Star Pattern Research Articles

Does the structure of Population III supernova ejecta affect the elemental abundance of extremely metal-poor stars?

ABSTRACT The first generation of metal-free (Population III) stars are crucial for the production of heavy elements in the earliest phase of structure formation. Their mass scale can be derived from the elemental abundance pattern of extremely metal-poor (EMP) stars, which are assumed to inherit the abundances of uniformly mixed supernova (SN) ejecta. If the expanding ejecta maintains its initial stratified structure, the elemental abundance pattern of EMP stars might be different from that from uniform ejecta. In this work, we perform numerical simulations of the metal enrichment from stratified ejecta for normal core-collapse SNe (CCSNe) with a progenitor mass $25 \ {\rm M_{\bigodot }}$ and explosion energies 0.7–10 B ($1 \ {\rm B} = 10^{51} \ \rm erg$). We find that SN shells fall back into the central minihalo in all models. In the recollapsing clouds, the abundance ratio [M/Fe] for stratified ejecta is different from the one for uniform ejecta only within ±0.4 dex for any element M. We also find that, for the largest explosion energy (10 B), a neighbouring halo is also enriched. Only the outer layers containing Ca or lighter elements reach the halo, where [C/Fe] = 1.49. This means that C-enhanced metal-poor stars can form from the CCSN even with an average abundance ratio [C/Fe] = −0.65.

KELT-17: a chemically peculiar Am star and a hot-Jupiter planet

Context. There is very little information to be found in the literature regarding the detection of planets orbiting chemically peculiar stars. Aims. Our aim is to determine the detailed chemical composition of the remarkable planet host star KELT-17. This object hosts a hot-Jupiter planet with 1.31 MJup detected by transits, and it is one of the more massive and rapidly rotating planet hosts seen to date. We set out to derive a complete chemical pattern for this star, in order to compare it with those of chemically peculiar stars. Methods. We carried out a detailed abundance determination in the planet host star KELT-17 via spectral synthesis. Stellar parameters were estimated iteratively by fitting Balmer line profiles and imposing the Fe ionization balance using the SYNTHE program together with plane-parallel ATLAS12 model atmospheres. Specific opacities for an arbitrary composition and microturbulence velocity vmicro were calculated through the opacity sampling (OS) method. The abundances were determined iteratively by fitting synthetic spectra to metallic lines of 16 different chemical species using SYNTHE. The complete chemical pattern of KELT-17 was compared to the recently published average pattern of Am stars. We estimated the stellar radius using two methods: a) comparing the synthetic spectral energy distribution with the available photometric data and the Gaia parallax, and b) using a Bayesian estimation of stellar parameters using stellar isochrones. Results. We found over-abundances of Ti, Cr, Mn, Fe, Ni, Zn, Sr, Y, Zr, and Ba, together with subsolar values of Ca and Sc. Notably, the chemical pattern agrees with those recently published for Am stars, making KELT-17 the first exoplanet host whose complete chemical pattern is unambiguously identified with this class. The stellar radius derived by two different methods agrees to each other and with those previously obtained in the literature.

A Novel Inertial-Aided Star Pattern Matching Method for Distributed Multiple FoVs

An aerospace vehicle in high-speed flight involves distributed multiple fields of view (FoVs) of a star sensor, and the maneuvering of the vehicle requires inertial-aided star pattern matching. Accordingly, an inertial-aided star pattern matching method for distributed multiple FoVs is proposed. First, the observation and fusion principles of distributed multiple FoVs are illustrated. Then, an inertial-aided star pattern matching scheme is designed based on the space-time distribution of the line-of sight (LoS) vector and inertial measurement information. Next, an LoS vector estimation method assisted by inertial information and the dynamic establishment of a distributed local catalog are proposed. Finally, in a simulation, the dynamic establishment of the part catalog improves the efficiency of star pattern matching by reducing the catalog scale, and the usability of inertial-aided star pattern matching is analyzed for different gyro and accelerometer precisions.

CRL optics and silicon drift detector for P06 Microprobe experiments at 35 keV

A provisional setup for X-ray microprobe experiments at 35 keV is described. It is based on compound refractive lenses (CRLs) for nanofocusing and a Vortex silicon drift detector with 2 mm sensor thickness for increased sensitivity at high energies. The Microprobe experiment (PETRA III) generally uses Kirkpatrick-Baez mirrors for submicrometer focusing in the energy range of 5–21 keV. However, various types of scanning X-ray microscopy experiments require higher excitation energies. The CRL optics were characterized by X-ray ptychography and X-ray fluorescence (XRF) knife edge scans on a siemens star pattern and showed beam sizes down to 110 nm. The performance of the new setup for microscopic X-ray diffraction (XRD)–XRF scanning X-ray microscopy measurements at 35 keV is demonstrated on a cross-section of a painting fragment.

