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The fallback disk model is widely accepted to explain long-period neutron stars (NSs) that cannot be simulated by magnetic dipole radiation. However, there was no confirmed detection of disks from the newly discovered long-period pulsars GLEAM-X 162759.5-523504.3 and GPM J1839-10 and the slowest known isolated NS 1E 161348-5055. This might be because the disks have either been in a noninteracting/inactive state where their emission is too weak to be detected or have been disrupted. In this work, we conduct simulations to examine the lifetime of supernova fallback disks around isolated NSs. We assume that the disks' mass varies in a self-similar way, and their interaction with the NS occurs only in an interacting/active state. Our results reveal that nearly all the interacting lifetimes for the disks are shorter than 105 yr, while the existence lifetimes are considerably longer. [ABSTRACT FROM AUTHOR]

Recently, two ultralong-period radio transients, GLEAM-X J162759.5-523504.3 (J1627) and GPM J1839-10 (J1839), were discovered with spin periods longer than 1000 s. The origin of these two ultralong-period radio transients is intriguing in understanding the spin evolution of neutron stars (NSs). In this work, we examine whether the interaction between strong magnetized NSs and fallback disks can spin NSs down to the observed ultralong period. Our simulations found that the magnetar + fallback disk model can account for the observed period, period derivative, and X-ray luminosity of J1627 in the quasi-spin-equilibrium stage. To evolve to the current state of J1627, the initial mass-accretion rate of the fallback disk and the magnetic field of the NS are in the range of (1.1–30) × 1024 g s−1 and (2–5) × 1014 G, respectively. In the active lifetime of the fallback disk, it is impossible for J1839 to achieve the observed upper limit of the period derivative. Therefore, we propose that J1839 may be in the second ejector phase after the fallback disk becomes inactive. Those NSs with a magnetic field of (2–6) × 1014 G and a fallback disk with an initial mass-accretion rate of ∼1024–1026 g s−1 are possible progenitors of J1839. [ABSTRACT FROM AUTHOR]

Recent discoveries of gravitational wave (GW) events most likely originating from black hole (BH) + neutron star (NS) mergers reveal the existence of BH+NS binaries. The formation of BH+NS binaries and their merger rates through isolated binary evolution have been investigated extensively with population synthesis simulations. A detailed stellar evolution modeling of the formation of this population, however, is missing from the literature. In this work, we create the first complete 1D model of more than 30 BH+NS progenitor systems, which are calculated self-consistently until collapse of the iron core with infall velocity exceeding 1000 km s−1. Focusing on the progenitors of BH–NS GW sources, we apply the MESA code starting from a post-common-envelope binary with short orbital period (<1 day) consisting of a BH and a zero-age main-sequence helium star that experiences stable mass transfer. The (ultra)stripped supernova explosion is subsequently modeled using a semianalytic method to reveal final remnant masses and momentum kicks. Three example systems (A, B, and C) eventually evolve into BH+NS binaries with component masses of (M BH, M NS) = (8.80, 1.53), (8.92, 1.45), and (5.71, 1.34) M ⊙, respectively. These NS masses could be significantly larger depending on the exact mass cut during the supernova explosion. These BH+NS systems are likely to merge and produce GW events within a Hubble time. System C is a potential progenitor of a GW200115-like event, while Systems A and B are possible candidates for a GW200105-like event and may represent the final destiny of the X-ray binary SS 433. [ABSTRACT FROM AUTHOR]

In young dense clusters, an intermediate-mass black hole (IMBH) may get a companion star via exchange encounters or tidal capture and then evolve toward the IMBH X-ray binary by the Roche lobe overflow. It is generally thought that IMBH X-ray binaries are potential ultraluminous X-ray sources (ULXs); hence, their evolution is very significant. However, the irradiation-driven winds by the strong X-ray flux from the accretion disks around the IMBHs play an important role in determining the evolution of IMBH X-ray binaries and should be considered in the detailed binary evolution simulation. Employing the models with the MESA code, we focus on the influence of irradiation-driven winds on the evolution of IMBH X-ray binaries. Our simulations indicate that a high wind-driving efficiency (f = 0.01 for Z = 0.02, and f = 0.002 for Z = 0.001) substantially shortens the duration in the ULX stage of IMBH X-ray binaries with an intermediate-mass (5 M⊙) donor star. However, this effect can be ignored for high-mass (10 M⊙) donor stars. The irradiation effect (f = 0.01 or 0.002) markedly shrinks the initial parameter space of IMBH binaries evolving toward ULXs with high luminosity (LX > 1040 erg s−1) and hyperluminous X-ray sources in the donor-star mass versus orbital period diagram. Furthermore, the irradiation effect results in an efficient angular momentum loss, yielding to IMBH X-ray binaries with relatively close orbits. In our simulated parameter space, about 1% of IMBH binaries would evolve toward compact X-ray sources owing to short initial orbital periods, some of which might be detected as low-frequency gravitational-wave sources. [ABSTRACT FROM AUTHOR]

