The wavelength calibration obtained for each spectrum was transformed
into a velocity scale in the rest frame of the star. Such a
transformation is achieved by means of the Doppler effect. If
corresponds to the zero velocity then
where c is the speed of light.
For Pa Beta
, while for Br Gamma 
. These
wavelengths correspond to the vacuum wavelengths of the Pa Beta and Br
Gamma transitions, respectively.
In order to make this velocity scale such that zero velocity corresponds to the rest velocity of the star, the radial velocity of the latter relative to the observer must be taken into account. The heliocentric radial velocities used were those determined from this data (see Table 3.3), except for those stars for which such a determination was not possible. When that is the case, those shown in Table 2.1 were used. Since the stellar radial velocities used are heliocentric, the motion of the observer relative to the Sun had also to be taken into account. It was computed for the date of the observations using Starlink's RV program.
After correcting the velocity scale obtained by using the Doppler law for the radial velocity of the star the result is a velocity scale on the rest frame of the star. Such velocity scale was computed for every observed spectra and it is the scale displayed in Figures 5.1 to 5.2 where the observed line profiles are shown.