Sazuna/UAT_keywords huggingface dataset:
Deep Synoptic Array Science: Searching for Long Duration Radio Transients with the DSA-110. We describe the design and commissioning tests for the DSA-110 Not-So-Fast Radio Burst (NSFRB) search pipeline, a 1.4 GHz image-plane single-pulse search sensitive to 134 ms−160.8 s radio bursts. Extending the pulse width range of the Fast Radio Burst search by 3 orders of magnitude, the NSFRB search is sensitive to the recently discovered Galactic Long Period Radio Transients (LPRTs or LPTs). The NSFRB search operates in real-time, utilizing a custom GPU-accelerated search code, cerberus, implemented in Python with JAX. We summarize successful commissioning sensitivity tests with continuum sources and pulsar B0329+54, estimating the 90% completeness 25σ flux (fluence) limit to be ∼1200 mJy (∼160 Jy ms). Future tests of recovery of longer timescale transients, e.g., CHIME J1634+44, are planned to supplement injection testing and B0329+54 observations. An offline DSA-110 NSFRB Galactic Plane Survey was conducted to search for LPRTs, covering −3 .° 5 &lt; b &lt; 5 .° 7 and 141° &lt; l &lt; 225° (∼770 square degrees) in Galactic coordinates. We estimate an upper limit Poissonian burst rate ∼2 hr−1 per square degree (∼17 hr−1 per 3° × 3° survey grid cell) maximized across the inner ∣b∣ &lt; 0 .° 25 of the surveyed region. By imposing the ∼1200 mJy flux limit on two representative models (the magnetar plastic flow model and the White Dwarf-M Dwarf binary model), we reject with 95% confidence the presence of White Dwarf-M Dwarf binary LPRTs (beamed in a detectable direction) with periods between ∼10 and 50 s within ∼95% of the surveyed region. Combined with the prevalence of LPRTs in the Galactic Plane, our results motivate further consideration of both White Dwarf-M Dwarf binary models and isolated magnetar models. We will continue to explore novel LPRT search strategies during real-time operations, such as triggered periodicity searches and additional targeted surveys.

Keywords: White dwarf stars, Pulsars, Magnetars, Radio interferometry, Time series analysis, Radio transient sources
Multi-wavelength Flux and Polarization Variability of OJ 248 During 2011─2014 Outburst. We collected multi-wavelength light curves (from MJD 55500 to 57000) and polarization data (PD) (from MJD 55000 to 57000) of the flat-spectrum radio quasar OJ 248 to investigate the location and acceleration mechanism of the emission region within its jet. The study revealed that the optical PD reached peak values of (18.09 ± 0.09)% and (15.71 ± 0.07)% at MJD 56214 and MJD 56304, respectively, while no noticeable variation was observed in radio PD. Moreover, the light curves across different bands displayed varying degrees of variability. The average PD at 1 mm is consistently higher than that at 3 mm in each activity period, indicating an energy-dependent trend in PD, with the degree gradually decreasing from higher to lower energies. The relationship between PD and the fluxes in the R and V bands reveals a positive correlation. Given that the variations in optical PD were accompanied by multi-band flux variations, we employed the interpolation cross-correlation function to conduct a time lag analysis, thereby constraining the relative locations of radiation regions across different wavelength bands within the jet. Interestingly, the optical emission region is inferred to be located upstream of the X-ray emitting region. The dramatic increase in optical PD can be explained by a shock-in-jet model. Radiation originating from regions near the shock front becomes more highly polarized as a result of the ordered magnetic field produced by shock compression.

