X-ray astronomy of radioactivity in SN 1987A

Observations of newly synthesized radioactive nuclei can provide a wealth of information about nucleosynthesis and dynamics of supernovae. This has been realized first for the extensively observed SN 1987A, through both direct (γ-ray line) and indirect (light curve power and infrared line) studies. We would like to extend this into the soft X-ray band, with the possibility of direct detection of electron capture decay of several radioactive isotopes in supernovae, supernova remnants, and the interstellar medium. Here, we discuss several possibilities and then present the results of searching Chandra X-ray spectra of SN 1987A for evidence of 5.9 keV Mn Kα line emission due to the decay of radioactive 55Fe. This isotope is produced directly and as short-lived parent 55Co in the innermost ejected regions of core collapse supernovae, and is the source of 55Mn in nature. The escape of X-rays from the decay of 55Fe depends on the mixing of core material into the envelope. Despite expectation of detectable line flux, we find only an upper limit near 3 × 10−7 cm−2 s−1.