Ground-based optical telescopes necessitate prompt and spatially detailed information regarding dome-scale cloud coverage to facilitate target-specific shuttering and scheduling decisions. When only coarse or delayed atmospheric data are available, observatories risk inefficient use of scarce dark time and the irreversible loss of scientific exposures. To address this, we introduce the WOANC dataset, a pixel-annotated nighttime full-dome dataset acquired at an operational observatory, alongside NightCloudSegNet, a fisheye-aware segmentation framework specifically designed for low-light astronomical imaging. Evaluated on the WOANC test set, NightCloudSegNet achieves a mean intersection-over-union (mIoU) of 86.6% and a pixel-level F1 score of 92.8%. Furthermore, when tested on the external SWINSEG dataset, the model attains an mIoU of 86.2% and an F1 score of 92.6%, thereby demonstrating robust performance under conditions of fisheye distortion and low illumination. By translating pixel-level segmentation masks into per-target observability indicators, this approach has the potential to support informed shuttering and scheduling decisions, which is expected to enhance observational efficiency in automated telescope operations.

Lithium niobate (LiNbO3) crystals and devices have many important applications in laser frequency doubling and electro-optic frequency comb generation. Especially for Nd3+-doped LiNbO3, holding optical gain, electro-optic modulation, and frequency conversion concurrently, serves as the promising platform for on-chip integrated optical applications. However, despite of the first discovery over fifty years, the fundamental transition selection rules of Nd-doped LiNbO3 crystal still remain elusive due to the complex Stark levels and undefined local symmetry. In this work, we present a comprehensive characterization of Nd:MgO:LiNbO3 crystals, including crystal growth, optical spectrum, and transition selection rules. Based on the absorption spectrum and polarized fluorescence emission, we clarify the Stark splitting levels in Nd:MgO:LiNbO3 crystal and give a panorama for 4F3/2→4I9/2, 4I11/2, 4I13/2 transitions. Meanwhile, we first employed the Γ4, Γ5, and Γ6 irreducible representation to calibrate the Stark levels of Nd3+ ions, which can establish a theoretical foundation for laser with different polarization characteristics in LiNbO3. Moreover, we performed the polarized laser generation at 1.08, 1.09, 1.38, and 1.4 μm to check the validity of fine energy level diagram and the electric-dipole selection rules by light polarization. To the best of our knowledge, this is the first report on laser oscillation at 1.4 μm in Nd:MgO:LiNbO3 crystals.

We investigate the underlying stochastic processes driving the multiwavelength variability of the blazar BL Lacertae over the past two decades. Observations from Weihai Observatory over 224 nights reveal that the power spectral slopes of intra-night variability follow a Gaussian distribution, ranging from approximately 0.4–2.6, with an average trend consistent with the long-term variability power spectrum. Using power spectral analysis methods, such as the classical periodogram and the Lomb–Scargle periodogram, in combination with modeling techniques such as the power spectral response method, the multiple fragment variance function, and the continuous time autoregressive moving average, we study the multiband power spectral characteristics across a wide range of timescales (∼7 dex). The results demonstrate that, at lower frequencies, the power spectral density across different bands shows remarkable consistency, suggesting that these variations may be driven by a common stochastic process related to the accretion disk. However, significant discrepancies arise at higher frequencies, indicating the presence of multiple stochastic processes. We propose that the variability is governed by at least two distinct processes: one related to disk stochastic processes, dominating the long-term variability, and another associated with jet stochastic processes, which may result from turbulence, particle acceleration, and shock interactions within the jet, and drive the short-term, high-frequency variations. These findings provide unique insights into the complex mechanisms underlying blazar variability and suggest an intrinsic connection between the accretion disk and jet dynamics.

The variation mechanism of the blazar is still an open question. In this study, we collect the long-term multi-wavelength data of 3C 454.3 to conduct a comprehensive study. The local cross-correlation functions were computed between the $$\gamma$$ -ray and R band fluxes, as well as between B and K band fluxes. No significant time lags were found among these bands, which suggests that the optical and $$\gamma$$ -ray emissions are co-spatial. The color indices variation behavior showed a redder-when-brighter trend in the lower state, and a saturation state in the higher state. The slope of the linear correlations between the logarithms of synchrotron and inverse-Compton fluxes changed from 0.61 to 3.34 for different band pairs, which could be explained by a model of Doppler-boosted log-parabolic synchrotron emission combined with stable background contamination. The model could also reproduce the spectral energy distributions at different brightness. This study can help us to better understand the variation mechanism of blazars.

