Bright Objects Research Articles

A strange sky: Security atmospheres and the technological management of geopolitical conflict in the case of Israel's Iron Dome

AbstractThis paper uses Israel's technologically advanced Iron Dome short‐range missile defence system as a deep empirical case study to examine how affective atmospheres mediate the relationship between state power and the agency of technological objects deployed to govern (in)security. Drawing theoretically from productive tensions between more‐than‐human theories of object‐oriented ontology, actor‐network theory and affect theory, it evaluates Iron Dome as a scintillating ‘bright object’ with variable capacities and limitations that exceed the sum of its components. Iron Dome both overreaches and contradicts the intentions and governance logics of state elites within a spatio‐temporally distributed array of architectures, infrastructures and practices. Within this milieu, its affective power is ambivalent and capricious, and can both enhance and undermine the atmospheric production of security in ways that exceed both instrumental functionality and human intentions. These findings indicate how a geography of security that attends to the affective dimension of object politics can account for the complex and non‐causal ways in which technologies can either reinforce or inhibit security as an anthropocentric endeavour.

Quality Improvement Project: Number of Neurofibromatosis Type I Patients with Unidentified Bright Objects (UBOs) on MRI that Developed Subsequent Gliomas (P3-9.005)

Quality Improvement Project: Number of Neurofibromatosis Type I Patients with Unidentified Bright Objects (UBOs) on MRI that Developed Subsequent Gliomas (P3-9.005)

A first eROSITA view of ultracool dwarfs

We present the first X-ray detections of ultracool dwarfs (UCDs) from the first all-sky survey of the extended ROentgen Survey with an Imaging Telescope Array (eROSITA) onboard the Russian Spektrum-Roentgen-Gamma mission. We use three publicly available input catalogs of spectroscopically confirmed UCDs and Gaia-selected UCD candidates that together comprise nearly 20000 objects. In a careful source identification procedure we first extracted all X-ray sources from the catalog of the first survey, eRASS1, that have a UCD or candidate within three times their positional uncertainty. Then we examined all Gaia objects in the vicinity of these 96 X-ray sources and we associated them to the most plausible counterpart on the basis of their spatial separation to the X-ray position and their multiwavelength properties. This way we find 40 UCDs that have a secure identification with an X-ray source (that is bonafide UCD X-ray emitters) and 18 plausible UCD X-ray emitters for which we consider it likely that the X-ray source has its origin in the UCD. Twenty-one of the bonafide and plausible X-ray emitting UCDs have a spectroscopic confirmation, while the others have been selected based on Gaia photometry and we computed spectral types from the G–J color. The spectral types of the X-ray emitting UCDs and candidates range between M5 and M9. The distances of the eRASS1 UCDs range from 3.5 to 190 pc. The spectroscopically confirmed UCDs at the high end of the distance distribution are known to be members of nearby star forming regions. The majority of the UCDs from the eRASS1 sample show a ratio of X-ray to bolometric luminosity well above the canonical saturation limit of log (Lx/Lbol) ≈ −3. For the two most extreme outliers, we verified the hypothesis that these high values are due to flaring activity through an analysis of the eRASS1 light curve. X-ray spectra could be analyzed for the two brightest objects in terms of count rate, both showing an emission-measure weighted plasma temperature of 〈kT〉 = 0.75 keV. These observations demonstrate the potential of eROSITA for advancing our knowledge on the faint coronal X-ray emission from UCDs by building statistical samples for which the average X-ray brightness, flares, and coronal temperatures can be derived.

«Что делали для нас статуэтки?» Магия и агентность в преистории Балкан и Карпат

The work of Mary Helms and Alfred Gell on cultural transformations, object colour and brilliance and their links to ritual power emphasises the most important aspect of magic for objects — its agency. The aesthetic of exotic, bright and colourful objects in the Neolithic and Copper Age of ‘Old Europe’ was central to the objects’ agency. However, the vast majority of figurines from this region was neither polished nor highly coloured, nor even decorated — sometimes showing signs of rapid production for short-term usage. Yet there is a widespread notion that figurines had the potential to produce special effects in ritual practice. Just as the agency of figurines is ‘culture-specific’ as well as context-specific, their potency depended upon a widespread underlying acceptance of what this particular class of objects could do for people. Here we pose two questions: how did figurines perform their agency? and was figurine’s agency fundamentally different from the agency of bright, colourful, exotic objects? We present four examples of the magical effects — i. e. the agency — of figurines from the Mesolithic, Neolithic and Copper Age of Old Europe: the efficacy of Lepenski Vir fish-persons; how figurines contributed to the practice of black magic in the Vinča group; the ability of the fragmentation of shiny, black Hamangia figurines to achieve significant social effects; and the arrangement of Cucuteni figurine sets to educate women about (in)fertility.

