Telescope Concepts in Gamma-Ray Astronomy

Siegert, Thomas; Horan, D.; Kanbach, G.

doi:10.48550/arxiv.2207.02248

Cited by 1 publication

(3 citation statements)

References 89 publications

(121 reference statements)

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“…1.1 and 1.2. Measurements in the MeV regime suffer from a scarcity of photons from astrophysical sources, carrying a million times more energy in one quantum than optical photons, for example, large instrumental background (Diehl et al, 2018;Siegert et al, 2019b), and apertures which align more with particle detectors in space rather than telescopes (Siegert et al, 2022d). Images are therefore often either 'reconstructed', i.e.…”

Section: A Puzzling Picturementioning

confidence: 99%

“…It is not excluded that the disk may actually not be the Galactic disk, but rather halo emission or even foreground. In the latter two cases, inferences with SPI would suffer from its coded aperture mask design, being almost incapable of measuring isotropic emission or shallow gradients (Caroli et al, 1987;Siegert et al, 2022d). In addition, Siegert et al (2019b) showed that there is hardly a trend of Doppler-shifts in the 511 keV line along Galactic longitudes, which would verify a rotation curve and the extended emission beyond the bulge as the Galactic disk.…”

Section: Introduction 1what Do We See?mentioning

confidence: 99%

“…Coded-mask telescopes, such as the currently best telescope to observe the 511 keV emission, INTEGRAL/SPI, cannot, or only hardly, observe isotropic emission as they rely on the contrast between emission and no emission to distinguish the instrumental background from the total signal. Shallow gradients in the morphology are also difficult to reliably detect with coded aperture masks(Siegert et al, 2022d) …”

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confidence: 99%

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The Positron Puzzle

Siegert¹

2023

Preprint

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The Positron Puzzle is a half-century old conundrum about the origin of the Galactic γ-ray emission line at photon energies of 511 keV, and the shape of its morphology, showing a bulge-to-disk luminosity ratio of ∼ 1 -unlike any astrophysical source distribution. Positrons (e + s) that have been cooled to the eV scale capture electrons (e − s) and form the intermediate bound state of Positronium (Ps) which decays on a nano-second timescale into two or three photons. Assuming the emission to originate from the Galactic bulge, centre, and disk, a visible annihilation rate in the Milky Way of ∼ 5 × 10 43 e + s −1 has to be explained, either by a quasi-steady state of production and annihilation, or by possibly multiple burst-like events that flood the Galaxy with e + s, then fading away on a Myr timescale. In this paper, I will review what the real Positron Puzzle is, where data and simulations have been used inadequately which resulted in false claims and an apparent quandary, what we really know and absolutely not know about the topic, and how this epistemic problem might be advancing.

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Section: A Puzzling Picturementioning

confidence: 99%