# Titanium hidden in dust

## TL;DR

This paper explores the hypothesis that radioactive titanium-44 may be embedded in large dust grains within the supernova remnant Cassiopeia A, supported by gamma-ray observations and historical pre-supernova activity.

## Contribution

It proposes a novel idea that radioactive titanium-44 could be locked in dust grains in Cas A, integrating observational data with historical records and supernova dust production models.

## Key findings

- Gamma-ray observations suggest presence of radioactive 44Ti.
- Infrared spectral data supports dust grain formation hypotheses.
- Historical pre-supernova outburst may relate to dust formation processes.

## Abstract

Cassiopeia A, one of the most intriguing galactic supernova remnants, has been a target of many observational efforts including most recent observations by 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 as well as 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 years 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.