Return of the TEDI: revisiting the Triple Evolution Dynamical Instability channel in triple stars. (arXiv:2107.13620v2 [astro-ph.SR] UPDATED)
<a href="http://arxiv.org/find/astro-ph/1/au:+Hamers_A/0/1/0/all/0/1">Adrian S. Hamers</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Perets_H/0/1/0/all/0/1">Hagai B. Perets</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Thompson_T/0/1/0/all/0/1">Todd A. Thompson</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Neunteufel_P/0/1/0/all/0/1">Patrick Neunteufel</a>
Triple-star systems exhibit a phenomenon known as the Triple Evolution
Dynamical Instability (TEDI), in which mass loss in evolving triples triggers
short-term dynamical instabilities, potentially leading to collisions of stars,
exchanges, and ejections. Previous work has shown that the TEDI is an important
pathway to head-on stellar collisions in the Galaxy, significantly exceeding
the rate of collisions due to random encounters in globular clusters. Here, we
revisit the TEDI evolutionary pathway using state-of-the-art population
synthesis methods that self-consistently take into account stellar evolution
and binary interactions, as well as gravitational dynamics and perturbations
from passing stars in the field. We find Galactic TEDI-induced collision rates
on the order of 1e-4/yr, consistent with previous studies which were based on
more simplified methods. The majority of TEDI-induced collisions involve main
sequence stars, potentially producing blue straggler stars. Collisions are also
possible involving more evolved stars, potentially producing eccentric
post-common-envelope systems, and white dwarfs collisions leading to Type Ia
supernovae (although the latter with a negligible contribution to the Galactic
rate). In our simulations, the TEDI is not only triggered by adiabatic wind
mass loss, but also by Roche lobe overflow in the inner binary: when the donor
star becomes less massive than the accretor, the inner binary orbit widens,
triggering triple dynamical instability. We find that collision rates are
increased by ~17% when fly-bys in the field are taken into account. In addition
to collisions, we find that the TEDI produces ~1e-4/yr of unbound stars,
although none with escape speeds in excess of 1e3 km/s.
Triple-star systems exhibit a phenomenon known as the Triple Evolution
Dynamical Instability (TEDI), in which mass loss in evolving triples triggers
short-term dynamical instabilities, potentially leading to collisions of stars,
exchanges, and ejections. Previous work has shown that the TEDI is an important
pathway to head-on stellar collisions in the Galaxy, significantly exceeding
the rate of collisions due to random encounters in globular clusters. Here, we
revisit the TEDI evolutionary pathway using state-of-the-art population
synthesis methods that self-consistently take into account stellar evolution
and binary interactions, as well as gravitational dynamics and perturbations
from passing stars in the field. We find Galactic TEDI-induced collision rates
on the order of 1e-4/yr, consistent with previous studies which were based on
more simplified methods. The majority of TEDI-induced collisions involve main
sequence stars, potentially producing blue straggler stars. Collisions are also
possible involving more evolved stars, potentially producing eccentric
post-common-envelope systems, and white dwarfs collisions leading to Type Ia
supernovae (although the latter with a negligible contribution to the Galactic
rate). In our simulations, the TEDI is not only triggered by adiabatic wind
mass loss, but also by Roche lobe overflow in the inner binary: when the donor
star becomes less massive than the accretor, the inner binary orbit widens,
triggering triple dynamical instability. We find that collision rates are
increased by ~17% when fly-bys in the field are taken into account. In addition
to collisions, we find that the TEDI produces ~1e-4/yr of unbound stars,
although none with escape speeds in excess of 1e3 km/s.
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