uncertainty and collects time-resolved spectra of their prompt emission in the 14-150 keV energy range;
The X-Ray Telescope (XRT) is a grazing incidence, soft X-ray telescope with a CCD detector in its focal plane, sensitive in the 0.3-12 keV energy range. Its images allow to evaluate the coordinates of GRB afterglows with a positional accuracy of a few arcsec. XRT also allows to study the afterglow light curve and time-resolved spectrum in great detail;
The UV/Optical Telescope (UVOT), co-aligned with XRT, collects images and spectra (with a grism filter) of GRB afterglows during follow-up observations.
While waiting for a new GRB detection, Swift observes targets included in a pre-planned schedule. Following a GRB discovery by an onboard algorithm running in real-time on BAT data, an automatic repointing of the satellite is triggered, in order to perform follow-up observations of the GRB with the X-ray Telescope and the UV/Optical Telescope within less than 2 minutes from the GRB onset. All data collected by Swift are immediately released to the astrophysical community in a public archive.
With a harvest of about 100 GRBs per year, Swift has revolutionized our understanding of these astrophysical phenomena. As a second legacy of the mission, stacking of BAT data is yielding the most sensitive all-sky survey in the hard X-ray band ever performed. Furthermore, thanks to its multiwavelength capabilities, to its scheduling flexibility (allowing for a fast response to external triggers), Swift has evolved into a major general observing facility. In 2011, more than 65% of its observing time has been devoted to non-GRB science, with a large fraction of target of opportunity observations from the astrophysical community. Ground-breaking discoveries have been obtained, ranging from the detection of a supernova shock breakout X-ray flare, to the observation of the tidal disruption of a star eaten by a black hole.
IASF Milan hosts several members of the Italian Swift team. Several research project at IASF Milan are based on Swift data, ranging e.g. from statistical studies of the GRB population properties, to long-term monitoring of peculiar Galactic accreting binaries, to studies of the temporal properties of magnetars' emission, to the search for X-ray counterparts of gamma-ray sources detected by the Fermi mission.