SIMBAD references

GRB 250221A is a short gamma-ray burst (GRB) at redshift z = 0.768, with a duration of 1.8 s and no extended emission in either Swift/Burst Alert Telescope or Konus-Wind bands. A remarkable rebrightening feature in both optical and X-ray bands was observed at ∼0.6 days after the burst trigger, but no supernova or kilonova signature was detected. The burst properties and empirical correlations or distributions (e.g., duration, spectral hardness, location in the Amati correlation, ε value, f_eff parameter, and physical offset) favor a compact binary merger origin. However, a dense circumburst medium with n ∼ 80 cm^–3, obtained by adopting the energy injection into a jet to interpret the late-time rebrightening, is inconsistent with the compact binary merger origin. In this paper, we propose a two-component jet model to explain the multiwavelength afterglow observations of GRB 250221A, in which the relativistic narrow jet (${\theta }_{{\rm{c}}}\sim 3\mathop{.}\limits^{^\circ }8$) produces the prompt and the early decay afterglow emission, while the mildly relativistic wide jet (${\theta }_{{\rm{w}}}\sim 4\mathop{.}\limits^{^\circ }4$) dominates at later times, resulting in the observed rebrightening feature. If this is the case, one can obtain a lower medium density with n ∼ 0.72 cm^–3, which is a little bit higher than that of short GRBs in merger environments, but falls into the reasonable and acceptable range. Finally, a possible kilonova emission is also discussed within the scenario of compact star merger origin of GRB 250221A.