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Abstract We present a start-to-end simulation aimed at studying the long-term fate of high-mass X-ray binaries and whether a Thorne–Żytkow object (TŻO) might ultimately be assembled. We analyze results from a 3D hydrodynamical simulation that models the eventual fate of LMC X-4, a compact high-mass X-ray binary system, after the primary fills its Roche lobe and engulfs the neutron star companion. We discuss the outcome of this engulfment within the standard paradigm of TŻO formation. The post-merger angular momentum content of the stellar core is a key ingredient, as even a small amount of rotation can break spherical symmetry and produce a centrifugally supported accretion disk. Our findings suggest the inspiraling neutron star, upon merging with the core, can accrete efficiently via a disk at high rates (≈10−2M⊙s−1), subsequently collapsing into a black hole and triggering a bright transient with a luminosity and duration typical of an ultra-long gamma-ray burst. We propose that the canonical framework for TŻO formation via common envelope needs to be revised, as the significant post-merger accretion feedback will unavoidably unbind the vast majority of the surrounding envelope.
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Photons from Neutrinos: The Gamma-Ray Echo of a Supernova Neutrino Burst
Abstract When a star undergoes core collapse, a vast amount of energy is released in a ∼10 s long burst of neutrinos of all species. Inverse beta decay in the star’s hydrogen envelope causes an electromagnetic cascade that ultimately results in a flare of gamma rays—an “echo” of the neutrino burst—at the characteristic energy of 0.511 MeV. We study the phenomenology and detectability of this flare. Its luminosity curve is characterized by a fast, seconds-long rise and an equally fast decline, with a minute- or hour-long plateau in between. For a near-Earth star (distanceD≲ 1 kpc) the echo will be observable at near future gamma-ray telescopes with an effective area of 103cm2or larger. Its observation will inform us on the envelope size and composition. In conjunction with the direct detection of the neutrino burst, it will also give information on the neutrino emission away from the line of sight and will enable tests of neutrino propagation effects between the stellar surface and Earth.
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- PAR ID:
- 10522485
- Publisher / Repository:
- DOI PREFIX: 10.3847
- Date Published:
- Journal Name:
- The Astrophysical Journal
- Volume:
- 969
- Issue:
- 2
- ISSN:
- 0004-637X
- Format(s):
- Medium: X Size: Article No. 149
- Size(s):
- Article No. 149
- Sponsoring Org:
- National Science Foundation
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