Fig. 2: Spectral evolution of the GRB afterglow and kilonova.
From: A nearby long gamma-ray burst from a merger of compact objects
a, SED combining gamma-ray (diamonds), X-ray (circles) and UVOIR (squares) data at different times, as indicated by the labels. It shows that non-thermal radiation (solid line) dominates at early times and at higher energies. At lower energies, we identify the emergence of a thermal component peaking at blue wavelengths at 5 h, and rapidly shifting toward redder colours. Error bars represent 1σ; upper limits (downward triangles) are 3σ. For plotting purposes, each epoch was rescaled by the following factors (from top to bottom): 1, 1, 10−0.8, 10−1.6, 10−2.4, 10−3.2. b–d, The bolometric luminosity (b), temperature (c) and emitting radius (d) of the thermal component are similar to AT2017gfo27 (grey circles). Solid lines show the best-fit power-law models to the dataset. Dashed lines in d show the predicted radius for constant expansion velocities of 0.3c and 0.6c (c, speed of light in a vacuum).
