  We present here a small anomalous radial velocity (RV) signal expected to be
present in RV curves measured during planetary transits. This signal is induced
by the convective blueshift (CB) effect --- a net blueshift emanating from the
stellar surface, resulting from a larger contribution of rising hot and bright
gas relative to the colder and darker sinking gas. Since the CB radial
component varies across the stellar surface, the light blocked by the planet
during a transit will have a varying RV component, resulting in a small shift
of the measured RVs. The CB-induced anomalous RV curve is different than, and
independent of, the well known Rossiter-McLaughlin (RM) effect, where the
latter is used for determining the sky-projected angle between the host star
rotation axis and the planet's orbital angular momentum axis. The observed RV
curve is the sum of the CB and RM signals, and they are both superposed on the
orbital Keplerian curve. If not accounted for, the presence of the CB RV signal
in the spectroscopic transit RV curve may bias the estimate of the spin-orbit
angle. In addition, future very high precision RVs will allow the use of
transiting planets to study the CB of their host stars.
