The O'Connell effect is an asymmetry in the photometric light curve of certain close eclipsing binary stars. It was named after the astronomer Daniel Joseph Kelly O'Connell, SJ[1] of Riverview College in New South Wales who in 1951 studied this phenomenon and distinguished it from the so-called periastron effect described by earlier authors, as it does not necessarily appear near the periastron, when tidal effects and an increase in mutual radiation may cause an increase in luminosity.[2]