Physics Division Seminars bring us speakers on a variety of physics related subjects. Usually these are held in the Building 6008 large Conference Room, at 3:00 pm on the chosen day, but times and locations may vary. For more information, contact our seminar chairman,
Tel (Office): (865) 574-6124 (FAX): (865) 574-1268
Gamma-ray bursts (GRBs) are one-off transient events, believed to be associated with the collapse of massive progenitor stars. Occurring about once per day in the universe, and lasting only some tens of seconds, they produce about 1043 Joules of energy in gamma-rays in highly relativistic, jetted outflows, along with longer-lived, longer-wavelength afterglows. GRBs are found in distant star-forming galaxies, with the earliest observed to date occurring when the universe was less than 1 billion years old. The radiation mechanism that produces the non-thermal spectra of GRBs up to MeV energies is most likely to be synchrotron emission in most cases, although other possibilities exist. Pioneering efforts to measure GRB polarisation are underway, in an attempt to zero-in on the radiation mechanism and the magnetic field properties.
The proposed future ‘GRIPS’ experiment is one example of a purpose-built instrument for GRBs, with polarimetric capability. It is a combined pair-tracker and Compton telescope design, surrounded by a calorimeter. An R&D programme is currently underway to determine the suitability of silicon photomultipliers for use in the GRIPS calorimeter and to assess new scintillator materials that may be suitable for use in such a space-based instrument.
Contact: Alfredo Galindo-Uribarri, (865) 574-6124