Polarization of MeV gamma-rays and 511 keV line shape as probes of SNIa asymmetry and magnetic field

Abstract

We discuss gamma-ray signatures associated with an asymmetric explosion and transport of positrons in SN Ia ejecta. In particular, Compton scattering of gamma-ray line photons can induce polarization in the continuum, which would be a direct probe of the asymmetries in the distribution of radioactive isotopes and/or of the scattering medium. Even more interesting would be a comparison of the shapes of $\gamma$-ray lines and that of the electron-positron annihilation line at 511 keV. The shapes of $\gamma$-ray lines associated with the decay of Co56 (e.g., lines at 847 and 1238 keV) directly reflect the velocity distribution of Co56. On the other hand, the 511 keV line arises from the annihilation of positions, which are also produced by the Co56 decay but can propagate through the ejecta before they slow down and annihilate. Therefore, the shape of the annihilation line might differ from other gamma-ray lines, providing constraints on the efficiency of positrons propagation through the ejecta and, as consequence, on the topology of magnetic fields in the ejecta and on the fraction of positrons that escape to the interstellar medium. We illustrate the above effects with two models aimed at capturing the main predicted signatures.

10 pages, 10 figures; replaced with accepted version (MNRAS)

References in corpus (7)

• Spectropolarimetry of Supernovae
• Early 56Ni decay γ-rays from SN2014J suggest an unusual explosion
• Spectropolarimetry of superluminous supernovae: insight into their geometry
• Gamma-rays from Type Ia supernova SN2014J
• Thermonuclear Supernovae: Probing Magnetic Fields by Late-Time IR Line Profiles
• Expectations for the Hard X-ray Continuum and Gamma-ray Line Fluxes from the Type Ia supernova SN 2014J in M82
• Gamma-Ray emission from SN2014J near maximum optical light

Cited by in corpus (4)

• Using Gamma Ray Monitoring to Avoid Missing the Next Milky Way Type Ia Supernova
• Gamma Ray polarimetry; a new window for the non-thermal Universe
• Evaluation of the performance of a CdZnTe-based soft $\gamma$-ray detector for CubeSat payloads
• Performance Evaluation of a silicon-based 6U Cubesat detector for soft $\gamma$-ray astronomy