TY - JOUR

T1 - Stellar response after stripping as a model for common-envelope outcomes

AU - Vigna-Gomez, Alejandro

AU - Wassink, Michelle

AU - Klencki, Jakub

AU - Istrate, Alina

AU - Nelemans, Gijs

AU - Mandel, Ilya

PY - 2022/2/11

Y1 - 2022/2/11

N2 - Binary neutron stars have been observed as millisecond pulsars, gravitational-wave sources, and as the progenitors of short gamma-ray bursts and kilonovae. Massive stellar binaries that evolve into merging double neutron stars are believed to experience a common-envelope episode. During this episode, the envelope of a giant star engulfs the whole binary. The energy transferred from the orbit to the envelope by drag forces or from other energy sources can eject the envelope from the binary system, leading to a stripped short-period binary. In this paper, we use one-dimensional single stellar evolution to explore the final stages of the common-envelope phase in progenitors of neutron star binaries. We consider an instantaneously stripped donor star as a proxy for the common-envelope phase and study the star's subsequent radial evolution. We determine a range of stripping boundaries that allow the star to avoid significant rapid re-expansion and that thus represent plausible boundaries for the termination of the common-envelope episode. We find that these boundaries lie above the maximum compression point, a commonly used location of the core/envelope boundary. We conclude that stars may retain fractions of a solar mass of hydrogen-rich material even after the common-envelope episode. If we consider orbital energy as the only energy source available, all of our models would overfill their Roche lobe after ejecting the envelope, whose binding energy includes gravitational, thermal, radiation, and recombination energy terms.

AB - Binary neutron stars have been observed as millisecond pulsars, gravitational-wave sources, and as the progenitors of short gamma-ray bursts and kilonovae. Massive stellar binaries that evolve into merging double neutron stars are believed to experience a common-envelope episode. During this episode, the envelope of a giant star engulfs the whole binary. The energy transferred from the orbit to the envelope by drag forces or from other energy sources can eject the envelope from the binary system, leading to a stripped short-period binary. In this paper, we use one-dimensional single stellar evolution to explore the final stages of the common-envelope phase in progenitors of neutron star binaries. We consider an instantaneously stripped donor star as a proxy for the common-envelope phase and study the star's subsequent radial evolution. We determine a range of stripping boundaries that allow the star to avoid significant rapid re-expansion and that thus represent plausible boundaries for the termination of the common-envelope episode. We find that these boundaries lie above the maximum compression point, a commonly used location of the core/envelope boundary. We conclude that stars may retain fractions of a solar mass of hydrogen-rich material even after the common-envelope episode. If we consider orbital energy as the only energy source available, all of our models would overfill their Roche lobe after ejecting the envelope, whose binding energy includes gravitational, thermal, radiation, and recombination energy terms.

KW - stars: binaries (including multiple): close

KW - stars: binaries: general

KW - stars: massive

KW - stars: neutron

KW - BINDING-ENERGY PARAMETER

KW - BLACK-HOLE

KW - NEUTRON-STAR

KW - CONVECTIVE BOUNDARIES

KW - BINARY

KW - EVOLUTION

KW - MODULES

KW - SYSTEM

KW - PROGENITORS

KW - DISCOVERY

U2 - 10.1093/mnras/stac237

DO - 10.1093/mnras/stac237

M3 - Journal article

VL - 511

SP - 2326

EP - 2338

JO - Royal Astronomical Society. Monthly Notices

JF - Royal Astronomical Society. Monthly Notices

SN - 0035-8711

IS - 2

ER -