The Neil Gehrels Swift Observatory is a NASA medium explorer satellite developed in collaboration with Italy and the United Kingdom and dedicated to the study of gamma-ray bursts (GRB) science.

On board, Swift has three instruments (BAT, UVOT, XRT) working at different wavelenghts (gamma-ray, X-ray and optical) to observe, for the first time, bursts from the very beginning to finish.

The main mission objectives for Swift are:

• determine the origin of gamma-ray bursts;
• classify gamma-ray bursts and search for new types;
• determine how the blastwave evolves and interacts with the surrunding environment;
• use gamma-ray bursts to study the early universe;
• carry out a sensitive survey of the sky in the hard X-ray band.

Since the discovery of the first afterglows and host galaxies of short GRBs and the discovery of GRBs belonging to the era of re-ionization, Swift has proven to be very successful in these objectives.

With accurate arcsec positions, light curves and spectra for most GRBs (> 80% of the total), Swift has already provided a large sample of GRBs that currently contains more than 1500 objects and is continuously growing, providing a database of results to draw upon for many years to come.

The Swift mission patch depicts both the spacecraft and the bird for which it was named. The observatory is named after a small, nimble bird that can grab up insects as it flies through the sky. Similarly, the observatory can swiftly turn and point its instruments to catch a gamma-ray burst "on the fly" to study both the burst and its afterglow. This afterglow phenomenon follows the initial gamma-ray flash in most bursts and it can linger in X-ray light, visible light and radio waves for hours or weeks, providing great detail for observations. Credits: NASA E/PO, Sonoma State University/Aurore Simonnet.

Designed to discover and study GRBs and transient sources in general, thanks to its wide band sensitivity (from hard X up to 150 keV, to soft X, to optical-UV) and rapidity and flexibility of re-pointing, over the years Swift has been and is used to study all types of sources: from comets to stars, to compact galactic objects, to AGNs, to galaxies and clusters of galaxies, often making new discoveries in every sector, becoming a reference point for the time domain astronomy.
To date, no satellite rotates, moves and re-points faster than Swift.

Artist’s impression of the Swift spacecraft. Credits NASA/Swift.

Swift’s Ultraviolet/Optical Telescope imaged the kilonova produced by merging neutron stars in the galaxy NGC 4993 (box) on Aug. 18, 2017, about 15 hours after gravitational waves and the gamma-ray burst were detected. The source was unexpectedly bright in ultraviolet light. It faded rapidly and was undetectable in UV when Swift looked again on Aug. 29. This false-color composite combines images taken through three ultraviolet filters. Inset: Magnified views of the galaxy. Credits: NASA/Swift

The Brera Astronomical Observatory (INAF-OAB) supplied the optics for the X-Ray Telescope (XRT) and built a small rapid reaction automatic optical-infrared telescope (REM) dedicated to monitor the prompt IR/optical afterglow of gamma-ray bursts.
Several OAB staff are active members of the Swift-Italy group and participate in the scientific management of the satellite as Burst Advocate (BA) and XRT Burst Specialist (XBS), for the prompt and follow-up observations of GRBs detected by the Swift satellite.
The analysis and interpretation of these observations, i.e. data coming from the Swift satellite coupled with simultaneous observations from ground based telescopes, allows to study the properties of GRBs in order to understand their nature.