The afterglow rapidly declines whereas the supernova explosion gains in brightness over a period of a few weeks, and then gradually fades away. The new study reports on the observations of GRB 980326 carried out at the W. M. Keck Observatory's 10-m telescope located atop Mauna Kea, Hawaii. As in many other cases, a visible light afterglow was found following the burst, which then rapidly faded away. Normally, the optical light of a gamma-ray burst vastly outshines its host galaxy for weeks. Three optical pictures of the same part of the sky at three different times.
Darker colors correspond to brighter objects.
The object at the center image was originally interpreted as the host galaxy. Instead, the object at the middle picture is now argued by Bloom et al. in Nature to be the underlying supernova accompanying the gamma-ray burst. The size of these images on the sky is about the size of a postage stamp as seen across a football field. Clearly, what we were seeing is a new source of light brightening one month and then fading away. This is something quite new.