Schnörringen Telescope Science Institute (STScI), Ringweg 7, 51545 Waldbröl, Germany, www.stsci.de

Equivalent width measurements for rapid line variability in atomic spectral lines are degraded by increasing error bars with shorter exposure times. We derive an expression for the error of the line equivalent width (W) with respect to pure photon noise statistics and provide a correction value for previous calculations.

Accepted by Astronomical Notes
Preprints from eversberg@stsci.de
or on the web at www.stsci.de