Peak Luminosities of Bursts from GRO J1744-28 measured with the RXTE PCA

Abstract

GRO J1744-28, discovered by BATSE in December 95, is the second neutron star system known to produce frequent accretion powered bursts. The system has been regularly monitored with the RXTE PCA since the peak of the first outburst in January 96 at which time the observed persistent and bursting count rates were ~25,000 ct/sec and ~150,000 ct/sec, with corresponding instrumental deadtimes of ~10% and > 50%. We present a model which allows the reconstruction of the true incident count rate in the presence of enormous deadtime and use the model to derive a history of the peak luminosities and fluences of the bursts as a function of time. During the peak of the January 1996 and January 1997 outbursts, when the persistent emission was > 1 Crab, we infer peak luminosities of ~100 times the Eddington luminosity, and a ratio of persistent emission to integrated burst emission of ~34.