2024A&A...690A.278M

Aims. G321.3-3.9 was first identified as a partial shell at radio frequencies a few decades ago. Although it continued to be observed, no additional studies were undertaken until recently.
Methods. In this paper, we present results from a large selection of radio and X-ray data that cover the position of G321.3-3.9. We confirmed G321.3-3.9 as a new supernova remnant (SNR) using data collected by several radio surveys, spanning a frequency range from 200 to 2300 MHz. Stacked eROSITA data from four consecutive all-sky surveys (eRASS:4) provide spectro-imaging information in the energy band 0.2-8.0 keV.
Results. G321.3-3.9 has an elliptical shape with major and minor axes of approximately $\[1^{\circ}_\cdot7 \times 1^{\circ}_\cdot1\]$. From CHIPASS and S-PASS data, we calculate a spectral index α = -0.8 ± 0.2, consistent with synchrotron emission from an expanding shell in the radiative phase. The eROSITA data show an X-ray diffuse structure filling almost the entire radio shell. Based on our spectral analysis, we found the temperature to be approximately 0.6 keV and the column absorption density about 10²¹ cm^–2. Comparing this absorption density to optical extinction maps, we estimated the distance to fall within the range of (1.0-1.7) kpc, considering the 1σ uncertainty range.