标题： 与位于恒星形成星系中的短硬伽马射线暴 GRB 070724A 相关的放射性驱动辐射的限制 显示英文标题

标题： Limits on Radioactive-Powered Emission Associated With a Short-Hard GRB 070724A in a Star-Forming Galaxy

摘要： 我们展示了针对短时长、硬谱伽马射线暴（GRB）070724A 的一次广泛观测活动的结果，该活动旨在探测可能由双星合并或涉及致密天体的塌缩所引发的放射性驱动辐射。 我们的多波段观测覆盖了所谓的 Li-Paczynski 小型超新星可能活跃的时间范围，从伽马射线暴触发后的三小时内开始，代表了对这种辐射最深且最全面的搜索之一。 我们未发现此类活动的证据，并对可能在核密度物质快速膨胀过程中形成的放射性同位素的丰度和寿命设定了限制。 此外，我们的限制比之前检测到的任何与其它伽马射线暴相关的宽线型 Ic 超新星（SN）的峰值亮度都要暗得多，有效地排除了这一事件中存在类似长伽马射线暴超新星的可能性。 考虑到宿主星系的明确红移（z=0.456），GRB 070724A 是少数几个已知的具有明确物理/本征量的短硬伽马射线暴之一。 GRB 070724A 的宿主星系是一个适度恒星形成率的星系，具有较老的恒星群体成分和相对较高的金属丰度（12+log(O/H)_KD02=9.1）。 我们没有发现视线方向上有大量可能掩盖超新星爆炸存在的消光现象，并估计了与假定宿主对齐的概率较小。 我们讨论了我们得出的限制如何符合短硬伽马射线暴及其潜在前身星和它们被认为产生环境的演变图景。 显示英文摘要

摘要： We present results of an extensive observing campaign of the short duration, hard spectrum gamma-ray burst (GRB) 070724A, aimed at detecting the radioactively-powered emission that might follow from a binary merger or collapse involving compact objects. Our multi-band observations span the range in time over which this so-called Li-Paczynski mini-supernova could be active, beginning within 3 hours of the GRB trigger, and represent some of the deepest and most comprehensive searches for such emission. We find no evidence for such activity and place limits on the abundances and the lifetimes of the possible radioactive nuclides that could form in the rapid decompression of nuclear-density matter. Furthermore, our limits are significantly fainter than the peak magnitude of any previously detected broad-lined Type Ic supernova (SN) associated with other GRBs, effectively ruling out a long GRB-like SN for with this event. Given the unambiguous redshift of the host galaxy (z=0.456), GRB 070724A represents one of a small, but growing, number of short-hard GRBs for which firm physical/restframe quantities currently exist. The host of GRB 070724A is a moderately star-forming galaxy with an older stellar population component and a relatively high metallicity of 12+log(O/H)_KD02=9.1. We find no significant evidence for large amounts of extinction along the line of sight that could mask the presence of a SN explosion and estimate a small probability for chance alignment with the putative host. We discuss how our derived constraints fit into the evolving picture of short-hard GRBs, their potential progenitors, and the host environments in which they are thought to be produced.