SIMBAD references

We have used the ROSAT High Resolution Imager to search for quiescent X-ray counterparts to four gamma-ray bursts (GRBs) which were localized to small (≤10 arcmin²) error boxes with the Interplanetary Network. The observations took place years after the bursts, and the effective exposure times for each target varied from ∼16 to 23 ks. We have not found any X-ray sources inside any of the error boxes. The 0.1-2.4 keV 3 σ flux upper limits range from around 5x10^–14 to 6x10^–13 ergs.cm^–2.s^–1 depending on the burst and the assumed shape of the quiescent spectrum. We consider four types of X-ray-emitting galaxies (normal, active galactic nucleus, faint, and star forming) and use the flux upper limits to constrain their redshifts. We then use the GRB fluences to constrain the total energies of the bursts.