ASASSN-14ko is a periodically repeating nuclear transient. We conducted high-cadence, multiwavelength observations of this source, revealing several recurrent early bumps and rebrightenings in its UV/optical light curves. The energy released during these bumps and rebrightenings shows a diminishing trend in recent UV/optical outbursts, which we monitored through multiwavelength observations. These features can be ascribed to the interaction between stream debris and the expanded disk in the repeated partial tidal disruption event. The X-ray light curve exhibits an inverse pattern compared to the UV/optical bands, displaying sporadic outbursts. Furthermore, our observations demonstrate that the blackbody temperature and radius in each outburst increase with the UV/optical luminosity, and such evolution resembles that observed in X-ray quasiperiodic eruptions, distinguishing it from typical tidal disruption events.

This study presents multi-band photometric observations and detailed period analysis of a totally eclipsing binary system exhibiting low photometric amplitude. The system exhibits characteristic W Ursae Majoris (EW)-type light curves with complete eclipses. In our light curve modeling, we tested two setups: one excluding third light and the other including it as a free parameter (accounting for a potential tertiary component). Photometric analysis reveals that ASASSN-V J171815.10+450432.9 (hereafter J171815) represents a marginal contact binary system with an extreme mass ratio (the more massive component is designated as the primary star), approaching the theoretical lower limit for stable contact configurations. Furthermore, our investigation of orbital period variations uncovers a long-term period increase at a rate of dPdt=(1.08±0.05)×10−6dayyr−1, which is likely attributable to ongoing mass transfer between components. This interpretation aligns with the system’s geometric configuration and observed light curve asymmetries. The unique characteristics presented by this binary system serve as a rare opportunity for in-depth research on the mass ratio theory, and also provide an important opportunity for testing the Thermal Relaxation Oscillation (TRO) theory.

We present photometric observations of the BL Lacertae object S5 0716+714 with a temporal resolution of 120 s in the Sloan i' and r' bands. These observations were conducted using the Comet Search Program telescope at Xingming Observatory from 2018 December 22 to 2020 February 15, and more than 5600 effective images were obtained on each filter across 79 nights. Additionally, we compiled long-term variability data spanning 34 yr in the optical UBVRI bands. Using the power-enhanced F-test and nested ANOVA test, we found intraday variability (IDV) on 31 nights and possible IDV on 20 nights in the i' band. Similarly, IDV was detected on 35 nights in the r' band, while possible IDV was observed on 22 nights. The minimum variability timescale is 7.33 minutes, and the estimated black hole masses are (0.68- 5.12)*10^8 Msun. The spectral variability and long-term optical light curves reveal a bluer-when-brighter trend on intraday timescales. The long-term optical flux density and spectral index exhibit periodic variability with a timescale of about 1038 days. An anticorrelation between optical flux and spectral index was observed, with a time delay of -140 days. Variability across different optical bands exhibited a strong correlation, with no discernible time lag. From the IDV, spectral variability, correlation, and time delays between different bands, we conclude that these radiation characteristics may result from the shock-in-jet model scenario.

ABSTRACT This paper presents the photometric and spectroscopic analysis of a long-period totally eclipsing contact binary (HAT 307-0007476) for the first time. This system is a low mass ratio ($q\sim 0.114$) and medium contact binary ($f\sim 37.1~{{\ \rm per\ cent}}$). Two flare events were detected in multiple bands observations in December 2022. The interval between the two flare events is 4 d. The average duration of these two flares is about 2289 s. Both the two flares achieve the energy levels of superflares. The excess emission of the H$_\alpha$ line in the LAMOST spectra of this object was analysed, indicating its chromospheric activity. The O–C diagram showed a long-term orbital period increase, which is due to the mass transfer between the two component stars. We conclude that HAT 307-0007476 is currently in a stable region based on both Jspin/Jorb and the comparison between the instability parameters and its current values.

