用極廣視野望遠鏡WIDGET尋找偶發的光學閃燄; A Serendipitous Search for Optical Flash by Ultra-Wide Field Telescope WIDGET

Please use this identifier to cite or link to this item: http://ir.lib.ncu.edu.tw/handle/987654321/43741

Title:	用極廣視野望遠鏡WIDGET尋找偶發的光學閃燄;A Serendipitous Search for Optical Flash by Ultra-Wide Field Telescope WIDGET
Authors:	林紅妙;Hung-Miao Lin
Contributors:	天文研究所
Keywords:	瞬變天體;篩選系統;transient;WIDGET;pipeline
Date:	2010-07-29
Issue Date:	2010-12-08 14:17:48 (UTC+8)
Publisher:	國立中央大學
Abstract:	我們尋找在短時間內星等變化很大的瞬變天體。截至目前為止，有三個這樣的天體被發現。兩個是(GRB990123 and GRB 080319B)分別都在十秒內出現極其亮的光學餘暉。另一個則是在六分鐘的時間範圍內出現了高達星等九等變化的 OT J004240.69+405142.0。為了要以有組織並有獨立性的作業方式找尋這類的天體，我們使用 WIDGET (WIDe-field telescope for GRB Early Timing) 望遠鏡的資料並開發了兩個作業系統去做資料處理和尋找瞬變天體。由於WIDGET擁有極大天區，且其曝光時間只有五秒鐘，正好可以對大天區進行這種瞬時觀測。我們對影像進行光學像差所造成的扭曲做評估，並建立一套自動化的像差校正(天體測定)系統。最後其精準度高達到0.81像素(其均方根約45角秒)。我們還利用簡易影像對減方式開發了一套自動化瞬變天體找尋系統，其中有五種篩選機制以及界定各個挑選準則。然而，我們引用2009年3月17日持續11分鐘的晴天影像進去該系統做測試。該系統從對減的影像中挑出3795個天體，並成功地篩選了擾亂的天體(如：移動天體、亮星、微變變星)。最後有18個天體被該系統挑選出作為真正瞬變天體的候選者。 We search for the totally new transient which shows the high time variability and large brightness amplitudes. There are three examples. Two GRBs (GRB990123 and GRB 080319B) show the extremely bright optical flashes with the several 10 sec duration. The OT J004240.69+405142.0 shows 9th mag. object within 6 min interval. In order to make systematic and independent survey, we use the WIDGET (WIDe-field telescope for GRB Early Timing) data which has the ultra-wide field and acquiring data with 5s exposure. The instrument is particularly suited to perform this survey. We make two pipelines for data calibration and transient search. We evaluated the optics geometric distortion and established the automatic astrometric pipeline. The final products have the astrometric accuracy of 0.81 pixel level (rms 45”). We also developed the transient search pipeline using image subtraction technique. To select suitable transient candidates, we made five selection criteria for the products of the image subtraction. We applied the pipelines to 11 minute clear data obtained on March 17, 2009. The pipeline picked up 3795 sources from subtracted images, and well filtered the noise (e.g. moving objects, bright stars and variables with small variation). There are 18 sources as the real candidates.
Appears in Collections:	[Graduate Institute of Astronomy] Electronic Thesis & Dissertation

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