Astronomical Events Research Articles

Exploiting Isospin Symmetry to Study the Role of Isomers in Stellar Environments.

Proton capture on the excited isomeric state of ^{26}Al strongly influences the abundance of ^{26}Mg ejected in explosive astronomical events and, as such, plays a critical role in determining the initial content of radiogenic ^{26}Al in presolar grains. This reaction also affects the temperature range for thermal equilibrium between the ground and isomeric levels. We present a novel technique, which exploits the isospin symmetry of the nuclear force, to address the long-standing challenge of determining proton-capture rates on excited nuclear levels. Such a technique has in-built tests that strongly support its veracity and, for the first time, we have experimentally constrained the strengths of resonances that dominate the astrophysical ^{26m}Al(p,γ)^{27}Si reaction. These constraints demonstrate that the rate is at least a factor ∼8 lower than previously expected, indicating an increase in the stellar production of ^{26}Mg and a possible need to reinvestigate sensitivity studies involving the thermal equilibration of ^{26}Al.

Revealing the cosmic reionization history with fast radio bursts in the era of Square Kilometre Array

ABSTRACT Revealing the cosmic reionization history is at the frontier of extragalactic astronomy. The power spectrum of the cosmic microwave background (CMB) polarization can be used to constrain the reionization history. Here, we propose a CMB-independent method using fast radio bursts (FRBs) to directly measure the ionization fraction of the intergalactic medium (IGM) as a function of redshift. FRBs are new astronomical transients with millisecond time-scales. Their dispersion measure (DMIGM) is an indicator of the amount of ionized material in the IGM. Since the differential of DMIGM against redshift is proportional to the ionization fraction, our method allows us to directly measure the reionization history without any assumption on its functional shape. As a proof of concept, we constructed mock non-repeating FRB sources to be detected with the Square Kilometre Array, assuming three different reionization histories with the same optical depth of Thomson scattering. We considered three cases of redshift measurements: (A) spectroscopic redshift for all mock data, (B) spectroscopic redshift for 10 per cent of mock data, and (C) redshift estimated from an empirical relation of FRBs between their time-integrated luminosity and rest-frame intrinsic duration. In all cases, the reionization histories are consistently reconstructed from the mock FRB data using our method. Our results demonstrate the capability of future FRBs in constraining the reionization history.

“仲康日食”与夏朝历史的天文学新证据（The "Zhongkang Solar Eclipse" and New Astronomical Evidence for the History of Xia Dynasty）

Chinese Abstract: “仲康日食”是古代著名的天文学事件，对这起具体事件的天文与文献考据由来已久， 古今学者测算其发生时间大致在前2165~前1876年之间。在《发现夏朝》一书中，详细论证了古埃及文明就是夏朝，第十三王朝后期国王默克赫佩尔就是仲康。我们通过使用开源天文软件Stellarium 发现与第十三王朝默克赫佩尔统治时期相近的公元前1700年10月20日的农历秋季，在古埃及地区上空的天蝎座（房宿与心宿）位置，果然发生了一次日食。这次天文学现象，与史书关于“仲康日食”发生的时间和位置描述“乃季秋月朔，辰弗集于房”高度吻合。这既说明“仲康日食”真实发生过，为夏朝历史的真实存在，及古埃文明就是夏朝，增添了新的天文学证据，也说明《尚书·夏书·胤征》和《竹书纪年》等上古资料具有重要的史学和埃及学价值。 English Abstract: The Solar Eclipse is a significant astronomical event in ancient times, of which a long history of extensive research and documentation exist. Ancient and modern scholars estimated the range of time for the event fall in the range of 2165-1876 BC. In the book Discovery of Xia Dynasty, it was demonstrated that the ancient Egyptian civilization was the Xia Dynasty recorded in ancient Chinese literatures, and Egyptian pharaoh Merkheperre of the late Thirteenth Dynasty was Chinese emperor Zhongkang of Xia Dynasty. Using Stellarium opensource software we found that in the lunar autumn of October 20, 1700 BC, which was close to the reign of Merkheperre of the Thirteenth Dynasty, a solar eclipse occurred in the position of Scorpio (House and Heart constellation) over ancient Egypt. This astronomical phenomenon is highly consistent with the description of the time and location of the Solar Eclipse in ancient Chinese chronicles. This indicates that the Solar Eclipse exists, adding new astronomical evidence for the existence of the Xia Dynasty and the ancient Egyptian civilization was indeed the Xia Dynasty. This finding also enhances the significance and importance of ancient Chinese chronicles such as Shangshu.Xiashu.Yinzheng and Bamboo Annals for Egyptology studies.

