A picture is sometimes worth a thousand words, and this plot from Santerne et al (2015) illustrates quite well some of the commonly used line-profile indicators.
Currently, the following line profile indicators are implemented in iCCF
FWHM
The FWHM is simply the full width at half maximum of the Gaussian fit to the CCF. It is measured in the same units as the radial velocity, tipically km/s.
BIS (bisector span)
The bisector is made up of the mid-points of horizontal line segments bounded by the sides of the line profile [Toner & Gray 1988].
Vspan
Suggested by Boisse et al 2011, obtained from the RV difference measured by fitting two Gaussian functions to the top and to the bottom parts of the line profile. The limits between the top and the bottom of the line profile are defined as the \(\pm 1 \sigma\) limit from the measured RV.
BiGauss 😢
raise NotImplementedError
Vasy 😢
raise NotImplementedError
Wspan
Santerne et al (2015) defined another indicator of line asymmetry, the Wspan, obtained from fitting two Gaussian functions to the blue and red wings of the line profile.