Extending the FIP bias sample to magnetically active stars

Abstract

Context. The different elemental abundances of the photosphere and the corona are striking features of not only the Sun, but of other stars as well. This phenomenon is known as the first ionisation potential (FIP) effect, 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. Aims. We aim to extend the Teff−FIP bias relationship to a larger stellar sample and analyse the effect of other astrophysical parameters on the relation (e.g. surface gravity, age, activity indicators). Methods. 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 that may influence the stellar FIP bias. Results. Adding stars to the Teff−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 Teff 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. Conclusions. The new branch of the Teff−FIP bias diagram contains stars with higher activity level, in terms of X-ray flux and rotational velocity. The Rossby number also seems to be important, indicating possible dependence on the type of dynamo operating in these stars influencing their FIP bias. 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 they end 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.

Understanding the Relationship between Solar Coronal Abundances and F10.7 cm Radio Emission

“…This result highlights the importance of magnetic field strength or magnetic flux density and the F10.7 cm emission when linking coronal composition to the different spectral types of stars. In addition to the stellar coronal composition investigation done in Wood & Linsky (2010) and Seli et al (2022), a full-cycle observation should also be considered to fully understand stellar composition variability.…”

“…These stars may also show cyclic effects, and the chemical composition of their coronae likely depends on magnetic activity rather than just the fixed properties of the star. However, a saturation of the first ionization potential (FIP) bias is often observed in high-activity stars (Wood & Linsky 2010;Laming 2015;Seli et al 2022), with a typical FIP bias of ∼1 or lower. In fact, this saturation is also observed in Brooks et al (2017).…”

Detection of Stellar-like Abundance Anomalies in the Slow Solar Wind

“…Furthermore, the IFIP effect was recently shown to be present also on stars with higher surface temperatures, if they have evolved off the main sequence and have some indicators of magnetic activity, e.g., a high rotation rate or X-ray luminosity (Seli et al 2022). But studies of the IFIP effect are relatively less developed because until recently it had only been observed on unresolved stellar targets.…”

Element Fractionation by the Ponderomotive Force

“…The deficit in magnetic field of ∼ 1500G at a density of ∼ 10 17 cm −3 translates to a wave amplitude of ∼ 10 km s −1 if the magnetic field is destroyed by subphotospheric reconnection and the energy is converted to fast mode waves. See also Seli et al (2022).…”