Sazuna/UAT_keywords huggingface dataset:
CCSNscore: A Multi-input Deep Learning Tool for Classification of Core-collapse Supernovae Using SED-machine Spectra. Supernovae (SNe) come in various flavors and are classified into different types based on emission and absorption lines in their spectra. SN candidates are now abundant with the advent of large systematic sky surveys like the Zwicky Transient Facility (ZTF), however, the identification bottleneck lies in their spectroscopic confirmation and classification. Fully robotic telescopes with dedicated spectrographs optimized for SN follow-up have eased the burden of data acquisition. However, the task of classifying the spectra still largely rests with the astronomers. Automating this classification step reduces human effort and can make the SN type available sooner to the public. For this purpose, we have developed a deep-learning based program for classifying core-collapse supernovae (CCSNe) with ultra-low resolution spectra from the SED-machine spectrograph on the Palomar 60 inch telescope. The program consists of hierarchical classification task layers, with each layer composed of multiple binary classifiers running in parallel to produce a reliable classification. The binary classifiers utilize recurrent neural networks and convolutional neural networks architecture and are designed to take multiple inputs to supplement spectra with g- and r-band photometry from ZTF. On non-host-contaminated and good quality SEDM spectra ("gold" test set) of CCSNe, CCSNscore is ∼94% accurate in distinguishing between hydrogen-rich (Type II) and hydrogen-poor (Type Ibc) CCSNe. With light curve input, CCSNscore classifies ∼83% of the gold set with high confidence (score ≥0.8 and score-error &lt; 0.05), with ∼98% accuracy. Based on SNIascore's and CCSNscore's real-time performance on bright transients (mpk ≤ 18.5) and our reporting criteria, we expect ∼0.5% (∼4) true SNe Ia to be misclassified as SNe Ibc and ∼6% (∼17) of true CCSNe to be misclassified between Type II and Type Ibc annually on the Transient Name Server.

Keywords: Classification, Core-collapse supernovae, Neural networks
NCPA Correction Method for AO Systems Based on Phase Diversity. Astronomical large aperture high-resolution telescopes adopt adaptive optics (AO) to improve resolution. Due to the physical separation of wavefront detection and imaging optical paths, non-common optical path aberration (NCPA) must be corrected. To correct NCPA, we propose a simple and effective method based on phase diversity (PD) wavefront aberration detection combined with AO closed-loop correction. This technology generates a known defocus aberration through the deformable mirror and collects the focused and defocused spot images of the AO system after closed-loop in a time-division manner. The distorted wavefront aberration is measured by PD algorithm and the corresponding sub-aperture slopes used to modify the wavefront sensor (WFS) reference of the wavefront is calculated by the virtual Hartmann-Shack approach. After several iterations of the AO closed-loop data acquisition, the PD wavefront distortion measurement and the WFS reference modification, the far-field focused spot will gradually converge to the diffraction limit Airy spot of the imaging system. The NCPAs of 705.6 nm and 656.3 nm bands in the solar adaptive optics system of the 1.8 m Chinese Large Solar Telescope are measured and corrected in this article, and the strehl ration values of focused spot images increase from 0.689 and 0.373 to 0.839 and 0.770, corresponding to the rms values of compensated NCPA wavefront aberrations being 50.05 nm and 72.91 nm respectively. The experiments verify the effectiveness of the proposed method, and the results show that this method has extremely high NCPA correction accuracy, which has important application value in fields such as solar AO system and extreme AO system.

Keywords: Solar optical telescopes, Optical observatories, Astronomy data analysis
SPGrid: A Straightforward Parallel Gridding Approach for Single-dish Radio Telescope. The gridding operation, resampling irregularly distributed raw data onto a regular grid map, is the most data-intensive and compute-intensive step in radio astronomical data processing pipelines. Therefore, in order to tackle the vast amount of data generated by modern large radio telescopes, many parallel convolution-based gridding algorithms are developed on multi-core CPU platforms or heterogeneous computing platforms to take full advantage of the processors. Most of these algorithms adopted gather mode, which relies on a fast lookup scheme to avoid write conflict and improve throughput. However, practical applications have shown that constructing a lookup table incurs substantial costs and usually becomes the bottleneck of the gather mode when handling large data sets. So we employ a straightforward parallel gridding approach, that is the scatter mode, to develop the SPGrid code. Several optimization strategies are proposed for CPU and GPU architecture separately. The code improves throughput further while avoiding the heavy overhead of constructing a lookup table. Compared with the representative gather-based gridding code such as Cygrid and HCGrid, the scatter-based SPGrid achieves a maxiumum 4.1× and 3.7× speedup on CPU and GPU platform, respectively.

