The Gravitational wave Optical Transient Observer - facility operations 2024-2027

The direct detection of gravitational waves using the Ligo gravitational wave detectors in September 2015 was one of humankind's greatest achievements. It was the equivalent of measuring the distance to the nearest star to our Sun better than the thickness of a human hair. Gravitational waves offer a route straight to the heart of the most extreme systems in nature and environments that are inaccessible to conventional astronomical techniques. This makes them powerful probes of extreme conditions and beacons to the distant universe.

However, gravitational wave detectors are currently not able to accurately pin-point the location in the sky of these waves. It will be rather like the bird watcher hearing an interesting call in the distance; the direction can be determined roughly but then the searcher must scan visually for signs of movement to pinpoint the cause. Although merging black holes are not expected to show an immediate optical signal, merging neutron stars are.

The problem is that the detectors can only locate the merging system to an area thousands of times the area of the moon. If the region can be mapped quickly enough new sources can be identified which were not present before the event took place. This idea was spectacularly demonstrated when in Sept 2017 a merging neutron star binary was detected first in gravitational waves and then a few days later in optical, radio and X-rays. This event became one of the most well studied astronomical events ever made and indicated that gold may well originate in these violent events.

The Gravitational-wave Optical Transient Observer (GOTO) is an array of telescopes across two sites allowing us to cover 100 times the area of the moon in one go. As soon as a gravitational wave is triggered, the facility will start taking images of the part of the sky where the event was expected to be.

This proposal aims to obtain funding to operate the GOTO facility on both La Palma (north) and Australia (south) sites. The telescopes cover most of the observable sky quickly and ensure that we obtain an image of the same patch of sky every few days which is essential if we are going to weed out new sources which are not the gravitational wave event but other events such as supernovae, accreting binaries or flare stars. Although somewhat confusing the search for neutron stars mergers, those other types of sources are at the same time another very useful science product that the project can produce. Our design ensures we are able to compete with other world class facilities.