With the rapid growth of astronomical datasets, efficient and accessible methods for catalog management and retrieval are crucial. Database systems offer powerful queries but incur setup and maintenance overhead, while file-based management is straightforward yet lacks efficient indexing. Conventional single-level sky-partitioning indexes may reach their limit as data volume increases. To address these limitations, this study proposes a two-level spatial indexing framework that combines sky partitioning with secondary spatial indexing. HEALPix provides a coarse-grained, first-level index; within each partition, an R-tree index is built for fine-grained spatial filtering. For a cone search centered at (292 degrees, 10 degrees) with a 0.1 degrees radius on the Gaia DR3 catalog, the proposed method reduces the number of angular-distance calculations by 97.1% (from 342,749 to 13,246) and decreases query time from 9098 ms to 1874 ms at partitioning level 7, compared with single-level HEALPix indexing. Experiments across multiple regions further demonstrate stable performance improvements across different source-density conditions. Deployed on the Lijiang 2.4-meter Telescope's server, this framework furthermore supports batch object identification and catalog fusion, demonstrating its practical scalability as a general-purpose extension to traditional single-level indexing.

We present strong evidence that mass segregation in the young open cluster NGC 2422 (age ≈84 Myr) is primarily driven by tidal stripping. Analysis of the radial mass distribution reveals a significant overabundance of low-mass stars ( M < 0.85 M _⊙ ) preferentially located near and beyond the cluster’s tidal radius ( r _t = 14.4 pc), a hallmark of ongoing tidal stripping. This spatial signature is corroborated by kinematic evidence: the cluster’s outskirts exhibit an elevated velocity dispersion ( σ _3d = 14.9 km s ^−1 , F-test p < 0.001) and strong radial anisotropy ( β = 0.94 ±0.4), both classic signatures of tidal influence. The cluster’s age is significantly greater than its half-mass relaxation time ( t _rh = 44.2 Myr), confirming it is dynamically evolved. Crucially, binary stars show no significant radial segregation from single stars (KS-test p ≈ 0.51), ruling them out as the primary driver. Collectively, these results establish tidal stripping as the dominant mechanism currently reshaping the structure and stellar content of NGC 2422.

Mass segregation is a fundamental prediction of dynamical relaxation in stellar systems, yet direct evidence in young open clusters remains scarce. Here, we report the discovery and characterization of a totally eclipsing binary system (TIC 189854044) in the core of the young open cluster ASCC 23. By combining multiwavelength photometry from Gaia, 2MASS, and Pan-STARRS, we employed a machine learning approach to identify robust cluster members and applied Bayesian inference to determine the cluster's fundamental parameters. Detailed modeling of the binary's light curve yields precise physical parameters. The eclipsing binary TIC 189854044, located in the core region of ASCC 23, exhibits a total system mass of 2.86M circle dot. Statistical analysis using the Minimum Spanning Tree technique, we find that the cluster has not yet undergone global dynamical mass segregation. This lack of global segregation highlights the unique status of TIC 189854044. Situated deep within the cluster core, this massive binary stands in contrast to the surrounding spatially unsegregated population, suggesting it may have formed in situ or experienced rapid localized sedimentation. This system serves as a valuable benchmark for testing binary evolution models in young, dynamical environments.

In this paper, we present a detailed analysis of the light variation of KIC 5623923 using high-precision time-series data from the Kepler mission. The analysis reveals this target is an eclipsing binary system with delta Scuti-type pulsations from the primary component, rather than from the secondary as previously reported. The frequency analysis of three short-cadence data reveals 41 significant frequencies, including the orbital frequency (forb = 0.827198 day-1) due to orbital motion from the binary system and the pulsational frequencies. Most of the pulsational signal lies in the frequency range of 20-32 day-1, with amplitude between 0.3 and 8.8 mmag, in which seven peaks are identified as "independent" modes. The strongest one (f3 = 28.499399 day-1) likely corresponds to a high-order radial mode. In other peaks (f7, f10, and f18), several pairs of multiplet structures centered on them are found. The fitting of spectral energy distribution using the collected photometry measurement of multiple bands reveals the effective temperatures of the primary and secondary components as 8348-225+230 K and 4753-229+237 K, respectively, which place the primary star in the classical pulsating instability zone. The characteristic light-curve morphology and short orbital period are consistent with a tidally locked system. Based on the characteristics of amplitude spectra of pulsating stars in close binaries, the analysis of the multiplet structures reveals that three independent frequencies (i.e., f7, f10, and f18) correspond to nonradial modes with l = 2, while the associated sidelobes are produced by the orbital motion. We highlight the potential of this method in future studies of pulsating binary stars.

