arXiv subjects

Xuefei Chen

Publications and source records attributed to Xuefei Chen.

At least 19 recordsLinked to original sources

arXiv2026

Stage-dependent superhump waveform evolution and non-stationary positive-superhump timing in the near-period-gap dwarf nova YZ Cancri

We present a photometric and timing study of the near-period-gap SU~UMa-type dwarf nova YZ~Cancri, based on nearly continuous Transiting Exoplanet Survey Satellite (TESS) photometry and long-baseline ground-based observations. Our main observational result is that the positive-superhump (SH) waveform follows a repeatable, stage-dependent sequence during superoutbursts (SOs). In the two well-covered TESS SOs, and consistently in the long-baseline ground-based SO sample, the plateau waveform evolves from an early saw-tooth profile (ST), through a double-humped profile with unequal maxima (DHd), to a more symmetric double-humped profile with nearly similar maxima (DHs). The global and time-resolved Lomb--Scargle periodograms show that power near the positive-SH time scale and its harmonics is concentrated during SOs, whereas quiescent and normal-outburst intervals lack a comparably persistent SH-band signal. The dense TESS maxima--minima timing sequence shows different clock stability in different waveform stages: precursor modulations have slightly longer local periods, the middle-to-late DHs plateau is the most regular timing interval, and the post-plateau evolution is affected by phase switching and possible secondary/late-SH contamination. The TESS data also reveal profile-clock coupling, with SH amplitude and rise/decay durations evolving together with the timing residuals. As a secondary timing constraint, we obtain a common TESS-timing-based mean positive-SH period of $P'_{\rm sh}=0.09043(27)$~d, corresponding to a SH excess of $4.03(31)\%$ and an approximate mass ratio of $q=0.175(11)$. The repeatable ST--DHd--DHs sequence makes YZ~Cnc a useful system near the lower edge of the period gap, and may trace the growth, redistribution, stabilization, and decay of the light source associated with an eccentric, precessing accretion disk during SOs.

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arXiv2026

First double red giant Algol system with active mass transfer

Double red giant stars are very important for studies of the stability of mass transfer, common-envelope evolution, and the formation of double white dwarfs with short orbital periods. However, no double red giant system undergoing mass transfer has yet been found. We present the discovery of a close Algol-type binary system composed of two red giant stars. This is the first known semi-detached system observed during the very short phase when the accretor has expanded into a red giant just before entering the common envelope phase. The $H_\alpha$ line suggests that the system has recently lost some material, which is now moving toward us. We present a consistent analysis of all the available spectroscopic and photometric observations of this system, constraining its orbital parameters and the fundamental properties of the components. Our findings are supported by a binary evolution model that successfully reproduces the currently observed parameters. The model suggests that the system will eventually merge into a single star.

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arXiv2026

Revisiting atmospheric Roche lobe overflow in symbiotic binaries

Classical binary evolution models predict dynamically unstable mass transfer in symbiotic stars with high mass ratios, leading to a common envelope. However, many observed S-type symbiotic systems show long-lived interaction, suggesting that an additional stabilizing mechanism may be at work. We investigate whether atmospheric Roche-lobe overflow can prolong the mass-transfer phase and help reconcile theory with observations. We implement the Rapid Unified Mass Transfer framework in \texttt{MESA} and compute a grid of white-dwarf--giant binaries covering a wide range of donor masses, mass ratios, and orbital periods. We then compare the resulting lifetimes and evolutionary tracks with well-constrained Galactic S-type symbiotic systems. For convective giant donors, our models recover stable mass transfer up to $q \simeq 1.5$, while atmospheric overflow strongly extends the symbiotic phase. RGB and early-AGB systems with $q \lesssim 1.5$ can remain interacting for up to $10^6$ yr at $\dot{M} \gtrsim 10^{-9},M_{\odot},{\rm yr}^{-1}$, much longer than the commonly assumed $\sim 10^3$ yr pre-common-envelope lifetime. In these systems, the orbit shrinks mildly and may re-expand after mass-ratio reversal. Systems with higher mass ratios still evolve toward a common envelope, but even for $q \simeq 2$--$4$ the symbiotic phase can last $10^4$--$10^5$ yr. The synthetic distribution in the orbital-period--mass-ratio plane and individual evolutionary tracks are broadly consistent with observed S-type symbiotic binaries, including recurrent novae. The RUMT framework, which incorporates atmospheric RLOF, provides an explanation for the long-term stability of many symbiotic binaries and may account for their high observed occurrence rate.

