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Accurate early positions for Swift GRBS: enhancing X-ray positions with UVOT astrometry

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 نشر من قبل Dr Michael R. Goad
 تاريخ النشر 2007
  مجال البحث فيزياء
والبحث باللغة English
 تأليف M.R. Goad




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Here we describe an autonomous way of producing more accurate prompt XRT positions for Swift-detected GRBs and their afterglows, based on UVOT astrometry and a detailed mapping between the XRT and UVOT detectors. The latter significantly reduces the dominant systematic error -- the star-tracker solution to the World Coordinate System. This technique, which is limited to times when there is significant overlap between UVOT and XRT PC-mode data, provides a factor of 2 improvement in the localisation of XRT refined positions on timescales of less than a few hours. Furthermore, the accuracy achieved is superior to astrometrically corrected XRT PC mode images at early times (for up to 24 hours), for the majority of bursts, and is comparable to the accuracy achieved by astrometrically corrected X-ray positions based on deep XRT PC-mode imaging at later times (abridged).



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