Three-dimensional General-relativistic Simulations of Neutrino-driven Winds from Rotating Proto-neutron Stars

Abstract

We explore the effects of rapid rotation on the properties of neutrino-heated winds from proto-neutron stars (PNS) formed in core-collapse supernovae or neutron-star mergers by means of three-dimensional general-relativistic hydrodynamical simulations with M0 neutrino transport. We focus on conditions characteristic of a few seconds into the PNS cooling evolution when the neutrino luminosities obey L ν e + L ν ¯ e ≈ 7 × 10 51 erg s−1, and over which most of the wind mass loss will occur. After an initial transient phase, all of our models reach approximately steady-state outflow solutions with positive energies and sonic surfaces captured on the computational grid. Our nonrotating and slower rotating models (angular velocity relative to Keplerian Ω/ΩK ≲ 0.4; spin period P ≳ 2 ms) generate approximately spherically symmetric outflows with properties in good agreement with previous PNS wind studies. By contrast, our most rapidly spinning PNS solutions (Ω/ΩK ≳ 0.75; P ≈ 1 ms) generate outflows focused in the rotational equatorial plane with much higher mass-loss rates (by over an order of magnitude), lower velocities, lower entropy, and lower asymptotic electron fractions, than otherwise similar nonrotating wind solutions. Although such rapidly spinning PNS are likely rare in nature, their atypical nucleosynthetic composition and outsized mass yields could render them important contributors of light neutron-rich nuclei compared to more common slowly rotating PNS birth. Our calculations pave the way to including the combined effects of rotation and a dynamically important large-scale magnetic field on the wind properties within a three-dimensional GRMHD framework.

On a Spectral Method for β-particle Bound Excitation Collisions in Kilonovae

“…As the two compact objects inspiral due to the emission of gravitational waves, the neutron star(s) will be tidally disrupted, causing neutron-rich mass to eject and become gravitationally unbound. The merger results in a compact remnant (neutron star or black hole) surrounded by an accretion disk, from which various mechanisms produce further (post-merger) ejecta (see, for example, Perego et al 2014;Martin et al 2015;Desai et al 2022). The detailed EM spectra and broadband magnitudes from the observation of KN AT2017gfo (see, for example, Arcavi et al 2017;Cowperthwaite et al 2017;Drout et al 2017;Kasliwal et al 2017;Smartt et al 2017;Tanvir et al 2017;Troja et al 2017;Villar et al 2017), in concert with the gravitational-wave observation GW170817 (Abbott et al 2017a(Abbott et al , 2017b, provided an unprecedented window into the pre-and post-merger phases of the transient, and by examining the nuclear decay pattern in the ejecta seemed to confirm neutron star mergers are a source of r-process elements (Rosswog et al 2018).…”

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).…”