HEAO 1 observation of a type I burst from MXB 1728-34

Results are presented for an analysis of data on a type I X-ray burst from MXB 1728-34 observed by three large-area instruments on HEAO 1. The measurements cover the energy range from 2 to 150 keV and provide the capability of resolving significant intensity variations on a time scale of milliseconds and spectral changes on a scale of tenths of seconds. The initial rise of the burst is discussed, millisecond intensity variations are examined, and the spectral evolution of the burst is described. Physical parameters are estimated for various source models, and the total X-ray flux at energies of 85 to 180 keV during the burst is shown to have been no more than about 6% of the total observed X-ray flux at energies below 25 keV.