Pre-Supernova Multiple Giant Eruptions in Massive Stars

TL;DR

This paper investigates the effects of three consecutive giant eruptions (MGEs) on a 100 M$_\odot$ star using the MESA stellar evolution code, exploring two mass-loss rates ($\dot{M}=10^{-2}$ and $10^{-1}$ M$_\odot$ yr$^{-1}$) and two metallicities ($Z=0.02$ and $Z=0.008$). Eruptions trigger a rapid convective-envelope response, with an initial luminosity rise followed by a pronounced drop, and the star then recovers toward a new quasi-equilibrium; recovery timescales and the magnitude of luminosity declines depend strongly on both $\dot{M}$ and metallicity. Higher $\dot{M}$ yields larger energy losses ($\sim 9\times10^{46}$–$9\times10^{47}$ erg per GE) and longer recoveries, while lower metallicity generally shortens recovery and reduces the luminosity decline for a given eruption. The outer envelope shows thermal-imbalance-driven oscillations during recovery at higher $\dot{M}$ and Galactic metallicity, suggesting conditions favorable for subsequent eruptions. These results advance our understanding of pre-SN evolution, LBV-like variability, and the potential role of MGEs in shaping the fate of massive stars.

Abstract

Massive stars can exhibit giant eruptions with high mass loss shortly before their explosion as a core-collapse Supernova. These multiple giant eruptions (MGEs) may have a commutative effect that brings the star to a different state, possible one that favors the explosion. To address this problem, we evolve a 100 solar mass star and initiate a series of three giant eruptions lasting one year each, testing different mass loss rates and different metallicities. Following each eruption, we track the recovery phase to examine the post-eruption behavior of the star and its recovery timescale. The MGEs lead to a decrease in luminosity, accompanied by a slight increase in temperature. Later, during the recovery phases as the star starts to retain its equilibrium state, its luminosity increases. The recovery time-scale varies significantly after each eruption for independent on the mass loss rate, but it is shorter for lower metallicities. For the higher mass-loss rates during the recovery phase, the outer layers of the star exhibit oscillations and undergo compression at higher metallicity. These oscillations are most likely a consequence of thermal imbalance in the outer envelope. This behavior at higher mass-loss rates also suggests that the thermal readjustments during recovery may create favorable conditions for a subsequent eruption of the star.

Figures (6)

• Figure 1: The stellar tracks of luminosity and temperature (HR diagram) for a $\rm 100~M_{\odot}$ star with Galactic metallicity, obtained using mesa, are shown. Here, A represents the zero-age-MS phase in both panels. Panel (a) depicts the evolution of a $\rm 100~M_{\odot}$ star undergoing three cycles of giant eruptions with a mass loss rate of $\rm 10^{-2}~M_{\odot}~yr^{-1}$ over 1 year, including the recovery phases (Model 1). Panel (b) shows the evolution of a $\rm 100~M_{\odot}$ star undergoing three cycles of giant eruptions with a mass loss rate of $\rm 10^{-1}~M_{\odot}~yr^{-1}$ over a 1 year period, along with the recovery phases (Model 2). Here, the evolutionary tracks during the three cycles of GE in both panels are overlapping, so we only show the first GE for both models. Additionally, in both models, the first GE is initiated at the same location but is labelled differently: in model 1, it corresponds to point B, while in model 2, it corresponds to point P.
• Figure 2: The variation in luminosity $L$ (panel a), radius $R$, effective temperature $T_{\rm eff}$ (panel c) of the star during the MGEs, and recovery phases are shown for both model above. Here, the dashed line represents the GEs and recovery phases for $Z$ = 0.02, while the solid line represents the GEs and recovery for at $Z$ = 0.008.
• Figure 3: Figure shows the variation in the temperature from the outer layers to the interior of the star. During the recovery phase, contraction occurs, and thus the temperature and radius decrease. Although the temperature changes are minimal, they lead to a significant increase in opacity, as shown in the bottom panel, in the outer layers at point T2 due to the thermal imbalance.
• Figure 4: The relation between the mass loss rate during the eruption $\log \dot{M}$ and the decline in luminosity $\log |\Delta L|$ for two metallicities: $Z$ = 0.02 (blue) and $Z$ = 0.008 (red). The dashed lines represent the best-fit lines for each metallicity (see equation \ref{['eq1']}).
• Figure 5: The variation in the stellar properties, including temperature, density, pressure, mass, and entropy of a $\rm 100~M_{\odot}$ during the MGEs, and recovery phase are shown above for Model 1. Here points, C, B', C', B", C", and B"' represent the last profile of 1st GE, the last profile of 1st recovery, the last profile of 2nd GE, the last profile of 2nd recovery, the last profile of the 3rd GE, and last profile of the 3rd recovery phase. Here, the dashed line represents the stellar parameters at the Galactic metallicity, while the solid line represents the stellar parameters at LMC metallicity.