Gamma-ray emission from decays of boosted nuclei in protomagnetar jets

TL;DR

This paper explores the potential to detect gamma-ray lines from radioactive decay of nuclei in relativistic jets of protomagnetars, which could reveal details about the central engine and explosion dynamics.

Contribution

It introduces the concept of observing Lorentz-boosted gamma-ray lines from radioactive nuclei in protomagnetar jets, highlighting their detectability and potential to inform supernova models.

Findings

Instruments like e-ASTROGAM and INTEGRAL/SPI can detect boosted gamma-ray lines from 10 kpc within days.

Detection is feasible for on-axis jets at extragalactic distances in rapidly spinning protomagnetar models.

Off-axis jet detection remains challenging, especially for supernovae at the Galactic Center.

Abstract

We examine the detectability of $\gamma$-ray emission originating from the radioactive decays of unstable nuclei that are synthesized in relativistic outflows launched in magnetorotational core-collapse supernovae. The observed lines have enhanced energies due to the Lorentz boosted nuclei and can also be seen until later times due to time dilation of the rest-frame half-lives. We find that instruments like \textit{e-ASTROGAM} and \textit{INTEGRAL/SPI} are sensitive to these boosted line emissions from hundreds of keV to tens of MeV at a distance of 10 kpc over timescales of tens of days. For favorable viewing angles, these decays can be detected to extragalactic distances for rapidly spinning protomagnetar models. On the other hand, detection for off-axis jets is challenging, even for a supernova at the Galactic Center. Measuring multiple decay lines in addition to the integrated luminosity over $\sim10$ days postbounce would allow for the ability to distinguish between models and shed light on central engine properties like magnetic field and spin.