Binary star sequence in the outskirts of the disrupting Galactic open cluster UBC 274

We report the identification of a numerous binary star population in the recently discovered ∼3 Gyr old open cluster UBC 274. It becomes visible when the cluster color-magnitude diagram is corrected by differential reddening and spans mass ratio (q) values from 0.5 up to 1.0. Its stellar density radial profile and cumulative distribution as a function of the distance from the cluster center reveal that it extends out to the observed boundaries of the tidal tails of the cluster (about six times the cluster radius) following a spatial distribution indistinguishable from that of cluster main-sequence (MS) stars. Furthermore, binary stars withqvalues lower or higher than 0.75 do not show any spatial distribution difference either. FromGaiaDR2 astrometric and kinematics data we computed Galactic coordinates and space velocities with respect to the cluster center and mean cluster space velocity, respectively. We found that cluster members located throughout the tidal tails move relatively fast, regardless of whether they are a single or binary star. The projection of their motions onto the Galactic plane resembles that of a rotating solid body, while the motions along the radial direction from the Galactic center and perpendicular to the Galactic plane suggest that the cluster is being disrupted. The similarity of the spatial distributions and kinematic patterns of cluster MS and binary stars reveals that UBC 274 is facing an intense process of disruption that has apparently swept out any signature of internal dynamic evolution, such as mass segregation driven by two-body relaxation.

Bilateral Idiopathic Neuroretinitis

BACKGROUND: Neuroretinitis is a clinical entity characterized by an acute loss of vision associated with disc edema and a star pattern of exudates in the macula. It can be divided into two, those with a specific infectious agent or idiopathic. Most infectious cases are due to cat-scratch disease caused by Bartonella species and other infectious agents. Case with a clear infectious is categorized as idiopathic. Most patients with idiopathic neuroretinitis recover excellent visual acuity with or without intervention. Although the presentation is most often unilateral, bilateral cases of neuroretinitis have been reported.
 CASE REPORT: A 20-year-old woman with a 2-weeks history of sudden progressive visual loss both eyes (visual acuity: RE 3/60; LE 20/200). The optic disc was edema and the hard exudate on the macular area. Two weeks follow-up, funduscopic shows a macular star and the optic disc’s edema was reduced. Perimetric test shows general depressed in both eyes. The blood tests and the brain computed tomography scan were normal. She received methyl prednisolone 48 mg for 2 weeks. Eight months follow-up, VA: RE 20/50, LE 20/40 with the pinhole 20/15 in both eyes. The funduscopic still showed edema and slight paling. There was an improvement in central visual acuity after steroid treatment but leave residual abnormal funduscopic.
 CONCLUSION: Neuroretinitis is generally self-limited. The visual acuity recovers excellent with the steroid, but the abnormal disc in this case related to a vaso-occlusive mechanism of prelamin arterioles with subsequent disc infraction.

Space Object Data Association Using Spatial Pattern Recognition Approaches

Identification of known space objects is a critical step in maintaining accurate catalogs for space situational awareness activities. With increasing numbers of objects in orbit, optical measurements of space objects become more populated with detections, stressing the algorithms used to track and identify these objects. Traditional algorithms used for identifying space objects, such as elliptical gating, suffer from ambiguous or incorrect classifications as gates tend to overlap in dense detection environments. An algorithm is developed that couples elliptical gating with a star pattern recognition algorithm called the planar triangle method to overcome the difficulties found in spatially dense observations. Unlike star catalogs, cataloged resident space objects often contain considerable uncertainty, further challenging the identification of objects in a cluttered field-of-view. The proposed approach leverages uncertainties of the catalog as well as the optical measurement sensor uncertainty to support the space object identification. Simulation results using the gating-assisted planar triangle method show a significant improvement in robust identification of space objects as compared to traditional elliptical gating methods when faced with highly cluttered observations.

