arXiv subjects

Hui-Fang Xue

Publications and source records attributed to Hui-Fang Xue.

At least 19 recordsLinked to original sources

arXiv2026

BE Lyncis: A Pulsating Star in the Most Eccentric Binary with a Massive Unseen Companion

We report the discovery of an exceptionally eccentric binary system, BE Lyncis (BE Lyn), which might host a compact companion with mass $\gtrsim 2.5~M_{\odot}$. By combining TESS photometry with an extensive set of times of maximum light spanning 39 years, we identify BE Lyn as a high-amplitude $δ$ Scuti star in a binary with an orbital period of $\approx15.9$ years and an extraordinary eccentricity of $e=0.9989^{+0.0008}_{-0.0021}$ ($>0.9968$ at 95% confidence) -- the most extreme eccentricity reliably measured for any binary system. Dynamical constraints limit the orbital inclination to $i \lesssim 10^{\circ}.1$, implying a companion mass $M_2 \gtrsim 2.5~M_{\odot}$, which identifies the companion as a compact object. This mass points to it most likely being a black hole; if instead it is a rapidly rotating neutron star, it would be the most massive known. If the black hole interpretation holds, it would be the closest such object to Earth. This system provides a unique laboratory for studying asteroseismology in strong gravitational fields, as well as the formation and evolution of extremely eccentric binaries. Our work demonstrates the use of the light-travel time effect in a pulsating star to reveal a compact companion, offering a novel method for detecting black holes in noninteracting binaries.

astro-ph.SR↗

arXiv2025

Discovery of resonating integration modes in triple-mode high-amplitude $δ$ Scuti stars: A new evolutionary phase indicator

High-amplitude $δ$ Scuti stars (HADS) that pulsate in their first three radial modes are rare in current samples. Here, we analyse five such triple-mode HADS observed by the Transiting Exoplanet Survey Satellite (TESS) and {report that the previously considered second overtone mode ($f_2$) is actually the non-radial component of a resonating integration mode (RI mode, resulting from resonance between a radial p-mode and a non-radial p-g mixed mode), which shows significant amplitude and frequency variations over short timescales (approximately 20 days).} This RI mode appears to be widespread among these stars. Notably, all five stars are in the post-main sequence evolutionary phase, actively crossing the Hertzsprung gap. These stars offer valuable insights into stellar evolution during the Hertzsprung gap, which is one of the most rapid evolutionary stages in a star's life.

astro-ph.SR↗

arXiv2025

Period Variation Rates of Four Radial Single-Mode High-Amplitude Delta Scuti Stars

In this work, we present a study on the long time-scale period variations of four single-mode high-amplitude delta Scuti stars (HADS) via the classical $O-C$ analysis. The target HADS are (i) XX Cygni, (ii) YZ Bootis, (iii) GP Andromedae, and (iv) ZZ Microscopii. The newly determined times of maximum light came from the Transiting Exoplanet Survey Satellite (TESS), American Association of Variable Star Observers (AAVSO), and Bundesdeutsche Arbeitsgemeinschaft f$\ddot{\rm u}$r Ver$\ddot{\rm a}$nderliche Sterne (BAV) projects. Together with the times of maximum light obtained in the historical literature, the $O-C$ analysis was performed on these HADS, in which we obtained the linear period variation rates $\dot{P}/P$ as $(9.2 \pm 0.2) \times 10^{-9} \ \mathrm{yr^{-1}}$, $(3.2\pm 0.2)\times 10^{-9} \ \mathrm{yr^{-1}}$, $(4.22\pm 0.03) \times 10^{-8} \ \mathrm{yr^{-1}}$, and $(-2.06 \pm 0.02) \times 10^{-8} \ \mathrm{yr^{-1}}$, respectively. Based on these results and some earlier research, we also discuss the evolutionary stages and the mechanisms of the period variation of these four HADS.

