Power density spectra morphologies of red-giant asteroseismic binaries with overlapping oscillations

Spatially unresolved red-giant binaries can be mistaken for single stars when their oscillation spectra overlap in an almost identical frequency range. Identifying these systems is important to avoid biases in estimating asteroseismic global parameters (νmax and Δν), which can lead to inaccurate stellar parameters. Here, we predict the power density spectra (PDS) morphology of seismically unresolved red-giant asteroseismic binaries. We created 5,000 artificial asteroseismic binaries to provide examples that can help identify such unresolved systems among observed stars. We focus on ~8% of artificial binaries whose stellar components have similar brightness and classify them into four categories based on their PDS morphology. We find that complex oscillation patterns are common among these artificial binaries, suggesting that observed stars with complex PDS can be considered as candidates for asteroseismic binaries. We compare our findings with an observed red giant asteroseismic binary that exhibits complex PDS and discuss the potential mass biases in other observed stars with complex oscillation signals.