Supernova 1987A: neutrino-driven explosions in three dimensions and light curves

Abstract

Context. The well-observed and well-studied type IIP Supernova 1987A (SN 1987A), produced by the explosion of a blue supergiant in the Large Magellanic Cloud, is a touchstone for the evolution of massive stars, the simulation of neutrino-driven explosions, and the modeling of light curves and spectra. Aims. In the framework of the neutrino-driven explosion mechanism, we study the dependence of explosion properties on the structure of different blue supergiant progenitors and compare the corresponding light curves with observations of SN 1987A. Methods. Three-dimensional (3D) simulations of neutrino-driven explosions are performed with the explicit, finite-volume, Eulerian, multifluid hydrodynamics code Prometheus, using of four available presupernova models as initial data. At a stage of almost homologous expansion, the hydrodynamical and composition variables of the 3D models are mapped to a spherically symmetric configuration, and the simulations are continued with the implicit, Lagrangian radiation-hydrodynamics code Crab to follow the blast-wave evolution into the SN outburst. Results. All of our 3D neutrino-driven explosion models, with explosion energies compatible with SN 1987A, produce 56 Ni in rough agreement with the amount deduced from fitting the radioactively powered light-curve tail. Two of our models (based on the same progenitor) yield maximum velocities of around 3000 km s −1 for the bulk of ejected 56 Ni, consistent with observational data. In all of our models inward mixing of hydrogen during the 3D evolution leads to minimum velocities of hydrogen-rich matter below 100 km s −1 , which is in good agreement with spectral observations. However, the explosion of only one of the considered progenitors reproduces the shape of the broad light curve maximum of SN 1987A fairly well. Conclusions. The considered presupernova models, 3D explosion simulations, and light-curve calculations can explain the basic observational features of SN 1987A, except for those connected to the presupernova structure of the outer stellar layers. All progenitors have presupernova radii that are too large to reproduce the narrow initial luminosity peak, and the structure of their outer layers is not suitable to match the observed light curve during the first 30-40 days. Only one stellar model has a structure of the helium core and the He/H composition interface that enables sufficient outward mixing of 56 Ni and inward mixing of hydrogen to produce a good match of the dome-like shape of the observed light-curve maximum, but this model falls short of the helium-core mass of 6 M inferred from the absolute luminosity of the presupernova star. The lack of an adequate presupernova model for the well-studied SN 1987A is a real and pressing challenge for the theory of the evolution of massive stars.

Neutrino-Driven Explosions

“…Kifonidis et al (2006) showed that the RT growth rate is considerably boosted by the initial asymmetries that support the onset of neutrino-driven explosions, and Hammer et al (2010) and Wongwathanarat et al (2015) demonstrated, performing 3D simulations of neutrino-driven explosions continuously from core bounce until shock breakout at the stellar surface, that this interaction of initial and secondary instabilities can facilitate the penetration of 56 Ni and 44 Ti with high velocities (up to more than 4000 km s −1 for the fastest clumps) deep into the hydrogen envelope as well as inward mixing of significant amounts of hydrogen to velocities as low as ∼100 km s −1 . For blue supergiant progenitors with compact, small helium cores (∼4-4.5 M ) both effects in combination are efficient enough to produce a good match of the wide, dome-like shape of the light-curve maximum observed for SN 1987A (Utrobin et al, 2015). Wongwathanarat et al (2015), however, found that the interaction of initial and secondary instabilities depends extremely sensitively, and in a subtle way, on the detailed density structure of the progenitor star, which determines the acceleration and deceleration phases of the outgoing shock and therefore the RT growth rates in the unstable layers as well as the time when the reverse shocks collide with the material of the expanding metal core.…”

A Two-Parameter Criterion for Classifying the Explodability of Massive Stars by the Neutrino-Driven Mechanism

“…The calibration aims at producing the explosion energy and ejected 56 Ni mass of SN1987A compatible with observations, for which the best values are E exp =(1.50±0.12)×10 51 erg (Utrobin 2005), E exp ∼1.3×10 51 erg (Utrobin & Chugai 2011), and M Ni =0.0723-0.0772 M e (Utrobin et al 2014), but numbers reported by other authors cover a considerable range (see Handy et al 2014 for a compilation). The explosion energy that we accept for an SN1987A model in the calibration process is guided by the ejected 56 Ni mass (which fully accounts for short-time and long-time fallback) and a ratio of E exp to ejecta mass in the ballpark of estimates based on light-curve analyses (see Table 1 for our values).…”

“…Because of the "gentle" acceleration of the SN shock by the neutrino-driven mechanism (also in 3D simulations;see Utrobin et al 2014), it is difficult to produce this amount of ejected 56 Ni just by shock-induced explosive burning. M Ni 56 in Table 1 mainly measures this component but also contains 56 Ni from proton-rich neutrino-processed ejecta.…”

Abundance anomalies in metal-poor stars from Population III supernova ejecta hydrodynamics

“…When the plumes cross the interface between the C-O and He shells, a hydrodynamic process akin to the Rayleigh-Taylor instability stretches them into long, narrow fingers. Some three-dimensional neutrino-driven, core-collapse explosions of Wongwathanarat et al (2013Wongwathanarat et al ( , 2015 and Utrobin et al (2014) It should be emphasized that the production of nickel fingers is sensitive to the precise shock kinematics inside the star; not all stellar models in Wongwathanarat et al (2015) produce fingers. When the forward shock crosses the He-H interface (if the progenitor star has retained its hydrogen envelope), it slows down dramatically, and this excites a reverse shock propagating backward, toward smaller mass coordinates.…”

“…This, of course, has pivotal implications for chemical enrichment. Under which specific conditions are fingers expected is the subject of recent, rapidly developing research (Hammer et al 2010;Wongwathanarat et al 2013Wongwathanarat et al , 2015Utrobin et al 2014).…”