Abstract
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 language | English |
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Article number | 0135 |
Number of pages | 6 |
Journal | Nature Astronomy |
Volume | 1 |
Early online date | 22 Apr 2017 |
Publication status | Published - 22 May 2017 |
Keywords
- Astrophysics - High Energy Astrophysical Phenomena
- Astrophysics - Astrophysics of Galaxies
- High Energy Physics - Phenomenology