He-star donor AM CVn stars and their progenitors as LISA sources

Liu, W.-M.; Yungelson, L. R.; Куранов, А. Г.

doi:10.1051/0004-6361/202244225

“…Their scientific aims are to detect low-frequency GW signals with frequencies between 10 −4 and 0.1 Hz in the Galaxy, which originate from compact binaries with an orbital period of less than 5 hr (van der Sluys 2011). To date, several potential lowfrequency GW sources in the Galaxy have been extensively investigated in some compact binaries such as CVs, double white dwarfs (WDs; Nelemans 2003;Korol et al 2017Korol et al , 2018Kremer et al 2017;, AM CVn (Nelemans 2003;Nelemans et al 2004;Liu et al 2021Liu et al , 2022, NS-WD binaries (Tauris 2018;Chen 2021;Pol et al 2021;Yu et al 2021), double NSs (Yu & Jeffery 2015;Tauris et al 2017;Pol et al 2021), NS ultracompact X-ray binaries (UCXBs; Chen et al 2020;Chen 2021;Wang et al 2021;Chen et al 2021), and compact intermediate-mass BH X-ray binaries (Chen 2020; Han et al 2021).…”

Section: Introductionmentioning

confidence: 99%

Black Hole Ultracompact X-Ray Binaries: Galactic Low-frequency Gravitational Wave Sources

Qin

¹

,

Jiang

²

,

Chen

³

2023

ApJ

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In the Galaxy, close binaries with compact objects are important low-frequency gravitational wave (GW) sources. As potential low-frequency GW sources, neutron star/white dwarf (WD) ultracompact X-ray binaries (UCXBs) have been investigated extensively. Using the Modules for Experiments in Stellar Astrophysics code, we systematically explored the evolution of black hole (BH)-main-sequence star (MS) binaries to determine whether their descendants can be detected by space-borne GW detectors. Our simulations showed that BH-MS binaries with an initial orbital period less than the bifurcation period can evolve into BH UCXBs that can be detected by LISA. Such an evolutionary channel would form compact mass-transferring BH-WD systems rather than detached BH-WD systems. The calculated X-ray luminosities of BH UCXBs that can be detected by LISA at a distance d = 1 kpc are ∼1033–1035 erg s−1 (∼1034–1035 erg s−1 for d = 10 kpc); hence, it is possible to detect their electromagnetic counterparts. It is worth emphasizing that only some BH-MS systems with an initial orbital period very close to the bifurcation period can evolve toward low-frequency GW sources whose chirp masses can be measured. The maximum GW frequency of BH UCXBs forming via the BH-MS pathway is about 3 mHz, which is smaller than the minimum GW frequency (6.4 mHz) of mass-transferring BH-WDs originating from a dynamic process. Furthermore, we obtain an initial parameter space (donor-star masses and orbital periods) of progenitors of BH UCXB-GW sources, which can be applied to future population synthesis simulations. By a rough estimation, we predict that LISA would only be able to detect a few BH UCXB-GW sources formed by the BH-MS channel.

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“…As a consequence, binary systems consisting of a compact object and a He star are potential galactic strong X-ray sources. Furthermore, they are also promising low-frequency GW sources in the Galaxy (Wang et al 2021;Liu et al 2022). Therefore, it is of great significance to study the evolution of BH binaries including He stars.…”

Section: Introductionmentioning

confidence: 99%

Black Hole Ultracompact X-Ray Binaries as Galactic Low-frequency Gravitational Wave Sources: The He Star Channel