Ground-based astronomical observations face inherent challenges from weather changes, target visibility window constraints, and observational requirements. Enhancing the efficiency and effectiveness of telescope operations has long been a key objective for many observatories because of the high cost of observational resources. In this study, we formalize observation scheduling as a time-dependent combinatorial optimization problem. To achieve this, we implement a pointer network with temporal attention that is capable of planning observations while accounting for time-varying factors such as moonlight interference, target altitude, and air mass, which impact the exposure time and image quality. To support the training of the deep neural network, we propose a scoring mechanism to evaluate the effectiveness of the observations, which is optimized through a refined REINFORCE algorithm with a baseline. Furthermore, an exposure time calculator and an equipment kinematic model are incorporated to dynamically estimate the time costs during the decision-making process. The simulation results demonstrated that the trained model significantly outperformed both manual scheduling and a greedy algorithm in terms of theoretical reward scores and the total number of scheduled targets. Observation experiments conducted using a dual-telescope system at Muztaga observatory further validated the superiority of our approach, demonstrating a 45.8% enhancement in the total signal-to-noise ratio across all observed targets and a 24.1% increase in the number of completed tasks under the same observing conditions.

This paper presents the first analysis of the contact binary TYC 3801-1529-1. We observed four sets of multiple bands complete light curves and one set of radial velocity curve of the primary component. Based on a simultaneous investigation of our observed and TESS light curves and the radial velocity curve, we found that TYC 3801-1529-1 is an extremely low-mass-ratio, medium contact binary with q = 0.0356, with the contribution of the third light at a level of about 10%. Its mass ratio is lower than V1187 Her, making TYC 3801-1529-1 the lowest mass-ratio contact binary ever found in the universe. The light curves observed in 2022 are asymmetric, which is aptly explained by a hot spot on the primary component. A 16-year eclipse timings analysis indicates a secular increase orbital period with a rate of dp/dt = 7.96(+/- 0.35)x10(-7) d yr(-1). We studied the stability of this target and identified that not only the value of J(spin)/J(orb), but also the mass ratio surpass the unstable boundary. Hence, TYC 3801-1529-1 presents a challenge to theoretical research and ought to be considered a progenitor of a contact binary merger.

We analyzed the light curve of the total eclipse contact binary V1320 Cas, obtained reliable photometric solutions, confirmed it to be a W-type contact binary with a mass ratio of 3.404 and a contact degree of 23.9%, a cool spot is discovered on the less massive component. Orbital period analysis indicates that the period of V1320 Cas is decreasing at a rate of dPdt=1.78×10−7 day yr−1, superimposed with a cyclic modulation with a period of 1.425 yr, long-term period decrease may be caused by the combination of mass transfer and angular momentum loss, and the cyclic modulation may be caused by the third companion. Using the photometric solutions and Gaia distance, we calculated the absolute physical parameters and plotted mass-luminosity and mass–radius diagrams to analyze the evolutionary status of V1320 Cas, the more massive component is a main sequence star, while the less massive component has higher luminosity and radius than those of main sequence stars with the same mass. With the decreasing orbital period, the two components of V1320 Cas will be gradually closer, while the binary may evolve toward deep contact.

As the core equipment of multi-state energy system, multi-energy conversion equipment can realize efficient conversion, cooperative management and optimal operation among various energy sources. As the core physical module of multi-energy conversion equipment, high-frequency transformer can realize electrical isolation, power regulation and AC/DC flexible conversion, etc., which provides an effective solution for large-scale distributed energy reliable grid-connection and flexible transmission of different voltage levels. At present, the main diagnostic methods of transformer internal local discharge are pulse current method, ultrasonic method and oil chromatography. These traditional methods are easy to cause secondary damage to the transformer, and with the increase of excitation frequency, the increase of vibration noise is inevitable. High-frequency transformer vibration sound signal contains important information about the fault state, and can reflect the transformer internal office discharge fault to a certain extent. Therefore, it is necessary to consider and explore the sources of high-frequency transformer vibration signals and analyze vibration signals.

