Tales of stellar and binary co-evolutionand stellar cannibalism

Tales of stellar and binary co-evolution – and stellar cannibalism <<< This Work: Beck, P.G. 2025, A&A (under rev.) and on TASC review Additional References: [1] Pinsonneault+ 2025, ApJS, 276, 69; [2] Mathur+2022,A&A, 657,A31;[3] Gaia Col., Arenou+ 2023, A&A, 674, A34; [4] Beck+ 2024, A&A, 667, A31; [5] Moe & Stefano, 2017, ApJS, 230, 15; [6] Offner+ 2023, ASPCS, 534, 275; [7] Patton+ 2024, MNRAS, 528, 3232; [8] Godoy-Rivera+ 2025, A&A, 696, A243; [9] Pourbaix+ 2004, A&A, 424, 727. PGB acknowledges support by the Spanish Ministry of Science and Innovation with the Ramón y Cajal fellowship number RYC-2021-033137-I and number MRR4032204 at ULL and the Proyecto Plan Nacional PLAtoSOnG (grant number PID2023-146453NB-100, PI: Beck) at IAC. Full Sample APOKASC3 Two-Body Orbit solutions (TBO) NSS Non-linear & Acceleration Solutions Renorm. Unit Weight Err. (RUWE) & Binary Union Flag [8] All Oscillating Rapid Rotators µ= 1.3 Mo µ= 1.9 Mo <RGB>: µ= 1.3 Mo <HeCB>: µ= 1.3 Mo µ= 1.2 Mo µ= 1.0 Mo •Red giants (RG) are increasingly used as probes of stellar population due to their well-understood evolution & asteroseismology. •However, stellar binarity can alter observable properties and introduce strong biases into the stellar populations. Such effects can introduce unwanted systematics in the scaling relations and render potential benchmark systems unusable for calibration. •We aim on assessing a holistic picture of the binary population and evolution in the red giant phase. •By studying the characteristics of the binary population in the APOKASC3 sample, we shed light on the star-binary co-evolution: Paul G. Beck ULL & IAC Tener if e, Spai n à The signature of stellar cannibalism •At Tip of RGB: M≲1.8M⦿: R≈200R⦿, while M≳1.8M⦿: 200≳ R/R⦿≳80. Low-mass stars require P≳800d to avoid mass transfer or merging events. à The He-core burning binary sample is depleted of low-mass stars, with respect to the full APOKASC3 sample (Fig.C) and systems below 800d (Fig.D). à Mass-Period relation for He-core burning phase (Fig.E): •For RC & 2RC: the larger the primary’s mass, the shorter the limiting period à 2RC: Shrinking radius with increasing mass allows shorter systems to exist. •The few short-periodic and low-mass outliers are mainly rapidly rotating stars. à Indication that these are merger products. A. Distribution of the binary stars from the Gaia Binary sample in the Hertzsprung-Russel Diagram. The red line indicates the separation between the low and high luminous RGB. C. Probability distributions of seismic masses, separated by the type of binary solutions from the Gaia’s Non-Single Star Catalog and the identification as rapid rotating giants with vsini≥5 km/s [7]. Mass transfer & merging events will alter the stellar evolution, substantially departing from the classical single-star evolution Consequences a) stellar ages and galactic archaeology: Due to the mass gain or loss stars will appear prematured or rejuvenated; b) stellar modelling: Low-mass helium-core burning systems (P ≲1000d) are not suited as benchmark objects. Binary Attrition in low-mass evolution •~1350 binaries are identified from a crossmatch of APOKASC3 [1], mainsequence oscillators [2], and Gaia’s Non-Single-Star catalog (NSS) [3]. •Two-Body-Orbit solutions (TBO) are sensitive to Porb≲1000d[4]. Other binary indicators favor longer Porb. Seismic evolutionary state & masses are key parameters showing (Fig.A&B): à% are lower boundaries àStrong binary attrition between consecutive evolutionary phases. àMass dependency (M≷1.8M⦿) [5,6] is enhanced in RG phase. àFor M≤1.8M⦿ the binary attrition is significant along the RG-branch. à30% binaries among FGK dwarfs. B. Binary rate for solar-like oscillators in each evolutionary state in the mag-limited sample. Solid lines indicate statistically significant variation, following a ꭓ2 test. D. Distribu]on of the orbital parameters for the binary systems with known solu]ons from the TBO. The color code depicts the primary’s evolu]onary status. The heatmap in the background represent the distribu]on of the full SB9 catalogue [9]. E. Mass vs Orbital period for stars with seismic masses. The broken power law in red line indicates the approximate short period cutoff for the orbital period as a function of mass. M>1.8M⦿ M≤1.8M⦿ RGB RC 2RC 500 days Gaia base line: ~1000 days