Tales of stellar and binary co-evolution, told by stellar oscillations -- Binary demographics and their impact on stellar mass, orbits, and age estimates in main-sequence and red-giant stars

TL;DR

This paper investigates how binary star interactions affect the observable properties and evolutionary estimates of red giants, revealing significant binary attrition and biases in age and mass determinations due to stellar expansion and interactions.

Contribution

It provides a comprehensive analysis of binary populations in red giants using asteroseismic, spectroscopic, and astrometric data, highlighting the impact on stellar evolution and parameter estimation.

Findings

Binary fractions decrease from main-sequence to red giant phase.

Short-period binaries are depleted during red-giant evolution.

Binary interactions can bias stellar age and mass estimates.

Abstract

Red giants are increasingly used as stellar population tracers due to their well-understood evolution and the availability of asteroseismic observables. However, stellar binarity can alter observable properties and introduce strong biases. We aim to provide a holistic picture of the binary population and its evolution in the red giant phase by characterizing a sample of binaries hosting oscillating red giants from a combination of extensive asteroseismic, spectroscopic, and astrometric surveys. We investigate the binary properties of evolved stars in the APOKASC3 and APO-K2 catalogs, leveraging asteroseismic constraints and Gaia DR3 non-single-star solutions. We explore the mass distribution of red-giant binary systems and analyze the evolution of their binary fraction. For stars with M$\leq$1.8M$_\odot$, we find binary fractions $\sim$31% and $\sim$41% for oscillating and non-oscillating solar-like stars on the main-sequence (MS). By the power excess ($\nu_\mathrm{max}$) as luminosity proxy, we detect a binary attrition of $\sim$69% and $\sim$81% on the low- and high-luminosity red-giant branch (RGB) and an additional $\sim$38% to the red clump (RC), with respect to the MS. Binaries hosting RC and secondary clump stars (2RC) stars are largely depleted at $P_\mathrm{orb}\lesssim$500 and $\lesssim$200 days, respectively. Mass-dependent differences in binary fractions and orbital properties point to more substantial binary attrition for stars with M $\leq$1.8 M$_\odot$. The distinct mass distributions and the depletion of short-period binaries during the red-giant phase underscore the impact of stellar expansion and binary interactions on stellar evolution. RC systems with $P_\mathrm{orb}\lesssim$800 to 1,000 days are likely shaped by past interactions, such as mass transfer or loss, which can lead to significantly biased age estimates if not accounted for.