Pulsational Pair-Instability Supernovae

Abstract: The final evolution of stars in the mass range 70 - 140 solar masses is explored. Depending upon their mass loss history and rotation rates, these stars will end their lives as pulsational pair-instability supernovae producing a great variety of observational transients with total durations ranging from weeks to millennia and luminosities from 10$^{41}$ to over 10$^{44}$ erg s$^{-1}$. No non-rotating model radiates more than $5 \times 10^{50}$ erg of light or has a kinetic energy exceeding $5 \times 10^{51}$ erg, but greater energies are possible, in principle, in magnetar-powered explosions which are explored. Many events resemble Type Ibn, Icn, and IIn supernovae, and some potential observational counterparts are mentioned. Some PPISN can exist in a dormant state for extended periods, producing explosions millennia after their first violent pulse. These dormant supernovae contain bright Wolf-Rayet stars, possibly embedded in bright x-ray and radio sources. The relevance of PPISN to supernova impostors like Eta Carinae, to super-luminous supernovae, and to sources of gravitational radiation is discussed. No black holes between 52 and 133 solar masses are expected from stellar evolution in close binaries.

• The paper demonstrates that pulsational pair-instability in 70–140 solar mass stars triggers repeated nuclear bursts and episodic mass ejections.
• It employs the KEPLER code to model stellar evolution, capturing transient luminosities from 10^41 to 10^44 erg s⁻¹ and kinetic energies up to 10^51 erg.
• The study predicts an absence of black holes between 52 and 133 solar masses and suggests that PPISN can influence gravitational wave event formation.

An Expert Analysis of "Pulsational Pair-Instability Supernovae"

The paper "Pulsational Pair-Instability Supernovae" authored by S.E. Woosley offers a comprehensive examination of the final evolutionary stages of massive stars within an intriguing mass range of 70 - 140 solar masses. This study explores the conditions under which these stars undergo Pulsational Pair-Instability Supernovae (PPISN), a process characterized by pulsating nuclear flashes that lead to the ejection of stellar material in multiple stages.

Core Concepts and Methodology

The investigation hinges on the phenomenon of pair-instability, a result of thermal instabilities induced by the production of electron-positron pairs in extremely massive, low metallicity stellar cores. This process reduces the adiabatic index, causing dynamic instability. For helium cores between 30 and 133 solar masses, the instability prompts a contracting phase followed by violent nuclear burning. If the core mass exceeds approximately 133 solar masses, the structure is disrupted completely, leading to a Pair-Instability Supernova (PISN).

Utilizing the KEPLER code, this study employs detailed stellar evolution models, computing from the main sequence phase through to the late stages of convective and nuclear instability. The models carefully account for non-rotating and rotating star scenarios, adopting varying metallicity levels and mass loss prescriptions to simulate realistic stellar environments.

Numerical Outcomes and Observations

Key numerical simulations are presented, revealing diverse transient phenomena with luminosities from 10^41 to over 10^44 erg s^-1, and kinetic energies peaking around 10^51 erg in typical PPISN events. Notably, non-rotating models emit no more than 5 × 10^50 erg in light. These events encapsulate the rich variability of PPISN, where mass ejected by nuclear pulses can resemble different supernova types—Type Ibn, Icn, and IIn, and even protracted supernovae spans ranging from days to several thousand years.

The study also predicts the absence of black holes between 52 and 133 solar masses—a significant implication for understanding the final fate of massive isolated and binary systems in close proximity. It further speculates on PPISN's contribution to gravitational wave events, noting that preceding mass ejections can lead to legacy factors in binary black hole formation scenarios—akin to the characteristics inferred from GW 150914.

Theoretical Implications and Future Directions

Woosley's research offers theoretical underpinnings that have implications for a multitude of fields, notably transient astronomy and stellar synthesis. The proposed correlation between PPISN and supernova impostors like Eta Carinae, which exhibits similarly recurrent and diverse explosive phenomena, is a notable outcome. Therein lies potential to observationally validate theoretical predictions and refine models pertaining to stellar evolution in massive stars.

Going forward, the discussion invites further exploration into the mechanisms that might enable PPISN to generate superluminous supernovae through potential rotation-inducing phenomena, notably magnetar-driven explosions. In contemplating such dynamics, methodologies involving multi-dimensional modeling will be vital to sharpen predictions and simulate the complex interplay of mass, radiation, and gravity in these colossal celestial events.

In conclusion, Woosley's profound analysis and simulation of PPISN phenomena not only unveils various multi-phase explosive mechanisms but also sets a precedent for further targeted exploration into the assembly of massive stellar remnants and their evolutionary pathways. The insights provided in this extensive research have far-reaching ramifications across astrophysical and cosmological study, contributing richly to both theoretical frameworks and observational criteria.