Swift XRT and VLT Observations of the Afterglow of GRB 041223
journal contributionposted on 15.05.2018, 15:22 by D. N. Burrows, J. E. Hill, G. Chincarini, G. Tagliaferri, S. Campana, A. Moretti, P. Romano, D. Malesani, J. L. Racusin, S. Kobayashi, B. Zhang, P. Meszaros, P. T. O'Brien, R. Willingale, Julian Paul Osborne, G. Cusumano, P. Giommi, L. Angelini, A. F. Abbey, L. A. Antonelli, A. P. Beardmore, M. Capalbi, S. Covino, P. D'Avanzo, M. R. Goad, J. A. Kennea, D. C. Morris, C. Pagani, K. L. Page, L. Stella, J. A Nousek, A. A. Wells, N. Gehrels
GRB 041223 was the first gamma-ray burst detected by the Swift X-Ray Telescope (XRT), beginning 4.6 hr after the burst. The X-ray detection triggered a VLT observation of the optical/near-infrared (NIR) counterpart, located about 1farcs1 from the XRT position. The X-ray counterpart faded rapidly, with a power-law index of -1.72 ± 0.20, with an average unabsorbed X-ray flux of 6.5 × 10-12 ergs cm-2 s-1 in the 0.5-10 keV band for a power-law spectrum of photon index 2.02 ± 0.13 with Galactic absorption. The NIR counterpart was observed at three epochs between 16 and 87 hr after the burst and faded with a power-law index of -1.14 ± 0.08 with a reddening-corrected spectral energy distribution power-law slope of -0.40 ± 0.03. We find that the X-ray and NIR data are consistent with a two-component jet in a wind medium.