The Lobster Eye Imager for Astronomy (LEIA) detected a new X-ray transient on 2022 November 7, identified as a superflare event occurring on a nearby K-type giant star HD 251108. The flux increase was also detected in follow-up observations at X-ray, UV, and optical wavelengths. The flare lasted for about 40 days in soft X-ray observations, reaching a peak luminosity of ∼1.1 × 10 ^34 erg s ^−1 in 0.5–4.0 keV, which is roughly 60 times the quiescent luminosity. Optical brightening was observed for only one night. The X-ray light curve is well described by a double fast rise and exponential decay model, attributed to the cooling process of a loop arcade structure formed subsequent to the initial large loop with a half-length of ∼1.9 × 10 ^12 cm. Time-resolved X-ray spectra were fitted by a four-temperature apec model (with three components being the quiescent background), showing significant evolution of plasma temperature and emission measure over time. The estimated energy released in the LEIA band is ∼3 × 10 ^39 erg, suggesting that this is likely the most energetic X-ray stellar flare with the longest duration detected to date.

Semidetached binaries, distinguished by their mass transfer phase, play a crucial role in elucidating the physics of mass transfer within interacting binary systems. To identify these systems in eclipsing binary light curves provided by large-scale time-domain surveys, we have developed a methodology by training two distinct models that establish a mapping relationship between the parameters (orbital parameters and physical parameters) of semidetached binaries and their corresponding light curves. The first model corresponds to scenarios where the more massive star fills its Roche lobe, while the second model addresses situations where the less massive star does so. In consideration of the O’Connell effect observed in the light curves, we integrated a cool spot parameter into our models, thereby enhancing their applicability to fit light curves that exhibit this phenomenon. Our two-model framework was then harmonized with the Markov Chain Monte Carlo algorithm, enabling precise and efficient light-curve fitting and parameter estimation. Leveraging 2 minute cadence data from the initial 67 sectors of the Transiting Exoplanet Survey Satellite, we successfully identified 327 systems where the less massive component fills its Roche lobe, alongside three systems where the more massive component fills its Roche lobe. Additionally, we offer comprehensive fundamental parameters for these binary systems, including orbital inclination, relative radius, mass ratio, and effective temperature.

Low mass-ratio contact binary systems are a fascinating class of eclipsing binaries; they are widely regarded as the potential progenitors of stellar mergers. For this study we analyzed 40 newly discovered low mass-ratio totally eclipsing contact binary systems identified from the Catalina Sky Survey data. The relative parameters for these systems were inferred using a neural network model combined with a Bayesian inference-based Hamiltonian Monte Carlo (HMC) algorithm, with uncertainties estimated from the posterior distributions generated by the HMC algorithm. The absolute parameters were then calculated using these relative parameters, along with distances and temperatures provided by Gaia Data Release 3. Among the 40 systems, 24 are deep low mass-ratio overcontact binaries, characterized by fill-out factors of 0.5 or higher and mass ratios of 0.25 or lower. Notably, two systems, CSS_J071952.5+243224 and CSS_J155519.0+135855, have mass ratios below 0.1, specifically 0.094 +/- 0.006 and 0.086 +/- 0.004, respectively. Furthermore, we compared the parameters obtained in this study with those from 39 low mass-ratio contact binary systems identified in previous research, finding that the estimated parameters are largely consistent. Finally, to evaluate the evolutionary status of the 40 systems, we calculated the ratio of spin angular momentum to orbital angular momentum for each and found that all are currently in a relatively stable evolutionary phase.