Qin,

Xu,

Liu

et al. 2024

ApJ

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Black hole (BH) ultracompact X-ray binaries (UCXBs) are potential Galactic low-frequency gravitational wave (GW) sources. As an alternative channel, BH UCXBs can evolve from BH+He star binaries. In this work, we perform a detailed stellar evolution model for the formation and evolution of BH UCXBs evolving from the He star channel to diagnose their detectability as low-frequency GW sources. Our calculations found that some nascent BH+He star binaries after the common-envelope (CE) phase could evolve into UCXB-LISA sources with a maximum GW frequency of ∼5 mHz, which can be detected in a distance of 10 kpc (or 100 kpc). Once BH+He star systems become UCXBs through mass transfer, they would emit X-ray luminosities of ∼1038 erg s−1, making them ideal multimessenger objects. If the initial He-star masses are ≥0.7 M ⊙, those systems are likely to experience two Roche lobe overflows, and the X-ray luminosity can reach a maximum of 3.5 × 1039 erg s−1 in the second mass-transfer stage. The initial He-star masses and initial orbital periods of progenitors of Galactic BH UCXB-LISA sources are in the range of 0.32–2.9 M ⊙ and 0.02–0.19 days, respectively. Nearly all BH+He star binaries in the above parameter space can evolve into GW sources whose chirp masses can be accurately measured. Employing a population synthesis simulation, we predict the birthrate and detection number of Galactic BH UCXB-LISA sources evolving from the He star channel are R = 2.2 × 10−6 yr−1 and 33 for an optimistic CE parameter, respectively.

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“…For example, the evolutionary channel to merging binary neutron stars includes two stripped stars (Tauris et al 2017;Vigna-Gómez et al 2020;Ye et al 2020). In addition, stripped stars are also so small that they can emit low-frequency gravitational waves detectable with the Laser Interferometer Space Antenna (LISA), when stripped by a compact object (Nelemans et al 2004;Wu et al 2018;Götberg et al 2020b;Kupfer et al 2020;Wu et al 2020;Liu et al 2022). Furthermore, with their high effective temperatures (T eff ∼ 50-100 kK), stripped stars should emit most of their radiation in the ionizing regime, thus providing a boost of ionizing emission several tens of millions of years after a starburst (Stanway et al 2016;Götberg et al 2019Götberg et al , 2020a.…”

Section: Introductionmentioning

confidence: 99%

Stellar Properties of Observed Stars Stripped in Binaries in the Magellanic Clouds

Götberg,

Drout,

Ji

et al. 2023

ApJ

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Massive stars (∼8–25 M ⊙) stripped of their hydrogen-rich envelopes via binary interaction are thought to be the main progenitors for merging neutron stars and stripped-envelope supernovae. We recently presented the discovery of the first set of such stripped stars in a companion paper. Here, we fit the spectra of 10 stars with new atmosphere models in order to constrain their stellar properties precisely. We find that the stellar properties align well with the theoretical expectations from binary evolution models for helium-core burning envelope-stripped stars. The fits confirm that the stars have high effective temperatures (T eff ∼ 50–100 kK), high surface gravities ( log g ∼ 5), and hydrogen-poor/helium-rich surfaces (X H,surf ∼ 0–0.4) while showing for the first time a range of bolometric luminosities (103–105 L ⊙), small radii (∼0.5–1 R ⊙), and low Eddington factors (Γ e ∼ 0.006–0.4). Using these properties, we derive intermediate current masses (∼1–8 M ⊙), which suggest that their progenitors were massive stars (∼5–25 M ⊙) and that a subset will reach core-collapse, leaving behind neutron stars or black holes. Using the model fits, we also estimate the emission rates of ionizing photons for these stars, which agree well with previous model expectations. Further, by computing models for a range of mass-loss rates, we find that the stellar winds are weaker than predicted by any existing scheme ( M ̇ wind ≲ 10 − 9 M ⊙ yr−1). The properties of this first sample of intermediate-mass helium stars suggest they both contain progenitors of type Ib and IIb supernovae, and provide important benchmarks for binary evolution and population synthesis models.

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He-star donor AM CVn stars and their progenitors as LISA sources

Cited by 6 publications

References 105 publications

Black Hole Ultracompact X-Ray Binaries: Galactic Low-frequency Gravitational Wave Sources

Black Hole Ultracompact X-Ray Binaries: Galactic Low-frequency Gravitational Wave Sources

Black Hole Ultracompact X-Ray Binaries as Galactic Low-frequency Gravitational Wave Sources: The He Star Channel

Stellar Properties of Observed Stars Stripped in Binaries in the Magellanic Clouds

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