Observable Signatures of Supernova Shock Breakout in Confined Circumstellar Medium

@misc{chen2026observable,
  title = {{Observable Signatures of Supernova Shock Breakout in Confined Circumstellar Medium}},
  author = {Wun-Yi Chen and Ke-Jung Chen and Keiichi Maeda and Friedrich K. Röpke},
  howpublished = {arXiv},
  year = {2026},
  month = oct,
  doi = {10.48550/arxiv.2609.13540},
  eprint = {2609.13540},
  archivePrefix = {arXiv},
  url = {https://arxiv.org/abs/2609.13540},
  note = {CC BY-NC-SA 4.0},
}

TY  - UNPB
TI  - Observable Signatures of Supernova Shock Breakout in Confined Circumstellar Medium
AU  - Wun-Yi Chen
AU  - Ke-Jung Chen
AU  - Keiichi Maeda
AU  - Friedrich K. Röpke
PY  - 2026
DA  - 2026/10/29
PB  - arXiv
DO  - 10.48550/arxiv.2609.13540
UR  - https://arxiv.org/abs/2609.13540
AB  - Supernova shock breakout encodes rich information about stellar explosions, including the properties of the progenitor, the explosion mechanism, and the circumstellar environment. We present the first two-dimensional multigroup radiation-hydrodynamic simulations of shock breakout from Red Supergiant (RSG) progenitor stars embedded in confined circumstellar medium (CSM) produced shortly before core collapse. Our simulations reveal that radiation escaping ahead of the shock forms a radiative precursor that modifies the shock dynamics, drives multidimensional mixing within the radiating gas layers, and alters the emergent radiation from the CSM. For the CSM models explored here, the resulting bolometric light curves reach peak luminosities of ∼1−3 × 10^44 erg s^−1 with durations of ∼4−35~hr, with these signatures controlled by the CSM mass and the confined radius. Our multi-wavelength calculations further reveal a pronounced extreme-ultraviolet emission, where ionizing photons of energies ≥54.4~eV can sustain flash-ionized He II and power strong emission from its recombination line of λ4686 mathringA. Furthermore, we identify diagnostic signatures of shock breakout with dense CSM and assess their detectability with Einstein Probe and ULTRASAT. Our models and predictions provide promising diagnostics of shock breakout in CSM that may be detectable by current and forthcoming high-cadence ultraviolet and X-ray space telescopes.
ER  -