Totally eclipsing contact binaries provide a unique opportunity to accurately determine mass ratios through photometric methods alone, eliminating the need for spectroscopic data. Studying low mass ratio (LMR) contact binaries is crucial for advancing our understanding of binary star evolution and the formation of rare optical transients known as red novae. We identified 143 totally eclipsing contact binaries from the Transiting Exoplanet Survey Satellite. These high-precision light curves reveal a distinct O’Connell effect, which we interpret by introducing a cool spot on the primary star. Training a neural network model that includes cool spot parameters can generate a high-precision light curve 2 orders of magnitude faster than Phoebe. Utilizing the neural network (NN _nol _3 ) model combined with the Markov Chain Monte Carlo algorithm, we rapidly derived the fundamental parameters of these systems. By leveraging the relationship between orbital period and semimajor axis using the Random Sample Consensus algorithm, we estimated their absolute parameters. Our analysis identified 96 targets with mass ratios below 0.25, all of which were not listed in any previous catalog, thus signifying the discovery of new LMR system candidates. Assuming all 143 binary systems are affected by a third light during parameter estimation, we train a neural network (NN _l _3 ) model considering the third light. Then we calculate the residuals between the mass ratio q _l _3 (considering the third light) and q _nol _3 (neglecting it). For these residuals, the 25th percentile ( Q _1 ) is 0.012, the median ( Q _2 ) is 0.026, and the 75th percentile ( Q _3 ) is 0.05.

Starting from more than 11,200 short-period (less than 0.5 days) EW-type eclipsing binary candidates with the All-Sky Automated Survey for Supernovae V -band light curves, we use the Markov Chain Monte Carlo algorithm and neural networks to obtain the mass ratio ( q ), orbital inclination ( incl ), fill-out factor ( f ), and temperature ratio ( T _s / T _p ). After crossmatching with the Gaia DR3 database, the final sample contains parameters of 2399 A-type and 8712 W-type contact binaries (CBs). We present the distributions of parameters of these 11,111 short-period CBs. The mass ratio ( q ) and fill-out factor ( f ) are found to obey log-normal distributions, and the remaining parameters obey normal distributions. There is a significant period–temperature correlation of these CBs. Additionally, the temperature ratio ( T _s / T _p ) tends to increase as the orbital period decreases for W-type CBs. There is no significant correlation between them for A-type CBs. The mass ratio and fill-out factor ( q − f ) diagram suggest there is no significant correlation between these two parameters. A clear correlation exists between the mass ratio and radius ratio. The radius ratio increases with the mass ratio. Moreover, the deep fill-out CBs tend to fall on the upper boundary of the q − R _s / R _p distribution, while the shallow fill-out CBs fall on the lower boundary.

TIC 157365951 has been classified as a delta Scuti type by the International Variable Star Index. Through the spectra from Large Sky Area Multi-Object Fiber Spectroscopic Telescope and its light curve, we further discovered that it is a binary system. This binary system comprises a red-dwarf star and a compact star. Through the spectral energy distribution fitting, we determined the mass of the red dwarf star as M 1 = 0.31 +/- 0.01M circle dot and its radius as R 1 = 0.414 +/- 0.004R circle dot. By fitting the double-peaked H alpha emission, we derived the mass ratio of q = 1.76 +/- 0.04, indicating a compact star mass of M 2 = 0.54 +/- 0.01M circle dot. Using Phoebe to model the light curve and radial velocity curve for the detached binary system, we obtained a red dwarf star mass of M 1 = 0.29 +/- 0.02M circle dot, a radius of R 1 = 0.39 +/- 0.04R circle dot, and a Roche-lobe filling factor of f = 0.995 +/- 0.129, which is close to the f = 1 expected for a semidetached system. The Phoebe model gives a compact star mass M 2 = 0.53 +/- 0.05M circle dot. Constraining the system to be semidetached gives M 1 = 0.34 +/- 0.02M circle dot, R 1 = 0.41 +/- 0.01R circle dot, and M 2 = 0.62 +/- 0.03M circle dot. The consistency of the models is encouraging. The value of the Roche-lobe filling factor suggests that there might be ongoing mass transfer. The compact star mass is as massive as a typical white dwarf.