Pulmonary Hypertension Clinical Trials and COVID-19: A Discussion With John Ryan and Roham Zamanian

Pulmonary Hypertension Clinical Trials and COVID-19: A Discussion With John Ryan and Roham Zamanian

High cadence optical transient searches using drift scan imaging II: Event rate upper limits on optical transients of duration <21 ms and magnitude <6.6

Abstract We have realised a simple prototype system to perform searches for short timescale optical transients, utilising the novel drift scan imaging technique described by Tingay (2020). We used two coordinated and aligned cameras, with an overlap field of view of approximately 3.7 deg $^2$ , to capture over $34\,000 \times 5$ second images during approximately 24 h of observing. The system is sensitive to optical transients, due to an effective exposure time per pixel of 21 ms, brighter than a V magnitude of 6.6. In our 89.7 deg $^2$ h of observations, we find no candidate astronomical transients, giving an upper limit to the rate of these transients of 0.8 per deg $^2$ per day, competitive with other experiments of this type. The system is triggered by reflections from satellites and various instrumental effects, which are easily identifiable due to the two camera system. The next step in the development of this promising technique is to move to a system with larger apertures and wider fields of view.

Classification of multiwavelength transients with machine learning

ABSTRACT With the advent of powerful telescopes such as the Square Kilometer Array and the Vera C. Rubin Observatory, we are entering an era of multiwavelength transient astronomy that will lead to a dramatic increase in data volume. Machine learning techniques are well suited to address this data challenge and rapidly classify newly detected transients. We present a multiwavelength classification algorithm consisting of three steps: (1) interpolation and augmentation of the data using Gaussian processes; (2) feature extraction using wavelets; and (3) classification with random forests. Augmentation provides improved performance at test time by balancing the classes and adding diversity into the training set. In the first application of machine learning to the classification of real radio transient data, we apply our technique to the Green Bank Interferometer and other radio light curves. We find we are able to accurately classify most of the 11 classes of radio variables and transients after just eight hours of observations, achieving an overall test accuracy of 78 per cent. We fully investigate the impact of the small sample size of 82 publicly available light curves and use data augmentation techniques to mitigate the effect. We also show that on a significantly larger simulated representative training set that the algorithm achieves an overall accuracy of 97 per cent, illustrating that the method is likely to provide excellent performance on future surveys. Finally, we demonstrate the effectiveness of simultaneous multiwavelength observations by showing how incorporating just one optical data point into the analysis improves the accuracy of the worst performing class by 19 per cent.

‘The moon quivered like a snake’: A medieval chronicler, lunar explosions, and a puzzle for modern interpretation

Despite some scepticism, the suggestion by Hartung in 1976 that the report in the chronicle of Gervase of Canterbury corresponded to a meteorite impact with the moon in 1178, creating the Giordano Bruno crater, retains considerable support, particularly in popular scientific writing. Nevertheless, a series of studies of images of the crater from orbiting satellites, although confirming its young geological age, have indicated that it was not created within recorded human history. In this paper, we examine astronomical entries in Gervase’s chronicle relating to eclipses and conclude that, despite there being descriptions of miracles elsewhere in the manuscript, he himself was a reliable reporter of astronomical events. On this basis an alternative suggestion can be put forward for the splitting of the horns and writhing of the body of the new moon, reported to Gervase: atmospheric turbulence. Although general atmospheric turbulence has been previously dismissed as too small an effect, it is possible to show that the description is consistent with viewing the new moon through a column of hot air from a fire, at a moderate distance and out of the line of sight of the observers. This interpretation of the medieval evidence as credible but unrelated to a lunar event is consistent with twenty-first century lunar studies.

