Program: GN-2011B-Q-19

What makes a Type Ia Supernova? Viable models involve either (i) accretion from a donor star onto a white dwarf or (ii) the merger of two white dwarfs. In the context of the former scenario, we seek to identify the donor star of SN1572. We have analyzed high-resolution spectroscopy of nearly all bright stars in the inner volume of the remnant. None are plausible donor stars. The sole remaining object, Star-A2, lies close to a star some 4 mag brighter. Adaptive optics in the infrared is the only possible way to obtain a spectrum. A S/N ~ 15 GNIRS SV spectrum revealed an intriguingly high spatial velocity, a key signature expected of a donor star. An additional higher S/N spectrum is necessary to confirm the radial velocity and to measure stellar parameters, chemical abundances and rotational velocity. The proposed observations are the only way to test if Star-A2 is the donor star and will complete our definitive study of the progenitor of SN1572.