2019MNRAS.485.3288I

Cassiopeia A, one of the most intriguing Galactic supernova remnants, has been a target of many observational efforts including most recent observations by Atacama Large Millimeter/submillimeter Array (ALMA), Hubble, Herschel, Spitzer, NuSTAR, INTEGRAL, and other observatories. We use recent gamma-ray lines observations of the radioactive products of Cas A supernova explosive nucleosynthesis and spectral energy densities derived for Cas A at infrared wavelengths to speculate about the possibility of radioactive ⁴⁴Ti being locked into large dust grains. This suggestion is also supported by the possible observation of a pre-supernova outburst about 80 yr before the actual Cas A supernova explosion in 1671 AD by Italian astronomer G. D. Cassini. The plausibility of such a scenario is discussed also with reference to recent supernovae, and to the contribution of core-collapse supernovae to the overall dust production in the Galaxy.