Multi-band photometric observations and period investigations of the total eclipsing binary WISE J141530.7+592234 (hereinafter J141530), whose mass ratio close to the low mass ratio limit, were carried out for the first time. The stellar atmospheric parameters of the primary component were calculated by the spectral fitting, yielding the following results: T eff = 5890 ± 22 K, [Fe/H] = 0.01 ± 0.03 dex, log g = 4.53 ± 0.04 cm s −2 . Our observations show that the light curve of V -band on May 2 is about 0.1 mag brighter than that observed in February and March at phase 0.6. Comparing with the small amplitude (about 0.2 mag), the variations are remarkable. Meanwhile, obvious light curve variations and quick reversal of O’Connell effects are found in Transiting Exoplanet Survey Satellite data, which is likely caused by magnetic activity. Photometric solutions derived from multi-band light curves indicate that J141530 has a high contact degree ( f ∼ 70%) and a very low mass ratio ( q ∼ 0.0546). Based on the O − C diagram, a long-term period increase was found. The period increase rate is calculated to be dP / dt = 3.90 × 10 −7 day yr −1 , which can be explained by mass transfer from the low mass component to the large mass component. By analyzing the merging criterion, such as the ratio of spin angular momentum ( J spin ) to the orbital angular momentum ( J orb ), the instability separation and the instability mass ratio, J141530 can be regarded as a potential progenitor of luminous red novae.

The photometric and spectroscopic investigations of ten contact binaries were presented for the first time. It is discovered that the mass ratios of all the ten targets are smaller than 0.15, they are extremely low mass ratio contact binaries. Seven of them are deep contact binaries, two are medium contact binaries, while only one is a shallow contact system. Five of them show O'Connell effect, and a dark spot on one of the two components can lead to a good fit of the asymmetric light curves. The orbital period studies of the ten binaries reveal that they all exhibit long-term period changes, six of them are increasing, while the others are shrinking. The LAMOST spectra were analyzed by the spectral subtraction method, and all the ten targets exhibit excess emissions in the H$_α$ line, indicating chromospheric activity. The evolutionary states of the two components of the ten binaries were studied, and it is found that their evolutionary states are identical to those of the other contact binaries. Based on the study of the relation between orbital angular momentum and total mass, we discovered the ten systems may be at the late evolutionary stage of a contact binary. The initial masses of the two components and the ages of them were obtained. By calculating the instability parameters, we found that the ten contact binaries are relatively stable at present.

Photometric observations for the totally eclipsing binary system TYC 4002-2628-1, were obtained between November 2020 and November 2021. To determine the stellar atmospheric parameters, a spectral image was taken with the 2.16 m telescope at National Astronomical Observatory of China (NAOC). TYC 4002-2628-1 is a low-amplitude (about 0.15 mag for V band) short-period (0.3670495 d) contact eclipsing binary with a total secondary eclipse. Intrinsic light curve variations and the reversal of the O'Connell effect are detected in the light curves, which may be due to spot activity. Based on the photometric solutions derived from the multiband time series light curves, TYC 4002-2628-1 is an extremely low-mass ratio contact binary with a mass ratio of q similar to 0.0482 and a fill-out factor of f similar to 5 per cent. By analysing the O - C variations, we find that its orbital period remains unchanged when BJD < 2458321. Then the orbital period changed suddenly around BJD 2458743 and has an increasing rate of dP/di = 1.62 x 10(-5) d.yr(-1) = 140 s.century(-1). If confirmed, TYC 4002-2628-1 would be the contact binary with the highest orbital period increasing rate so far. By investigating the ratio of orbital angular momentum to the spin angular momentum (J(orb)/J(spin )< 3), the instability mass ratio (q(inst)/q = 1.84) and the instability separation (A(inst)/A = 1.35), TYC 4002-2628-1 can be regarded as a merger candidate.

We present a novel, easy-to-use method based on the photon-mapping technique to simulate photometric images of moving targets. Realistic images can be created in two passes: photon tracing and image rendering. The nature of light sources, tracking mode of the telescope, point spread function (PSF), and specifications of the CCD are taken into account in the imaging process. Photometric images in a variety of observation scenarios can be generated flexibly. We compared the simulated images with the observed ones. The residuals between them are negligible, and the correlation coefficients between them are high, with a median of 0.9379_-0.0201^+0.0125 for 1020 pairs of images, which means a high fidelity and similarity. The method is versatile and can be used to plan future photometry of moving targets, interpret existing observations, and provide test images for image processing algorithms.

