r-Process Nucleosynthesis and Radioactively Powered Transients from Magnetar Giant Flares
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arXiv
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| Autori principali: | , , , , , |
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| Natura: | Preprint |
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2025
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| _version_ | 1866913921716191232 |
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| author | Patel, Anirudh Metzger, Brian D. Goldberg, Jared A. Cehula, Jakub Thompson, Todd A. Renzo, Mathieu |
| author_facet | Patel, Anirudh Metzger, Brian D. Goldberg, Jared A. Cehula, Jakub Thompson, Todd A. Renzo, Mathieu |
| contents | We present nucleosynthesis and light-curve predictions for a new site of the rapid neutron capture process ($r$-process) from magnetar giant flares (GFs). Motivated by observations indicating baryon ejecta from GFs, Cehula et al. (2024) proposed mass ejection occurs after a shock is driven into the magnetar crust during the GF. We confirm using nuclear reaction network calculations that these ejecta synthesize moderate yields of third-peak $r$-process nuclei and more substantial yields of lighter $r$-nuclei, while leaving a sizable abundance of free neutrons in the outermost fastest expanding ejecta layers. The final $r$-process mass fraction and distribution are sensitive to the relative efficiencies of $α$-capture and $n$-capture freeze-outs. We use our nucleosynthesis output in a semi-analytic model to predict the light curves of novae breves, the transients following GFs powered by radioactive decay. For a baryonic ejecta mass similar to that inferred of the 2004 Galactic GF from SGR 1806-20, we predict a peak UV/optical luminosity of $\sim 10^{39}$-$10^{40}\,\rm erg\,s^{-1}$ at $\sim 10$-$15$ minutes, rendering such events potentially detectable following a gamma-ray trigger by wide-field transient monitors such as ULTRASAT/UVEX to several Mpc. The peak luminosity and timescale of the transient increase with the GF strength due to the larger ejecta mass. Although GFs likely contribute 1-10% of the total Galactic $r$-process budget, their short delay-times relative to star-formation make them an attractive source to enrich the earliest generations of stars. |
| format | Preprint |
| id |
arxiv_https___arxiv_org_abs_2501_17253 |
| institution | arXiv |
| publishDate | 2025 |
| record_format | arxiv |
| spellingShingle | r-Process Nucleosynthesis and Radioactively Powered Transients from Magnetar Giant Flares Patel, Anirudh Metzger, Brian D. Goldberg, Jared A. Cehula, Jakub Thompson, Todd A. Renzo, Mathieu High Energy Astrophysical Phenomena We present nucleosynthesis and light-curve predictions for a new site of the rapid neutron capture process ($r$-process) from magnetar giant flares (GFs). Motivated by observations indicating baryon ejecta from GFs, Cehula et al. (2024) proposed mass ejection occurs after a shock is driven into the magnetar crust during the GF. We confirm using nuclear reaction network calculations that these ejecta synthesize moderate yields of third-peak $r$-process nuclei and more substantial yields of lighter $r$-nuclei, while leaving a sizable abundance of free neutrons in the outermost fastest expanding ejecta layers. The final $r$-process mass fraction and distribution are sensitive to the relative efficiencies of $α$-capture and $n$-capture freeze-outs. We use our nucleosynthesis output in a semi-analytic model to predict the light curves of novae breves, the transients following GFs powered by radioactive decay. For a baryonic ejecta mass similar to that inferred of the 2004 Galactic GF from SGR 1806-20, we predict a peak UV/optical luminosity of $\sim 10^{39}$-$10^{40}\,\rm erg\,s^{-1}$ at $\sim 10$-$15$ minutes, rendering such events potentially detectable following a gamma-ray trigger by wide-field transient monitors such as ULTRASAT/UVEX to several Mpc. The peak luminosity and timescale of the transient increase with the GF strength due to the larger ejecta mass. Although GFs likely contribute 1-10% of the total Galactic $r$-process budget, their short delay-times relative to star-formation make them an attractive source to enrich the earliest generations of stars. |
| title | r-Process Nucleosynthesis and Radioactively Powered Transients from Magnetar Giant Flares |
| topic | High Energy Astrophysical Phenomena |
| url | https://arxiv.org/abs/2501.17253 |