Corrosion resistance study of UNS A96110 aluminum alloy in chloride-sulphate solution

Electrochemical analysis of the corrosion resistance of UNS A96110 aluminum alloy (UN6110) in neutral chloride media at 0.5%, 1%, 1.5%, 2%, 2.5%, 3% and 3.5% NaCl concentration, and 3.5% NaCl/sulphuric acid solution at concentrations of 0.00625 M and 0.1 M by potentiodynamic polarization method. UN6110 exhibited lower corrosion in the acid chloride solution compared to the results obtained from the neutral chloride media. The lowest corrosion rate (0.097 mm/y) was obtained from the neutral chloride solution at 0.5% NaCl corresponding to corrosion current density of 8.78 x 10-6 A/cm2 and polarization resistance of 2927 Ω while the highest value 0.344 mm/y was obtained at 3.5% NaCl concentration. Polarization plot showed significant variation at the anodic portion of the polarization plots with visible potential transients on the passivation portion of the plot. The aluminium alloy exhibited passivation reaction mechanisms due to formation and breakdown of the inert protective oxide. Variation of the cathodic polarization plots shows activation controlled reduction reactions. In sulphate-chloride solution, corrosion rate UN6110 significantly increased to 15.855 mm/y at 0.00625 M and 20.017 mm/y 0.1 M. Optical images obtained from the neutral chloride solution showed the presence of large micro corrosion pits and grooves due to the electrochemical action of chlorides. This differs from the images obtain from the acid chloride solution which showed general surface deterioration couple with well-defined micro and macro corrosion pits.

Serious Gaming for Virtual Archaeoastronomy

Many cultures worldwide have left traces of sacred architecture and monuments which often show correlation to astronomical events like solstitial sunrises. Virtual archaeology can be used to explore such orientation patterns using digital reconstructions and positions of celestial objects computed from modern astronomical models. Most 3D editing systems used to build virtual reconstructions of such monuments however fail to provide astronomically accurate solar illumination models which can recreate the slightly different solar positions of antiquity or even prehistory, and even worse, any usable representation of the night sky. In recent years, two systems created independently by the authors of this study have been utilized for investigations into the orientation of architecture with respect to celestial processes. Both had their advantages and shortcomings compared to each other. One extended a dedicated open-source desktop astronomy program with a 3D rendering engine where such monuments can be investigated in the first-person perspective by interactive walkthrough. The other system uses a game engine and external online resources which provides only solar or planetary positions, but no star data. This study presents ways of connecting both systems in an attempt to take advantage of the best of both approaches.

Classifying image sequences of astronomical transients with deep neural networks

ABSTRACT Supervised classification of temporal sequences of astronomical images into meaningful transient astrophysical phenomena has been considered a hard problem because it requires the intervention of human experts. The classifier uses the expert’s knowledge to find heuristic features to process the images, for instance, by performing image subtraction or by extracting sparse information such as flux time-series, also known as light curves. We present a successful deep learning approach that learns directly from imaging data. Our method models explicitly the spatiotemporal patterns with deep convolutional neural networks and gated recurrent units. We train these deep neural networks using 1.3 million real astronomical images from the Catalina Real-Time Transient Survey to classify the sequences into five different types of astronomical transient classes. The TAO-Net (for Transient Astronomical Objects Network) architecture outperforms the results from random forest classification on light curves by 10 percentage points as measured by the F1 score for each class; the average F1 over classes goes from $45{{\ \rm percent}}$ with random forest classification to $55{{\ \rm percent}}$ with TAO-Net. This achievement with TAO-Net opens the possibility to develop new deep learning architectures for early transient detection. We make available the training data set and trained models of TAO-Net to allow for future extensions of this work.

A new era of radio transients

AbstractLaura Driessen reviews the history of radio transient astronomy, details current investigations of a wide range of radio transients with Square Kilometre Array pathfinder and precursor instruments, and discusses what the SKA will reveal about the changing radio sky.

