Yost, S. A.Aharonian, F.Akerlof, C. W.Ashley, M. C. B.Barthelmy, S.Gehrels, N.Goegues, E.2025-01-272025-01-2720070004-637X1538-4357https://doi.org/10.1086/521668https://hdl.handle.net/20.500.12428/22537We present several cases of optical observations during gamma-ray bursts (GRBs) which resulted in prompt limits but no detection of optical emission. These limits constrain the prompt optical flux densities and the optical brightness relative to the gamma-ray emission. The derived constraints fall within the range of properties observed in GRBs with prompt optical detections, although at the faint end of optical/gamma-ray flux ratios. The currently accessible prompt optical limits do not require a different set of intrinsic or environmental GRB properties, relative to the events with prompt optical detections.eninfo:eu-repo/semantics/openAccessEarly Optical AfterglowGamma-Ray BurstsSpectral EvolutionEmissionRadiationFlashesArticle66921107111410.1086/521668Q1WOS:0002507605000362-s2.0-38849161924Q1