Keywords: Open source software, Astronomy software, Astronomy data analysis, Computational methods, GPU computing, Astronomy data visualization, Astronomy data reduction
Development and Performance Validation of a Versatile VLBI Digital Backend Using the ROACH2 Platform. Customized digital backends for Very Long Baseline Interferometry (VLBI) are critical components for radio astronomy observatories. There are several serialized products such as the Digital Baseband Converter, Reconfigurable Open Architecture Computing Hardware (ROACH) Digital BackEnd, and Chinese Data Acquisition System (CDAS). However, the reliance on high-speed analog-to-digital converters and Field Programmable Gate Arrays often necessitates dedicated hardware platforms with long development cycles and prohibitive cost, limiting scalability and adaptability to evolving observational needs. To address these challenges, we propose a design leveraging the versatile and cost-effective ROACH2 hardware platform, developed by Collaboration for Astronomy Signal Processing and Electronics Research. ROACH2's mature technology and streamlined firmware development capabilities significantly reduce the hardware platform's development cycle and cost, making it ideal for modern astronomical applications. This VLBI digital backend, based on the ROACH2 platform, incorporates key technologies such as Polyphase Filter Banks algorithm implementation, digital complex-to-real baseband signal conversion, Mark5B data formatter design and two-bit optimal threshold quantization. These features ensure compatibility with existing systems while providing enhanced performance. The backend's performance was validated through multi-station VLBI experiments, demonstrating its ability to achieve good correlation fringes compared to the customized CDAS2-D system. Furthermore, this platform offers flexibility for rapid deployment of additional digital backends, such as those for spectral line observations, showcasing its potential for broader astronomical applications.

Keywords: Observatories, Very long baseline interferometry, Radio astrometry, Astronomy data acquisition
GMACS: A Moderate-dispersion Optical Spectrograph for the Giant Magellan Telescope. Giant Magellan Telescope Multi-object Astronomical and Cosmological Spectrograph (GMACS) is a first-light moderate-dispersion imaging spectrograph under development at the Center for Astrophysics and Steiner Institute for the Giant Magellan Telescope. GMACS operates between 330 and 1050 nm with resolution 1000 &lt; R &lt; 5000 using a 0 7 wide slit. The total slit length is 7' with a field 6' wide in the dispersion direction. GMACS carries 17 exchangeable aperture masks. Resolution &gt; 10,000 is possible with the MANIFEST optical fiber front end that will initially address a 14' diameter field. Standing 5 m tall with a mass of 11,000 kg, GMACS has two arms with 260 mm collimated beams split with a dichroic at 630 nm.

Keywords: Spectroscopy
SPARC4 Control System. SPARC4 is a new astronomical instrument developed entirely by Brazilian institutions, currently installed on the 1.6 m Perkin-Elmer telescope of the Pico dos Dias Observatory. It allows the user to perform photometric or polarimetric observations simultaneously in the four SDSS bands (g, r, i, and z). In this paper, we describe the control system developed for SPARC4. This system is composed of S4ACS, S4ICS, and S4GUI softwares and associated hardware. S4ACS is responsible for controlling the four EMCCD scientific cameras (one for each instrument band). S4ICS controls the sensors and motors responsible for the moving parts of SPARC4. Finally, S4GUI is the interface used to perform observations, which includes the choice of instrument configuration and image acquisition parameters. S4GUI communicates with the instrument subsystems and with some observatory facilities, needed during the observations. Bench tests were performed for the determination of the overheads added by SPARC4 control system in the acquisition of photometric and polarimetric series of images. In the photometric mode, SPARC4 allows the acquisition of a series of 1400 full-frame images, with a deadtime of 4.5 ms between images. Besides, several image series can be concatenated with a deadtime of 450 ms plus the readout time of the last image. For the polarimetric mode, measurements can be obtained with a deadtime of 1.41 s plus the image readout time between subsequent waveplate positions. For both photometric and polarimetric modes, the user can choose among operating modes with image readout times between 5.9 ms and 1.24 s, which ultimately defines the instrument temporal performance.

