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Multicolor optical observation of grb061121 by mitsume

Abstract:

GRB061121, a bright Swift GRB of interest, was observed with the 3-color 50 cm MITSuME Telescope at Akeno, Japan starting at 17:36:34 November UT, 134 minutes after the trigger. We obtained 60s×115 frames of images in Ic, Rc, and g′ bands. The magnitudes of the co-added images based on Landolt (I-band, R-band) and SDSS (g′-band) are g′=19.89±0.12, Rc=19.16±0.13, Ic=18.78±0.15. Our data, combined with UVOT, as well as other early and late time ground-based observations, reveal a detailed evolution of SED. Our color measurements also show indication of intrinsic absorption in the host galaxy at z=1.314. The combined afterglow light curve also suggests an achromatic break at ∼70000 seconds after trigger, which may be inconsistent with the Ghirlanda relation which pbkp_redicts a jet break at a later epoch. © 2008 American Institute of Physics.