astro-ph.SR↗

arXiv2025

CY Aquarii: A Triple System with Twin Companions

In this study, we conducted a comprehensive analysis of the SX Phoenicis (SX Phe) type star CY Aquarii (CY Aqr). Our investigation included a detailed $O-C$ analysis based on a 90-year observational dataset, augmented by 1,367 newly determined times of maximum light. The $O-C$ diagram reveals that (i) the primary star of CY Aqr exhibits a linear period variation rate of $(1/P_0)(\mathrm{d} P/ \mathrm{d} t) = (2.132 \pm 0.002) \times 10^{-8} \mathrm{yr}^{-1}$ for its dominant pulsation mode; (ii) the primary star is disturbed by two companions and part of a triple system; (iii) Companion A has an orbital period of approximately 60.2 years and Companion B has an orbital period of approximately 50.8 years. It is highly probable that both Companion A and B are white dwarfs, with Companion A's elliptical orbit displaying an eccentricity of $e = 0.139 \pm 0.002$, which is the lowest confirmed value in similar binary and triple systems to date. Most notably, Companion A and B have masses that are identical within the uncertainties, with a mass ratio exceeding 0.99. Whether this is considered a coincidental event or the result of an underlying mechanism, CY Aqr is an exceptionally rare case that broadens our understanding of multiple star systems and offers a unique opportunity to delve into the enigmatic evolutionary histories of such configurations. Further intriguing characteristics of this system warrant investigation in future studies, based on additional observational data.

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arXiv2024

Exploring the unexpected: Disharmonized harmonic pulsation modes in high-amplitude $δ$ Scuti stars

Harmonics are a ubiquitous feature across various pulsating stars. They are traditionally viewed as mere replicas of the independent primary pulsation modes and have thus been excluded from asteroseismological models. Recent research, however, has uncovered a significant discrepancy: in high-amplitude $δ$ Scuti (HADS) stars, harmonics exhibit uncorrelated variations in amplitude and frequency relative to their independent primary pulsation modes. The nature of these disharmonized harmonics is a question of critical importance. In our study we analysed five triple-mode HADS stars observed by the Transiting Exoplanet Survey Satellite (TESS) and discovered some pervasive patterns of disharmonized harmonics in both the fundamental ($f_0$) and first overtone ($f_1$) pulsation modes. Intriguingly, through an in-depth frequency interaction analysis of V1393 Cen, we identified $2f_1$ as an independent pulsation mode, distinct from $f_1$, and identified it as the progenitor of the frequency variations observed in $3f_1$, $4f_1$, $5f_1$, and $6f_1$. Similar behaviour can be found in DO CMi and GSC 06047-00749, in which $2f_1$ and $3f_1$ are the independent pulsation modes, respectively. Notably, we found an interesting pattern when decomposing the harmonics that might suggest a generation process of harmonics. These findings serve as a new window on the research of harmonics, which remains a hidden corner of contemporary asteroseismology.

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arXiv2024

Possible Dark Matter Signals from White Dwarfs

In our galaxy, the white dwarfs (WDs) will inevitably capture the dark matter (DM) particles streaming through them, if there exist interactions between DM particles and nuclei/electrons. At the same time, these DM particles can also be evaporated by the nuclei/electrons in a WD if they have proper mass and the WD is not too cold. The evaporation of DM particles will lead to a faster cooling evolution than that predicted by the stellar evolution theory. In this work, we ascribe the faster cooling evolution of three observed WDs to the capture and evaporation of DM particles, and get the possible DM particle's mass and DM-electron cross section as follows: for $F(q) = 1$, $40\ \mathrm{MeV}/c^{2} \lesssim m_χ \lesssim 70\ \mathrm{MeV}/c^{2}$ and $10^{-57} \mathrm{cm}^{2} \lesssim σ_{χ,e} \lesssim 10^{-55} \mathrm{cm}^{2}$; for $F(q) = (αm_{e})^{2}/q^{2}$, $30\ \mathrm{MeV}/c^{2} \lesssim m_χ \lesssim 60\ \mathrm{MeV}/c^{2}$ and $10^{-53} \mathrm{cm}^{2} \lesssim σ_{χ,e} \lesssim 10^{-51} \mathrm{cm}^{2}$. These results are beyond the detection capabilities of current direct detection experiments and should be cross checked by more novel scenarios in the future.