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arXiv2026

Three-Dimensional Simulations of Type Ia Supernova Remnants I: Effects of a Main-Sequence Companion Star

Type Ia supernovae (SNe Ia) serve as one of cosmic standard candles, but their exact progenitor channel is still an open question. SNe Ia commonly come from binary star evolution. Therefore, one of the major differences among the proposed progenitor channels is whether there is a more-or-less intact companion star remaining at the time of explosion, which causes the SN ejecta to be more asymmetrical. As the SN ejecta evolved into supernovae remnants (SNR), the imprint formed by the companion interaction may affect the morphology of the SNR. In addition, the progenitor systems may have experienced different mass transfer histories and therefore led to formation of different circumstellar material (CSM) environments, which may also affect the early evolution of SNR. In this study, we use GADGET and RAMSES codes to simulate these physical effects and follow the evolution into early-phases of SNRs. In our simulations, we consider different ejecta models and track the element distribution. We compare our simulation with actual observations and conclude that despite some SNRs having morphology resemblance to our simulation results, their highly asymmetric expansion rates are hard to explain by interaction between SN ejecta and a companion star alone.

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arXiv2026

Unraveling the mysteries of supernovae with SKA+VLBI

Supernovae (SNe) drive cosmic chemical enrichment and shape galactic feedback, yet the link between progenitors and explosion outcomes remains poorly constrained because the earliest phases are rarely resolved. Radio emission traces synchrotron radiation where the fastest ejecta interact with the circumstellar medium (CSM), providing a uniquely penetrating probe of these phases. SKA-Mid phased into global VLBI will move from simple detections to routine interferometric imaging of nearby extragalactic SNe. Sub-$\mu$Jy sensitivity and mas-scale SKA+VLBI imaging, complemented by visibility-domain model fitting for sub-beam radius measurements at 5-15 GHz will allow us to follow the expanding shocks of stripped-envelope SNe out to $\sim$25 Mpc, measure deceleration indices ($m$) and axial ratios to $\approx 5-10\%$, and directly test jet-assisted versus neutrino-driven explosion mechanisms. For interacting SNe (Type IIn/Ibn), SKA+VLBI will resolve clumpy and toroidal CSM on progenitor scales, constraining the timing and geometry of eruptive pre-explosion mass loss. Deep limits on Type Ia SNe will tightly restrict the allowed single-degenerate parameter space, while late-time imaging will search for nascent compact remnants and pulsar wind nebulae. In synergy with optical, X-ray and gravitational wave facilities, SKA+VLBI will turn nearby SNe into laboratories for time-resolved shock physics and progenitor mapping.

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arXiv2026

Surface brightness-color relations for red giant branch stars: Observational constraints on metallicity effects using the ARD method

Aims: We aim to quantify the metallicity dependence of the SBCR for red giant branch (RGB) stars and to test the robustness of the relation using asteroseismic radii, Gaia distances, and atmospheric parameters from APOGEE. Methods: We selected more than 2,000 RGB stars from APOKASC-3 to calibrate and validate the SBCR. Johnson V magnitudes were synthesized from Gaia XP spectra and homogenized to widely used SBCR photometric systems, while K_s photometry was taken from 2MASS. Angular diameters derived from asteroseismic radii and Gaia distances (ARD) were used to construct the SBCR. We explored three fitting strategies: metallicity-free, metallicity-binned, and global metallicity-dependent relations. Results: Over the range V-K_s=2-3, the SBCR shows only a weak metallicity dependence. A change of 1 dex in [Fe/H] modifies the predicted angular diameter by less than 1%, well below the intrinsic scatter of the calibration (~0.05 mag). This result is consistent with theoretical expectations. Comparison with the interferometric sample reveals a systematic offset of ~1.5% toward smaller angular diameters in our SBCR predictions, with a mild color dependence. Conclusions: The metallicity effect on the SBCR is small in the color range explored here, but it becomes relevant for sub-percent distance measurements. Our results show that large RGB samples with asteroseismic radii and Gaia distances provide a powerful observational route for SBCR calibration, with clear potential for extension to cooler and redder giants as the precision and parameter coverage of the input data improve.