Testing thermodynamics method for salt intrusion during infrequent astronomical event

Knowledge of the processes governing salt intrusion in estuaries is important since it influences the eco-environment of estuaries as well as its water resource potential in many ways. The aim of this paper is to test the effectiveness of the new 1-D thermodynamic salt intrusion equation proposed by Zhang and Savenije (i.e., is an extreme power theory for the mixing of saline sea water and fresh river water in estuaries); and existing salt intrusion model (i.e., Van der Burgh method) at two previously unsurveyed estuaries in India and Morocco. To successfully perform the analysis using the 1-D models, real time data is required. Field measurements during infrequent astronomical event were recorded along the estuaries (31/01/2018 for Ashtamudi estuary (India); and during 31/01/2018 for Bouregreg estuary (Morocco)). Shape (geometry) and salinity analyses were performed on each of the estuaries. The results obtained show good agreement between the simulated and observed salinity distribution in the estuaries with high R 2 values. Finally, by utilizing the new predictive equation, we can estimate the minimum amount of river discharge needed, and the maximum allowable depth for dredging, to prevent saline water intruding further into the areas studied. Thus, the simple and effective approach presented in this study can describe the current state of salt intrusion in India and Morocco estuaries, and be used for future development.

MANTRA: A Machine-learning Reference Light-curve Data Set for Astronomical Transient Event Recognition

Abstract We introduce Many ANnotated TRAnsients (MANTRA), an annotated data set of 4869 transient and 71207 non-transient object light curves built from the Catalina Real-time Transient Survey. We provide public access to this data set as a plain text file to facilitate standardized quantitative comparison of astronomical transient event recognition algorithms. Some of the classes included in the data set are: supernovae, cataclysmic variables, active galactic nuclei, high proper motion stars, blazars, and flares. As an example of the tasks that can be performed on the data set we experiment with multiple data preprocessing methods, feature selection techniques, and popular machine-learning algorithms (support vector machines, random forests, and neural networks). We assess quantitative performance in two classification tasks: binary (transient/non-transient) and eight-class classification. The best-performing algorithm in both tasks is the random forest classifier. It achieves an F1 score of 96.25% in the binary classification and 52.79% in the eight-class classification. For the eight-class classification, non-transients (96.83%) is the class with the highest F1 score, while the lowest corresponds to high proper motion stars (16.79%); for supernovae it achieves a value of 54.57%, close to the average across classes. The next release of MANTRA includes images and benchmarks with deep learning models.

Simulations of Early Kilonova Emission from Neutron Star Mergers

Abstract We present radiative transfer simulations for blue kilonovae hours after neutron star (NS) mergers by performing detailed opacity calculations for the first time. We calculate atomic structures and opacities of highly ionized elements (up to the 10th ionization) with atomic number Z = 20–56. We find that the bound–bound transitions of heavy elements are the dominant source of the opacities in the early phase (t < 1 day after the merger) and that the ions with a half-closed electron shell provide the highest contributions. The Planck mean opacity for lanthanide-free ejecta (with electron fraction of Y e = 0.30–0.40) can only reach around at t = 0.1 days, whereas that increases up to at t = 1 day. The spherical ejecta model with an ejecta mass of M ej = 0.05 M ⊙ gives the bolometric luminosity of at t ∼ 0.1 days. We confirm that the existing bolometric and multicolor data of GW170817 can be naturally explained by the purely radioactive model. The expected early UV signals reach 20.5 mag at t ∼ 4.3 hr for sources even at 200 Mpc, which is detectable by the facilities such as Swift and the Ultraviolet Transient Astronomy Satellite (ULTRASAT). The early-phase luminosity is sensitive to the structure of the outer ejecta, as also pointed out by Kasen et al. Therefore, the early UV observations give strong constraints on the structure of the outer ejecta and the presence of a heating source besides r-process nuclei.

