Titanium 44 from type Ia supernovae
Understanding the origins of Type Ia supernovae (SNe Ia) remains a key challenge in astrophysics. These cosmic explosions are vital for measuring cosmic distances and enriching the universe with heavy elements — but the exact nature of their progenitors is still debated. In this study, we investigate the role of the radioactive isotope titanium-44 (\({}^{44}\mathrm{Ti}\)) as a diagnostic tool to distinguish between different explosion scenarios.
The production of \({}^{44}\mathrm{Ti}\) occurs primarily through explosive helium burning, a process that varies depending on the nature of the progenitor system. Models involving merging white dwarfs (so-called double-degenerate systems) are predicted to produce significantly more \({}^{44}\mathrm{Ti}\) than single-degenerate or near-Chandrasekhar mass explosions. We demonstrate that the amount and timing of \({}^{44}\mathrm{Ti}\) emission — especially at late times after a supernova — can help identify the progenitor pathway.
By analyzing light curves of both Type Ia supernovae and calcium-rich transients (a related class of explosions), we show that some events transition to being dominated by energy from \({}^{44}\mathrm{Ti}\) decay within a few years. This contrasts with slower transitions seen in explosions from near-Chandrasekhar mass progenitors. Gamma-ray observations of supernova remnants like Tycho, Kepler, and G1.9+0.3 are also examined to assess consistency with different theoretical models.
The study underscores the potential of \({}^{44}\mathrm{Ti}\) as a powerful observational tracer and advocates for future high-sensitivity gamma-ray missions to better constrain the origins of SNe Ia. This work not only informs supernova progenitor models but also has implications for understanding the Galactic distribution of positrons and the source of the 511 keV annihilation line.
Related publications / presentations
- Kosakowski, Ugalino et al. “Using \({}^{44}\mathrm{Ti}\) Emission to Differentiate Between Thermonuclear Supernova Progenitors.” Monthly Notices of the Royal Astronomical Society: Letters, vol. 519, no. 1, 2023, pp. L74–L78. Oxford Academic, doi:10.1093/mnrasl/slac152