arXiv subjects

Jian-Guo He

Publications and source records attributed to Jian-Guo He.

7 recordsLinked to original sources

arXiv2026

A Census of Stellar-mass Black Holes in the Milky Way with POPKIN. I. Isolated Black Holes

Gravitational-wave observations have revealed hundreds of stellar-mass black holes, yet only about two dozen are known in the Milky Way, almost all in binaries. We present POPKIN, a Python framework that couples single- and binary-star evolution with Galactic orbital dynamics to trace black-hole progenitors from the zero-age main sequence to the present-day isolated black-hole (IBH) population. Across ten models varying the supernova (SN) prescription, mass-transfer efficiency, and common-envelope ejection efficiency, the total IBH abundance is controlled primarily by the SN prescription. Our fiducial model, with a recently proposed metallicity- and stripping-history-dependent SN prescription, predicts $\sim4\times10^7$ IBHs in the Galaxy, including $\sim8\times10^4$ within $1\,\rm{kpc}$ of the Sun; alternative SN prescriptions predict $\sim(1-2)\times10^8$ IBHs. The fiducial model yields a bimodal mass distribution, peaking near $9\,M_{\odot}$ and $20\,M_{\odot}$, with a deficit at $13-17\,M_{\odot}$. This distinguishes it from alternative prescriptions, some of which populate the $2-5\,M_{\odot}$ mass-gap region. Non-kicked IBHs follow nearly circular orbits near the Galactic plane, with typical peculiar velocities of $20-30\,\rm{km\,s^{-1}}$, whereas kicked systems undergo stronger radial migration and span a broader velocity range. We estimate $\sim5\times10^3$ accreting IBHs with $F_{\rm X}>10^{-14}\,\rm{erg\,s^{-1}\,cm^{-2}}$, nearly all non-kicked; this estimate is sensitive to the adopted radiative-efficiency and hot-flow treatments. For a Roman-like bulge survey, our fiducial model predicts $\sim360$ intrinsic IBH microlensing events over five years in a $1.70\,\rm{deg^2}$ effective area, before survey-selection effects. We propose that long-timescale microlensing events from IBHs can strongly constrain the SN physics governing stellar-mass black hole formation.

astro-ph.GA↗

arXiv2026

A Rare Population of Intermediate-mass Helium Stars Between Hot Subdwarfs and Wolf-Rayet Stars

Helium stars stripped of their hydrogen envelopes represent pivotal phases in binary evolution, yet their origins, particularly within the intermediate-mass range of $2-8\, M_{\odot}$, still remain poorly understood. This population bridges the gap between low-mass hot subdwarfs and massive Wolf-Rayet stars, but has remained largely unobserved. In this study, we employ binary population synthesis to systematically investigate the formation and properties of intermediate-mass helium stars (IMHeS) across various galactic metallicities. Our results indicate that metallicity and common-envelope ejection efficiency are the dominant factors shaping the IMHeS population. We estimate that several thousand IMHeS exist in the Milky Way, with several hundred more in the Magellanic Clouds. The vast majority of IMHeS reside in binaries, with fewer than $10\%$ appearing as single stars. Among IMHeS binaries, $\gtrsim 50\%$ are expected to have main-sequence companions, and the remainder host compact companions (including helium stars, white dwarfs, neutron stars, or black holes). The former systems form mainly through stable mass transfer, whereas the latter arise predominantly from common envelope evolution. Our work provides quantitative predictions for the populations of these elusive stars formed through binary interactions and offers guidance for future observational searches.

astro-ph.SR↗

arXiv2026

Formation of Recycled Pulsars in Common Envelope Binaries

We present a systematic study of the evolution of low- and intermediate-mass X-ray binaries (L/IMXBs) consisting of a $1.4\,M_{\odot}$ neutron star (NS) and a donor star of mass $1-8\,M_{\odot}$. Using grids of detailed MESA simulations, we show that for donor masses of $2-8\,M_{\odot}$, mass transfer may be dynamically unstable, leading to a common envelope (CE) phase. By adopting CE ejection efficiencies in the range $α_{\rm CE} = 0.3-3.0$, we find that post-CE binaries frequently experience a CE decoupling phase (CEDP), which plays a critical role in determining their final orbital and compositional properties. Systems with initial donor masses $\gtrsim 3.5\,M_{\odot}$ predominantly evolve into NS binaries with carbon-oxygen or oxygen-neon white dwarfs (WDs) with masses between $0.5\,M_{\odot}$ and $1.4\,M_{\odot}$. Comparison with the observed population of binary pulsars with a WD companion shows better agreement with higher CE ejection efficiencies ($α_{\rm CE} = 3.0$). Furthermore, we demonstrate that NSs can accrete a sufficient amount of matter ($\gtrsim 0.01\,M_{\odot}$) during the CEDP and subsequent Case BA/BB/BC mass transfer phases to be effectively recycled into millisecond pulsars. We identify two distinct evolutionary channels capable of reproducing the observed characteristics of the millisecond pulsar PSR J1928+1815 with a helium-star companion. Our results highlight the importance of the CEDP in the formation of recycled pulsars and provide constraints on the CE ejection efficiency during binary evolution.

