2025/01/28 by Anirudh Patel, Patel, Anirudh, Brian D. Metzger +9 · 1 voice · 4 citations
Physics and Astronomy · #Astro and Planetary Science #Planetary Science and Exploration #Gamma-ray bursts and supernovae
paper · pdf · doi:10.3847/1538-4357/adceb7
Abstract 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, J. Cehula et al. proposed that 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 semianalytic 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 ∼10 39 –10 40 erg s −1 at ∼10–15 minutes, rendering such events potentially detectable to several Mpc following a gamma-ray trigger by wide-field transient monitors such as ULTRASAT/UVEX. 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.