An Etymological Dictionary of Astronomy and Astrophysics
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A → photometric system defined by reference to → monochromatic magnitudes in such a way that, when monochromatic → flux f_ν is measured in ergs sec^-1 cm^-2 Hz^-1, the magnitude will be: AB = -2.5 logf_ν - 48.60. The constant is set so that AB is equal to the V magnitude for a source with a flat → spectral energy distribution. The → zero point is defined by the flux of the star → Vega at 5546 Å. In this system, an object with constant flux per unit frequency interval has zero color.

→ magnitude; → system.