Diffuse Galactic antimatter from faint thermonuclear supernovae in old stellar populations

Roland M. Crocker, Ashley J. Ruiter, Ivo R. Seitenzahl, Fiona H. Panther, Stuart Sim, Holger Baumgardt, Anais Moller, David M. Nataf, Lilia Ferrario, J. J. Eldridge, Martin White, Brad E. Tucker, Felix Aharonian

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Our Galaxy hosts the annihilation of a few $\times 10^{43}$ low-energy positrons every second. Radioactive isotopes capable of supplying such positrons are synthesised in stars, stellar remnants, and supernovae. For decades, however, there has been no positive identification of a main stellar positron source leading to suggestions that many positrons originate from exotic sources like the Galaxy's central super-massive black hole or dark matter annihilation. %, but such sources would not explain the recently-detected positron signal from the extended Galactic disk. Here we show that a single type of transient source, deriving from stellar populations of age 3-6 Gyr and yielding ~0.03 $M_\odot$ of the positron emitter $^{44}$Ti, can simultaneously explain the strength and morphology of the Galactic positron annihilation signal and the solar system abundance of the $^{44}$Ti decay product $^{44}$Ca. This transient is likely the merger of two low-mass white dwarfs, observed in external galaxies as the sub-luminous, thermonuclear supernova known as SN1991bg-like.
Original languageEnglish
Article number0135
Number of pages6
JournalNature Astronomy
Early online date22 Apr 2017
Publication statusPublished - 22 May 2017


  • Astrophysics - High Energy Astrophysical Phenomena
  • Astrophysics - Astrophysics of Galaxies
  • High Energy Physics - Phenomenology


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