Swift UVOT detection of GRB 050318

M. Still, P. W.A. Roming, K. O. Mason, A. Blustin, P. Boyd, A. Breeveld, P. Brown, M. De Pasquale, C. Gronwall, S. T. Holland, S. Hunsberger, M. Ivanushkina, C. James, W. Landsman, K. Mcgowan, A. Morgan, T. Poole, S. Rosen, P. Schady, B. ZhangH. Krimm, T. Sakamoto, P. Giommi, M. R. Goad, V. Mangano, K. Page, M. Perri, D. N. Burrows, N. Gehrels, J. Nousek

Research output: Contribution to journalArticlepeer-review

25 Scopus citations


We present observations of GRB 050318 by the Ultraviolet/Optical Telescope (UVOT) on board the Swift observatory. The data are the first detections of a gamma-ray burst (GRB) afterglow decay by the UVOT instrument, launched specifically to open a new window on these transient sources. We showcase UVOT's ability to provide multicolor photometry and the advantages of combining UVOT data with simultaneous and contemporaneous observations from the high-energy detectors on the Swift spacecraft. Multiple filters covering 1800-6000 A reveal a red source with a spectral slope steeper than the simultaneous X-ray continuum. Spectral fits indicate that the UVOT colors are consistent with dust extinction by systems at z = 1.2037 and 1.4436, redshifts where absorption systems have been preidentified. However, the data can be most easily reproduced with models containing a foreground system of neutral gas redshifted by z = 2.8 ± 0.3. For both of the above scenarios, spectral and decay slopes are, for the most part, consistent with fireball expansion into a uniform medium, provided a cooling break occurs between the energy ranges of the UVOT and Swift's X-ray instrumentation.

Original languageEnglish (US)
Pages (from-to)1187-1191
Number of pages5
JournalAstrophysical Journal
Issue number2 I
StatePublished - Dec 20 2005

All Science Journal Classification (ASJC) codes

  • Astronomy and Astrophysics
  • Space and Planetary Science


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