hep-ph↗

arXiv2023

Unveiling the Intricate Symphony of Nonlinear Pulsation Mode Interactions in High-Amplitude $δ$ Scuti Stars

People can diagnose the interiors of stars by sensing their pulsations. Pulsation modes, which are determined by the internal state and structure of a star, are typically considered stable over short timescales. These independent pulsation modes have been used in asteroseismology to reconstruct the interior structure of stars. Here, we report the discovery of peculiar pulsation mode interaction details in the high-amplitude $δ$ Scuti star KIC 6382916 (J19480292+4146558), challenging the reliability of independent pulsation modes as indicators of the star's internal structure. Through analysis of archival data, we found distinct variations in amplitudes and frequencies of three independent pulsation modes and their harmonics/combinations over approximately 20 days. These variations can reach amplitudes of about 140% and frequency variations of about 12%. Correlation analysis of amplitude and frequency variations revealed additional pulsation mode interaction details and patterns. Notably, our findings regarding the phenomena related to harmonics of independent pulsation modes challenge the traditional understanding in this area. These discoveries serve as cornerstones for future research and advance nonlinear asteroseismology.

astro-ph.SR↗

arXiv2023

Pulsation Analysis of High-Amplitude $δ$ Scuti Stars with TESS

In this work, the pulsation analysis is performed on 83 high-amplitude $δ$ Scuti stars, which have been observed by the Transiting Exoplanet Survey Satellite (TESS). The results show that 49 of these HADS show single-mode pulsation, 27 of them show radial double-modes pulsation (in which 22 of them pulsate with the fundamental and first overtone modes and 5 of them pulsate with the first and second overtone modes), and 7 of them show radial triple-modes pulsation (3 of which are newly confirmed triple-mode HADS). The histogram of the fundamental periods and the ratios between the fundamental and first overtone periods show bimodal structures, which might be caused by the stellar evolution in this specific phase. Most of the radial triple-mode HADS have a fundamental amplitude of 41-54 mmag, and 50% of them have similar amplitudes of the fundamental and first overtone pulsation modes. All these hints require further confirmation not only in observations with more HADS samples, but also in theoretical models with suitable treatments of stellar evolution and pulsation.

astro-ph.SR↗

arXiv2023

Uncorrelated Amplitude and Frequency Variations of the Harmonics in SX Phoenicis Star XX Cygni

Harmonics are quite common in pulsating stars, and they are always considered to mimic the behaviors of their independent parent pulsation modes and not taken as the key information for asteroseismology. Here, we report an SX Phoenicis star XX Cygni, whose periodogram is dominated by the fundamental frequency $f_{0} = 7.41481 \pm 0.00004\ \mathrm{cd}^{-1}$ and its 19 harmonics. According to the analysis of the archival data from \TESS, we find that both the amplitudes and frequencies of the fundamental mode and the harmonics vary within TESS Sectors 14-17 and 54-57, which might be caused by the contamination by neighbouring stars. What is more interesting is that, the harmonics show significantly uncorrelated amplitude and frequency variations over time. Some possible origins and interesting issues are proposed to scheme the further research of this hidden corner in current asteroseismology.