Detached eclipsing binary (EB) systems are crucial for measuring the physical properties of stars that evolve independently. Large-scale time-domain surveys have released a substantial number of light curves for detached EBs. Utilizing the Physics of Eclipsing Binaries package in conjunction with Markov Chain Monte Carlo (MCMC) methods for batch parameter derivation poses significant computational challenges, primarily due to the high computational cost and time demands. Therefore, this paper develops an efficient method based on the neural network model and the stochastic variational inference method (denoted NNSVI) for the rapid derivation of parameters for detached EBs. For studies involving more than three systems, the NNSVI method significantly outperforms techniques that combine MCMC methods in terms of parameter inference speed, making it highly suitable for the batch derivation of large numbers of light curves. We efficiently derived parameters for 34,907 detached EBs, selected from the Optical Gravitational Lensing Experiment catalog and located in the Galactic bulge, using the NNSVI method. A catalog detailing the parameters of these systems is provided. Additionally, we compared the parameters of two double-lined detached EBs with those from previous studies and found the estimated parameters to be essentially identical.

A contact binary may be the progenitor of a red nova that eventually produces a merger event and have a cut-off period of around 0.2 days. Therefore, a large number of contact binaries is needed to search for the progenitor of red novae and to study the characteristics of short-period contact binaries. In this paper, we employ the Phoebe program to generate a large number of light curves based on the fundamental parameters of contact binaries. Using these light curves as samples, an autoencoder model is trained, which can reconstruct the light curves of contact binaries very well. When the error between the output light curve from the model and the input light curve is large, it may be due to other types of variable stars. The goodness of fit (R 2) between the output light curve from the model and the input light curve is calculated. Based on the thresholds for global goodness of fit (R 2), period, range magnitude, and local goodness of fit (R 2), a total of 1322 target candidates were obtained.

Semidetached binaries are in the stage of mass transfer and play a crucial role in studying the physics of mass transfer between interacting binaries. Large-scale time-domain surveys provide many light curves of binary systems, while Gaia offers high-precision astrometric data. In this paper, we develop, validate, and apply a pipeline that combines the Markov Chain Monte Carlo method with a forward model and DBSCAN clustering to search for semidetached binaries and estimate the inclination, relative radius, mass ratio, and temperature ratio of each using light curves. We train our model on the mock light curves from Physics of Eclipsing Binaries (PHOEBE), which provides broad coverage of light-curve simulations for semidetached binaries. Applying our pipeline to Transiting Exoplanet Survey Satellite sectors 1–26, we have identified 77 semidetached binary candidates. Utilizing the distance from Gaia, we determine their masses and radii with median fractional uncertainties of ∼26% and ∼7%, respectively. With the added 77 candidates, the catalog of semidetached binaries with orbital parameters has been expanded by approximately 20%. The comparison and statistical results show that our semidetached binary candidates align well with the compiled samples and the PARSEC model in T _eff – L and M – R relations. Combined with the literature samples, comparative analysis with stability criteria for conserved mass transfer indicates that ∼97.4% of samples are undergoing nuclear-timescale mass transfer, and two samples (GO Cyg and TIC 454222105) are located within the limits of stability criteria for dynamical- and thermal-timescale mass transfer, and are currently undergoing thermal-timescale mass transfer. Additionally, one system (IR Lyn) is very close to the upper limit of delayed dynamical-timescale mass transfer.

With the continuous development of large optical surveys, a large number of light curves of late-type contact binary systems (CBs) have been released. Deriving parameters for CBs using the the WD program and the PHOEBE program poses a challenge. Therefore, this study developed a method for rapidly deriving light curves based on the Neural Networks (NN) model combined with the Hamiltonian Monte Carlo (HMC) algorithm (NNHMC). The neural network was employed to establish the mapping relationship between the parameters and the pregenerated light curves by the PHOEBE program, and the HMC algorithm was used to obtain the posterior distribution of the parameters. The NNHMC method was applied to a large contact binary sample from the Catalina Sky Survey, and a total of 19,104 late-type contact binary parameters were derived. Among them, 5172 have an inclination greater than 70 deg and a temperature difference less than 400 K. The obtained results were compared with the previous studies for 30 CBs, and there was an essentially consistent goodness-of-fit (R2) distribution between them. The NNHMC method possesses the capability to simultaneously derive parameters for a vast number of targets. Furthermore, it can provide an extremely efficient tool for rapid derivation of parameters in future sky surveys involving large samples of CBs.

