SIMBAD references

Using the BATSE instrument on the Compton Gamma Ray Observatory, the X-ray bursters 4U 1820-30 and 4U 1915-05 have been monitored in the hard X-ray band. In four years of data neither source was detected. We derive 2σ upper limits on 20-100keV flux from 4U 1915-05 of 2.6x10^–2photons/cm²/s (90mCrab) for 1-day integrations and 9.0x10^–3photons/cm²/s (30mCrab) for 10-day integrations. For 4U 1820-30 the upper limits are 2.4x10^–2photons/cm²/s (80mCrab) for 1-day integrations and 1.0x10^–2photons/cm²/s (30mCrab) for 10-day integrations. These limits are not strong enough to constrain spectral models for the sources. The implications of these observations are discussed in light of BATSE results on other bursters.