Once a Triple, Not Always a Triple: The Evolution of Hierarchical Triples that Yield Merged Inner Binaries
Cheyanne Shariat, Smadar Naoz, Kareem El-Badry, Antonio C. Rodriguez,, Bradley M.S. Hansen, Isabel Angelo, and Alexander P. Stephan

TL;DR
This study investigates the evolution of hierarchical triple star systems, revealing that many wide double white dwarf binaries originate from merged triples and that stellar mergers influence blue straggler and white dwarf populations.
Contribution
The paper provides new insights into the dynamical evolution of hierarchical triples, quantifies the fraction of wide DWDs from triples, and links stellar mergers to observable binary properties.
Findings
26-54% of wide DWDs are merger products from triples
44±14% of observed wide DWDs originated in triple systems
Triple+merger channel explains some properties of blue straggler binaries
Abstract
More than half of all main-sequence (MS) stars have one or more companions, and many of those with initial masses <8 M are born in hierarchical triples. These systems feature two stars in a close orbit (the inner binary) while a tertiary star orbits them on a wider orbit (the outer binary). In hierarchical triples, three-body dynamics combined with stellar evolution drives interactions and, in many cases, merges the inner binary entirely to create a renovated `Post-Merger Binary' (PMB). By leveraging dynamical simulations and tracking binary interactions, we explore the outcomes of merged triples and investigate whether PMBs preserve signatures of their three-body history. Our findings indicate that in 26-54% of wide double WD binaries (s>100 au), the more massive white dwarf (WD) is a merger product, implying that these DWD binaries were previously triples. Overall, we estimate…
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Taxonomy
TopicsBusiness Strategy and Innovation