Low-mass-ratio ( q ) contact binary systems are progenitors of stellar mergers such as blue stragglers or fast-rotating FK Com stars. In this study, we present the first light curve analysis of two newly identified low mass-ratio contact binary systems, TIC 55007847 and TIC 63597006, that are identified from TESS. Both stars are classified as A-subtype contact binaries. We obtained the precise orbit periods for the two objects by using the O − C method, i.e., P = 0.6117108 day for TIC 55007847 and P = 0.7008995 day for TIC 63597006, and found an obvious periodic signal in the O − C curve of TIC 63597006. We suggest that the periodic signal comes from a third body. We further use the Markov chain Monte Carlo method with PHOEBE to derive the photometric solutions for the two binaries. The photometric solution for this object shows that the contribution of the third body is about 6%. Our analysis revealed that TIC 55007847 has an extremely low mass ratio of q = 0.08. By calculating the ratio of spin angular momentum to the orbital angular momentum J s / J o , we found that TIC 55007847 is very close to the instability threshold with J s / J o = 0.31, indicating that it may merge into a single, fast-rotating star in the future. For TIC 63597006, q = 0.14 and J s / J o = 0.15. This object is in a relatively stable evolutionary status at present.

ABSTRACT The TESS Survey has released a large number of high-precision light curves of contact binaries. However, using the Phoebe program and Markov chain Monte Carlo (MCMC) algorithm to obtain the posterior distribution of contact binary parameters is a time-consuming process. In order to obtain the contact binary parameters from the TESS survey, we build neural network (NN) models and combine them with the MCMC algorithm to obtain the contact binary parameters and parameter errors quickly. NN model is used in place of the physical model, which can generate a light curve with a precision of less than a millimagnitude. The NN model is capable of generating light curves at a speed that is four orders of magnitude faster than Phoebe running on the same computing platform. In this study, we have determined the parameters of 318 contact binary systems exhibiting relatively symmetric light curves. Subsequently, a statistical analysis was conducted on the derived parameters of these 318 targets. The coefficient of determination (R2) for 318 contact binaries between the light curves generated by Phoebe using these parameters obtained by the NN model and MCMC as inputs and the original light curves is greater than 0.99. Additionally, the distribution and correlation of the parameters for these 318 contact binary systems have been presented.

Polarimetry plays an important role in investigating physical properties for celestial objects. We present a polarimeter named YFPOL for the Cassegrain focus of the Lijiang 2.4 m Telescope (LJT) of Yunnan Observatories, Chinese Academy of Sciences. YFPOL is a traditional single-beam polarimeter with a rotating polarizer. As the focal-reducer instrument Yunnan Faint Object Spectrograph and Camera (YFOSC) is always positioned on the Cassegrain focal plane of LJT, we develop two sets of ultra-thin (thickness <12 mm) polarizer rotation control systems with wireless charging and control functions, which are suitable for mounting on the two front-wheels of YFOSC. One set is used as the polarimetric calibration unit, and the other is for the polarimetric modulation unit. Both of the polarizers have an ultra-high contrast ratio of 1,000,000:1 in the optical band. We investigate the instrumental polarization characteristics (IPCs) in the full field of view that is transferred from YFOSC. Furthermore, we identify that the IPCs change when the Cassegrain axis rotates. The spurious polarization from the IPCs can be effectively minimized by flat-fielding using the unpolarized domeflat, when the Cassegrain rotation angle is the same or nearest to that of the polarization observation. We develop a quasi-automatic pipeline for YFPOL and its effectiveness has been verified by tests of the polarimetric observation with blazar S5 0716+714. The calibration is performed by observing the zero-polarized and highly-polarized standard stars. We successfully reach high precision polarization in the 7 ′ field of view, and the systematic uncertainty is below 0.8% for a V = 11.68 target with a 10 s exposure. The instrument polarization angle offset is 2.°6. YFPOL is not only a simple polarimeter, but also a spectropolarimeter with grisms that can be considered in the future.

