Radio detection of the supernova remnant G310.7-5.4 and its γ-ray counterpart: The Abeona SNR

Context. The supernova remnant (SNR) candidate G310.7-5.4 was identified as a faint shell in the MGPS-2 survey. We followed up on it with multi-wavelength observations, confirming it to be an SNR at a high Galactic latitude that shows spatially coinciding γ-ray emission.

Aims. We conducted the first detailed investigation of the radio emission from the G310.7-5.4 region, aiming to characterise the radio structure, polarisation measurements, and the coinciding GeV emission.

Methods. We used recent radio continuum observations at 943.5 MHz from the EMU and POSSUM surveys with ASKAP, as well as 16.5 years of Fermi-LAT observations. We furthermore considered the multi-wavelength context of the object by investigating observations previously conducted with other instruments, such as IR and X-ray surveys.

Results. We confirm that G310.7-5.4 is indeed an SNR, which we have dubbed Abeona. We detect the presence of a faint, extended (30′ diameter) bilateral radio shell with an ASKAP radio flux density of 1.5_−0.1^+1.5 Jy with no obvious IR counterparts. With a radio surface brightness of about 2.4_−0.1^+2.4 × 10⁻²² W m⁻² Hz⁻¹ sr⁻¹, it is one of the faintest radio SNRs known. The northern part of the shell shows linearly polarised radio emission, which is characteristic of synchrotron emission in SNRs. The physical size of the SNR is estimated to be around 42₋₂₁⁺⁴² pc, which would correspond to a distance of around 4.9_−2.5^+4.9 kpc. Furthermore, the spatially coincident γ-ray source 4FGL J1413.9-6705 shows an energy flux of (1.26 ± 0.35) × 10⁻⁶ MeV cm⁻² s⁻¹ with a significance of 5.7 σ between 100 MeV and 100 GeV. We placed Abeona in context with other known high-latitude SNRs with γ-ray counterparts and compared their observational properties.

Conclusions. New radio surveys are discovering a population of faint high-Galactic-latitude SNRs with GeV counterparts in isolated environments. More sensitive observations with the CTAO in the next few years should provide valuable insights into particle acceleration and escape in these important cosmic ray accelerators.