Keywords: Blazars, Flat-spectrum radio quasars, Jets
HostSub_GP: Precise Galaxy Background Subtraction in Transient Long-slit Spectroscopy with Gaussian Processes. We present a novel host galaxy subtraction technique in long-slit spectroscopy for extragalactic transients. Unlike classic methods which generally estimate the background using simple interpolation of local galaxy flux in the 2D spectrum, our approach leverages multi-band archival images of the host galaxies to model the background emission from the galaxy in the 2D spectrum. Such imaging encodes the wavelength-dependent galaxy profile along the slit, and is readily accessible through wide-field imaging surveys. We construct a smooth prior for the 2D galaxy profile with a Gaussian process (GP) based on these reference images, and use another GP to model the correlated deviations from the prior in the observed spectrum. This enables accurate inference of the galaxy flux blended with the transient. On synthetic long-slit data of a spiral galaxy extracted from a Multi Unit Spectroscopic Explorer hyper-spectral cube, the GP method remains robust as long as the host galaxy is spatially resolved and consistently outperforms classic methods. We apply the method to archival Keck spectra of two real transients, SN 2019eix and AT 2019qiz, to further demonstrate how the method uniquely recovers weak spectral features amid strong galaxy contamination, enabling refined constraints on the properties of both transients. We have released the software implementation, HostSub_GP, a scalable toolkit that leverages JAX, with an MIT license.

Keywords: Astronomy data reduction, Time domain astronomy, Spectroscopy, Gaussian Processes regression
A High-frequency Geodetic VLBI Experiment for Optical Clock Comparison. An intercontinental metrological clock comparison between Italy and the Republic of Korea was performed by means of geodetic K-band VLBI observations. The comparison involved the hydrogen masers (H-masers) used at Medicina and Sejong radio telescopes. The same clocks were simultaneously compared by a satellite link and by high-precision optical clocks maintained at the National Metrology Institutes, KRISS in Korea and INRIM in Italy, and delivered to VLBI antennas via optical fiber. The H-masers frequency difference was estimated by extrapolating the clock rate from VLBI data using two geodetic VLBI software. This was subsequently compared with clock differences derived by satellite link and by local optical clocks. Results obtained with different approaches were in agreement at the level of 10−15 s s−1. This pilot study demonstrates that standard high-frequency (K-band) geodetic VLBI campaigns could be a viable approach to conduct intercontinental clock comparisons, now only possible via satellite links. This uncertainty can be reduced thanks to the planned installation of new-generation, broadband, high-frequency receivers on the involved telescopes. K/Q/W-band geodetic observations will allow an improvement of the accuracy of the resulting group delays through broad bandwidth synthesis from 20 to 100 GHz. Furthermore, the Frequency Phase Transfer method will also be explored together with the use of PCAL systems installed at the radio telescopes to improve phase stability and thus allow a better estimation of the station clock parameters.

Keywords: Very long baseline interferometry, Astronomical instrumentation, Astronomical methods, Quasars
An Efficient Framework for Automatic Carbon Star Detection Using Machine Learning Techniques on LAMOST DR9 and Gaia DR3. Carbon stars are characterized by carbon-rich atmospheres. They play a key role in stellar evolution, enrichment of the interstellar medium, and distance estimation. Therefore, assembling large samples of these stars is essential. Machine learning has become one of the most effective tools for identifying stars of specific types in large-scale surveys; however, its application to carbon stars remains challenging due to the small number of confirmed objects available for developing and validating such methods. In this work, we present a methodology for constructing a carbon star detection model, a set of algorithms capable of automatically identifying patterns in data. Our adopted model is both computationally efficient and accurate. The approach begins with the selection of features based on the C2 and CN spectral indices measured from LAMOST DR9 spectra combined with absolute magnitudes and colors from Gaia DR3. The model is trained and evaluated using the subset of sources with data available from both surveys. This procedure enables reliable identification of carbon stars, even considering the large disparity in numbers between carbon and non-carbon stars. Our model reached over 97% performance in identifying known carbon stars, demonstrating strong consistency. When applied to the full LAMOST data set, it identified 6372 carbon-star candidates, of which 5665 were not previously reported. The model's efficiency and reliability in recognizing carbon stars within large data sets were further supported by visual inspection of candidate spectra in the Orion region, where more than 94% of the model-identified stars exhibit clear spectral features consistent with carbon-rich atmospheres.

