鹿林山天文台一米望遠鏡(Lulin One-meter Telescope)之伽瑪射線爆(gamma-ray bursts)計畫於2003年7月開始進行。此計畫的主要科學目標為發現X射線瞬閃(X-ray flashes)以及長短伽瑪射線爆的光學餘暉(optical afterglows)且即時以多波段觀測這些光學餘暉以期得到詳細的餘暉光變曲線(light curves)。截至2006年11月為止，鹿林一米望遠鏡成功偵測15個伽瑪射線爆光學餘暉。透過與東亞伽瑪射線爆觀測網(EAFON)的望遠鏡以及其他天文台的合作，我們的團隊對於伽瑪射線爆研究領域提供了許多非常有價值觀測資料來研究光學餘暉的演化。在本論文一開始，我們針對鹿林一米望遠鏡所觀測的六個光學餘暉(GRB 040924、GRB 041006、GRB050319、GRB 050408、GRB 051028、GRB051111)做詳細的探討研究。我們發現這六個伽瑪射線爆其光變曲線的演化趨勢完全不同。這些餘暉雖然有著不同的演化趨勢，然而拐折(break)現象卻出現在其中的五個光學餘暉的光變曲線中，此現象暗示我們光學餘暉在演化的過程並不是一成不變，很有可能是周圍的星際物質的變化或是伽瑪射線爆噴流(ejecta)的形狀改變而造成光變曲線的拐折。研究這些拐折現象有助於我們深入了解伽瑪射線爆光學餘暉演化、伽瑪射線爆的噴流以及與周圍星際物質間的關係。為了有系統的研究此拐折現象，我們整理了二十二個有詳細的R波段觀測資料點之伽瑪射線爆光學餘暉並探討其演化情形，透過拐折的幅度(break amplitude)和伽瑪射線爆座標的拐折時間(reference break time)，我們簡單的將這二十二個餘暉依照理論模型的解釋分成五類。 The Lulin GRB program, which uses Taiwan's Lulin One-meter Telescope (LOT) started in July 2003. Its scienti c aim of this program is to discover optical counterparts of X-ray flashes (XRFs) and short- and long- Gamma-ray bursts (GRBs), and to quickly observe them in multiple bands. Up to November 2006, a total of fteen optical afterglows have been successfully detected. Cooperating with other telescopes in the east-Asia Follow-up Observation Network (EAFON) and other groups, the LOT team carried out valuable and useful observations to study GRB optical afterglows. In this research, we first present our results for six individual events -- GRB040924, GRB041006, GRB050318, GRB050408, GRB051028 and GRB051111. We found that temporal evolution of the six afterglows are quite different. However, variations of power-law index, called "breaks", are detected in five of the afterglows. Breaks in the afterglow evolution reflect important clues for studying GRB ejecta and the surrounding medium. Then we summarize and discuss the temporal evolution of the 22 optical afterglows, with detailed R⣵76;band measurements, and classify five populations according to the plots of the break amplitude and reference break time.