astro-ph.SR↗

arXiv2022

A rapidly evolving high-amplitude $δ$ Scuti star crossing the Hertzsprung Gap

In this work, we report the discovery of the rapidly evolving high-amplitude $δ$ Scuti star KIC 6382916 (J19480292+4146558) which is crossing the Hertzsprung gap. According to the analysis of the archival data, we find three independent pulsation modes, whose amplitudes and frequencies vary distinctly in 4 years. The linear period variation rates of the first two modes are about 3-4 times larger than the best seismic model constructed by the standard evolution theory, while that of the third one is about 8 times larger than the first two modes. What is more interesting is that, almost all the combinations of the third mode have frequency peaks $0.0815\ \mathrm{c\ d}^{-1}$ away from them in the frequency domain. A framework is proposed to interpret the markedly large frequency and amplitude variation rates of the third mode, in which we employ a new pulsation mode (resonating integration mode) generated by the resonance between a radial p-mode and a nonradial mixed mode. Moreover, a global analysis of the interactions between the three independent pulsation modes and their harmonics/combinations is performed based on the interaction diagrams of their amplitudes and phases, which would be a useful tool for the future asteroseismology research.

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arXiv2022

Precise Evolutionary Asteroseismology of High-Amplitude δ Scuti Star AE Ursae Majoris

Stellar structure and evolution theory is one of the basis in modern astronomy. Stellar inner structures and their evolutionary states can be precisely tested by asteroseismology, since the inner information is brought to the stellar surface by the global oscillating waves and becomes observable. For stellar evolutionary speed (i.e. how long time scale does a star stay at a special evolution phase?), because of the insurmountable gap between the time scales of the evolutionary history of human civilization and a star, it can only be roughly tested by ensemble of stars in different evolutionary stages in most cases, and all the snapshots of these stars make up our global view of stellar evolution. The effect of stellar evolution on the structure and the corresponding global size of a pulsating star will lead to tiny period variations of its pulsation modes, which are the most valuable indicators of its evolutionary state and can be used to test the stellar evolution theory by a single star rather than ensemble of stars. Here, we report a High-Amplitude $δ$ Scuti star AE Ursae Majoris, who locates in the post main-sequence (MS) evolutionary stage and its observed linear period variation rate can be practically ascribed to its evolutionary effect. The result tests the stellar evolution theory from the pre-MS to post-MS with an unprecedented precision by a single star, and the framework can be extended to other type of pulsating stars to perform precise evolutionary asteroseismology, which aims to test the current stellar evolution theory in different evolutionary stages, discover the discrepancies between the theory and observations, and ultimately build a complete and precise stellar evolution theory to backtrack the history of each of these stars.

astro-ph.SR↗

arXiv2020

DY Pegasi: An SX Phoenicis Star in a Binary System with an Evolved Companion

In this work, the photometric data from the American Association of Variable Star Observers are collected and analyzed on the SX Phoenicis star DY Pegasi (DY Peg). From the frequency analysis, we get three independent frequencies: $f_0 = 13.71249\ \rm{c\ days^{-1}}$, $f_1 = 17.7000\ \rm{c\ days^{-1}}$, and $f_2 =18.138\ \rm{c\ days^{-1}}$, in which $f_0$ and $f_1$ are the radial fundamental and first overtone mode, respectively, while $f_2$ is detected for the first time and should belong to a nonradial mode. The $O-C$ diagram of the times of maximum light shows that DY Peg has a period change rate $(1/P_0)(\mathrm{d} P_0/\mathrm{d} t) = -(5.87 \pm 0.03) \times 10^{-8} \ \mathrm{yr^{-1}}$ for its fundamental pulsation mode, and should belong to a binary system that has an orbital period $P_{\mathrm{orb}} = 15425.0 \pm 205.7 \ \mathrm{days}$. Based on the spectroscopic information, single star evolutionary models are constructed to fit the observed frequencies. However, some important parameters of the fitted models are not consistent with that from observations. Combing with the information from observation and theoretical calculation, we conclude that DY Peg should be an SX Phoenicis star in a binary system and accreting mass from a dust disk, which was the residue of its evolved companion (most probably a hot white dwarf at the present stage) produced in the asymptotic giant branch phase. Further observations are needed to confirm this inference, and it might be potentially a universal formation mechanism and evolutionary history for SX Phoenicis stars.