Longitudinal drift of Tayler instability eigenmodes as a possible explanation for super-slowly rotating Ap stars

Context. Rotation periods inferred from the magnetic variability of some Ap stars are incredibly long, exceeding ten years in some cases. An explanation for such slow rotation is lacking. Aims. This paper attempts to provide an explanation of the super-slow rotation of the magnetic and thermal patterns of Ap stars in terms of the longitudinal drift of the unstable disturbances of the kink-type (Tayler) instability of their internal magnetic field. Methods. The rates of drift and growth were computed for eigenmodes of Tayler instability using stellar parameters estimated from a structure model of an A star. The computations refer to the toroidal background magnetic field of varied strength. Results. The non-axisymmetric unstable disturbances drift in a counter-rotational direction in the co-rotating reference frame. The drift rate increases with the strength of the background field. For a field strength exceeding the (equipartition) value of equal Alfven and rotational velocities, the drift rate approaches the proper rotation rate of a star. The eigenmodes in an inertial frame show very slow rotation in this case. Patterns of magnetic and thermal disturbances of the slowly rotating eigenmodes are also computed. Conclusions. The counter-rotational drift of Tayler instability eigenmodes is a possible explanation for the observed phenomenon of super-slowly rotating Ap stars.

Structurally topological algorithm for star recognition and near-Earth space’ object detection

When solving a variety of celestial navigation tasks there is a problem of determining parameters of spacecraft motion and onboard primary payload orientation based on the coordinates of registered star images. Furthermore, unwanted objects, like active satellites, natural and artificial space debris, that reduce the probability of correct recognition may get into the field of view of a satellite sensor. This prompts the necessity to filter out such interference from the star field images. However, if the objects under recognition are bodies located in near-Earth space, in this case, the star images themselves will act as interferences. In addition, since the detection and cataloging of these objects from the Earth’s surface is complicated by their small size, the atmospheric effects, as well as other technical difficulties, it is worthwhile to use the existing equipment onboard spacecrafts to solve this task. The existing recognition algorithms for star groups, as well as their classification, are presented in this paper. Moreover, a structurally topological approach for identifying groups of stars based on the properties of enveloping polygons used in constructing topological star patterns is proposed. Specific features in the construction of topological configurations on the analyzed set of points, as well as the principles of dynamic space object detection within their limits are described. Results of the numerical experiments performed using the developed algorithm on the star field maps and model scenes are presented.

Compacting frequent star patterns in RDF graphs

Knowledge graphs have become a popular formalism for representing entities and their properties using a graph data model, e.g., the Resource Description Framework (RDF). An RDF graph comprises entities of the same type connected to objects or other entities using labeled edges annotated with properties. RDF graphs usually contain entities that share the same objects in a certain group of properties, i.e., they match star patterns composed of these properties and objects. In case the number of these entities or properties in these star patterns is large, the size of the RDF graph and query processing are negatively impacted; we refer these star patterns as frequent star patterns. We address the problem of identifying frequent star patterns in RDF graphs and devise the concept of factorized RDF graphs, which denote compact representations of RDF graphs where the number of frequent star patterns is minimized. We also develop computational methods to identify frequent star patterns and generate a factorized RDF graph, where compact RDF molecules replace frequent star patterns. A compact RDF molecule of a frequent star pattern denotes an RDF subgraph that instantiates the corresponding star pattern. Instead of having all the entities matching the original frequent star pattern, a surrogate entity is added and related to the properties of the frequent star pattern; it is linked to the entities that originally match the frequent star pattern. Since the edges between the entities and the objects in the frequent star pattern are replaced by edges between these entities and the surrogate entity of the compact RDF molecule, the size of the RDF graph is reduced. We evaluate the performance of our factorization techniques on several RDF graph benchmarks and compare with a baseline built on top gSpan, a state-of-the-art algorithm to detect frequent patterns. The outcomes evidence the efficiency of proposed approach and show that our techniques are able to reduce execution time of the baseline approach in at least three orders of magnitude. Additionally, RDF graph size can be reduced by up to 66.56% while data represented in the original RDF graph is preserved.