Based on 2-minute cadence TESS data from sectors 1-50, we report the results of the systematic extraction of $\delta$ Scuti-type pulsations in the 6431 eclipsing binaries with orbital periods shorter than 13 days. A total number of 242 pulsators were found in those systems, including 143 new discoveries. We examined their pulsation properties based on the H-R diagram and the relationships between the dominant pulsation period $P_{\rm dom}$, orbital period $P_{\rm orb}$, and effective temperature $T_{\rm eff}$. As a consequence, 216 targets are likely $\delta$ Scuti stars (123 new), 11 likely $\gamma$ Doradus-$\delta$ Scuti hybrid stars (8 new), 5 likely $\beta$ Cephei stars (4 new), 4 likely $\delta$ Scuti-$\gamma$ Doradus hybrid stars (3 new), 3 likely Maia stars (3 new), 2 likely pulsating red giants (1 new), and a new unclassified star. As for the 6 new $\delta$ Scuti pulsators in eclipsing binaries with $P_{\rm orb}$ $<$ 0.65 days, we found that 3 of them significantly exceed the upper limits of the $P_{\rm dom}$/$P_{\rm orb}$ ratio. This may indicate that $P_{\rm dom}$ and $P_{\rm orb}$ are uncorrelated for them. Finally, we statistically analyzed the dominant pulsation periods of the 216 $\delta$ Scuti stars in eclipsing binaries. Those stars concentrate around 225 $\mu$Hz and the proportion of stars in the high-frequency region is significantly higher than that of single stars, which could be ascribed to the mass transfer process.

Thanks to an enormous release of light curves of contact binaries, it is a challenge to derive the parameters of contact binaries using the Phoebe program and the Wilson–Devinney program with the Markov chain Monte Carlo (MCMC) algorithm. In this paper, we use neural network (NN) and MCMC algorithm to derive the parameters of contact binaries. The fitting of models is still done with the MCMC algorithm, but that the neural network is used to establish the mapping relationship between the parameters and the light curves generated beforehand by Phoebe. The NN model is trained with a set of Phoebe-generated light curves with known input parameters, and then combined with the MCMC algorithm to quickly obtain the posterior distribution of the parameters. Two NN models without and with the influence of third light are established, which can generate light curves with 100 points faster than Phoebe by about four orders of magnitude under the same running condition. In addition, the two models can generate the light curves with an error of less than a millimagnitude. The feasibility of NN and MCMC algorithm is also verified by the synthetic light curves generated by Phoebe and the light curves from Kepler survey data. NN and MCMC algorithms can quickly derive the parameters and the corresponding parameter errors of contact binaries from sky survey. These parameters can also be used as more precise initial input values for the objectives of individual detailed studies.

We present the results from a spectroscopic monitoring campaign to obtain reverberation mapping measurements and investigate the broad-line region (BLR) kinematics for active galactic nuclei (AGNs) of Mrk 817 and NGC 7469. This campaign was undertaken with the Lijiang 2.4 m telescope. The median spectroscopic sampling is 2.0 days for Mrk 817 and 1.0 day for NGC 7469. We detect time lags of the broad emission lines, including Hβ, Hγ, He ii, and He i for both AGNs, including Fe ii for Mrk 817 with respect to the varying AGN continuum at 5100 Å. Investigating the relationship between line widths and time lags of the broad emission lines, we find that the BLR dynamics of Mrk 817 and NGC 7469 are consistent with the virial prediction. We estimate the masses of central supermassive black holes (SMBHs) and the accretion rates of both AGNs. Using the data of this campaign, we construct the velocity-resolved lag profiles of the broad Hγ, Hβ, and He i lines for Mrk 817, which show almost the same kinematic signatures in that the time lags in the red wing are slightly larger than the time lags in the blue wing. For NGC 7469, we only clearly construct the velocity-resolved lag profiles of the broad Hγ and Hβ, which show very similar kinematic signatures to the BLR of Mrk 817. These signatures indicate that the BLR of Keplerian motion in both AGNs seemingly has outflowing components during the monitoring period. We discuss the kinematics of the BLR and the measurements, including SMBH mass and accretion rates.