Giménez, A.Reglero, V.Castro Rubio, Elisa DeFernández Figueroa, María José2023-06-202023-06-201991-080004-6361https://hdl.handle.net/20.500.14352/59715© EDP Sciences. © European Southern Observatory. The JKT, on the island of La Palma, is operated by the Royal Greenwich Observatory at the Spanish Roque de los Muchachos Observatory of the Instituto de Astro­física de Canarias. We want to express our gratitude to the observatory staff for their help during the observations. Dr. E.H. Olsen is gratefully acknowledged for his comments during the preparation of the first draft. This work has been supported by the Spanish Comisión Interministerial de Ciencia y Tecnolgía (PB87-0235 and PB86-0536).New photometric observations, using the uvby and Hß systems of 72 northern-hemisphere active binaries are discussed in order to explain the main characteristics of their spectral light intensity distribution. Values of the parameter δm_1 range from 0.0 to 0.3 mag, which cannot be explained in terms of metal underabundance alone. The existence of some mechanism, responsible for such a colour-index anomaly, is thus suggested and is found to be in close relation with the involved degree of solar-type activity.engjournal articlehttp://adsabs.harvard.edu/abs/1991A%26A...248..563Ghttp://adsabs.harvard.edu/http://www.aanda.orgopen access52Main-Sequence StarsPhotometryCalibrationsSystemsAstrofísicaAstronomía (Física)