Babylonian observations of a unique planetary configuration

In this paper, we discuss Babylonian observations of a “massing of the planets” reported in two Astronomical Diaries, BM 32562 and BM 46051. This extremely rare astronomical phenomenon was observed in Babylon between 20 and 30 March 185 BC shortly before sunrise when all five planets were simultaneously visible for about 10 to 15 min close to the horizon in the eastern morning sky. These two observational texts are not only interesting as records of an extremely rare planetary configuration, but also because (1) the observers appear to be confused by the presence of all planets simultaneously and mix them up in their reports, and (2) the two reports of the same observations are so different that we are forced to conclude that they were carried out by two different observers. There is an additional astronomical event which makes this planetary configuration even more unique: the exact conjunction of the planets Mars and Jupiter in the afternoon of 25 March 185 BC. An exact conjunction, where two planets are so close together that they appear as one object in the sky, is also extremely rare. Although this exact conjunction between Mars and Jupiter occurred during the day so that it was not observable, it was correctly predicted by the Babylonian scholars: a remarkable achievement and a nice illustration of their astronomical craftsmanship. Finally, our study clearly exposes one of the limitations of Babylonian naked-eye astronomy. When first appearances of the planets Mercury, Mars and Saturn are expected around the same date, it is nearly impossible to correctly identify them because their expected positions are only approximately known while they have about the same visual magnitude so that they become visible at about the same altitude above the horizon.

Measurement of the tilt of the Earth’s axis during a lunar eclipse using a simple method

In this study, the tilt of the Earth’s axis was measured during a lunar eclipse using a telescope based on the angle between the lunar orbit and ecliptic planes being considered as approximately zero. The presented method not only offers a practical and reliable way of measuring the axial tilt of the Earth during a lunar eclipse but also helps in providing a higher argumentation-based conceptual understanding and awareness of astronomical events and their results through the combination of observation with measurement.

Developing the Chemist’s Inner Coder: A MATLAB Tutorial on the Stochastic Simulation of a Pseudo-First-Order Reaction

The drive in computational methods and more intuitive software has seen a rise in the number of publications in this area in recent years. Computational simulations can be found in many areas of science from computational biology and chemistry to fundamental physics. These may help synthetic chemists in their drug discovery endeavors and cosmologists predicting astronomical events. This paper is designed to equip chemists with a basic understanding of how loops and conditional statements can be used within both the MATLAB syntax and Excel spreadsheets to simulate dynamic processes. Many commercial software packages require little to no programming and often do not explicitly display the underlying calculations. While these programs are often very efficient for solving a specific problem, they are somewhat limited. Principally, this practical uses a stochastic simulation algorithm to generate the kinetic data of a reversible association reaction. The kinetic data is analyzed using the standard rate laws to highlight to students the effectiveness of this method. Ultimately, the skills developed in this practical will help students in future computational projects, where bespoke coding is necessary.

Where are Solar storm-induced whale strandings more likely to occur?

AbstractWhale strandings occur in many places worldwide and numerous possible explanations for this phenomenon have been proposed, including the effects of astronomical events such as Solar eruptions on the Earth's magnetic field. Whales use the geomagnetic field for navigation, and its distortion can therefore result in whale strandings in certain regions. However, Solar storms do not have the same impact on the geomagnetic field across the whole of the Earth's surface, and positions nearer to the equator are less exposed to this phenomenon. It is therefore plausible that Solar storms can explain whale strandings at high latitude at least, but not necessarily worldwide. This review considers strandings in relation to the geographical and geomagnetic properties of locations at higher latitudes and to changes in the magnetic field over recent centuries. It also focuses on a Solar storm in December 2015. These considerations suggest that navigation errors due to Solar storms are more likely to occur at higher latitudes, particularly in sea areas where the animals might subsequently swim into a geographic trap and become stranded. For sperm whales (Physeter macrocephalus), the southern Norwegian Sea in conjunction with the shallow North Sea represents such an area.

Christmas 1668 and After: How Jesuit Astronomy Was Restored to Power in Beijing

This article offers new insights into a series of dramatic events that took place at the imperial Chinese court in December 1668, in which astronomy, politics, and religion all played major roles. Jesuit missionaries had served the Manchu rulers of the Qing 清dynasty as official astronomers since the dynasty seized Beijing in 1644. But in autumn 1664, the Jesuits at court were imprisoned as a result of a prosecution launched by a Chinese scholar, Yang Guangxian 楊光先. After initial sentences of death or banishment on those Jesuits principally concerned had been commuted to house arrest in May 1665, they spent the next few years confined to their residence, while their missionary colleagues elsewhere in China were removed to Canton. As a result of what took place during the months from December 1668 to summer 1669, the Jesuits were restored to imperial favour, and the responsibility for astronomy was once more placed in their hands. In this article, which arises from our research for a book-length study in preparation, we use a number of previously unexploited contemporary accounts in languages including Portuguese, French, Latin, Chinese, and Manchu to reveal a new picture of the close interplay of political and astronomical events that took place during the period of the Jesuits’ rehabilitation by the Qing court.

