Three-dimensional General-relativistic Simulations of Neutrino-driven Winds from Magnetized Proto–Neutron Stars

Abstract

Formed in the aftermath of a core-collapse supernova or neutron star merger, a hot proto–neutron star (PNS) launches an outflow driven by neutrino heating lasting for up to tens of seconds. Though such winds are considered potential sites for the nucleosynthesis of heavy elements via the rapid neutron capture process (r-process), previous work has shown that unmagnetized PNS winds fail to achieve the necessary combination of high entropy and/or short dynamical timescale in the seed nucleus formation region. We present three-dimensional general-relativistic magnetohydrodynamical simulations of PNS winds which include the effects of a dynamically strong (B ≳ 1015 G) dipole magnetic field. After initializing the magnetic field, the wind quickly develops a helmet-streamer configuration, characterized by outflows along open polar magnetic field lines and a “closed” zone of trapped plasma at lower latitudes. Neutrino heating within the closed zone causes the thermal pressure of the trapped material to rise in time compared to the polar outflow regions, ultimately leading to the expulsion of this matter from the closed zone on a timescale of ∼60 ms, consistent with the predictions of Thompson. The high entropies of these transient ejecta are still growing at the end of our simulations and are sufficient to enable a successful second-peak r-process in at least a modest ≳1% of the equatorial wind ejecta.

The Effects of r-Process Enrichment in Hydrogen-rich Supernovae

“…However, the standard neutrino-driven proto-neutron star (PNS) wind believed to accompany many, if not all, core-collapse SNe, likely fails to produce heavy r-process elements (e.g., Qian & Woosley 1996;Otsuki et al 2000;Thompson et al 2001;). This has prompted variations of the standard neutrino-wind models, such as convection-driven wave heating (e.g., Metzger et al 2007;Nevins & Roberts 2023), strong magnetic fields (e.g., Thompson 2003;Thompson et al 2004;Metzger et al 2007;Winteler et al 2012;Mösta et al 2014;Vlasov et al 2017;Thompson & ud-Doula 2018;Prasanna et al 2022;Desai et al 2023) and/or rapid rotation (e.g., Desai et al 2022;Prasanna et al 2023). In the (likely rare) case in which the core of the progenitor is rapidly spinning at the time of the collapse (e.g., Ma & Fuller 2019), the latter can lead to an accretion torus forming around the central compact object (e.g., MacFadyen & Woosley 1999; however, see Quataert et al 2019;Burrows et al 2023, who find disk formation from the collapse of a 40 M e progenitor even without initial rotation).…”

“…In this paper, we extend these works to consider the impact that r-process enrichment would have on Type IIP SNe (SNe IIP) resulting from the explosions of hydrogen-rich massive progenitor stars. Most scenarios for substantial r-process production in SNe require the birth of a rapidly rotating black hole or neutron star engine (e.g., Thompson et al 2004;Metzger et al 2007;Vlasov et al 2017;Prasanna et al 2022;Desai et al 2023;Prasanna et al 2023), an occurrence less frequently associated with the collapse of hydrogen-rich progenitors than stripped-envelope stars (e.g., Kasen & Bildsten 2010;Piran et al 2017;Metzger et al 2018;however, see Sukhbold & Thompson 2017;Dessart & Audit 2018). Nevertheless, with SNe IIP being the most common corecollapse explosion in the universe (Smith et al 2011), the large sample of light curves to be collected over the next years provides an opportunity to search for outlier events, comprising even a rare subset of the sample.…”