Keywords: Polarimeters, Photometer, Astronomical instrumentation
The Legacy of Henrietta Leavitt: A Re-analysis of the First Cepheid Period–Luminosity Relation. Henrietta Swan Leavitt's discovery of the relationship between the period and luminosity (hereafter the Leavitt Law) of 25 variable stars in the Small Magellanic Cloud, published in 1912, revolutionized cosmology. These variables, eventually identified as Cepheids, became the first known "standard candles" for measuring extragalactic distances and remain the gold standard for this task today. Leavitt measured light curves, periods, and minimum and maximum magnitudes from painstaking visual inspection of photographic plates. Her work paved the way for the first precise series of distance measurements that helped set the scale of the Universe, and later the discovery of its expansion by Edwin Hubble in 1929. Here, we re-analyze Leavitt's first Period–Luminosity relation using observations of the same set of stars but with modern data and methods of Cepheid analysis. Using only data from Leavitt's notebooks, we assess the quality of her light curves, measured periods, and the slope and scatter of her Period–Luminosity relations. We show that modern data and methods, for the same objects, reduce the scatter of the Period–Luminosity relation by a factor of two. We also find a bias brightward at the short period end, due to the nonlinearity of the plates and environmental crowding. Overall, Leavitt's results are in excellent agreement with contemporary measurements, reinforcing the value of Cepheids in cosmology today, a testament to the enduring quality of her work.

Keywords: Galaxy distances, Distance measure, Small Magellanic Cloud, Standard candles, Expanding universe, History of astronomy, Cepheid variable stars
Oxygen Isotope Ratios in Hydrogen-deficient Carbon Stars: A Correlation with Effective Temperature and Implications for White Dwarf Merger Outcomes. Hydrogen-deficient Carbon (HdC) stars are a class of supergiants with anomalous chemical compositions, suggesting that they are remnants of CO–He white dwarf (WD) mergers. This class comprises two spectroscopically similar subclasses—dusty R Coronae Borealis (RCB) and dustless Hydrogen-deficient Carbon (dLHdC) stars. Both subclasses have a stark overabundance of 18O in their atmospheres, but spectroscopic differences between them remain poorly studied. We present high-resolution (R ≈ 75,000) K-band spectra of six RCB and six dLHdC stars, including four newly discovered dLHdC stars, making this the largest sample to date. We develop a semi-automated fitting routine to measure 16O/18O ratios for this sample, tripling the number of dLHdC stars with oxygen isotope ratios measured from high resolution spectra. All six dLHdC stars have 16O/18O &lt; 1, while the RCB stars have 16O/18O &gt; 4. Additionally, for the first time, we find a trend of decreasing 16O/18O ratios with increasing effective temperature for HdC stars, consistent with predictions of theoretical WD merger models. However, we note that current models overpredict the low 16O/18O ratios of dLHdC stars by two orders of magnitude. We also measure abundances of C, N, O, Fe, S, Si, Mg, Na, and Ca for these stars. We observe a correlation between the abundances of 14N and 18O in our sample, suggesting that a fixed fraction of the 14N is converted to 18O in these stars via α-capture. Our results affirm the emerging picture that the mass ratio/total mass of the WD binary determine whether an RCB or dLHdC is formed post-merger.