The cutoff mass ratio is under debate for contact binaries. In this paper, we present the investigation of two contact binaries with mass ratios close to the low mass ratio limit. It is found that the mass ratios of VSX J082700.8+462850 (hereafter J082700) and 1SWASP J132829.37+555246.1 (hereafter J132829) are both less than 0.1 (q ∼ 0.055 for J082700 and q ∼ 0.089 for J132829). J082700 is a shallow contact binary with a contact degree of ∼19%, and J132829 is a deep contact system with a fill-out factor of ∼70%. The O − C diagram analysis indicated that the two systems manifested long-term period decreases. In addition, J082700 exhibits a cyclic modulation which is more likely resulting from the Applegate mechanism. In order to explore the properties of extremely low mass ratio contact binaries (ELMRCBs), we carried out a statistical analysis on contact binaries with mass ratios of q ≲ 0.1 and discovered that the values of J spin/J orb of three systems are greater than 1/3. Two possible explanations can interpret this phenomenon. One explanation is that some physical processes, unknown to date, are not considered when Hut presented the dynamic stability criterion. The other explanation is that the dimensionless gyration radius (k) should be smaller than the value we used (k 2 = 0.06). We also found that the formation of ELMRCBs possibly has two channels. The study of evolutionary states of ELMRCBs reveals that their evolutionary states are similar with those of normal W UMa contact binaries.

In this study two scanning methods are designed by combining photoelectric detection equipment having different apertures Further a capability evaluation model is established for the multi-photoelectric detection equipment The model is simulated and analyzed from the scanning mode arrangement mode and aperture of the telescope and the simulation results are evaluated The simulation results show that for the selected catalog space debris dataset the detection results obtained via single-elevation-area scanning are better than those obtained via multi-elevation-area scanning during the simulation time period Under the same field of view the number of debris detected using a combination of four 28-cm-aperture telescopes increases only by 2 4% single-elevation-area scanning and 3 6% multi-elevation-area scanning when compared with those detected using a 15-cm-aperture telescope combination The considerably cost-effective 15-cm-aperture telescope combination must be selected to maintain a catalog of the existing space debris and the 28-cm-aperture telescope combination must be selected for detecting small-sized space debris

We collect long term $\gamma$-ray, optical and radio $15$ GHz light curves of quasar object PMN J2345-1555. The correlation analyses between them are performed via the local cross-correlation function (LCCF). We found that all the optical $V$, $R$ band and the infrared $J$ band are correlated with the radio 15 GHz at beyond $3\sigma$ significance level, and the lag times are $-221.81^{+6.26}_{-6.72}$, $-201.38^{+6.42}_{-6.02}$ and $-192.27^{+8.26}_{-7.37}$ days, respectively. The $\gamma$-ray is strongly correlated with optical, but weakly correlated with the radio. We present that time lags between different frequencies can be used as an alternative parameter to derive the core-shift measurement. For this target, the magnetic field and particle density at 1 parsec in jet are derived to be $0.61$ Gauss and $1533/\gamma_{\rm min}$ cm$^{-3}$, respectively. The black hole mass and the 15 GHz core position in jet are estimated to be $10^{8.44} {\rm M}_{\odot}$ and $30$ parsec, respectively. The lag times enable us to derive that the optical and the $\gamma$-ray emitting regions coincide, which are located at $4.26^{+0.83}_{-0.79}$ pc away from 15 GHz core position in jet and beyond the broad line region (BLR). We found that a $3\sigma$ correlation between the color index and the radio light curve, which indicates that opacity may play an important role in the variation. The $\delta V-\delta R$ behaviors are complex, while the $R-J$ shows a bluer when brighter trend. As hinted from radio images, we proposed a positional dependent spectral index model to explain the color index behaviors, which is complementary for the shock in jet model. The curvature effects and contribution from accretion disk may also affect variables of blazars in many aspects.