Probing Circumstellar Material and Shock Acceleration in Core-Collapse Supernovae with High-Energy Neutrinos

TL;DR

The paper addresses HE neutrino production from ejecta–CSM interactions in core-collapse SNe, modeling how neutrino fluxes depend on the CSM density via $D_*$, the outer CSM radius $R_{ m csm}$, and microphysical parameters $\epsilon_p$ and $\epsilon_B$. It employs forward-shock acceleration with a time-dependent transport framework to compute $I_ u(E_ u,t)$ and explores detectability with IceCube using time- and energy-resolved likelihood analyses, producing realistic detection horizons on the order of $\sim 0.05$--$0.2$ Mpc for regular Type II SNe and up to $\sim 0.6$ Mpc for Type IIn SNe; a Galactic SN at $L\sim 10$ kpc could constrain $R_{ m csm}$ to within a factor of $\sim 2$--$3$, and $D_*$ and $\epsilon_p$ to $\sim 10$ times, with weaker constraints on $\epsilon_B$. The diffuse SN neutrino background from these channels remains well below IceCube's observed diffuse flux, indicating nearby SNe are the most promising targets. The study also demonstrates that, with high-statistics, time-resolved neutrino data, HE neutrino observations can meaningfully constrain the CSM density profile and shock-acceleration physics, enriching electromagnetic probes of stellar mass loss and pre-SN environments.

Abstract

We study high-energy (HE) neutrino production from interactions between supernova (SN) ejecta and the surrounding circumstellar material (CSM), focusing on regular Type~II and Type~IIn SNe. Using observationally inferred CSM density distributions, we calculate the resulting neutrino fluxes and examine their dependence on key parameters, including the CSM density normalization $D_*$, outer radius $R_{\rm csm}$, proton acceleration efficiency $ε_p$, and magnetic energy fraction $ε_B$. Detection prospects are assessed with a binned likelihood analysis for IceCube, indicating that nearby SNe with moderately dense, confined CSM can produce detectable signals, with a typical detection horizon of $\sim 0.1$ - 1 Mpc. For a Galactic SN at $\sim 10$ kpc, high-statistics neutrino data with detailed temporal and spectral information can constrain $D_*$, $R_{\rm csm}$, and $ε_p$ to within a factor of $\sim 10$ or to a precision of $\sim 20\%$, depending on the assumed values of $D_*$ and $R_{\rm csm}$. These neutrino signals thus provide a complementary probe of the CSM profile and shock acceleration, alongside traditional electromagnetic observations.

Figures (10)

• Figure 1: Normalized (to unity) distributions of $\dot M/V_{\rm w}$, or equivalently, $D_*$ [see Eq. \ref{['eq:D-mass-loss']}], for regular Type II (solid orange) and Type IIn (dashed blue) SNe. Assuming relative fractions of 90% (95%) for Type II and 10% (5%) for Type IIn, the corresponding weighted distribution combining both subtypes is shown by the red (green) curve.
• Figure 2: Maximal attainable proton energy $E_{p, \max}$ as a function of $D_*$ and $r$. The contours corresponding to $E_{p, \max}=1\,\mathrm{TeV}$ and $E_{p, \max}=1\,\mathrm{PeV}$ are shown by the blue and red lines, respectively. The green line indicates the condition $t_{\rm dyn}=t_{\rm cool}$, with $t_{\rm dyn}<t_{\rm cool}$ ($t_{\rm cool}<t_{\rm dyn}$) to the left (right) of the line. Also shown are the breakout radius $R_{\rm bo}$ (black dashed) and the deceleration radius $R_{\rm dec}$ (magenta dash--dotted), both varying with $D_*$. Note that $R_{\rm csm}=10^{16}$ cm is adopted when computing $R_{\rm bo}$ using Eq. \ref{['eq:Rbo']}.
• Figure 3: Expected all-flavor neutrino fluxes from a nearby CCSN at $L=10$ kpc using different values of $D_*$ (upper left), $R_{\rm csm}$ (upper right), $\epsilon_B$ (lower left), and $n$ and $\delta$ (lower right). In the upper panel, neutrino fluxes calculated with (thick) or without (thin) solving the proton transport equation are also compared. We adopt $D_* = 0.01$ or 1, $R_{\rm csm}=10^{15}$ cm, $\epsilon_B=0.1$, and $\epsilon_p=0.1$, unless otherwise specified.
• Figure 4: Expected all-flavor neutrino fluxes from a nearby SN at $L=10$ kpc with $D_*=0.01$ and 1. Five different time windows after the explosion have been considered. The same parameter values as in Fig. \ref{['fig:fluxes']} are taken.
• Figure 5: Expected track spectra at IceCube from a Type II SN (left panel) with $D_* = 0.01$ and $R_{\rm csm} = 4 \times 10^{14}\,\mathrm{cm}$, and from a Type IIn SN (right panel) with $D_* = 1$ and $R_{\rm csm} = 10^{16}\,\mathrm{cm}$, both located at a distance of $L = 10\,\mathrm{kpc}$. Two values of $\epsilon_B = 10^{-4}$ and 0.1 are adopted. For parameters not explicitly specified, the benchmark values listed in Table \ref{['tab:para']} are adopted.