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arXiv2026

Influence of mass-transfer stability on the formation of post-common-envelope binaries

Post-common-envelope binaries are the natural laboratories for constraining the physics of common envelope evolution, which is one of the most uncertain phases in binary stellar evolution. Traditional binary population synthesis models, adopting mass transfer stability criteria based on polytropic stellar models, systematically overpredict the number of post-common-envelope binaries with solar-type main-sequence companions. In this work, we present an updated binary population synthesis model using the rapid binary evolution code \textit{Binary Star Evolution}, incorporating a physically motivated mass transfer stability criterion and a self-consistent envelope binding energy prescription. We compile a comprehensive sample of classic white dwarf + main sequence post-common-envelope binaries with well-measured parameters, hosting both M-dwarf and A/F/G/K- stars. We find that the enhanced mass transfer stability is an additional mechanism responsible for the observed dearth of post-common-envelope binaries with solar-type main sequence companions; neither magnetic braking nor selection effects alone can fully account for this deficit, and a combination of all three processes is most likely required. Models with inefficient common envelope evolution ($\alpha_{\rm CE}=0.25$) provide the best overall match to the observed population. These results highlight the critical role of MT stability in shaping the observed post-common-envelope binaries population and provide new constraints on common envelope evolution.

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arXiv2026

Empirical colour--effective temperature relations in the SDSS system from IRFM temperatures of GALAH and APOGEE stars

Reliable estimates of stellar effective temperature ($T_{\mathrm {eff}}$) are fundamental to stellar population studies and Galactic astrophysics. However, the majority of stars observed in modern large-scale photometric surveys lack spectroscopic measurements, making empirical colour--$T_{\mathrm {eff}}$ relations essential tools. In this work, we present updated empirical colour--$T_{\mathrm {eff}}$ calibrations based on Sloan Digital Sky Survey (SDSS) $ugriz$ photometry combined with 2MASS $JHK_{\mathrm s}$ data. Effective temperatures are determined on a homogeneous InfraRed Flux Method (IRFM) scale using a combined sample of 3902 GALAH and 2535 APOGEE stars with high-quality photometry and well-characterised atmospheric parameters. Using this dataset, we establish empirical relations between $T_{\mathrm {eff}}$ and colour indices constructed from SDSS and 2MASS combinations. We provide both colour--metallicity--$T_{\mathrm {eff}}$ and colour--$T_{\mathrm {eff}}$ relations for dwarfs and giants. The calibrations are derived using low-order polynomial models with iterative $3\sigma$ clipping. Their performance depends on the adopted colour index, with long-baseline colours such as $(g-K_{\mathrm s})_0$ and $(g-z)_0$ achieving internal precisions of $\sim$30--50~K. Comparisons with previous calibrations show general agreement, with differences attributable to sample selection, photometric zero-points, and functional form. The resulting relations provide a homogeneous and internally consistent framework for estimating $T_{\mathrm {eff}}$ from SDSS and 2MASS photometry alone, and are well suited for application to large photometric surveys lacking spectroscopic information.

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arXiv2026

Recalibration of SDSS photometric zero-points based on the InfraRed Flux Method temperature scale

Accurate photometric zero-points are essential for translating observed magnitudes into physical fluxes, from comparing with models to ensuring consistency across surveys. We determine the zero-points needed to place the Sloan Digital Sky Survey (SDSS) $ugriz$ system on its nominal AB definition, by exploiting the sensitivity of the Infrared Flux Method (IRFM) to broadband flux calibration. Using benchmark effective temperatures for over 6,000 FGK-type stars, we invert the method to identify the zero-point corrections required for SDSS photometry to reproduce the adopted temperature scale. The $r$ band is found to be very well standardized, while the $i$ and $z$ bands show offsets of a few hundredths of a magnitude, consistent with previous studies. We also find a small offset in the $g$ band. The largest discrepancy occurs in the $u$ band, where the derived offset depends strongly on the adopted filter transmission curves, in particular whether one uses the original definition commonly adopted in the literature or the updated measurements that account for the presence of a red leak. This effect introduces a colour-dependent zero-point offset that becomes apparent when using a sample of late-type stars. Independent comparisons with CALSPEC spectrophotometric standards and Gaia XP spectra broadly support the offsets derived from the IRFM analysis. Our results provide a revised set of SDSS zero-points anchored to the IRFM temperature scale and demonstrate that large stellar samples can be used to constrain photometric calibration. The methodology presented here offers a complementary approach to traditional spectrophotometric calibration and may prove useful for future large-scale surveys.

