TITLE: GCN CIRCULAR NUMBER: 5900 SUBJECT: GRB061126: update on the Swift-XRT afterglow light curve DATE: 06/12/06 09:01:40 GMT FROM: Boris Sbarufatti at INAF-IASF-Pa B. Sbarufatti (INAF IASF Pa), G. Cusumano (INAF IASF Pa), T. Mineo (INAF IASF Pa), V. Mangano (INAF IASF Pa) report on behalf of the SWIFT team We have analyzed the afterglow light curve of GRB061126 (GCN 5854, Sbarufatti et al.) observed with XRT. The source is decaying as a simple power law with slope alpha=-1.31 +/- 0.01 since its first detection with XRT up to T+76ks. We do not find evidence of the possible jet break reported by Kann et al. (GCN 5875) - but not detected by Rol et al. (GCN 5876) - at 1.8 days after the trigger. A tentative fit with a broken powerlaw, albeit very poorly constrained, showed a marginal compatibility with a flattening of the light curve after T+1E5s, as opposed with the steepening expected from a jet break. XRT observation of the afterglow (which shows a count rate 1.5E-3 c/s at T+76 ks)are still ongoing. This circular is an official product of the Swift XRT Team.