The Poetics of Power: Latin Poetic Responses to Early Imperial Iconography by Nandini B. Pandey

Reviewed by: The Poetics of Power: Latin Poetic Responses to Early Imperial Iconography by Nandini B. Pandey Spencer Cole Nandini B. Pandey. The Poetics of Power: Latin Poetic Responses to Early Imperial Iconography. Cambridge: Cambridge University Press, 2018. Pp. xiii, 302. $105.00. ISBN 978-1-108-42265-9. Augustus' consolidation of autocratic rule is often credited to a concerted cultural project that normalized the emergent Principate with a pervasive new symbolic language of power. Paul Zanker's influential The Power of Images in the Age of Augustus (Ann Arbor 1988) is a classic analysis of this Augustan "cultural program" that serves as a touchstone for Pandey's erudite and engaging book. Like Zanker—and G. K. Galinsky's Augustan Culture: An Interpretive Introduction (Princeton 1996)—Pandey has a holistic approach that explores dialogic interactions of artifacts and architecture, ritual, and literary texts. Pandey's primary point of departure is a deeper engagement with Augustan poets, with a focus on their "public responses to imperial iconography as a tool for dissecting, debating, even disrupting imperial power" (5). Also central to this study is a sustained analysis of how these poets enact a collaborative public process of constructing authority in the formative years of imperial rule at Rome. For Pandey, imperial authority is not simply imposed by a unified, top-down master plan to orchestrate public perceptions; it also depends on critical affective roles of the populace/audience that determine meanings and delegate power. An important new dimension is therefore introduced into the conventional poet/ princeps power nexus: both modes of imperial and poetic authority are, in Pandey's estimation, produced by "a mutually constitutive relationship with a judging audience" (6). This approach is informed by reader response and reception theory, and questions about the perils of reconstructing ancient interpretive communities are answered with an apt assemblage of ancient evidence and modern scholarship. There is also an astute nod to the phenomenon of 21st-century fandom and its decentralized, social-media powered "participatory culture," although conceiving of ancient Roman social communication as a "bottom-up, largely unregulated process of distributed content creation by individuals from all rungs of society" (10) may be an anachronistic overcorrection of the top-down model that this book interrogates. The argument is structured around four symbolically rich Augustan sites and spectacles: Caesar's comet (Sidus Iulium), the Palatine hill, the Forum Augustum, and early imperial triumphal ritual. The first case-study (chapter 2: "History in Light of the Sidus Iulium") realizes a programmatic goal of the book "to dismantle the impression of finality and conscious design that still attaches to many Augustan symbols" (8). Pandey showcases an agile command of a range of ancient sources (especially literary and numismatic here) and offers powerful proofs of authorial and audience agency in developing and reshaping imperial imagery. The comet that appeared in 44 bce at Julius Caesar's funeral games becomes a principal symbol of Caesar's apotheosis, a symbol that has been seen since Servius as a product of Octavian's masterly spin in response to the fortuitous astronomical event. Pandey counters this reductive, retrospective causality with detailed analysis of representations of the comet on early coinage, and with close readings that track its decades-spanning reception in Horace, Propertius, Vergil, and Ovid. This rich chapter unravels a complex heterogeneous DNA for the comet imagery that belies notions of a calculated early cultural initiative directed by the future emperor. Pandey acknowledges that Augustan poets and their readers represent a "narrow Roman demographic" (4), but attention to public spaces and spectacles [End Page 228] in chapters 3 to 5 facilitates consideration of how broader audiences could participate in the generation of meaning and the granting of power. As with the comet coins, emphasis is placed on divergent receptions at different times and places as imperial buildings and rituals come into focus. Tracing representations of the Augustan Palatine complex from Propertius (2.31/32) through a later Ovidian visitation (Tristia 3.1) again reveals manifold, multi-year accretions of meaning rather than a preconceived program systematically imposed after Actium. The Aeneid plays a big part in this book: discussions of "internal audiences" that figure readers as co-viewers...