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arXiv2020

Some new hints on cosmic-ray propagation from AMS-02 nuclei spectra

In this work, we considered 2 schemes (a high-rigidity break in primary source injections and a high-rigidity break in diffusion coefficient) to reproduce the newly released AMS-02 nuclei spectra (He, C, N, O, Li, Be, and B) when the rigidity larger than 50 GV. The fitting results show that current data set favors a high-rigidity break at $\sim 325 \mathrm{GV}$ in diffusion coefficient rather than a break at $\sim 365 \mathrm{GV}$ in primary source injections. Meanwhile, the fitted values of the factors to rescale the cosmic-ray (CR) flux of secondary species/components after propagation show us that the secondary flux are underestimated in current propagation model. It implies that we might locate in a slow diffusion zone, in which the CRs propagate with a small value of diffusion coefficient compared with the averaged value in the galaxy. Another hint from the fitting results show that extra secondary CR nuclei injection may be needed in current data set. All these new hints should be paid more attention in future research.

astro-ph.HE↗

arXiv2019

Comment on "Probing the Dark Matter-Electron Interactions via Hydrogen-Atmosphere Pulsating White Dwarfs''

In Phys. Rev. D 98, 103023 (2018), a novel scenario was proposed to probe the interactions between dark matter (DM) particles and electrons, via hydrogen-atmosphere pulsating white dwarfs (DAVs) in globular clusters. The estimation showed that the scenario could hopefully test the parameter space: $5 \mathrm{GeV} \le m_χ \le 10^{4} \mathrm{GeV}$ and $σ_{χ,e} \ge 10^{-40} \mathrm{cm}^{2}$, where $m_χ$ is the DM particle's mass and $σ_{χ,e}$ is the elastic scattering cross section between DM and electron. In this comment, we have determined the exact lower limit of the testable DM particle mass $\sim 1.38 - 1.58 \mathrm{GeV}$, which depends on $σ_{χ,e}$. This gives us a credible lower limit of the testable DM particle mass in above scenario, and provide a clear upper limit of the DM particle mass which we should consider in future research.

hep-ph↗

arXiv2019

Bayesian analysis of the hardening in AMS-02 nuclei spectra

Based on the precise nuclei data released by AMS-02, we study the spectra hardening of both the primary (proton, helium, carbon, oxygen, and the primary component of nitrogen) and the secondary (anti-proton, lithium, beryllium, boron and the secondary component of nitrogen) cosmic ray (CR) nuclei. With the diffusion-reacceleration model, we consider two schemes to reproduce the hardening in the spectra: (i) A high-rigidity break in primary source injection; (ii) A high-rigidity break in diffusion coefficient. The global fitting results show that both schemes could reproduce the spectra hardening in current status. More precise multi-TV data (especially the data of secondary CR species) is needed if one wants to distinguish these two schemes. In our global fitting, each of the nuclei species is allocated an independent solar modulation potential and a re-scale factor (which accounts for the isotopic abundance for primary nuclei species and uncertainties of production cross section or inhomogeneity of CR sources and propagation for secondary nuclei species). The fitting values of these two parameter classes show us some hints on some new directions in CR physics. All the fitted re-scale factors of primary nuclei species have values that systematically smaller than 1.0, while that of secondary nuclei species are systematically larger than 1.0. Moreover, both the re-scale factor and solar modulation potential of beryllium have values which are obviously different from other species. This might indicate that beryllium has the specificity not only on its propagation in the heliosphere, but also on its production cross section. All these new results should be seriously studied in the future.

astro-ph.HE↗

arXiv2018

Probing the dark matter-electron interactions via hydrogen-atmosphere pulsating white dwarfs

