Origins of cosmic high-energy bursts
Compact stellar objects having high masses and densities such as stars, planets and black holes accumulate and incorporate stellar dust and gas in a process called accretion. The large mass of the object pulls the dust and gas toward it due to its gravitational field. The swirling gas and dust forms a rapidly spinning accretion disc around the compact object and is then incorporated into the object, adding to its mass. Jets, or tremendous bursts of matter and energy observed in the form of light, seem to be associated with all accreting systems yet the basis of disc-jet coupling is largely unknown. European scientists set out to investigate the physics of jets in accreting black holes, neutron stars and white dwarfs (WDs) (stars at the end of their life-cycles) as well as the nature of disc-jet coupling. With EU funding of the ‘Multiwavelength variability study of the jet variability in X-ray binaries.’ (Jetvar) project, the team took advantage of newly available experimental techniques together with advanced analysis methods. Jetvar studied a wealth of jet data in relation to rapid changes in emission over the entire electromagnetic spectrum (EM) including X-ray, infrared, optical (visible) and radio observations. In particular, they were interested in comparing the jet variability data from the different stellar sources to gain insight into the role of black hole spin in producing and powering jets. The Jetvar project enabled collection of a tremendous amount of data using newly available fast photometers (instruments that measure light intensity) on large telescopes. For the first time, scientists were able to study fast, multi-wavelength variability in accreting compact objects. This led to a number of firsts in terms of results. The Jetvar team produced the first independent estimate of the magnetic field in a jet and an estimate of jet speed. Overall, Jetvar successfully initiated what is now considered a new field of research, one that has been selected for study in a space mission by the European Space Agency (ESA).
