Gamma Ray Bursts in the Era of Rapid Follow-up

Gamma Ray Bursts - brief, intense and totally unpredictable flashes of high-energy gamma rays from the sky - are the instantaneously most luminous objects in the Universe and arguably the most significant new astrophysical phenomenon since the discovery of quasars and pulsars in the 1960s. Thought to be produced during the creation of a black hole when the core of a distant massive star collapses at the end of its life or when two compact objects (neutron stars or black holes) merge, GRBs act as 'laboratories' for extreme physics: acceleration of material to ultra-high speeds close to that of light, strong gravity and large magnetic fields, as well as acting as important probes of the very early universe. GRBs actually emit across the electromagnetic spectrum and fade from view on timescales ranging from seconds to days; the technical challenge of observing completely unpredictable, time-variable and rapidly fading signals from space has driven development of advanced technological capabilities in satellite- and ground-based observatories, in which STFC and NASA have invested heavily over the last five years and in which the Liverpool GRB team have taken a world leading role. Liverpool John Moores University developed the world's largest fully autonomous optical telescopes - the 2-m Liverpool and Faulkes Telescopes (LT, FTs); these unmanned telescopes in the Canary Islands, Hawaii and Australia are capable of making automatic decisions on observing priorities and modes within seconds of receiving an alert from a GRB detector satellite, such as NASA's Swift, giving us an international lead in probing the early-stage evolution of GRB physics. In turn, current theories have proven key to interpreting the growing datasets, while novel new instrumentation allowing measurement of the degree of polarisation of the optical light has recently confirmed fundamental predictions of existing models. The Liverpool JMU team is unique in having the capability to drive our observational studies and technology development with cutting-edge simulations of GRBs that have the power to predict observable phenomena, not merely to interpret them within current models. It is clear that whichever physical model ultimately explains differing properties of individual bursts, it must involve magnetic fields - required to produce the observed synchrotron radiation. The origin and role of magnetic fields in driving GRB ejecta, however, remains one of the most fundamental, unanswered questions in GRB physics and forms an key part of our team's focus. State-of-the-art relativistic magneto-hydrodynamic simulations to predict the optical behaviour of GRBs, in particular the role of magnetic fields will be used to drive an observational programme of time-critical multiwavelength imaging, polarimetry and spectroscopy. Rapid development of new instruments is a core capability of our team; our first polarimeter, RINGO, allowed us to make the first measurement of polarization in a GRB afterglow, providing important information on the role of magnetic fields in GRBs; a recently commissioned replacement, RINGO2, will extend this capability to a larger sample of objects and study their evolution. We are preparing other new instruments that will allow us to catch more distant and energetic GRBs, provide tighter constraints on physical conditions and also exploit triggers from non-electromagnetic detectors such as neutrino telescopes.