Computational Technique for the Qualification of Focal Spot Size and Shape of Industrial Radioscopy Equipment Using Star Patterns

Computational Technique for the Qualification of Focal Spot Size and Shape of Industrial Radioscopy Equipment Using Star Patterns

Selective flattening of magnon bands in kagome-lattice ferromagnets with Dzyaloshinskii-Moriya interaction

There is growing interest in revealing exotic properties of collective spin excitations in kagome-lattice ferromagnets such as magnon Hall effects, topological magnon insulators, and flat magnon bands. Using the well-established nearest-neighbor Heisenberg ferromagnet model with Dzyaloshinskii-Moriya interaction (DMI), in this study we uncover intriguing new aspects in the selectivity and topology of flat magnon bands. Among the three magnon bands (except for the top one, which is flat in the absence of DMI), we observe that each of the three bands can be selectively flattened at the critical DMI of $$D=\pm\sqrt{3}J/3$$ and $$D=\pm\sqrt{3}J$$ . With a general DMI, the magnon bands become non-flat; however, there are nested lines that create a David star pattern for all three magnon bands whose flatness is robust during changing exchange coupling or DMIs. Contrary to prevailing belief, we show that each of the three flat bands is actually topologically trivial at critical DMIs. Furthermore, we show that while the middle band remains topologically trivial, for the other two bands, D = 0 corresponds to the topological phase transition where their Chern numbers get interchanged; when $$D=\pm\sqrt{3}J$$ , the system undergoes a phase transition to the nonferromagnetic state. These central findings increase our understanding of spin excitations for future magnonics applications.

The complete mitochondrial genome of Ophiura kinbergi (Ophiuroidea, Ophiurina): genome structure and phylogenetics

The length of the complete mitochondrial genome was 16,626 bp for Ophiura kinbergi, containing 35 genes similar to other known ophiuroids. The GC content was 33.35%. The gene structure was identical to known mitochondrial genomes from the species of genus Ophiura. Phylogenetic results indicated conserved relationships between O. kinbergi and three other Ophiura species. These results could provide detailed information for better understanding the evolution patterns of brittle stars, especially for the genus Ophiura.

A Scientific Study of Eastern Zhou Bronze Weapons with Tin-Rich Surface Decoration

In this paper we examined three bronze weapons with tin-rich surface decoration from the Eastern Zhou period: a sword (1966,0222.1) with a trellis pattern, a spearhead (1947,0712.426) with a hexagonal star pattern in the British Museum collections, and a sword (GT698) with a trellis pattern from a private collection. These weapons may have come from south eastern China, a region renowned for its weaponry production in the Eastern Zhou period, as both their styles and decorations are comparable to the sword of the Yue King Goujian and the spearhead of Wu King Fuchai, two of the most typical objects of this type. The manufacturing and surface tin-rich decoration techniques were investigated using microscopy, X-ray CT imaging, X-ray fluorescence spectrometry, scanning electron microscopy equipped with energy dispersive X-ray spectroscopy, and X-ray diffraction. The results showed that all the objects were made of high tin bronzes. The swords were made by casting a grip around the pre-cast blade and the pommel. The spearhead was an integral casting. The trellis pattern on the swords was probably produced by heating up a tin-rich paste applied to the surface and the thin hexagonal star decoration pattern on the spearhead was probably produced by brush painting with a mercury-tin amalgam followed by heating.

William S. Shore

William S. Shore, 94, died on Dec. 6, 2019, in Davenport, Iowa. “My father was an inquisitive man to the day he died. He loved eclipses and world travel and wanted know the star patterns. He researched the local geology of wherever he was. He had topographical maps when he traveled about the United States and to other countries. He kept up with scientific progress and made sure those around him did too. He helped start the local chapter of the Honor Flight of the Quad Cities.”—Sarah J. Shore, daughter Most recent title: Environmental coordinator, Rock Island Arsenal Education: BS, chemical technology, Iowa State University, 1949; PhD, physical chemistry, University of Iowa, 1953 Survivors: Daughters, Catherine Martinez, Margaret, and Sarah; son, David To recognize your late loved one or colleague, submit obituary information at cenm.ag/obits.

Star Identification Based on Spider-Web Image and Hierarchical CNN

Unlike the traditional star pattern recognition algorithms that extract star features as a vector to be matched in a database, in this article, a spider-web image is constructed and a hierarchical convolution neural network (CNN) model is proposed to recognize this spider-web image. Stars are linked with different color lines based on the angle distance to enhance the discrimination of the spider-web images. A training dataset and testing dataset are constructed based on spider-web images for CNN model training. A hierarchical CNN model with two stages, which are designed to perform first step identification and recognize similar spider-web images, respectively, is proposed. Experiment results show that, compared with other algorithms, the proposed algorithm is more robust toward the position noise, magnitude noise, small numbers of stars in the field of view, and the presence of false stars.