The space gravitational wave (GW) detector Laser Interferometer Space Antenna (LISA) that is planned to be launched in the early 2030s will detect the low-frequency GW signals in the Galaxy. AM CVn stars were generally thought to be important low-frequency GW sources. Employing the MESA code, in this work we calculate the evolution of a great number of binary systems consisting of a white dwarf (WD) and a main sequence (MS) star, and diagnose whether their descendant-AM CVn stars will be visible with LISA. The simulated results show that the progenitors of these LISA sources, within a distance of 1 kpc, are WD–MS binaries with a donor star of 1.0–1.4 M⊙ (for initial WD mass of 0.5 M⊙) or 1.0–2.0 M⊙ (for initial WD mass of 0.7 M⊙), and an initial orbital period slightly smaller than the bifurcation period. Our simulations also indicate that 10 verification AM CVn sources can be reproduced by the standard magnetic braking model, and are potential LISA sources. Based on the birth rate of AM CVn stars simulated by the population synthesis, the birth rate of AM CVn-LISA sources evolving from the evolved donor star channel within a distance of 1 kpc can be estimated to be (0.6–1.4) × 10−6 yr−1, and the predicted number of AM CVn-LISA sources is about 340–810. Therefore, the evolved donor star channel plays an important role in forming AM CVn-LISA sources in the Galaxy. [ABSTRACT FROM AUTHOR]

The scientific aim of the space gravitational-wave (GW) detector Laser Interferometer Space Antenna (LISA) that was scheduled to launch in the early 2030s is to detect the low-frequency GW signals in the Galaxy. Its main candidate GW sources are compact binaries of white dwarfs and neutron stars. In this work, we examine whether compact intermediate-mass black hole (IMBH) X-ray binaries could be potential LISA sources. Our simulations indicate that an IMBH binary with a 1000 M⊙ IMBH and a 3 M⊙ donor star in an initial orbital period near the so-called bifurcation period of 0.77 day could evolve into an ultra-compact X-ray binary, which will emit GW signals with a maximum frequency of 2.5 mHz. According to the evolutionary tracks of characteristic strain, IMBH X-ray binaries with the initial donor-star masses of 1–3 M⊙ and the initial orbital periods slightly less than the bifurcation periods will be detectable by the LISA in a distance of 15 kpc. Assuming each of 60 Galactic globular clusters hosts a 1000 M⊙ IMBH, the maximum number of compact IMBH X-ray binaries that LISA will detect in the Galaxy should be less than ten. Therefore, the detectability of compact IMBH X-ray binaries by the LISA is not optimistic. [ABSTRACT FROM AUTHOR]

It is generally thought that an ultra-compact X-ray Binary is composed of a neutron star and a helium white dwarf donor star. As one of the most compact binaries, 4U 1820-303 in globular cluster NGC 6624 was predicted to have an orbital period of yr−1 if the mass transfer is fully driven by gravitational radiation. However, recent analysis of 16 year data from Rossi X-ray Timing Explorer and other historical records has yielded a negative orbital-period derivative in the past 35 years. In this work, we propose an evolutionary circumbinary (CB) disk model to account for this anomalous orbital-period derivative. 4U 1820-30 is known to undergo superburst events caused by runaway thermal nuclear burning on the neutron star. We assume that, for a small fraction of the superbursts, part of the ejected material may form a CB disk around the binary. If the recurrence time of such superbursts is ∼10,000 year and ∼10% of the ejected mass feeds a CB disk, the abrupt angular-momentum loss causes a temporary orbital shrink, and the donor’s radius and its Roche lobe radius do not keep in step. Driven by mass transfer and angular-momentum loss, the binary would adjust its orbital parameters to recover a new stable stage. Based on theoretical analysis and numerical simulation, we find that the required feed mass at the CB disk is approximately ∼10−8M⊙. [ABSTRACT FROM AUTHOR]

It is generally believed that ultracompact X-ray binaries (UCXBs) evolved from binaries consisting of a neutron star accreting from a low-mass white dwarf (WD) or helium star where mass transfer is driven by gravitational radiation. However, the standard WD evolutionary channel cannot produce the relatively long-period (40–60 minutes) UCXBs with a high time-averaged mass-transfer rate. In this work, we explore an alternative evolutionary route toward UCXBs, where the companions evolve from intermediate-mass Ap/Bp stars with an anomalously strong magnetic field (100–10,000 G). Including the magnetic braking caused by the coupling between the magnetic field and an irradiation-driven wind induced by the X-ray flux from the accreting component, we show that intermediate-mass X-ray binaries (IMXBs) can evolve into UCXBs. Using the MESA code, we have calculated evolutionary sequences for a large number of IMXBs. The simulated results indicate that, for a small wind-driving efficiency f = 10−5, the anomalous magnetic braking can drive IMXBs to an ultra-short period of 11 minutes. Comparing our simulated results with the observed parameters of 15 identified UCXBs, the anomalous magnetic braking evolutionary channel can account for the formation of seven and eight sources with f = 10−3, and 10−5, respectively. In particular, a relatively large value of f can fit three of the long-period, persistent sources with a high mass-transfer rate. Though the proportion of Ap/Bp stars in intermediate-mass stars is only 5%, the lifetime of the UCXB phase is ≳2 Gyr, producing a relatively high number of observable systems, making this an alternative evolutionary channel for the formation of UCXBs. [ABSTRACT FROM AUTHOR]