In this work, we propose a novel scenario to probe the interactions between dark matter (DM) particles and electrons, via hydrogen-atmosphere pulsating white dwarfs (DAVs) in globular clusters. In this special configuration, the DM particles, which are predominantly captured by multiple scattering with the electrons in a DAV, would annihilate by pairs and provide extra energy source to the DAV. This mechanism slows down the natural cooling evolution which can be presented by the period variation rates of pulsation modes. The differences between the secular rates predicted by the precise asteroseismology and the secular rates obtained from observation can reveal the DM-electron interactions. An important observable has been proposed and corresponding estimations have been made. According to the estimation, if this scenario could be implemented in the near future, the potential sensitivity on $m_χ$ (DM particle's mass) and $σ_{χ,e}$ (elastic scattering cross section between DM and electron) could be hopefully extended to a region $5 \mathrm{GeV} \lesssim m_χ \lesssim 10^{4} \mathrm{GeV}$ and $σ_{χ,e} \gtrsim 10^{-40} \mathrm{cm}^{2}$. Combining with indirect DM detection results, this could give us a cross check on the existence of such leptonphilic DM particles to some extent.

astro-ph.HE↗

arXiv2018

NGC 1893: a young open cluster rich in multi-type variable stars

In this work, we have studied the variable stars in the young open cluster NGC 1893 based on a multi-year photometric survey covering a sky area around the cluster up to $31' \times 31'$ wide. More than 23\,000 images in the $V$ band taken from January 2008 to February 2017 with different telescopes, complemented with 90 images in the $B$ band in 2014 and 2017, were reduced, and light curves were derived in $V$ for 5653 stars. By analyzing these light curves, we detected 147 variable stars (85 of them being new discoveries), including 110 periodic variables, 15 eclipsing binaries and 22 non-periodic variables. Proper motions, radial velocities, color-magnitude and two-color diagrams were used to identify the cluster membership of these variable stars, resulting in 84 members. Periodic variable members were then classified into different variability types, mainly according to their magnitudes and to their periods of variability, as well as to their positions in the Hertzsprung-Russell diagram for the early-type stars. As a result, among main-sequence periodic variable members, we identified five $β$ Cep candidates, seven slowly pulsating B-type candidates, and thirteen fast-rotating pulsating B-type (FaRPB) candidates (one of which is a confirmed classical Be star). While most of the FaRPB stars display properties similar to the ones discovered in NGC 3766 by Mowlavi et al. (2013), five of them have periods below 0.1~d, contrary to expectations. Additional observations, including spectroscopic, are called for to further characterize these stars. We also find a binary candidate harboring a $δ$-Scuti candidate.

astro-ph.SR↗

arXiv2018

Asteroseismology of the Double-Mode High-Amplitude $δ$ Scuti Star VX Hydrae

Bi-site time-series photometric and high-resolution spectroscopic observations were made for the double-mode high-amplitude $δ$ Scuti star VX\ Hya. The fundamental frequency $f_{0}=4.4763\ \rm{c\ days^{-1}}$, the first overtone $f_{1}=5.7897\ \rm{c\ days^{-1}}$ and 23 harmonics and linear combinations of $f_{0}$ and $f_{1}$ are detected by pulsation analysis. From the spectroscopic data, we get $\rm{[Fe/H] = -0.2\pm0.1\ dex}$. The period change rate of the fundamental mode is obtained by using the Fourier-phase diagram method, which gives the value of $(1/P_{0})(dP_{0}/dt)=(1.81\pm0.09) \times 10^{-7}\ \rm{yr}^{-1}$. With these results from the observations, we perform theoretical explorations with the stellar evolution code MESA, and constrain the models by fitting $f_{0}$, $f_{1}$, and $(1/P_{0})(dP_{0}/dt)$ within $3σ$ deviations. The results show that the period change of VX\ Hya could be ascribed to the evolutionary effect. The stellar parameters of VX\ Hya could be derived as: the mass $2.385\pm0.025\ M_{\odot}$, the luminosity $\log(L/L_{\odot})=1.93\pm0.02$ and the age $(4.43\pm0.13)\times 10^8$ years. VX\ Hya is found to locate at the post-main-sequence stage with a helium core and a hydrogen-burning shell on the H${-}$R diagram.

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