标题： 从伽马射线暴中观测到同时发生的光学辐射 显示英文标题

标题： Observation of contemporaneous optical radiation from a gamma-ray burst

摘要： 伽马射线暴（GRBs）的起源自其发现以来一直是个谜。 1997年，当快速获得爆发的精确坐标后，情况得到了显著改善，这使得检测微弱的光学和射电余辉成为可能——由此获得的光学光谱明确证明了这些爆发发生在宇宙学距离上。 但是，尽管多个小组进行了努力，迄今为止尚未在爆发的短暂持续时间内实现光学检测。 在这里，我们报告在爆发进行期间对GRB990123的明亮光学辐射的检测。 我们的观测开始于爆发开始后的22秒，并显示在最初的25秒内亮度增加了14倍；随后亮度下降了100倍，在此时刻（爆发开始后700秒），它低于我们的检测阈值。 该爆发的红移约为1.6，这意味着峰值光学光度为5乘以10^{49} erg每秒。 通常认为伽马射线暴的光学辐射发生在主要能量源与周围介质相互作用产生的激波前沿，伽马射线也可能在此处产生。 当光学辐射发展时，伽马射线光曲线没有显著变化，这表明伽马射线不是在激波前沿产生的，而是在原始爆炸地点更近的地方。 显示英文摘要

摘要： The origin of gamma-ray bursts (GRBs) has been enigmatic since their discovery. The situation improved dramatically in 1997, when the rapid availability of precise coordinates for the bursts allowed the detection of faint optical and radio afterglows - optical spectra thus obtained have demonstrated conclusively that the bursts occur at cosmological distances. But, despite efforts by several groups, optical detection has not hitherto been achieved during the brief duration of a burst. Here we report the detection of bright optical emission from GRB990123 while the burst was still in progress. Our observations begin 22 seconds after the onset of the burst and show an increase in brightness by a factor of 14 during the first 25 seconds; the brightness then declines by a factor of 100, at which point (700 seconds after the burst onset) it falls below our detection threshold. The redshift of this burst, approximately 1.6, implies a peak optical luminosity of 5 times 10^{49} erg per second. Optical emission from gamma-ray bursts has been generally thought to take place at the shock fronts generated by interaction of the primary energy source with the surrounding medium, where the gamma-rays might also be produced. The lack of a significant change in the gamma-ray light curve when the optical emission develops suggests that the gamma-rays are not produced at the shock front, but closer to the site of the original explosion.