Keywords: Stellar classification, Astrostatistics techniques
CARTA—Cube Analysis and Rendering Tool for Astronomy: A Tool for Big Imaging Data. Data generated by modern telescopes continues to grow rapidly as a result of these instruments' advanced capabilities, including wide-field imaging with high angular and spectral resolution. The resulting image cubes are often too large for end users to download and analyze on local desktop computers efficiently. Consequently, it is essential to provide visual analytics tools that can access these large data cubes remotely while enabling efficient and responsive local visualization. The Cube Analysis and Rendering Tool for Astronomy (CARTA; https://cartavis.org), presented in this paper, addresses this challenge. CARTA employs a client─server architecture: data processing is handled on the server side, while the client runs in the user's local web browser to render images and analysis results. This design minimizes data transfer, reduces latency, and enables seamless interaction with massive image cubes without the need for remote rendering. The paper outlines CARTA's implementation, including its architecture, deployment modes, interfaces, and codebase. It also provides an overview of its core features and analytics tools for different types of astronomical data. A long-term development plan for advanced features is also discussed.

Keywords: Astronomy data visualization, Astronomy data analysis, Astronomy software
Nonlinearity in H4RG-10 Near-infrared Detectors at Elevated Temperatures: Characterization and Data-driven Correction Method. We report a newly identified nonlinearity in H4RG-10 near-infrared detectors operating under moderately elevated-temperature conditions (114 K). This component, that potentially arises from illumination-independent defect currents, introduces additional nonlinearity not captured by conventional correction models. To address this issue, we propose a data-driven nonlinearity correction (NLC) method that models the nonlinear behavior of both the classical response and the defect currents, using dual-illumination measurements and a dark exposure. Applied to H4RG-10 detectors on the PRIME telescope, the method significantly improves signal linearity, especially for pixels with high defect current, while maintaining comparable performance elsewhere. By selecting the optimal correction model per pixel, reliable NLC is achieved across the full array. This study characterizes a nonlinearity intrinsic to H4RG-10 detectors and demonstrates that data-driven post-processing can effectively restore linearity in the presence of large defect currents. Although these effects are unlikely to be significant under nominal operating temperatures, the approach may provide a practical calibration framework for future warm-operation scenarios.

Keywords: Near infrared astronomy, Astronomical detectors, Flux calibration
Toward Millimagnitude Photometry at the Vera Rubin Observatory: Aerosol Monitoring with Quadband Dispersed Imaging. As the frontier of precision astronomical photometry continues to advance, correcting for time-variable atmospheric transmission becomes increasingly important. We describe an observational approach to monitoring optical attenuation due to atmospheric aerosols, using a multiband filter and disperser on the Auxiliary Telescope at the Vera C. Rubin Observatory. This configuration allows us to perform simple aperture photometry on four notched-out spectral regions, covering 347─618 nm. We see clear evidence of temporal variations in extinction across these bands, which we attribute to variation in the aerosol content of the atmosphere above the observatory. The observed differences in extinction between the reddest and bluest band can exceed 5 mmag/airmass, highlighting the importance of including variable aerosols in the transmission of the atmosphere. We aspire to using precise determinations of the optical transmission of the atmosphere to enable a forward-modeling approach to achieving mmag photometric precision with Rubin data.

Keywords: Broad band photometry, Atmospheric extinction
A New Astronomical Plate Digitizer at Shanghai Astronomical Observatory. The advancement of astronomy relies fundamentally on observational data. Between 1850 and 2000, astronomical observatories worldwide produced vast collections of photographic plates that remain invaluable for studying long-term celestial phenomena. However, these plates now face irreversible degradation, threatening their scientific value. Recognizing this urgency, Shanghai Astronomical Observatory (SHAO) developed a new plate digitizer incorporating a reliable air-bearing motion platform, a sophisticated imaging system, a stable illumination system, a design-optimized camera rotation mechanism and a custom-automated plate chamber. The system ensures the stability through active temperature and humidity control and vibration damping, while systematic error analysis and calibration further enhance operational performance. Tests show that the digitizing repeatability in positioning is better than 0.1 μm, repeatability in photometry is better than 0.01 mag, and the overall digitizing accuracy is about 0.3 μm in positioning and 0.02 mag in photometry. Currently, SHAO is collaborating internationally to digitize the endangered archives, providing support for the protection of scientific data heritage and research in long-term time-domain astronomy.

