Gamma-ray detection of newly discovered Ancora supernova remnant: G288.8–6.3

¹ Dublin Institute for Advanced Studies, Astronomy & Astrophysics Section, D IAS Dunsink Observatory, Dublin D15 XR2R, Ireland
e-mail: cburger@cp.dias.ie
² School of Physics, University College Dublin, Belfield, Dublin D04 V1W8, Ireland
³ School of Physical Sciences and Centre for Astrophysics & Relativity, Dublin City University, D09 W6Y4 Glasnevin, Ireland
⁴ Western Sydney University, Locked Bag 1797, Penrith South DC, NSW 2751, Australia
⁵ Université Paris Cité, CNRS, Astroparticule et Cosmologie, 75013 Paris, France
⁶ Centre for Space Research, North-West University, 2520 Potchefstroom, South Africa
⁷ Institute of Space Sciences (ICE, CSIC), Campus UAB, Carrer de Can Magrans s/n, 08193 Barcelona, Spain
⁸ Deutsches Elektronen-Synchrotron DESY, Platanenallee 6, 15738 Zeuthen, Germany
⁹ Astronomical Observatory of Ivan Franko National University of Lviv, Kyryla i Methodia 8, 79005 Lviv, Ukraine
¹⁰ Gran Sasso Science Institute, Via F. Crispi 7, 67100 L’Aquila, Italy

Received: 22 October 2023
Accepted: 23 January 2024

Abstract

Context. The supernova remnant (SNR) G288.8–6.3 was recently discovered as a faint radio shell at high Galactic latitude using observations with the Australian Square Kilometre Array Pathfinder (ASKAP) in the Evolutionary Map of the Universe (EMU) survey.

Aims. We performed the first detailed investigation of the γ-ray emission from the G288.8–6.3 region, aiming to characterise the high-energy emission in the GeV regime from the newly discovered SNR, dubbed Ancora.

Methods. Fifteen years of Fermi-Large Area Telescope (LAT) data were analysed at energies between 400 MeV and 1 TeV, and the excess seen in the region was modelled using different spatial and spectral models.

Results. We detect spatially extended γ-ray emission coinciding with the radio SNR, with detection significance up to 8.8 σ. A radial disk spatial model in combination with a power-law spectral model with an energy flux of (4.80 ± 0.91) × 10⁻⁶ MeV cm⁻² s⁻¹, with the spectrum extending up to around 5 GeV was found to be the preferred model. Morphologically, hotspots seen above 1 GeV are well correlated with the bright western part of the radio shell. The emission is more likely to be of leptonic origin, given the estimated gas density in the region and the estimated distance and age of the SNR, but a hadronic scenario cannot be ruled out.

Conclusions. Ancora is the seventh confirmed SNR detected at high Galactic latitude with Fermi-LAT. The study of this new population of remnants can provide insights into the evolutionary aspects of SNRs and their properties, and further advance efforts of constraining the physics of particle diffusion and escape from SNRs into the Galaxy.