We investigate six supernova remnant ( SNR ) candidates – \mathrm { G } 51.21 + 0.11 , \mathrm { G } 52.37 - 0.70 , \mathrm { G } 53.07 + 0.49 , \mathrm { G } 53.41 + 0.03 , \mathrm { G } 53.84 - 0.75 , and the possible shell around \mathrm { G } 54.1 + 0.3 – in the Galactic Plane using newly acquired LOw-Frequency ARray ( LOFAR ) High-Band Antenna ( HBA ) observations , as well as archival Westerbork Synthesis Radio Telescope ( WSRT ) and Very Large Array Galactic Plane Survey ( VGPS ) mosaics .
We find that \mathrm { G } 52.37 - 0.70 , \mathrm { G } 53.84 - 0.75 , and the possible shell around pulsar wind nebula \mathrm { G } 54.1 + 0.3 are unlikely to be SNRs , while \mathrm { G } 53.07 + 0.49 remains a candidate SNR . \mathrm { G } 51.21 + 0.11 has a spectral index of \alpha = -0.7 \pm 0.21 , but lacks X-ray observations and as such requires further investigation to confirm its nature .
We confirm one candidate , \mathrm { G } 53.41 + 0.03 , as a new SNR because it has a shell-like morphology , a radio spectral index of \alpha = -0.6 \pm 0.2 and it has the X-ray spectral characteristics of a 1000 - 8000 year old SNR .
The X-ray analysis was performed using archival XMM-Newton observations , which show that \mathrm { G } 53.41 + 0.03 has strong emission lines and is best characterized by a non-equilibrium ionization model , consistent with an SNR interpretation .
Deep Arecibo radio telescope searches for a pulsar associated with \mathrm { G } 53.41 + 0.03 resulted in no detection , but place stringent upper limits on the flux density of such a source if it is beamed towards Earth .