AI 中文总结
基于二十年Swift数据系统性搜寻邻近无超新星长伽马射线暴，发现其体积率与短暴相当，支持致密双星并合起源，但样本量有限，低光度尾部未受约束。
AI 中文摘要
一些长时标伽马射线暴（LGRBs）并未与明亮的超新星（SNe）相关联，表明其爆发机制不同于传统的坍缩星通道。无超新星的LGRBs较为罕见，因此目前尚不清楚它们是零星出现的离群事件，还是伽马射线暴群体中的重要组成部分。在本工作中，我们利用二十年的Swift观测数据，对邻近（$z\lesssim$0.35）且无确认超新星关联的LGRBs进行了系统性搜寻。我们的分析揭示了一个异质性群体，其中一部分与恒星形成或尘埃环境相关，另一部分则与宁静星系相关。通过分析它们的高能性质、余辉和环境，我们识别出一个具有可靠超新星上限和距离尺度的LGRB样本，使候选无超新星事件的数量增加了一倍以上。基于我们的基准样本，我们推导出未进行射束校正的体积率$R = (0.5 \pm 0.2) {\rm~Gpc^{-3}\\ yr^{-1}}$，这与短时标伽马射线暴（SGRBs）以及光度$L \gtrsim\\,10^{50}\\,{\rm erg\\,s^{-1}}$的带有超新星的标准LGRBs的表观率相当。对于合理的射束因子，无超新星LGRBs的推断率与几种致密双星并合通道一致，尽管如果将整个群体归因于单一前身星通道，允许的参数空间已经较为狭窄。由于候选事件数量较少及其距离尺度的不确定性，我们的样本未能约束低光度尾部。未来需要更大的样本来确定它们是已知前身星通道的暗弱尾部，还是相对论性爆炸不同路径的证据。
英文摘要
Some long duration gamma-ray bursts (LGRBs) are not associated with bright supernovae (SNe), indicating that their explosion mechanism differs from the traditional collapsar channel. SN-less LGRBs are rare, thus it remains unclear whether they are sporadic outliers or a substantial component of the GRB population. In this work, we use two decades of Swift observations to conduct a systematic search for nearby ($z\lesssim$0.35) LGRBs without a confirmed SN association. Our analysis reveals a heterogeneous population linked, in part, to star-forming or dusty environments and, in part, to quiescent galaxies. Through the analysis of their high-energy properties, afterglows, and environments, we identify a sample of LGRBs with robust SN limits and distance scales, more than doubling the number of candidate SN-less events. From our fiducial sample, we derive a volumetric rate, not corrected for beaming, of $R = (0.5 \pm 0.2) {\rm~Gpc^{-3}\ yr^{-1}}$, comparable to the apparent rate of short duration GRBs (SGRBs) and standard LGRBs with SNe with luminosities $L \gtrsim\,10^{50}\,{\rm erg\,s^{-1}}$. For plausible beaming factors, the inferred rate of SN-less LGRBs is consistent with several compact binary merger channels, although the allowed parameter space is already narrow if the entire population is attributed to a single progenitor channel. Owing to the small number of candidate events and the uncertainties in their distance scale, our sample leaves the low-luminosity tail unconstrained. A larger sample will be needed to determine whether they are the faint tail of known progenitor channels or evidence of a distinct route to relativistic explosions.
Comments24 pages, 11 figures, 1 interactive figure, 2 tables; submitted to ApJ; comments welcome
