Description of the BATSE instrument, which first reported the GRB 990123 to the community through GCN:

Gamma-ray light curve (a record of the intensity of gamma-rays as a function of time) from BATSE:

Burst location as detected by BATSE, Beppo-SAX, IPN, COMPTEL, and optical instruments:

Full description of the GCN computer system which provided communication between all the observers and instruments:

First discovery and announcement of the optical transient by Odewahn, Bloom, and Kulkarni:

Coincident optical images discovered by ROTSE:

ROTSE light curve superimposed on gamma-ray light curve: