An energetic dirty fireball detected in soft X-rays
Abstract
The collapse of massive stars drives explosions that power relativistic fireballs. If only a small amount of matter is entrained, such clean fireballs can expand with Lorentz factors , accounting for gamma-ray bursts (GRBs). It has been hypothesized that energetic explosions with more baryon contamination, dubbed ``dirty fireballs'', may exist in nature, but they have not been observed. Here we report the observation of an extragalactic fast X-ray transient, EP241113a, detected by Einstein Probe. Compared to GRBs, it has a similar isotropic energy of erg, but significantly lower spectral peak energy. Theoretical modeling of its early X-ray afterglow suggests a relativistic jet with a low Lorentz factor of aligned close to the line-of-sight, signifying the prototype of a dirty fireball.
Cite
@article{arxiv.2603.26213,
title = {An energetic dirty fireball detected in soft X-rays},
author = {C. -Y. Dai and J. Quirola-Vásquez and Y. -H. Wang and H. -L. Li and J. Yang and X. -L. Chen and A. -L. Wang and H. Sun and X. -Y. Wang and B. Zhang and P. G. Jonker and Y. Liu and W. Yuan and D. Xu and Z. -G. Dai and M. E. Ravasio and L. Piro and P. O'Brien and D. Stern and H. -M. Zhang and Y. -P. Yang and T. An and Y. -L. Qiu and L. -P. Xin and W. -X. Li and R. -Y. Liu and X. -F. Wu and C. -Y. Wang and D. -M. Wei and Y. -F. Huang and F. E. Bauer and W. -H. Lei and B. -B. Zhang and N. -C. Sun and H. Gao and V. S. Dhillon and J. An and C. -H. Bai and A. Martin-Carrillo and H. -Q. Cheng and J. A. Chacon Chavez and Y. Chen and G. -W. Du and J. N. D. van Dalen and A. Esamdin and Y. -Z. Fan and X. Gao and F. Harrison and J. -W. Hu and M. -Q. Huang and S. -M. Jia and A. J. Levan and C. -K. Li and D. -Y. Li and E. -W. Liang and S. Littlefair and X. -W. Liu and Z. -Y. Liu and Z. -X. Ling and D. B. Malesani and H. -W. Pan and A. Rodriguez and A. Rossi and D. Mata Sánchez and J. Sánchez-Sierras and X. -J. Sun and M. A. P. Torres and A. P. C. van Hoof and X. -F. Wang and Q. -Y. Wu and X. -P. Xu and Y. -F. Xu and Y. -W. Yu and C. Zhang and M. -H. Zhang and S. -N. Zhang and Y. Zhang and Y. -H. Zhang and Z. -P. Zhu},
journal= {arXiv preprint arXiv:2603.26213},
year = {2026}
}
Comments
61 pages, 14 figures. Manuscript under consideration at Science. In accordance with the journal's policy, this version is the original version submitted by the authors and does not reflect any revisions made in response to peer review