2024ApJ...962L..27D

Recently, a lack of supernova-associated with long-duration gamma-ray burst (GRB 230307A) at such a low redshift z = 0.065, but associated with a possible kilonova emission, has attracted great attention. Its heavy element nucleosynthesis and the characteristic of soft X-ray emission suggest that the central engine of GRB 230307A is a magnetar that is originated from a binary compact star merger. The calculated lower value of ε ∼ 0.05 suggests that GRB 230307A seems to have an ambiguous progenitor. The lower value of f_eff = 1.23 implies that GRB 230307A is not likely to be from the effect of “tip of iceberg.” We adopt the magnetar central engine model to fit the observed soft X-ray emission with varying efficiency and find that the parameter constraints of the magnetar falls into a reasonable range, i.e., B < 9.4 × 10¹⁵ G and P < 2.5 ms for Γ_sat = 10³, and B < 3.6 × 10¹⁵ G and P < 1.05 ms for Γ_sat = 10⁴. Whether the progenitor of GBR 230307A is from the mergers of neutron star-white dwarf (NS-WD) or neutron star-neutron star (NS-NS) remains unknown. The difference of GW radiation between NS-NS merger and NS-WD merger may be a probe to distinguish the progenitor of GRB 230307A-like events in the future.