Gamma-ray Novae: Rare or Nearby?

Morris, P.J.; Cotter, G.; Brown, A.M.; Chadwick, P.M.

Abstract

Classical novae were revealed as a surprise source of γ-rays in Fermi Large Area Telescope (LAT) observations. During the first 8 yr since the LAT was launched, 6 novae in total have been detected to >5σ in γ-rays, in contrast to the 69 discovered optically in the same period. We attempt to resolve this discrepancy by assuming all novae are γ-ray emitters, and assigning peak 1 d fluxes based on a flat distribution of the known emitters to a simulated population. To determine optical parameters, the spatial distribution and magnitudes of bulge and disc novae in M31 are scaled to the Milky Way, which we approximate as a disc with a 20 kpc radius and elliptical bulge with semimajor axis 3 kpc and axis ratios 2:1 in the xy plane. We approximate Galactic reddening using a double exponential disc with vertical and radial scaleheights of rd = 5 kpc and zd = 0.2 kpc, and demonstrate that even such a rudimentary model can easily reproduce the observed fraction of γ-ray novae, implying that these apparently rare sources are in fact nearby and not intrinsically rare. We conclude that classical novae with mR ≤ 12 and within ≈ 8 kpc are likely to be discovered in γ-rays using the Fermi LAT.

Citation

Morris, P., Cotter, G., Brown, A., & Chadwick, P. (2017). Gamma-ray Novae: Rare or Nearby?. Monthly Notices of the Royal Astronomical Society, 465(1), 1218-1226. https://doi.org/10.1093/mnras/stw2776

• Journal Article Type: Article
• Acceptance Date: Feb 20, 2017
• Online Publication Date: Oct 27, 2016
• Publication Date: Feb 11, 2017
• Deposit Date: Feb 20, 2017
• Publicly Available Date: Feb 21, 2017
• Journal: Monthly Notices of the Royal Astronomical Society
• Print ISSN: 0035-8711
• Electronic ISSN: 1365-2966
• Publisher: Royal Astronomical Society
• Peer Reviewed: Peer Reviewed
• Volume: 465
• Issue: 1
• Pages: 1218-1226
• DOI: https://doi.org/10.1093/mnras/stw2776
• Public URL: https://durham-repository.worktribe.com/output/1385981
• Related Public URLs: https://arxiv.org/abs/1610.09941