Optimal co-addition of imaging data for rapidly fading gamma-ray burst afterglows

Morgan A. N., Berk D. E. V., Roming P. W. A., Nousek J. A., Koch T. S., Breeveld A. A., ...Daha Fazla

ASTROPHYSICAL JOURNAL, cilt.683, sa.2, ss.913-923, 2008 (SCI-Expanded) identifier

  • Yayın Türü: Makale / Tam Makale
  • Cilt numarası: 683 Sayı: 2
  • Basım Tarihi: 2008
  • Doi Numarası: 10.1086/589639
  • Dergi Adı: ASTROPHYSICAL JOURNAL
  • Derginin Tarandığı İndeksler: Science Citation Index Expanded (SCI-EXPANDED), Scopus
  • Sayfa Sayıları: ss.913-923
  • Anahtar Kelimeler: gamma rays : bursts, methods : data analysis, OPTIMAL EXTRACTION ALGORITHM, LIGHT CURVES, SWIFT, CALIBRATION, UVOT
  • İstanbul Üniversitesi Adresli: Evet

Özet

We present a technique for optimal co-addition of image data for rapidly varying sources, with specific application to gamma-ray burst (GRB) afterglows. Unweighted co-addition of rapidly fading afterglow light curve data becomes counterproductive relatively quickly. It is better to stop co-addition of the data once noise dominates late exposures. A better alternative is to optimally weight each exposure to maximize the signal-to-noise ratio (S/N) of the final co-added image data. By using information about GRB light curves and image noise characteristics, optimal image co-addition increases the probability of afterglow detection and places the most stringent upper limits on nondetections. For a temporal power-law flux decay typical of GRB afterglows, optimal co-addition has the greatest potential to improve the S/N of afterglow imaging data (relative to unweighted co-addition) when the decay rate is high, the source count rate is low, and the background rate is high. The optimal co-addition technique is demonstrated with applications to Swift Ultraviolet/Optical Telescope (UVOT) data of several GRBs, with and without detected afterglows.