Keywords: Astronomical detectors, Astronomical instrumentation, Astronomy data analysis
Control Algorithms for Dual-wavefront Sensor Single-conjugate Adaptive Optics. High-contrast imaging systems using active control with adaptive optics (AO) are often limited by non-common path (NCP) aberrations that are seen only at the final science image. AO systems employing focal-plane wavefront sensors (FP-WFSs) are able to simultaneously correct NCP aberrations and measure science images, but they typically require a second stage of control that adds system cost and complexity. We present control algorithms to augment AO systems with FP-WFSs within their existing control setup. We demonstrate inter-arm NCP aberration transfer can be mitigated through temporal filtering, present frequency- and time-domain validation of controller stability and performance, and discuss the optimality of the chosen controllers. This work will enable the development, testing, and installation of FP-WFS technologies for direct imaging of exoplanets.

Keywords: Astronomical optics, Astronomical instrumentation
The R2Pub Telescopes for Surveying: An Overview and Performance Evaluation of the System. The R2Pub, built by Beijing Planetarium, is a state-of-the-art 60 cm equatorial binocular telescope located at the Daocheng Site (with an altitude of 4700 m) of Yunnan Observatories in China. This paper provides an overview of the R2Pub telescope system, discusses its design and capabilities, and presents an evaluation of its performance for astronomical surveys. R2Pub is a prime-focus binocular system, with each tube covering a field of view of about 18 deg2. This system is designed to detect various transients in local universe, including variables, eclipsing binaries, supernovae, gamma-ray bursts afterglow, tidal disruption events, Active Galactic Nuclei, and other unknown transients, which are ideal targets for both time-domain astronomy research and science population. The entire R2Pub system has completed the construction and installation of all observatory infrastructure, including the dome, equatorial mount, optical tube, and associated components, and has now entered the commissioning phase. The high-altitude location, good seeing, and dark background sky light at Daocheng site ensure optimal observational conditions for time-domain astronomy. Performance testing during the commissioning phase has demonstrated that the R2Pub system can achieve a 5σ limiting magnitude of approximately 18.7 mag in the Pan-STARRS r' band for 60 s exposures. The ongoing observations from R2Pub is expected to contribute significantly to the study of time-variable phenomena in the universe and greatly improve the public outreach in astronomy. In particular, the binocular telescope systems capable of simultaneous dual-band observations can obtain the instantaneous color information of transient sources, enabling more accurate characterization of their physical properties and evolution, and providing a significant advantage in rapid distinguishing different classes of variables and transients.

Keywords: Wide-field telescopes, Surveys, Astronomical instrumentation, Optical telescopes, Transient detection
Performance Study of an Intelligent Astronomical CMOS Camera. Mosaic sCMOS cameras are critical for wide-field astronomical surveys. However, the massive data volume generated by these high-resolution arrays imposes severe strains on traditional architectures, creating bottlenecks in data transmission bandwidth and system integration. To address these limitations, this paper presents the design and performance evaluation of the H-455, an intelligent mosaic camera integrating two SONY IMX455 Back-Side Illuminated sensors. Unlike conventional systems, the H-455 employs a System-on-Chip architecture combining an FPGA and an embedded Linux system, enabling autonomous onboard control and data processing. Specifically, we demonstrate the deployment of core algorithms from the Mini-SiTian Instrumental Effects Removal pipeline on the embedded platform, to perform real-time statistical noise characterization, high-precision flat-field synthesis, and satellite track identification. Systematic laboratory characterization demonstrates that the camera achieves scientific-grade performance, featuring a readout noise of ∼1.5 e− in high-gain mode, a linearity of R2 &gt; 0.9998, and a dark current of 0.0031 e− pixel−1 s−1 at −20°C. A comparative analysis of the two mosaic sensors reveals intrinsic performance disparities: one sensor exhibits superior background stability, while the other demonstrates tighter nonlinearity error control, highlighting the necessity for individual chip calibration in mosaic arrays. On-sky validation using the 1 m telescope at the NAOC Xinglong Observatory confirmed the system's observational capabilities, achieving a signal-to-noise ratio (SNR) of 13.6 for a 19.4 mag star with a 180 s exposure. Based on this measurement, the estimated limiting magnitude reaches approximately 20.47 mag (SNR = 5). These results validate the H-455 as a viable solution for future time-domain and deep-sky survey applications.

