Radioactive Scandium in the Youngest Galactic Supernova Remnant G1.9+0.3

TL;DR

This study reports the detection of radioactive scandium in the youngest Galactic supernova remnant G1.9+0.3, providing insights into nucleosynthesis processes and supernova explosion models.

Contribution

First detection of thermal X-ray emission from G1.9+0.3 revealing 44Sc, indicating synthesized 44Ti and offering new data on supernova nucleosynthesis.

Findings

Detected 44Sc line with high confidence

Estimated 44Ti mass consistent with supernova models

Observed high-velocity Fe emission

Abstract

We report the discovery of thermal X-ray emission from the youngest Galactic supernova remnant G1.9+0.3, from a 237-ks Chandra observation. We detect strong K-shell lines of Si, S, Ar, Ca, and Fe. In addition, we detect a 4.1 keV line with 99.971% confidence which we attribute to 44Sc, produced by electron capture from 44Ti. Combining the data with our earlier Chandra observation allows us to detect the line in two regions independently. For a remnant age of 100 yr, our measured total line strength indicates synthesis of $(1 - 7) \times 10^{-5}$ solar masses of 44Ti, in the range predicted for both Type Ia and core-collapse supernovae, but somewhat smaller than the $2 \times 10^{-4}$ solar masses reported for Cas A. The line spectrum indicates supersolar abundances. The Fe emission has a width of about 28,000 km/s, consistent with an age of about 100 yr and with the inferred mean shock velocity of 14,000 km/s deduced assuming a distance of 8.5 kpc. Most thermal emission comes from regions of lower X-ray but higher radio surface brightness. Deeper observations should allow more detailed spatial mapping of scandium, with significant implications for models of nucleosynthesis in Type Ia supernovae.