Given a flux density f, measured in ergs per second per square centimeter per hertz, the corresponding AB magnitude is defined as:

\,\! AB = -2.5 \log_{10} f - 48.60

The AB magnitude system is defined such that for any bandpass or filter being considered, the magnitude zero-point corresponds to a flux density of 3631 Jy

(1 Jy = 1 Jansky = 10⁻²⁶ W Hz⁻¹ m⁻² = 10⁻²³ erg s⁻¹ Hz⁻¹ cm⁻²) ^[1]

For fluxes in units of [erg/s/cm2/A] the AB magnitude is given by ^[2]

\,\! AB = -2.5 \log_{10} f - 5 \log_{10}(<\lambda>)-2.406

External links

• Conversion from AB magnitudes to Johnson magnitudes

References