The twin red giant branch system BD+20 5391
Year: 2025
Type: article
Abstract: Context. Understanding interactions of binary systems on the red giant branch is crucial to understanding the formation of compact stellar remnants such as helium-core white dwarfs (He-WDs) and hot subdwarfs. However, the detailed evolution of such systems, particularly those with nearly identical components, remains under-explored. Aims. We aim to analyse the double-lined spectroscopic binary system BD+20 5391, composed of two red giant stars, in order to characterise its orbital and stellar parameters and to constrain its evolution. Methods. Spectroscopic data were collected between 2020 and 2025 using the Ondřejov Echelle Spectrograph and the Mercator Échelle Spectrograph. The time-resolved spectra were fitted with models to determine the radial velocity curve and derive the system’s parameters. We then used the position of both stars in the Hertzsprung-Russell diagram to constrain the system’s current evolutionary state, and we discuss potential outcomes of future interactions between the binary components. Results. We find that the two stars in BD+20 5391 will likely initiate Roche lobe overflow (RLOF) simultaneously, leading to a double-core evolution scenario. The stars’ helium core masses at RLOF onset will be almost identical, at 0.33 M ⊙ . This synchronised evolution suggests two possible outcomes: common envelope ejection, resulting in a short-period double He-WD binary, or a merger without envelope ejection. In the former case, the resulting double He-WD may merge later and form a hot subdwarf star. Conclusions. This study provides a valuable benchmark example for understanding the evolution of interacting red giant binaries, which will be discovered in substantial numbers in upcoming large-scale spectroscopic surveys.
Source: Astronomy and Astrophysics
Language: English
Subfield: Astronomy and Astrophysics
Field: Physics and Astronomy
Domain: Physical Sciences
Open Access status: gold
Estimated APC paid: $1,865
Funders: National Science Foundation, National Aeronautics and Space Administration, Space Telescope Science Institute, European Space Agency, Royal Society, Deutscher Akademischer Austauschdienst, Deutsche Forschungsgemeinschaft, Deutsches Zentrum für Luft- und Raumfahrt, Fonds Wetenschappelijk Onderzoek, KU Leuven, Akademie Věd České Republiky, Agentúra na Podporu Výskumu a Vývoja, Vedecká Grantová Agentúra MŠVVaŠ SR a SAV, Vlaamse regering
Awards: The Mercator Telescope in the Era of the ESA Gaia and NASA TESS space missions., G1467920834, Od interagujúcich hviezd k exoplanétam, G2174669714, G3002814323, G3276639945, G3461672854, Extrasolárne planéty : extrémny prípad interagujúcich dvojhviezd, G3550382679, G433322167, G4518818167, SOUL: Stellar evOlution in fUll gLory: rotation, magnetism, oscillations, outflows, tides, and binarity, G464243087, G4693606035, MercatObs: The Mercator Observatory in the context of large space missions, G48481324, G5229195121, G58316358, G6273510985, G7060297222, G767601387, G775452760, G7761450427, G8210229802, G8266140671
OpenAlex ID: W4414196267