Keywords: High resolution spectroscopy, Abundance ratios, White dwarf stars, R Coronae Borealis variable stars, Hydrogen deficient stars
Realistic Predictions for Gaia Black Hole Discoveries: Comparison of Isolated Binary and Dynamical Formation Models. Astrometry from Gaia has enabled discovery of three dormant black holes (BHs) in au-scale binaries. Numerous models have been proposed to explain their formation, including several that have forecasted Gaia detections. However, previous works have used simplified detectability metrics that do not capture key elements of the Gaia astrometric orbit selection function. We apply a realistic forward-model of Gaia astrometric orbit catalogs to BH binary populations generated through (a) isolated binary evolution (IBE) and (b) dynamical formation in star clusters. For both formation channels, we analyze binary populations in a simulated Milky Way-like galaxy with a realistic metallicity-dependent star formation history and 3D dust map. We generate epoch astrometry for each binary from the Gaia scanning law and fit it with the cascade of astrometric models used in Gaia DR3. The IBE model of Chawla et al. predicts that no BH binaries should have been detected in DR3 and thus significantly underpredicts the formation rate of Gaia BHs. In contrast, the dynamical model of Di Carlo et al. overpredicts the number of BHs receiving DR3 orbital solutions by a factor of ∼8. The two models predict very different orbital period distributions, with the IBE model predicting only binaries that avoided common envelope evolution and have Porb ≳ 2000 days to be detectable, and the dynamical formation model predicting a period distribution that is roughly log-uniform. Adopting the dynamical channel as a fiducial model and rescaling by a factor of 1/8 to match DR3, we predict that ∼30 BH binaries will be detected in Gaia DR4, representing ∼0.1% of Milky Way BHs with luminous companions in au-scale orbits.

Keywords: Astrometric binary stars, Stellar mass black holes
Low-luminosity Type IIP Supernovae from the Zwicky Transient Facility Census of the Local Universe. I. Luminosity Function, Volumetric Rate. We present the luminosity function and volumetric rate of a sample of Type IIP supernovae (SNe) from the Zwicky Transient Facility Census of the Local Universe survey (CLU). This is the largest sample of Type IIP SNe from a systematic volume-limited survey to-date. The final sample includes 330 Type IIP SNe and 36 low-luminosity Type II (LLIIP) SNe with Mr,peak &gt; −16 mag, which triples the literature sample of LLIIP SNe. The fraction of LLIIP SNe is   of the total CLU Type IIP SNe population (  of all core-collapse SNe). This implies that while LLIIP SNe likely represent the fate of core-collapse SNe of 8─12 M⊙ progenitors, they alone cannot account for the fate of all massive stars in this mass range. To derive an absolute rate, we estimate the ZTF pipeline efficiency as a function of the apparent magnitude and the local surface brightness. We derive a volumetric rate of   for Type IIP SNe and   for LLIIP SNe. Now that the rate of LLIIP SNe is robustly derived, the unresolved discrepancy between core-collapse SN rates and star formation rates cannot be explained by LLIIP SNe alone.

Keywords: Core-collapse supernovae, Surveys, Type II supernovae, Massive stars, Transient sources, Supernovae
Tracking Evolution of Circumstellar Disks of Classical Be Stars Using Infrared L-band and H<SUB>α</SUB> Spectral Emissions. We present new L-band spectra for 28 Northern Galactic Be stars, obtained with the CID-InSb spectrograph at the 2.1 m telescope OAN/UNAM San Pedro Martir Observatory. For 19 of these stars we establish positions on the Lenorzer diagram, which is a diagnostic tool of circumstellar environments. It is constructed using flux ratios of the hydrogen infrared recombination lines (Brα, Hu14 and Pfγ) and gives information about the density of the emitting gas. We compare the positions on Lenorzer diagram with Hα emissions recorded on the BeSS database. Our main results show that over two decades, γ Cas has maintained a stable circumstellar disk (CSD); 28 Cyg has undergone at least one complete cycle of growth and dissipation of its disk, this being the first report of that cycle in the infrared range; the star 28 Tau seems to have experienced the dissipation and subsequent growth of a new CSD; and, 12 Vul seems to have completely lost its disk. In our analysis, we find a significant relation between the positions of Be stars on the Lenorzer diagram and the variation in the Hα emission. The emissions of optically thick media are consistent with positive Hα variations, while those of optically thin with negative variation; this accounts for the effects that changes on internal regions of Be disk have on the external ones.

Keywords: Emission line stars, H-alpha stars, Infrared astronomy, Spectroscopy, Circumstellar disks, Be stars
Solar System Objects Observed with TESS—Early Data Release 2: I. Spin-shape Recovery Potential of Multi-epoch TESS Observations. Using multidirectional measurements from the Transiting Exoplanet Survey Satellite (TESS), we investigated the viability of determining the approximate shape and spin axis orientations for 44 selected main belt asteroids, using light curve inversion, assuming Lommel-Seeliger ellipsoids. This study aims to investigate the applicability of low-degree-of-freedom shape models in those cases when rotation periods can be accurately determined, but light curves are only available in a limited number of geometries or orbital phases. Our results are compared with the shape and spin axis solutions obtained for the same set of asteroids by more complex light curve inversion methods using mainly ground-based measurements, available via the Database of Asteroid Models from Inversion Techniques (DAMIT). The best-fit spin-axis orientations show a moderately good match with the DAMIT solutions; however, a better agreement is reached with triaxial ellipsoid solution obtained from other large, independent surveys. This suggests that while TESS-only data works well for finding rotation periods, it has its limitations when determining asteroid shape and spin-axis orientation. We discuss the challenges and potential applications of this approach for studying large number of asteroids observed by TESS.

