A massive helium star with a sufficiently strong magnetic field to form a magnetar

Shenar, Tomer; Wade, Gregg A.; Marchant, Pablo; Bagnulo, Stefano; Bodensteiner, Julia; Bowman, Dominic M.; Gilkis, Avishai; Langer, Norbert; Nicolas-Chené, André; Oskinova, Lidia; Van Reeth, Timothy; Sana, Hugues; St-Louis, Nicole; de Oliveira, Alexandre Soares; Todt, Helge; Toonen, Silvia

doi:10.1126/science.ade3293

Cited by 15 publications

(2 citation statements)

References 94 publications

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“…At the basis, the formation mechanism of magnetars is still under debate. A few theories have been proposed to explain the origin of magnetars, including core-collapse supernovae (CCSNe; Schneider et al 2019;Shenar et al 2023), accretion-induced collapse of white dwarfs (Lipunov & Postnov 1985;Fryer et al 1999;Dessart et al 2007;Margalit et al 2019;Ruiter et al 2019), and double neutron star (DNS) mergers (Giacomazzo & Perna 2013;Margalit et al 2019). The light curves of a few X-ray transients are believed to be generated by extragalactic millisecond magnetars born from neutron star mergers (e.g., Xue et al 2019;Sun et al 2019;Ai & Zhang 2021).…”

Section: Introductionmentioning

confidence: 99%

VLBA Astrometry of the Fastest-spinning Magnetar Swift J1818.0−1607: A Large Trigonometric Distance and a Small Transverse Velocity

Ding,

Lower,

Deller

et al. 2024

ApJL

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In addition to being the most magnetic objects in the known Universe, magnetars are the only objects observed to generate fast-radio-burst-like emissions. The formation mechanism of magnetars is still highly debated and may potentially be probed with the magnetar velocity distribution. We carried out a 3 yr long astrometric campaign on Swift J1818.0−1607, the fastest-spinning magnetar, using the Very Long Baseline Array. After applying the phase-calibrating 1D interpolation strategy, we obtained a small proper motion of 8.5 mas yr−1 mag and a parallax of 0.12 ± 0.02 mas (uncertainties at 1σ confidence throughout the Letter) for Swift J1818.0−1607. The latter is the second magnetar parallax and is among the smallest neutron star parallaxes ever determined. From the parallax, we derived the distance 9.4 − 1.6 + 2.0 kpc, which locates Swift J1818.0−1607 at the far side of the Galactic central region. Combined with the distance, the small proper motion leads to a transverse peculiar velocity v ⊥ = 48 − 16 + 50 km s−1—a new lower limit to magnetar v ⊥. Incorporating previous v ⊥ estimates of seven other magnetars, we acquired v ⊥ = 149 − 68 + 132 km s−1 for the sample of astrometrically studied magnetars, corresponding to the three-dimensional space velocity ∼ 190 − 87 + 168 km s−1, smaller than the average level of young pulsars. Additionally, we found that the magnetar velocity sample does not follow the unimodal young pulsar velocity distribution reported by Hobbs et al. at >2σ confidence, while loosely agreeing with more recent bimodal young pulsar velocity distributions derived from relatively small samples of quality astrometric determinations.

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Section: Introductionmentioning

confidence: 99%

VLBA Astrometry of the Fastest-spinning Magnetar Swift J1818.0−1607: A Large Trigonometric Distance and a Small Transverse Velocity

Ding,

Lower,

Deller

et al. 2024

ApJL

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“…However, none of those classes occupy the mass range that has been predicted to produce most stripped-envelope supernovae or neutron star mergers ( 7 ). Only one hot helium star with an appropriate mass has been reported: the “quasi-WR” star in the system HD 45166 ( 18 , 19 ).…”

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confidence: 99%

An observed population of intermediate-mass helium stars that have been stripped in binaries

Drout,

Götberg,

Ludwig

et al. 2023

Science

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The hydrogen-rich outer layers of massive stars can be removed by interactions with a binary companion. Theoretical models predict that this stripping produces a population of hot helium stars of ~2 to 8 solar masses ( M ☉ ), however, only one such system has been identified thus far. We used ultraviolet photometry to identify potential stripped helium stars then investigated 25 of them using optical spectroscopy. We identified stars with high temperatures (~60,000 to 100,000 kelvin), high surface gravities, and hydrogen-depleted surfaces; 16 stars also showed binary motion. These properties match expectations for stars with initial masses of 8 to 25 M ☉ that were stripped by binary interaction. Their masses fall in the gap between subdwarf helium stars and Wolf-Rayet stars. We propose that these stars could be progenitors of stripped-envelope supernovae.

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Elusive hot stripped helium stars in the Galaxy

Yungelson,

Kuranov,

Postnov

et al. 2024

A&A

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Context. Stellar evolution theory predicts the existence of helium-core remnants of the primary components of intermediate-mass close binaries that lost most of their hydrogen-helium envelopes due to the mass exchange. These remnants are expected to be observed as hot helium-rich stars with masses of (1−7) M⊙, located in the area of the Hertzsprung-Russell diagram between OB subdwarfs and Wolf-Rayet stars. While several thousands of such stripped helium stars are expected to exist in the Galaxy, none of them have been identified so far. Aims. We aim to provide comprehensive predictions of the numbers and fundamental properties of stripped helium stars and their binary companions in the Galaxy. This is a necessary first step to guide observations, to enable a comparison between binary evolution models and realistic stellar populations, and to determine the feedback parameters of stripped helium stars in the Galaxy. Methods. We expanded the previously considered space of parameters describing close binary systems producing stripped helium stars and applied a population synthesis based on a grid of evolutionary models computed by the code MESA, using a spin-dependent algorithm for the treatment of mass and angular momentum loss from the system. Results. We show that the number of Galactic binaries hosting (1−7) M⊙ He-stars is ≃20 000 and that it steeply declines with an increase in the He-star mass (≃3000 with mass ≳2 M⊙). The decisive factor that defines the low number of stripped He-stars is runaway mass-loss after Roche lobe overflow (RLOF) by primary components of the binaries, which leads to the formation of common envelopes and the further merger of components. This effect strongly restricts the initial ranges of masses of components of the progenitors of stripped stars and orbital periods. In addition, stripped helium stars are much less numerous than expected, since a significant fraction of binaries in which the primaries have masses less than (5−7) M⊙ produce subdwarfs with masses ≲1 M⊙. Our calculations show that the overwhelming majority of helium stars reside in binaries with an early-type companion star and can be identified neither by the UV excess nor by emission features. The large periods of a significant fraction of binaries hosting stripped stars (≳several hundred days) also hamper their discovery.

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A massive helium star with a sufficiently strong magnetic field to form a magnetar

Cited by 15 publications

References 94 publications

VLBA Astrometry of the Fastest-spinning Magnetar Swift J1818.0−1607: A Large Trigonometric Distance and a Small Transverse Velocity

VLBA Astrometry of the Fastest-spinning Magnetar Swift J1818.0−1607: A Large Trigonometric Distance and a Small Transverse Velocity

An observed population of intermediate-mass helium stars that have been stripped in binaries

Elusive hot stripped helium stars in the Galaxy

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