Optical and Infrared Observations of Gamma-Ray Burst Afterglows

这个项目的目标是利用位于基特峰的密歇根-达特茅斯-麻省理工学院(MDM)2.4米望远镜的地面、光学/红外测光和光谱分析来快速跟踪伽马射线暴(GRB)余辉。自1998年以来，PI一直是这类研究的重要参与者之一，并且能够很好、迅速地接触到这类后续工作所必需的望远镜。利用BeppoSAX和/或RXTE卫星在数小时内定位的北半球每年大约6至8次爆发，该项目将继续利用MDM天文台的两个望远镜发现和表征伽马射线爆发的光学余辉的成功计划。从2000年HETE-II卫星发射开始，将有可能在伽玛暴事件发生后几分钟内进行光学识别，从而有机会在小型望远镜(如MDM1.3m)上获得多色光学光曲线，并在中型望远镜(如MDM2.4m)上获得吸收线红移。这些数据可用于研究余辉的时间衰减和光谱演变，以便诊断火球的能量，并模拟发生这些爆炸的星际环境，例如均匀的星际介质和恒星风。HETE-II还将对迄今为止尚未识别的短时伽马射线暴类别敏感，其伽马射线谱特性和通量分布与触发所有先前余辉探测的长持续时间伽马射线暴截然不同。这项工作的目标是揭示不同的伽玛射线暴祖先群体，例如，那些在银河系星际介质之外旅行的老年伽玛暴祖先，与那些在密集的恒星形成区域中结束了短暂生命的人。红外测光对于这种区分是至关重要的。快速红外光度法，特别是在K波段，提供了识别最高红移和/或最模糊的伽玛暴的机会。MDM 2.4M和ONIS红外相机可以在事件发生后一小时内轻松探测到中等遮挡的GRB到z=10。在更长的时间尺度上，可以跟踪几天的光曲线，以发现预测的(偶尔检测到的)时间陡化，这是喷气式余辉的特征。测量这种断裂对于量化光束对火球的能量以及对伽玛暴及其余辉的全球统计数据的影响至关重要。最后，可以对较亮和较近的事件的余辉进行几周的监测，以便在它们的后期光学光曲线中寻找底层超新星的特征。至少部分伽玛暴可能与大质量恒星的超新星有关，这有望成为人们长期寻求的伽玛暴本身的物理机制。该项目的资金由NSF河外天文与宇宙学计划(AST/EXC)提供。*

ABSTRACTAST-0071108HalpernThis project has as its objective the rapid follow-up of gamma-ray burst (GRB) afterglows using ground-based, optical/IR photometry and spectroscopy on the Michigan-Dartmouth-MIT (MDM) 2.4m telescope on Kitt Peak. The PI has been one of the important players in this type of research since 1998 and has the good, prompt access to the telescope which is necessary for this type of follow-up work.Using the approximately 6 to 8 bursts per year in the northern hemisphere that are located within hours by the BeppoSAX and/or RXTE satellites, this project will continue a successful program of discovering and characterizing the optical afterglows of gamma-ray bursts with the two telescopes of the MDM Observatory. Starting with the year 2000 launch of the HETE-II satellite, it will become possible to make optical identifications within minutes of a GRB event, which affords the opportunity to obtain multicolor optical light curves on small telescopes such as the MDM1.3m, and absorption-line redshifts on medium-sized telescopes such as the MDM 2.4m.These data can be used to study the temporal decay and spectral evolution of the afterglow in order to diagnose the energetics of the fireball, and to model the circumstellar environmentsin which these explosions occur, e.g., uniform interstellar medium vs. stellar wind. HETE-II will also be sensitive to the class of short-duration gamma-ray bursts, which have heretofore not been identified, and are distinct in their gamma-ray spectral properties and flux distribution from the long-duration bursts which have triggered all previous after- glow detections. This work has the goal of revealing a distinct population of GRB progenitor, for example, old ones that have traveled outside their galaxy's interstellar medium, versus those that end their short lives while still embedded in dense, star-forming regions. Infrared photometry is of utmost importance for this distinction. Prompt IR photometry, particularly in the K band, offers the opportunity to identify thehighest redshift and/or most obscured GRBs. The MDM 2.4m and ONIS IR camera, can easily detect a moderately obscured GRB to z = 10 within an hour of the event. On longer time scales, the light curves can be followed for several days in order to discover the predicted (and occasionally detected) temporal steepening which is the signature of jet-like afterglows. Measuring such breaks is crucial to quantifying the effects of beaming on the energetics of the fireball and on the global statistics of GRBs and their afterglows. Finally, the afterglows of the brighter and closer events can be monitored for several weeks in order to search for the signatures of underlying supernovae in their late-time optical light curves. The possible association of at least some GRBs with supernovae of massive stars promises to be the long-sought handle on the physics of the GRB itself. Funding for this project was provided by the NSF program for Extragalactic Astronomy & Cosmology (AST/EXC).***