Pre-Supernova Eruptions Triggered by Sudden Energy Deposition in Low-Mass Core-Collapse Supernova Progenitors

TL;DR

This study probes pre-supernova eruptions in low-mass core-collapse progenitors ($M_{\rm ZAMS}\approx9$–$10\,M_\odot$) by modeling a sudden energy release in the deep stellar interior. Using 1D non-radiative hydrodynamics with SNEC, deposited energy $E_{\rm dep}=f_{\rm dep}E_{\rm bind,tot}$ drives shocks that unbind part of the envelope, and the ejecta mass $M_{\rm ej}$ scales with the energy gained by the H-rich envelope as $M_{\rm ej}\propto E_{\rm gain}^{3.5}$, with only modest scatter across 9–10 $M_\odot$ progenitors ($\sim$2.6). The eruption also flattens the bound envelope, potentially altering the ensuing SN light curve, while radiative-transfer calculations with STELLA predict faint, long-lasting precursor emission ($L_{\rm bol}\sim10^{38.5}$–$10^{40}$ erg s$^{-1}$; $T_{\rm bb}\sim2000$–$3000$ K) peaking in the infrared. Overall, the work provides a framework to connect the energetics of deep nuclear flashes to observable precursors and late-time SN properties, and publicly shares the resulting profiles and light curves for future studies.

Abstract

In low-mass core-collapse supernova (CCSN) progenitors, nuclear burning beyond oxygen can become explosive under degenerate conditions, triggering eruptive mass loss before the final explosion. We investigate such pre-SN eruptions using \texttt{SNEC} hydrodynamic simulations and realistic stellar models, parameterizing the nuclear energy deposition as a fraction of the binding energy of the combined He layer and H-rich envelope. For the lowest-mass model (9 $M_\odot$), the ejecta mass ($M_{\rm ej}$) scales with the energy gained by the H-rich envelope via a power law (index$\sim$3.5). Across 9-10 $M_\odot$, this relation shows limited scatter within a factor of $\sim$2.6, enabling an estimation of the gained energy from $M_{\rm ej}$. The shock passage also flattens the bound envelope, which can affect the SN light curve morphology and provide another diagnostic for the eruption. Then, we compute the associated precursor light curves for the 9 $M_\odot$ model with the multi-group radiative-transfer code \texttt{STELLA}. These signals are typically faint, with bolometric luminosities of $\sim10^{39}$ erg s$^{-1}$ lasting hundreds of days. Their cool black-body spectra make them brighter in the infrared, yet several magnitudes fainter than observed pre-SN precursors at the threshold for full envelope ejection. To aid future studies, we make our post-eruption stellar profiles and precursor light curves publicly available.

Figures (9)

• Figure 1: Profiles of density (left panel) and binding energy (right panel, computed as Eq. \ref{['eq:eb']}) as a function of mass coordinate for our employed progenitor models ($M_{\rm ZAMS}=9$-10 $M_\sun$) alongside three more massive ones up to 12 $M_\sun$ for comparison. All models are from 2016ApJ...821...38S.
• Figure 2: Density profiles as a function of radius at selected times for 3 eruption simulations using the 9 $M_\sun$ model. Fractional energy deposition ($f_{\rm dep}\equiv E_{\rm dep}/E_{\rm bind,tot}$) is 0.6, 0.8, and 1.0 from left to right. The solid gray and dashed cyan lines represent the results at 1 year for the full and H-only simulations, respectively. After 1 year, we only plot the results for the long-term H-only simulations.
• Figure 3: Time evolution of the ejecta mass ($M_{\rm ej}$, left panel) and mean velocity ($\langle v_{\rm ej} \rangle$, right panel) for selected fractional energy deposition ($f_{\rm dep}=E_{\rm dep}/E_{\rm bind,tot}$). Solid curves represent the full simulations including the He layer and H-rich envelope, while "$\times$" symbols show simulations where the He layer was removed at 80 days.
• Figure 4: Profiles of total specific energy ($e_{\rm tot}$; top) and velocity (bottom) as a function of mass coordinate for the progenitor model (black) and for $f_{\rm dep} = 0.8$ (green) and 0.9 (red) at 5 years post energy deposition. A signed logarithmic scale is used for $e_{\rm tot}$ to enhance clarity.
• Figure 5: The fraction of ejected mass relative to the mass of the H-rich envelope ($M_{\rm ej}/M_{\rm Henv}$) as a function of fractional energy deposition ($f_{\rm dep}$, left panel) and fractional energy gained by the H-rich envelope ($f_{\rm gain}$, right panel). Black bars show the results at 1, 5 and 10 years (from bottom to top) while the open circles mark the results at 3 years after energy deposition. In each panel, the magenta curves is a power-law fit to the data. In the right panel, the blue stars show the results with fractional energy deposited at the base of the H-rich envelope which show excellent agreement with the main results.