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arXiv2026

Mass-Orbital Period Distribution of Massive White Dwarfs Formed Through Stable Mass Transfer

White dwarfs (WDs) in binaries can form through either the stable mass-transfer process or common envelope evolution (CEE). Compared to CEE, the stable mass-transfer process can lead to a distinct mass-orbital period ($M_{\mathrm{WD}}-P_{\mathrm{orb}}$) relation. Thus, this relation of WDs contains the information about the evolution channels. We can study the relation in WD binary systems to determine whether their progenitors undergo a CEE. We use the stellar evolution code MESA as our primary computational tool and adopt the quasi-adiabatic criterion to ensure that our models satisfy the conditions for stable mass transfer. Our study considers different mass-transfer schemes, varying metallicities, and the relation for both low-mass and intermediate-mass progenitors. Previous studies have focused on the relation for low-mass progenitors, which cannot explain some long-period, high-mass WD binaries. Our results show that the relations for intermediate-mass progenitors whose cores remain non-degenerate prior to central helium burning can account for the formation channels of long-period and massive WD binaries.

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arXiv2026

Formation of Extremely Low-mass White Dwarf Binaries Undergoing Enhanced Angular Momentum Loss

Extremely low-mass white dwarfs (ELM WDs) are helium (He) WDs with masses below $\sim 0.3\ M_{\odot}$, mainly formed through binary interaction. ELM WD binaries typically are formed from two channels, namely the stable Roche lobe overflow (RLOF) channel and the common envelope ejection channel. For ELM WD binaries produced from RLOF channel, the ELM WD mass has a strong correlation with the orbital period, i.e., the so-called WD mass-orbital period relation. However, the observations in the ELM Survey show that the orbital periods of ELM WD binaries from the RLOF channel are typically shorter than the theoretically predicted values. Extra angular momentum loss (AML) may be needed to explain such a phenomenon. In this work, we assumed that part of the transferred mass from the donor is lost at the outer Lagrangian point and simulated the formation of ELM WD binaries. Enhanced AML enables more mass to be lost during thermal-timescale mass transfer, thereby affecting nuclear burning in the transfer phase and producing ELM WDs with distinct internal structures. These structural differences alter the (pre-)He WD mass-radius relation at the end of mass transfer, which in turn shifts the WD mass-orbital period relation downward. These adjustments enable our model to successfully reproduce the majority of observed systems from the relevant survey projects.

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arXiv2026

Discovery and Characterization of White Dwarf-FGK Main-Sequence Binaries within the Optical Main-Sequence Locus

White dwarf main-sequence (WDMS) binaries provide important laboratories for studying binary evolution and the formation of low-mass white dwarfs. In this work, we identify 654 reliable WDMS candidates with FGK-type companions from an initial set of 772 ultraviolet-excess sources, selected using stellar atmospheric parameters from LAMOST spectroscopy and subsequently refined with \textit{Gaia} DR3 astrometry and photometry together with ultraviolet data from \textit{GALEX}. Candidates were selected based on ultraviolet excess relative to the \textit{Gaia} main-sequence locus and refined using isochrone constraints to exclude systems inconsistent with MS companions. Binary spectral energy distribution fitting yields effective temperatures and radii for both components, as well as distance and extinction estimates. The MS companions are dominated by G-type stars ($\sim52\%$), with comparable fractions of F- and K-type companions, and no A-type primaries. Using white-dwarf evolutionary cooling models, we find that the WD components are predominantly low-mass ($M_{\rm WD}\,\sim\,0.2\text{--}0.4\,M_\odot$), including a substantial population of extremely low-mass ($<0.3\,M_\odot$) WDs likely produced through binary interaction. The WDs are generally hot ($\sim1.5\times10^4\,\mathrm{K}$), consistent with the ultraviolet selection bias favoring luminous, large-radius WDs. Multi-epoch LAMOST radial velocities show larger amplitudes than those of a comparison sample of MS stars, supporting the close-binary nature of these systems. Although subject to strong selection effects, the catalog offers a clean and well-characterized sample of FGK+WD binaries.