Keywords: Astronomical detectors, Astronomical instrumentation, Astronomy data analysis, Astronomy data reduction
Detailed TESS-Based Light Curve Modeling and Fundamental Parameter Estimation of 27 W UMa-Type Contact Binaries. We performed a comprehensive analysis of 27 short period contact binary systems for which no light curve analysis had previously been reported. Photometric time-series data from the TESS mission were used in this analysis. The observational results were validated using additional TESS sectors, along with complementary photometric observations from the ASAS-SN survey. The photometric light curves of the 27 contact binary systems were analyzed with the BSN application. Model solutions were obtained through iterative fitting followed by MCMC-based refinement to derive reliable system parameters, and starspot configurations were incorporated for seven targets exhibiting O'Connell effect asymmetries. The absolute parameters of the target systems were derived using the empirical parameter relationship between orbital period and semimajor axis. Based on the results of the light curve solutions and the estimated absolute parameters, five of the analyzed systems are identified as A-subtype, while the remaining targets belong to the W-subtype. We analyzed a sample of 484 W UMa contact binaries to identify the physical and orbital parameters that most effectively distinguish A-subtype from W-subtype systems using t-statistics. Three targets exhibited extremely low mass ratios, and their orbital analysis confirmed that they are dynamically stable. The evolutionary states of the systems were examined, showing that lower-mass companions are generally more evolved, while more massive components remain less evolved. The positions of the systems and their stellar components were compared across four diagrams derived from empirical parameter relationship studies, showing good agreement with the linear fits.

Keywords: Close binary stars, Eclipsing binary stars, Fundamental parameters of stars
KMT-2016-BLG-1337L: A Saturn-mass Planet Orbiting Within a Binary System of Low-mass Stars. We report the discovery and characterization of a planetary companion in the microlensing event KMT-2016-BLG-1337, which was produced by a binary system of low-mass stars. The light curve of the event exhibits a short-term anomaly superposed on the profile of a binary-lens single-source (2L1S) model. To investigate the nature of this anomaly, we performed detailed modeling under both the binary-lens binary-source (2L2S) and triple-lens single-source (3L1S) interpretations. The 3L1S model provides a substantially better fit to the data, strongly favoring the presence of a planetary companion in the lens system. Two viable 3L1S solutions describe the event nearly equally well. In one solution, the planet has a mass of M3 ∼ 0.3 MJ and lies at a projected separation of a⊥,3 ∼ 4 au from the heavier member of the host binary. In the alternative solution, the planet has a mass of M3 ∼ 7 MJ and a projected separation of a⊥,3 ∼ 1.5 au. The host binary consists of early M-type dwarfs with masses of M1 ∼ 0.54 M⊙ and M2 ∼ 0.40 M⊙, separated in projection by a⊥,2 ∼ 3.5 au. The system is located at a distance of DL ∼ 7 kpc toward the Galactic bulge. This event demonstrates the sensitivity of microlensing to planets in dynamically complex stellar environments, including systems beyond the reach of other detection techniques. It thereby contributes to a more comprehensive understanding of planet formation in multiple-star systems.

Keywords: Gravitational microlensing, Exoplanet detection methods