G321.3–3.9: A new supernova remnant observed with multi-band radio data and in the SRG/eROSITA All-Sky Surveys

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.