Peter A. Milne

The Advanced Compton Telescope

The Advanced Compton Telescope (ACT), the next major step in gamma-ray astronomy, will probe the fires where chemical elements are formed by enabling high-resolution spectroscopy of nuclear emission from supernova explosions. During the past two years, our collaboration has been undertaking a NASA mission concept study for ACT. This study was designed to (1) transform the key scientific objectives into specific instrument requirements, (2) to identify the most promising technologies to meet those requirements, and (3) to design a viable mission concept for this instrument. We present the results of this study, including scientific goals and expected performance, mission design, and technology recommendations.

Late light curves of SN Ia

A “positron phase” exists in type Ia supernovae, during which the energy deposition into the SN ejecta is dominated by the slowing of 56Co→56Feu2009β+ decay positrons. Comparisons of model-generated bolometric light curves with V and B band photometry during this phase suggests that the magnetic field is either too weak to confine positrons, or is radially combed. In each case, positrons escape the ejecta leading to a deficit of energy deposition. Ramifications of this escape upon other studies of SN Ia emission is discussed.