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arXiv2026

Asteroseismic rotation rates of hot subdwarf B stars hint at transient accretion from leftover common envelope matter

Asteroseismology enabled measuring the rotation rate in the deep stellar interiors of stars across several evolutionary phases, advancing the theory of angular momentum transport in single stars from the main sequence to the white dwarf phase. However, binary stellar evolution products have not yet been studied in the context of angular momentum transport constrained by asteroseismology. Hot subdwarf B (sdB) stars can pulsate in non-radial modes, enabling probing of their internal rotation. Those in binary systems form through mass transfer, thus they can be used to probe theories of internal rotation in post-mass transfer stars. Here, we interpret observed asteroseismic core and envelope rotation rates of sdB stars in unsynchronised binary systems that formed through the common-envelope channel, using stellar evolution models of rotating sdB stars with internal magnetic fields. We find that when sdB stars form with the angular momentum content of red giant cores prior to common-envelope ejection, their predicted core rotation rates are two to ten times lower than measured asteroseismic rotation rates, and their envelope rotation rates are lower by two to five orders of magnitude. This suggests that the angular momentum content of sdB stars increases during their formation. Since sdB stars in close binary systems may host circumstellar matter from a past common-envelope ejection, we show that if they accrete a small amount of matter, the combination of internal magnetic fields with angular momentum transfer through accretion spins up both the core and envelope to match their measured asteroseismic rotation rates.

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arXiv2026

A New Pathway to Single Be Stars: Ejected Companions from Type Ia Supernovae

Be stars are rapid rotators generally produced by binary interactions. The single Be stars in the observations pose challenges to the Be star formation theory. In this paper, we propose a new pathway for the formation of single Be stars, in which the Be star is taken as the ejected companion star from a Type Ia supernova (SN Ia) explosion. Recent numerical simulations suggest that explosive oxygen burning, initiated via the convective Urca process in certain helium (He) stars near the Chandrasekhar mass limit, can set off a SN Ia. Based on this proposition, we further demonstrate that about $0.4\%$ of He star + main-sequence (MS) star binaries may evolve into single Be stars, where the MS star is spun up due to the mass accretion from the He star, and then the He star explodes as a SN Ia. We employ detailed binary evolutionary simulations and find the parameter space that would produce single Be stars via the SN Ia channel. Around $22\%$ of Be stars from the SN Ia progenitor channel exhibit peculiar tangential velocities exceeding $24\ \rm km/s$, classifying them as runaway stars. This suggests that the SN Ia channel plays a meaningful role in forming single Be stars, particularly within the runaway star population.

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arXiv2026

A Path to Constraints on Common Envelope Ejection in Massive Binaries: Full Evolutionary Reconstruction of Three Black Hole X-ray Binaries

The massive binary common envelope (CE) phase plays a pivotal role in the formation of close black hole/neutron star (BH/NS) binaries, yet significant uncertainties remain in our understanding of this process. In this study, we aim to constrain the massive binary CE phase by systematically reconstructing three observed BH X-ray binaries (BHXBs): GRO J1655-40, SAX J1819.3-2525, and 4U 1543-47. Through comprehensive binary evolution simulations and parametric supernova (SN) modeling, we establish lower limits for the CE efficiency parameters under different energy considerations within the standard energy formalism. Specifically, we derive minimum values for three cases: $\alpha_{\rm 0.5U}$ and $\alpha_{\rm U}$ representing CE efficiencies with half and all of the internal energy contributing to the envelope ejection, respectively, and $\alpha_{\rm H}$ accounting for the envelope's enthalpy. Our analysis reveals that the self-consistent formation of these three BHXBs requires CE efficiency parameters satisfying: $\alpha_{\rm 0.5U}\gtrsim 6.7$, $\alpha_{\rm U}\gtrsim 4.2$ and $\alpha_{\rm H}\gtrsim 1.7$. Notably, we find no viable solutions with CE efficiency values below unity, even when considering the most extreme scenarios in which the envelope binding energy is significantly reduced through enthalpy inclusion. {Our results strongly imply that either additional energy sources are required, or the formalism itself must be revised.} Furthermore, we quantitatively assess the impact of BH natal kicks on our results. A key finding is that 4U 1543-47's formation requires substantial natal kicks ($\gtrsim 50 \;\rm km/s$), as lower kick velocities are incompatible with isolated binary evolution.

