München 2019 – scientific programme

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SYMD: Symposium SMuK Dissertationspreis 2019

SYMD 1: SMuK Dissertationspreis 2019

SYMD 1.4: Invited Talk

Monday, March 18, 2019, 15:30–16:00, Plenarsaal

Positron Annihilation Spectroscopy throughout the Milky Way — •Thomas Siegert — Max-Planck-Institut für extraterrestrische Physik, Garching, Deutschland

For more than four decades, astrophysicists are puzzled by a bright but unique signal appearing from the centre of our Galaxy. Unlike at any other observable wavelength, the 511 keV emission from electron-positron annihilation is dominated by the bulge region of the Milky Way, with only a faint and puffed up galactic disk. Per second, of the order of 10⁴³ positrons annihilate in the interstellar medium. This amount of antimatter particles has to be supplied, but the sources which come into consideration are versatile - and yet to be determined. Among the most promising origins are radioactive nucleosynthesis ejecta from massive star winds, core-collapse supernovae, and thermonuclear supernovae. Also compact objects, such as highly magnetised neutron stars or black hole binary systems, are energetic enough to produce positrons. Even dark matter is invoked to explain this mysterious signal.

This talk will recap the physics of positron production, propagation, and annihilation in space by using the cumulative measurements of more than ten years of data from the gamma-ray telescope SPI onboard ESA’s INTEGRAL satellite. With these measurements, positrons are caught either in the act of their making or their final fate. This paves the path through the many positron-producing astrophysical objects and phenomena that will be presented towards a budgeting of the positrons throughout the Milky Way.