本論文呈獻在昴星團望遠鏡深場(Subaru Deep Field)中發現的一個不尋常可見光瞬變天體——SDF-05M05。昴星團望遠鏡深場具有高極限星等、廣視野、多色、與長時間監測等特性，使其成為一絕佳之找尋瞬變天體的星場資料。在找尋瞬變天體的過程中，我們首先利用影像相減以找尋其中有光度變化的天體，然後依據其光變曲線及顏色進行分類。在搜尋到的瞬變天體中，SDF-05M05 具有下列特殊性質：在觀測者座標系下，SDF-05M05 持續的時間超過800 天，其i'-與z'-band 最亮時達到近23 星等。我們在五個昴星團望遠鏡深場影像的觀測波段皆能找到其暗的寄主星系(host galaxy)，藉此我們得到其光度紅移約為0.6、最亮時的絕對星等則約為-20、而總散發的能量為10^51爾格。由於SDF-05M05 的光度與顏色變化特性與我們已知一般超新星的特性不同，故其可能是在中等紅移的新類型瞬變天體。透過昴星團望遠鏡新一代的廣視野照相機——HSC，搭配計畫性的時域尋天(time-domain survey)，我們將能有更多無價的發現。

We present results of SDF-05M05, an unusual optical transient, in the Subaru Deep Field (SDF). The SDF is one of the best surveys to perform transient search due to its deep limiting magnitude, wide field of view, multi-band observation, and long-term coverage (7 years). The transient search process was starting with image subtraction for finding variable sources in the field. Afterward we classified the sources according to their light curves and color information. Among the results of this transient search, SDF-05M05 showed peculiar properties. The duration of SDF-05M05 is at least 800 days in the observer frame, and the maximum brightness during observation reached approximately 23 mag in the i'- and z'-band. The faint host galaxy is clearly identified in all 5 bands of the deep SDF images. The photometric redshift of the host yields z~0.6, and the corresponding absolute magnitude at maximum is ~−20. The total radiated energy during our observation was 10^51 ergs. The light curves and color evolution are inconsistent with all known typical supernova types. We suggest that the transient may be a new type of event at intermediate redshift. The planned strategic survey with a time-domain-survey cadence using the new wide-field imager, HSC, attached to Subaru will prove invaluably.

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