Galactic Positron-Annihilation Distribution Explanation

Our Galaxy hosts the annihilation of a few 10^43 low-energy positrons every second. Radioactive isotopes capable of supplying such positrons are synthesized 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 supermassive black hole or dark matter annihilation. Here we show that a single type of transient source, deriving from stellar populations of age 3–6 Gyr and yielding ∼0.03M ⊙ 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 SN 1991bg-like.

https://www.nature.com/articles/s41550-017-0135.epdf?referrer_access_token=pVDIL6sZQwyKJNLdmR26ydRgN0jAjWel9jnR3ZoTv0NsQ6DPIuGo0Hl8A1hHbwL-9_LAk-6u-C4bfocizScITnLuUS-T3wW9PBtBZIq6o_iZSwTIl5Xgaqs9bfpbbsUeWbmrvCQX11Nza1QWgaQWmNReelhkDo-tqYi1QIkqbuxQ8Xdk4RHy1ZMG80BZWGR2M0QxtOsZVAbpqdd86kQxPgJpE0_SjQxW8IC00eWG2cvUwl9GoCsQn3flcaswNpd1UzXxkrnZCw1JzgFvjSKWhDzuiiTxhkCz8JWOcw7yQJU=&tracking_referrer=www.space.com

 

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Interesting summary, Walter - will read original later . . . . BTW: what do you think (IYO) of annhilation of positrons as a source for CMBR? . . . .might 'kill several birds with one stone'!

 

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no need for exotic explanations that don't appear to work. cmbr has a 'black-body' spectrum that is well-measured. annihilation gamma radiation is very distinctive (511 KeV). and would show a 'spectrum' consistent with the recession from the region of space where emitted. ps, the summary is from the article, which i copied. the title of the thread is my own. 511 Kev is the distinctive signature of annihilation, and is routinely used daily in our nuclear medicine laboratories with PET, including the recent Ga-68 for which I did a short thread a few weeks ago.

 

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