What do you do when you are studying an exciting transient optical phenomenon and the Sun rises, rendering further observations impossible from your observatory? Well, there is always dark sky somewhere else!

A project dubbed Global Relay of Observatories Watching Transients Happen (GROWTH), a collaboration among twelve institutions spread around the globe including OKC, has been awarded a $4.5 million over five years from NSF to perform coordinated follow-up studies of optical transients, as shown by the figure below.

The project, led by the Caltech astrophysicist Mansi Kasliwal, is an important addition to the OKC involvement in iPTF and its successor, the Zwicky Transient Facility (ZTF). ZTF discoveries will be followed around the clock ensuring we can study phenomena with characteristic time-scales shorter than one day.

The GROWTH network will include ground- and space-based telescopes to observe cosmic transients at X-ray, ultraviolet, infrared, optical, and radio wavelengths. The rapid and efficient temporal coverage will vastly facilitate the identification of new types of transients. This is particularly timely, in view that the gravitational wave (GW) horizon has been expanded by Advanced LIGO.

One of the main goals of GROWTH is to identify electromagnetic counterparts of GW signals: ripples in the fabric of space and time that are predicted to accompany violent events in the universe such as the merger of a neutron star with a black hole. These cosmic collisions are expected to also produce short bursts of optical light that could be discovered already today by iPTF and by ZTF after 2017. GROWTH will help distinguishing these events from other variable phenomena. A secure identification of a GW signal would be a major scientific breakthrough.

The GROWTH project has also a strong educational component: students from the twelve involved universities will have a chance to visit the other host institutions. A great opportunity for students at OKC!