Measuring the smearing of the Galactic 511 keV signal: positron propagation or supernova kicks?

Siegert, Thomas; Crocker, Roland M.; Macias, Oscar; Panther, Fiona H.; Calore, Francesca; Song, Deheng; Horiuchi, Shunsaku

doi:10.48550/arxiv.2109.03691

Cited by 5 publications

(9 citation statements)

References 91 publications

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“…We note that SPI also detects photons above 8 MeV; however, the official tools do not provide an imaging or spectral response at these energies. On the other hand, the SPI spectrum below 0.5 MeV is already well determined, and we refer the reader to Bouchet et al (2011) and Siegert et al (2021b) for details about this low-energy band. Extending the spectrum in either direction is beyond the scope of this paper.…”

Section: Spectrummentioning

confidence: 99%

Diffuse Galactic emission spectrum between 0.5 and 8.0 MeV

Siegert,

Berteaud,

Calore

et al. 2022

Preprint

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The last measurement of the diffuse emission spectrum of the Milky Way in the megaelectronvolt (MeV) photon energy range was performed by CGRO/COMPTEL more than 20 years ago. We report a new analysis with the spectrometer SPI aboard INTEGRAL in the band 0.5-8.0 MeV, finally superseding the signal-to-noise ratio of the historic observations. This is possible thanks to an elaborate instrumental background model and careful considerations of the selected data, which are strongly affected by solar activity. We base our analysis on energy-dependent spatial template fitting in a region of ∆l × ∆b = 95 • × 95 • around the Galactic centre. Our flux estimates are consistent with COMPTEL measurements and show no 'MeV bump'. The spectrum follows a power-law shape with index −1.39 ± 0.09 stat ± 0.10 syst and an integrated flux of (5.7 ± 0.8 stat ± 1.7 syst ) × 10 −8 erg cm −2 s −1 between 0.5 and 8.0 MeV. We find that cosmic-ray electrons and propagation models consistent with the latest Fermi/LAT, Voyager 1, and AMS-02 data are broadly in agreement with the inferred inverse Compton spectral shape. However, a mismatch of a factor of 2-3 in normalisation with respect to baseline expectations may point to enhanced target photon densities and/or electron source spectra in the inner Galaxy, slightly modified diffusion properties, or the presence of an unresolved population of MeV γ-ray sources.

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Section: Spectrummentioning

confidence: 99%

Diffuse Galactic emission spectrum between 0.5 and 8.0 MeV

Siegert,

Berteaud,

Calore

et al. 2022

Preprint

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“…The function f (f Ps , F 511 ) for the Positronium continuum and 511 keV line can be found in Ref. [38] and is only parametrized by the Positronium fraction f Ps and the 511 keV line flux F 511 . Likewise, the function g(f PBH , M PBH ) is described in detail in the main text and parametrized through the fraction f PBH to account for possible PBH evaporation of a monochromatic PBH mass distribution centered at M PBH .…”

Section: Appendix A: Integral/spi Data Setmentioning

confidence: 99%

Strong constraints on primordial black hole dark matter from 16 years of INTEGRAL/SPI observations

Berteaud,

Calore,

Iguaz

et al. 2022

Preprint

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We present a new analysis of the diffuse soft γ-ray emission towards the inner Galaxy as measured by the SPectrometer aboard the INTEGRAL satellite (SPI) with 16 years of data taking. The analysis implements a spatial template fit of SPI data and an improved instrumental background model. We characterize the contribution of Primordial Black Holes (PBH) as dark matter (DM) candidates evaporating into O(1) MeV photons by including, for the first time, the spatial distribution of their signal into the fitting procedure. No PBH signal is detected, and we set the strongest limit on PBH DM for masses up to 4 × 10 17 g, significantly closing in into the so-called asteroid mass range.

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“…As of now, only a dozen nuclear lines of astrophysical origin have been observed with HEAO-3, COMPTEL, RHESSI, SPI (and NuSTAR). These include the positron annihilation line from the centre of the Galaxy at 511 keV [e.g., 11,12,13,14,15,16], short-and long-lived ejecta from massive stars and their supernovae such as 44 Ti [e.g., 17,18,19,20,21,22, at 68, 78, 1157 keV], 26 Al [e.g., 23,24,25,26,27, at 1809 keV], and 60 Fe [e.g., 28, 29, 30, at 1173 and 1332 keV], short-lived isotopes powering the early light-curves of type Ia supernovae [e.g., 31, 32, 33, 34, with 56 Ni and 56 Co at 158, 812, and 847, 1238 keV, respectively], as well as nuclear excitation lines from solar flares [e.g., 35, 36, with 511 keV from electron-positron annihilation, 2 H at 2223, 12 C at 4438, and 16 O at 6129 keV, among others]. With a factor of ten improvement in the line sensitivity, the number of detected lines, and therefore the science enabled by this, could increase by the same order of magnitude, eventually finding CR excitation of interstellar medium material, ejecta from classical novae, and multiple supernova lines [e.g., 37].…”

Section: The 'Mev Sensitivity' Gapmentioning

confidence: 99%

Telescope Concepts in Gamma-Ray Astronomy

Siegert¹,

Horan²,

Kanbach³

2022

Preprint

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This chapter outlines the general principles for the detection and characterisation of high-energy γ-ray photons in the energy range from MeV to GeV. Applications of these fundamental photon-matter interaction processes to the construction of instruments for γ-ray astronomy are described, including a short review of past and present realisations of telescopes. The constraints encountered in operating telescopes on high-altitude balloon and satellite platforms are described in the context of the strong instrumental background from cosmic rays as well as astrophysical sources. The basic telescope concepts start from the general collimator aperture in the MeV range over its improvements through coded-mask and Compton telescopes, to pair production telescopes in the GeV range. Other apertures as well as understanding the measurement principles of γ-ray astrophysics from simulations to calibrations are also provided.

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Measuring the smearing of the Galactic 511 keV signal: positron propagation or supernova kicks?

Cited by 5 publications

References 91 publications

Diffuse Galactic emission spectrum between 0.5 and 8.0 MeV

Diffuse Galactic emission spectrum between 0.5 and 8.0 MeV

Strong constraints on primordial black hole dark matter from 16 years of INTEGRAL/SPI observations

Telescope Concepts in Gamma-Ray Astronomy

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