Algorithm with Patterned Singular Value Approach for Highly Reliable Autonomous Star Identification.

In the work reported in this paper, a lost-in-space star pattern identification algorithm for agile spacecraft was studied. Generally, the operation of a star tracker is known to exhibit serious degradation or even failure during fast attitude maneuvers. While tracking methods are widely used solutions to handle the dynamic conditions, they require prior information about the initial orientation. Therefore, the tracking methods may not be adequate for autonomy of attitude and control systems. In this paper a novel autonomous identification method for dynamic conditions is proposed. Additional constraints are taken into account that can significantly decrease the number of stars imaged and the centroid accuracy. A strategy combining two existing classes for star pattern identification is proposed. The new approach is intended to provide a unique way to determine the identity of stars that promises robustness against noise and rapid identification. Moreover, representative algorithms implemented in actual space applications were utilized as counterparts to analyze the performance of the proposed method in various scenarios. Numerical simulations show that the proposed method is not only highly robust against positional noise and false stars, but also guarantees fast run-time, which is appropriate for high-speed applications.

Traditional Ecological Knowledge for Climate Change Assessment and Rainfall Prediction: A Case of Adami Tulu Jido Kombolcha District, Oromia Region, Ethiopia

Data on environmental problems of the area, local manifestations of climate change, climate change coping strategies, rainfall prediction mechanisms and their threats were collected in three systematically selected administrative units of the study area using focus group discussion, key informant interview and household (HH) survey from May to June, 2017. Focus group (FG) discussion that participate youth, elders, women, religion and tradition leaders and experts with average members of 15 was organized at each administrative units. Sample key informants (KI) were selected by the focus group members by setting criteria to get deep information. HH survey was conducted from randomly selected 92 HHs samples determined by Kothari (2004). Qualitative data analysis method was used to summarize the information. Results showed that environmental problems in the area are directly or indirectly related to climate. And the communities rely on their indigenous rainfall prediction using meteorological, astronomic and animal behavioral indicators. The main indicators are: wind direction, appearance and shape of cloud, star pattern, moon’s appearance, cattle behavior, chirping of bird, bee’s migration, and color of lake and appearance of rainbow. The study also depicted that most (85%) of the communities heavily rely on the indigenous knowledge for planning agricultural activities or early warnings for preparedness. However, it has been threatened due to critics by religious people, lack of trust of young generation, degradation of the indicators and lack of documentation. There is need for careful evaluation and enhancement for social-ecological resilience of the vulnerable communities.

Improved Grid Algorithm Based on Star Pair Pattern and Two-dimensional Angular Distances for Full-Sky Star Identification

A fast and robust star identification algorithm is proposed in this paper. The algorithm is derived from the grid algorithm but significantly improves the robustness by increasing the probability of the correct close neighbor star and reducing the pattern noise. Firstly, star pair patterns are constructed rather than star patterns. And a traversal method is adopted to find all the possible closest neighbor stars, which improves the robustness towards brightness noise. Secondly, the two-dimensional angular distance features are used instead of grid features in Cartesian coordinates to improve the robustness towards positional noise. The simulation results show that the proposed algorithm is quite robust to a variety of noise conditions. The identification rate of the proposed algorithm is higher than the grid algorithm and similar to the pyramid algorithm, while the identification speed is up to dozens times faster than the pyramid algorithm.

Characterization of manufacturability of microstructures for micro-injection moulding of micro devices using star patterns

The replication accuracy of micro features plays a very important role in polymeric micro devices, such as microfluidic and micro optics. However, there is no effective way at the moment for the assessment of manufacturability of such microstructures. This study develops a new method of using a star pattern with a continuous change of width and aspect ratio to characterize the manufacturability of microstructures. The designed patterns have a width from 20 microns to 320 microns with an aspect ratio from 2.5 to 0.156. Concentric markers are designed on the star patterns for the easy identification of achievable feature accuracy under various processes. It is found that the dry etching and electroforming cause a depth error of less than 5%, while the maximum error from injection moulding is 2.8% where the channel aspect ratio is less than 1. However, when the aspect ratio of protrusion microstructures is higher than 1 with a width of 50 µm, insufficient filling occurs under nominal injection moulding conditions with relative error more than 10%. The designed star patterns are proved to be an easy and fast way to determine achievable feature accuracy for polymer micro replication processes, including injection moulding and hot embossing.