Hardness Test of GRB 950830 as a Gravitationally Lensed Echo

Abstract Cumulative hardness comparisons are a simple but statistically powerful test for the presence of gravitational lensing in gamma-ray bursts (GRBs). Since does not change photon energies, all source images should have same spectra—and hence hardness. Applied to recent claim that two pulses GRB 950830 lensed pulse, measured flux ratio between main be at energies. After summing up counts both 950830's four BATSE energy bands, it was found channel 3, second pulse appears somewhat weak. In comparison with other channels, difference significant above 90%. This model-independent indicates case involving lens may intriguing—but considered proven.