This award will provide funds for the Robotic Optical Transient Search Experiment (ROTSE) to observe gamma-ray bursts (GRBs) and other energetic transients, concentrating on the prompt observations of GRBs detected by the Swift BAT and GLAST LAT detectors and the detection of supernovae (SNe) at early stages of their rising lightcurves. The next few years will be a period of unique opportunity with these two gamma-ray missions operating in space. Data from GLAST is likely to illuminate a significant puzzle of GRBs: the emission of photons of very high energies. The wide field of view of the ROTSE instruments will enable localization of a large fraction of the detected events, a task exceedingly difficult for more conventional ground-based instruments. The response time of the ROTSE telescopes is short enough to begin observations while many bursts are still emitting gamma-rays or X-rays.
Over the past few years, ROTSE has collected data that, in conjunction with contemporaneous X-ray data, indicate that previous assumptions about the dynamics of GRB afterglows are inadequate to explain the combined measurements. ROTSE data analyses have identified 30 SNe, most spectacularly SN2005ap, SN2006gy and SN2007if. These remarkable events exhibit a peak brightness 10 times greater than type-IA SNe, thus pointing to a new class of explosions. Although the aperture of the telescopes is modest, their wide field of view enables the discovery of SNe shortly after the initial explosion and thus enables more a complete exploration of the dynamics.
ROTSE has been a rich source of data for the study of astrophysical transient phenomena. Recently, an educational outreach program in Thailand has signed an agreement to provide ?sky patrol? data to a consortium of high schools throughout that country. The ROTSE project spans 4 continents bringing research in optical astronomy to Namibia for the first time and considerably augmenting the facilities in Turkey.
The ROTSE-III project by any measure has been a successful and satisfying effort to explore the night sky for astrophysical optical transients, particularly gamma-ray bursts (GRBs) and supernovae. For GRBs, over a four-year period, ROTSE responded rapidly to 71 burst alerts and detected optical radiation from 19 of these. This information greatly extends the observed spectral range for these poorly understood explosions and puts some limits on possible theoretical models. For supernovae, the major contribution that ROTSE has provided is the discovery of superluminous Type Ia events. Since these events are brighter than the average population, they do not undercut the evidence for "dark energy" which is primarily based on the existence of apparently sub-luminous SNe at cosmological distances. Nevertheless, these discoveries dictate a certain amount of caution when claims are made that the behavior of Ia's are accurately understood. The ROTSE Collaboration was also a very nice example of an effort that spanned four continents including Africa and Asia. The inclusion of ROTSE-IIId in Turkey gave astronomers there a first opportunity to engage in optical astronomical observations that were of general interest to the international community. A number of undergraduate students have participated here at Michigan in ROTSE and via one of our graduates, Wiphu Rujopakarn, ROTSE images have been used in astronomy camps for middle and high school students in Thailand. With transfer of the ROTSE image archive to SMU, exploration of our night sky images is likely to still continue.