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arXiv2026

Adiabatic Mass Loss In Binary Stars. VI. Massive Helium Binary Stars

The stability of binary mass transfer is a critical problem for binary evolution. We systematically calculate the adiabatic mass-loss model for naked helium stars with masses ranging from 10$M_{\odot}$ to 80$M_{\odot}$ to study the critical mass ratio ($q_\textrm{crit}$) of Wolf-Rayet binaries. We set up two prescriptions about Wolf-Rayet stellar wind and consider the isotropic re-emission effect during adiabatic mass loss. Results of the critical mass ratio for conserved dynamically unstable mass transfer show that most of the no-wind helium stars on the main sequence (HeMS) have $0.7<q_\textrm{crit}<3.0$ and on the Hertzsprung gap (HeHG) have $1.5<q_\textrm{crit}<27$. With the Wolf-Rayet star wind effect, the $q_\textrm{crit}$ gets lower on a certain evolutionary stage. With the isotropic re-emission effect, the $q_\textrm{crit}$ gets larger for early-evolutionary stage helium stars and lower for late-evolutionary stage helium stars. Based on fully non-conserved mass transfer, the criteria for HeMS stars are $1.0<q_\textrm{crit}<2.8$ and HeHG stars are $1.5<q_\textrm{crit}<5.0$. Compared with the widely used criterion $q_\textrm{crit}=3$ (HeMS) and $q_\textrm{crit}=4$ (HeHG), our result becomes more unstable for the HeMS stars and more stable for the HeHG stars. Our work could be applied to the binary mass transfer stage of massive helium binaries, such as Wolf-Rayet star binaries and high mass X-ray binaries with Wolf-Rayet star companions. It can be applied to the binary population synthesis studies for the formation of special objects, such as double black hole mergers.

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arXiv2026

Stellar Parameters and Orbital Period Estimates for Composite-Spectrum sdB+MS Binaries from LAMOST

Hot subdwarf (sdB) stars in binary systems with main-sequence (MS) companions provide valuable insights into mass transfer and envelope ejection processes in binary evolution. Their mass ratios, orbital periods, and stellar properties encode key information about their evolutionary histories. In this work, we analyze a sample of 123 composite-spectrum sdB+MS binaries identified from the Large Sky Area Multi-Object Fiber Spectroscopic Telescope Low-Resolution Survey (LAMOST-LRS) Data Release (DR) 8. We adopt atmospheric parameters from spectral decomposition and estimate stellar masses and radii using theoretical evolutionary tracks. Radial velocities for both the hot subdwarfs and cool companions are measured independently through cross-correlation with synthetic templates. Orbital periods are statistically estimated using single-epoch RV separations and a Monte Carlo method that accounts for random inclination and orbital phase. We find that sdB masses are narrowly distributed around 0.5 Msun, consistent with expectations for core helium-burning stars, while MS companion masses span 0.6-1.9 Msun, with most falling between 1.0 and 1.4 Msun. The inferred orbital-period distribution shows a clear concentration toward long periods, broadly consistent with expectations for binaries formed through stable Roche-lobe overflow. Given that our sample consists of composite-spectrum sdB binaries, mainly sdB+FGK systems, the prevalence of long periods is largely driven by observational selection effects rather than the intrinsic period distribution of the sdB binary population. This study provides one of the largest uniform catalogs of composite spectrum sdB binaries to date, offering new observational constraints on their physical properties and formation channels.

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arXiv2026

Expected evolution of the binary system ATLAS J1138-5139

ATLAS J1138-5139 is a newly detected ultra-compact double white dwarf (DWD) system which is composed of a $1.02\,M_{\odot}$ carbon-oxygen white dwarf (CO WD) and a $0.24\,M_{\odot}$ helium (He) WD with an orbital period of about 27.68 min, making it one of the shortest-period DWD systems known. The future evolution and final fate of this system remain unexplored. In this work, we investigate the evolution of ATLAS J1138-5139 with the one-dimensional stellar evolution code Modules for Experiments in Stellar Astrophysics (MESA). We find that ATLAS J1138-5139 will evolve into an AM Canum Venaticorum (AM CVn) system in about \sim 6.3 Myr. Afterwards, the transferred material from the He WD companion start to build up to form a He shell near the surface of the CO WD. This accumulated He-shell masses can be up to approximately $0.12\,M_{\odot}$, which is likely to trigger a double-detonation (DDet) explosion of the CO WD. We therefore expect that ATLAS J1138-5139 will likely explode as a type Ia supernova eventually through the DDet explosion mechanism. Moreover, our calculations show that ATLAS J1138-5139 will be a promising target for gravitational-wave (GW) detection by future detectors like LISA, Tianqin and Taiji.

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