Gamma ray bursts
Gamma-ray bursts (GRBs) are the most luminous explosions known to man. With their origin in massive stars and visible from enormous distances (redshifts of up to 8 have been measured for GRBs), they are an invaluable tool to probe star formation across the ages, but they can also be used as a backlight for observations of their host and intervening galaxies. Furthermore, the burst and resulting afterglow are a unique laboratory in themselves: bulk Lorentz factors of 300 have been calculated for the outflow of the material that hits the circumstellar material, something hard to produce elsewhere. GRBs are thought to originate in massive stars, either through the collapse of a massive, rapidly rotating star (a "collapsar" or "failed supernova"), or from the merger of two compact objects such as neutron stars or black holes. This progenitor division appears visible in observations by the placement of the burst with respect to the centre of their host galaxy, and by the duration of the actual burst itself (the prompt emission, in contrast to the longer-lasting afterglow).
Amsterdam has been a long-time center for research into GRBs, mainly their afterglows. The first optical afterglow was discovered in Amsterdam in 1997, and one year later the connection between GRBs and supernovae was also discovered in Amsterdam (which confirmed their origin in massive stars). The research on afterglows currently focuses on a few topics:
- The optical spectra obtained from afterglows, which provide a wealth of information on the host galaxies and the direct surroundings of the grb.
- The evolution of the outflow (in particular the afterglow), modelled using hydrodynamic code, which forms the basis to understand the kinematics that go into the explosion.
Contact persons are:
The following people are working on this topic: