2025A&A...700A.254G

Context. Deriving the mass and large-scale asymmetries of radioactive isotopes offers valuable insights into the complex phases of a supernova explosion. Important examples include ⁵⁶Ni, with its decay products ⁵⁶Co and ⁵⁶Fe, and ⁴⁴Ti, which are studied through their X-ray emission lines, and provide a powerful diagnostic tool to probe the explosive nucleosynthesis processes in the inner layers of the exploding star.
Aims. In this framework, SN 1987A provides a privileged laboratory, being the youngest supernova remnant from which the mass of Ti has been estimated. However, some uncertainty remains in determining the initial mass of ⁴⁴Ti. Previous analyses, relying on NuSTAR and INTEGRAL data, report M₄₄ = (1.5 ± 0.3) × 10^–4M_⊙ and M₄₄ = (3.1 ± 0.8) × 10^–4M_⊙, respectively. In this paper, we estimate the initial mass of ⁴⁴Ti via its decay product, the ⁴⁴Sc emission line at 4.09 keV, using Chandra observations.
Methods. We performed multi-epoch spectral analysis focusing on the inner part of the remnant, to minimize the contamination from the X-ray emission stemming from the shocked plasma. As a result, we report the detection of ⁴⁴Sc emission line in the central part of SN 1987A with a ∼99.7% (3 σ) significance.
Results. The simultaneous fit of the spectra extracted from observations between 2016 and 2021 yields a line flux of 6.8_–2.3^+2.2 × 10^–7 photons s^–1 cm^–2, corresponding to a ⁴⁴Ti mass of M₄₄ = (1.6 ± 0.5) × 10^–4M_⊙ (errors at the 90% confidence level). The results obtained with our spectral analysis appear to align with those derived with NuSTAR.