  The different elemental abundances of the photosphere and the corona are
striking features of not only the Sun, but other stars as well. This phenomenon
is known as the FIP effect (FIP stands for first ionization potential), and its
strength can be characterized by the FIP bias, the logarithmic abundance
difference between low- and high-FIP elements in the corona, compared to the
photosphere. The FIP bias was shown to depend on the surface temperature of the
star. We compiled FIP bias and other parameters for 59 stars for which coronal
composition is available, now including evolved stars. Using principal
component analysis and linear discriminant analysis, we searched for
correlations with other astrophysical parameters within the sample which may
influence the stellar FIP bias. Adding stars to the $T_{\rm eff}-$FIP bias
diagram unveiled new features in its structure. In addition to the previously
known relationship, there appears to be a second branch, a parallel sequence
about 0.5 dex above it. While the $T_{\rm eff}$ remains the main determinant of
the FIP bias, other parameters such as stellar activity indicators also have
influence. We find three clusters in the FIP bias determinant parameter space.
One distinct group is formed by the evolved stars. Two groups contain main
sequence stars in continuation separated roughly by the sign change of the
FIP-bias value. The new branch of the $T_{\rm eff}-$FIP bias diagram contains
stars with higher activity level, in terms of X-ray flux and rotational
velocity. The two main sequence clusters run from the earliest spectral types
of A-F with shallow convection zones through G-K-early M stars with gradually
deeper convection zones, and end up with the fully convective M dwarf stars,
depicting the change of the dynamo type with the internal differences of the
main sequence stars in connection with the FIP-bias values.
