Optical and Infrared Observations of Gamma-Ray Burst Afterglows

Halperdam项目的目标是利用位于基特峰的美国麻省理工学院-达特茅斯分校（MDM）2.4米望远镜上的地基光学/红外测光和光谱学对伽马射线暴（GRB）余辉进行快速跟踪。自1998年以来，研究所一直是这类研究的重要参与者之一，并能及时、良好地使用这类后续工作所需的望远镜，利用BeppoSAX和/或RXTE卫星在数小时内定位的北方半球每年约6至8次爆发，该项目将继续利用MDM天文台的两台望远镜成功地发现和表征伽马射线爆发的光学余辉。从2000年发射HETE-II卫星开始，将有可能在伽马射线暴事件发生后几分钟内进行光学鉴定，这就有机会在诸如MDM 1.3m之类的小型望远镜上获得伽马射线的光学光变曲线，和吸收线的红移这些数据可以用来研究余辉的时间衰减和光谱演化，以诊断火球的能量学，并模拟这些爆炸发生的星周环境，例如，均匀星际介质与恒星风。HETE-II还将对迄今尚未确定的短持续时间伽马射线爆发类别敏感，并且其伽马射线光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爆发不同。这项工作的目标是揭示GRB祖先的不同群体，例如，已经在银河系星际介质之外旅行的老一代，而那些结束短暂生命的人仍然嵌入在致密的恒星形成区域。红外测光是最重要的这一区别。即时红外测光，特别是在K波段，提供了机会，以确定最高的红移和/或最模糊的伽玛暴。MDM 2.4m和ONIS IR相机可以在事件发生后一小时内轻松检测到z = 10的中度模糊GRB。在更长的时间尺度上，光变曲线可以跟踪几天，以发现预测的（偶尔检测到的）时间变陡，这是喷流状余辉的特征。测量这种破裂对于量化光束对火球能量学的影响以及对伽马射线暴及其余辉的全球统计数据的影响至关重要。最后，更明亮和更接近的事件的余辉可以被监测几个星期，以便在其后期光学光变曲线中寻找潜在超新星的特征。至少有一些伽玛暴可能与大质量恒星的超新星有关，这有望成为伽玛暴本身物理学的长期追求。该项目的资金由NSF河外天文宇宙学计划（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).***