Keywords: Asteroid rotation, Asteroids
Picking-up Local GRB Candidates Based on Their Host Galaxies. Rapid identification of candidates of high-value gamma-ray bursts (GRBs), including both high-z and local events, is crucial for outlining subsequent observational strategy. In this paper, we present a model that enables an on-duty astronomer to rapidly identify candidates of local GRBs prior to spectroscopy, provided that these events have been localized at an arcsecond's precision. After taking into account the mass distribution of the host galaxies of GRBs, the model calculates the two-dimensional cross-match probabilities between a localized GRB and its surrounding nearby galaxies, and then returns the best match with the highest probability. The model is evaluated not only by the observed GRB sample with redshifts up to z = 4, but also through the simulated GRB samples. By using the recently published GLADE+ galaxies catalog with a completeness of 95% up to 500 Mpc, along with the NED-LVS catalog, the Precision and Recall of the model are determined to be 0.23–0.33 and 0.75, respectively, at the best performance. A dedicated web service, which will be integrated into the SVOM Science User Support System, has been developed to deploy the model.

Keywords: Galaxies, Gamma-ray bursts, Astrostatistics
Parametric Methods for Coherent Time-domain Canceling of Radio Frequency Interference. Anthropogenic interference has been a long-standing problem for radio astronomy. In a previous paper, we presented a study of interference mitigation methods based on the concept of coherent time-domain canceling, which ideally allows one to "look through" interference, as opposed to avoiding the interference or deleting the afflicted data. The focus of that paper was on "reference antenna" methods, in which a separately acquired signal containing the interference waveform is used to identify the interference waveform in the primary signal. In this paper, we shift focus to methods in which the reference signal is instead a parametric model of the waveform, so that no additional antenna is needed. As in our previous paper, we present a rigorous theoretical analysis of performance. Findings are demonstrated using real-world interference from the Iridium system. We find that interference suppression is possible if the product of the interference-to-noise ratio and the number of statistically independent samples is greater than 1, and that suppression increases linearly with this product. However good performance is achieved only for interferers whose bandwidth is much less than the sample rate, and algorithm parameters must be carefully selected to avoid undesirable distortion of the noise spectral baseline.

Keywords: Astronomical instrumentation, Astronomy data analysis
Identifying Eclipsing Binary Stars with TESS Data Based on a New Hybrid Deep Learning Model. Eclipsing binary systems (EBs), as foundational objects in stellar astrophysics, have garnered significant attention in recent years. These systems exhibit periodic decreases in light intensity when one star obscures the other from the observer's perspective, producing characteristic light curves (LCs). With the advent of the Transiting Exoplanet Survey Satellite (TESS), a vast repository of stellar LCs has become available, offering unprecedented opportunities for discovering new EBs. To efficiently identify such systems, we propose a novel method that combines LC data and generalized Lomb-Scargle periodograms (GLS) data to classify EBs. At the core of this method is CNN_Attention_LSTM Net (CALNet), a hybrid deep learning model integrating Convolutional Neural Networks (CNNs), Long Short-Term Memory (LSTM) networks, and an Attention Mechanism based on the Convolutional Block Attention Module. We collected 4225 EB samples, utilizing their 2-minute cadence LCs for model training and validation. CALNet achieved a recall rate of 99.1%, demonstrating its robustness and effectiveness. Applying it to TESS 2-minute LCs from Sectors 1 to 74, we identified 9351 new EBs after manual visual inspection, significantly expanding the known sample size. This work highlights the potential of advanced deep-learning techniques in large-scale astronomical surveys and provides a valuable resource for further studies on EBs.

Keywords: Eclipsing binary stars, Convolutional neural networks, Light curve classification