astro-ph.HE↗

arXiv2024

Modeling High Mass X-ray Binaries to Double Neutron Stars through Common Envelope Evolution

We present detailed evolutionary simulations of wide binary systems with high-mass ($8-20\,M_{\odot}$) donor stars and a $1.4\,M_{\odot}$ neutron star. Mass transfer in such binaries is dynamically unstable and common envelope (CE) evolution is followed. We use a recently developed prescription to deal with CE evolution and consider various CE ejection efficiencies varying in the range of $0.1-3.0$. We focus on the evolutionary consequences of the binaries survived CE evolution. We demonstrate that it is possible for the binaries to enter a CE decoupling phase (CEDP) when the donor stars are partially stripped leaving a hydrogen envelope of $\lesssim1.0-4.0\,M_\odot$ after CE evolution. This phase is expected to last $\sim 10^4-10^5\,\rm yr$, during which mass transfer occurs stably via Roche lobe overflow with super-Eddington rates. Identification of some X-ray binaries in a CEDP is important for the understanding of the physics of CE evolution itself, the origin of ultraluminous X-ray sources, and the recycling process of accreting pulsars. Also, we discuss the formation of double neutron stars and the occurrence of ultra-stripped supernovae according to the results from our simulations. On the whole, the properties of post-CE binaries are sensitive to the options of CE ejection efficiencies.

astro-ph.SR↗

arXiv2024

IC 10 X-1: A Double Black Hole Progenitor Probably Formed through Stable Mass Transfer

IC 10 X-1 is one of close X-ray binaries containing a Wolf-Rayet donor, which can provide an evolutionary link between high-mass X-ray binaries and gravitational wave sources. It is still unclear about the precise nature of the accreting compact object in IC 10 X-1, although it looks more like a black hole than a neutron star. In this work, we use a binary population synthesis method to simulate the formation of IC 10 X-1 like binaries by assuming different common-envelope ejection efficiencies. This work represents a big step forward over previous studies since we adopt new criteria of mass-transfer stability. These criteria allow the formation of IC 10 X-1 like systems without experiencing common envelope evolution. Based on our calculations, we propose that the compact object in IC 10 X-1 is a black hole with mass of $\sim 10-30M_\odot$ and the progenitor evolution of this binary probably just experienced stable mass transfer.

astro-ph.HE↗

arXiv2024

Constraining Mass Transfer Models with Galactic Neutron Star$-$White Dwarf Binaries as Gravitational Wave Sources

Neutron star$-$white dwarf (NSWD) binaries are one of the most abundant sources of gravitational waves (GW) in the Milky Way. These GW sources are the evolutionary products of primordial binaries that experienced many processes of binary interaction. We employ a binary population synthesis method to investigate the properties of Galactic NSWD binaries detectable by the Laser Interferometer Space Antenna (LISA). In this paper, only the NSWD systems with a COWD or ONeWD component are included. We consider various models related to mass transfer efficiencies during primordial binary evolution, supernova explosion mechanisms at NS formation, common envelope ejection efficiencies, and critical WD masses that determining the stability of mass transfer between WDs and NSs. Based on our calculations, we estimate that tens to hundreds of LISA NSWD binaries exist in the Milky Way. We find that the detection of LISA NSWD binaries is able to provide profound insights into mass transfer efficiencies during the evolution of primordial binaries and critical WD masses during mass transfer from a WD to an NS.

astro-ph.HE↗

arXiv2023

Detection Prospects of Fast-merging Gravitational Wave Sources in M31

It is widely accepted that quite a number of double compact objects (DCOs) in the Milky Way can be identified by future space-based gravitational wave (GW) detectors, while systematic investigations on the detection of the GW sources in nearby galaxies are still lacking. In this paper, we present calculations of potential populations of GW sources for all types of DCOs in the Local Group galaxy M31. For M31, we use an age-dependent model for the evolution of the metallicity and the star-formation rate. By varying assumptions of common-envelope ejection efficiencies and supernova-explosion mechanisms during binary evolution, we make predictions on the properties of DCOs that can be detected by the Laser Interferometer Space Antenna (LISA). Our calculations indicate that a few (a dozen) DCOs are likely to be observed by LISA during its 4 (10) yr mission. We expect that the sources with black-hole components are more likely to be firstly identified during a 4-yr mission since these binaries have relatively large chirp masses, while the systems with white-dwarf components dominate the overall population of detectable GW sources during a 10-yr mission. LISA can only detect very tight fast-merging systems in M31, corresponding to the peak of orbital period distribution from $\sim 2$ min for double white dwarfs to $\sim 20$~min for double black holes.

astro-ph.HE↗