THE END OF AMNESIA: A NEW METHOD FOR MEASURING THE METALLICITY OF TYPE Ia SUPERNOVA PROGENITORS USING MANGANESE LINES IN SUPERNOVA REMNANTS

摘要

We propose a new method to measure the metallicity of Type la supernova progenitors using Mn and Cr lines in the X-ray spectra of young supernova remnants. We show that the Mn-to-Cr mass ratio in Type la supernova ejecta is tightly correlated with the initial metallicity of the progenitor, as determined by the neutron excess of the white dwarf material before thermonuclear runaway. We use this correlation, together with the flux of the Cr and Mn Kα X-ray lines in the Tycho supernova remnant recently detected by Suzaku, to derive a metallicity of log (Z) = -1.32_(0.33)~(+0.67) for the progenitor of this supernova, which corresponds to log (Z/Z_☉) = 0.60+(-0.60)~(+0.31) according to the latest determination of the solar metallicity by Asplund and coworkers. The uncertainty in the measurement is large, but metallicities much smaller than the solar value can be confidently discarded. We discuss the implications of this result for future research on Type la supernova progenitors.