Double-Shock Radiation in Supernova Wind Breakout and EP260321a

@misc{li2026doubleshock,
  title = {{Double-Shock Radiation in Supernova Wind Breakout and EP260321a}},
  author = {Zhuo Li and Rui-Ze Shi and Qiang Wang},
  howpublished = {arXiv},
  year = {2026},
  month = oct,
  doi = {10.48550/arxiv.2610.29226},
  eprint = {2610.29226},
  archivePrefix = {arXiv},
  url = {https://arxiv.org/abs/2610.29226},
}

TY  - UNPB
TI  - Double-Shock Radiation in Supernova Wind Breakout and EP260321a
AU  - Zhuo Li
AU  - Rui-Ze Shi
AU  - Qiang Wang
PY  - 2026
DA  - 2026/10/21
PB  - arXiv
DO  - 10.48550/arxiv.2610.29226
UR  - https://arxiv.org/abs/2610.29226
AB  - We study the supernova (SN) shock breakout (SBO) from an optically thick stellar wind. The SN ejecta-wind interaction forms a forward shock (FS) plus reverse shock (RS) structure. The RS's internal energy and shock velocity are both a fraction μ≲1/6 of the FS's. The lower RS velocity makes it easier to build up local thermal equilibrium (LTE) and generate blackbody (BB) emission. In the same time a μ^−1≳6 times larger non-BB emission may be produced by the likely non-LTE FS. We apply the theory to analyze the recent detected type Ic-BL SN2026gzf associated X-ray flash EP260321a, and find it is naturally accounted for by a SN wind breakout: the ∼0.13\,keV, thermal SBO emission can be produced by the RS during the interaction of a typical type Ic-BL SN ejecta (E_k∼10^52erg and M_e∼1M_⊙) and a stellar wind with a mass M_w∼10^−4M_⊙ confined within a radius r_w∼10^13cm; the X-ray rise time is mainly determined by the RS emission time, whereas the long duration and decrease time are due to the scatterings of SBO photons by a distant shell-like medium which has a large photosphere, r_ph∼10^14\,cm; the early, within 30\,ks, optical emission can be naturally explained by the cooling emission of a shocked pure C/O envelope, since the observed SBO onset is delayed by ≳ a few ks due to the large medium photosphere. BB+non-BB components from RS and FS, respectively, may be common in SN wind breakouts. SBO observations can be crucial in the study of progenitor stars by providing information for the ejecta from the SN explosion and the nearby wind from the pre-SN activities.
ER  -