Constrained Attitude Maneuvering via Modified-Rodrigues-Parameter-Based Motion Planning Algorithms

The attitude dynamics and control of a spacecraft becomes complex in the presence of constraints in its orientation. Such constraints consist in not pointing sensitive payload toward bright objects in space or, vice versa, keeping the same bright objects within some instrument’s field of view. This paper investigates the applicability of nonsingular attitude motion planning algorithms to navigate a three-dimensional grid in the Modified Rodrigues Parameter configuration space. The aim is to compute a constraint-compliant reference trajectory in Modified Rodrigues Parameter space that can be tracked to reorient a spacecraft from an initial attitude to a final attitude while also attempting at minimizing the required control effort. Nonzero initial and final angular rates are considered to yield a general solution. The path is constructed with B-spline curves that pass through each attitude waypoint. Further, a constant angular maneuver rate is imposed, which influences the speed at which the reference attitude traverses the B-spline solution. Simulations illustrate that constraint-compliant, control-torque-minimizing paths are found if the grid spacing is chosen to be fine enough.

Radial distributions of globular clusters trace their host dark matter halo: insights from the E-MOSAICS simulations

ABSTRACT Globular clusters (GCs) are bright objects that span a wide range of galactocentric distances, and can therefore probe the structure of dark matter (DM) haloes. In this work, we explore whether the projected number density radial profiles of GCs can be used to infer the structural properties of their host DM haloes. We use the simulated GC populations in a sample of 166 central galaxies from the $(34.4~\rm cMpc)^3$ periodic volume of the E-MOSAICS project. We find that more massive galaxies host stellar and GC populations with shallower density profiles that are more radially extended. In addition, metal-poor GC subpopulations tend to have shallower and more extended profiles than metal-rich subsamples, which we relate to the preferentially accreted origin of metal-poor GCs. We find strong correlations between the power-law slopes and effective radii of the radial profiles of the GC populations and the structural properties of the DM haloes, such as their power-law slopes, Navarro–Frenk–White scale radii, and concentration parameters. Accounting for a dependence on the galaxy stellar mass decreases the scatter of the two-dimensional relations. This suggests that the projected number counts of GCs, combined with their galaxy mass, trace the density profile of the DM halo of their host galaxy. When applied to extragalactic GC systems, we recover the scale radii and the extent of the DM haloes of a sample of early-type galaxies with uncertainties smaller than $0.2~\rm dex$. Thus, extragalactic GC systems provide a novel avenue to explore the structure of DM haloes beyond the Local Group.

Thethesanproject: Lyman-α emission and transmission during the Epoch of Reionization

ABSTRACTThe visibility of high-redshift Lyman-alpha emitting galaxies (LAEs) provides important constraints on galaxy formation processes and the Epoch of Reionization (EoR). However, predicting realistic and representative statistics for comparison with observations represents a significant challenge in the context of large-volume cosmological simulations. The thesan project offers a unique framework for addressing such limitations by combining state-of-the-art galaxy formation (IllustrisTNG) and dust models with the arepo-rt radiation-magnetohydrodynamics solver. In this initial study, we present Lyman-alpha centric analysis for the flagship simulation that resolves atomic cooling haloes throughout a $(95.5\, \text{cMpc})^3$ region of the Universe. To avoid numerical artefacts, we devise a novel method for accurate frequency-dependent line radiative transfer in the presence of continuous Hubble flow, transferable to broader astrophysical applications as well. Our scalable approach highlights the utility of LAEs and red damping-wing transmission as probes of reionization, which reveal nontrivial trends across different galaxies, sightlines, and frequency bands that can be modelled in the framework of covering fractions. In fact, after accounting for environmental factors influencing large-scale ionized bubble formation such as redshift and UV magnitude, the variation across galaxies and sightlines mainly depends on random processes including peculiar velocities and self-shielded systems that strongly impact unfortunate rays more than others. Throughout the EoR local and cosmological optical depths are often greater than or less than unity such that the exp (− τ) behaviour leads to anisotropic and bimodal transmissivity. Future surveys will benefit by targeting both rare bright objects and Goldilocks zone LAEs to infer the presence of these (un)predictable (dis)advantages.

A Brightness Classification Boundary in the Kuiper Belt Population

Abstract The Kuiper Belt contains a large number of minor bodies that collectively constrain the dynamical history of the solar system. These bodies are often classified into distinct populations. This note identifies a well-defined boundary (at H-magnitude = 5.65) that separates bright (large) objects from dimmer (smaller) objects. The probability that the two sub-samples are drawn from the same underlying distribution is p ∼ 10−15. The larger bodies (estimated radius R ≳ 125 km) are dynamically hot, as measured by their locations in the e- sin i plane, and likely represent an implanted population. The smaller bodies (R ≲ 125 km) are dynamically colder and are likely to be primordial. The bright/large/hot population currently contains ∼200 members, including all ∼50 dwarf planet candidates in the Kuiper Belt.

Analysis of a JWST NIRSpec Lab Time Series: Characterizing Systematics, Recovering Exoplanet Transit Spectroscopy, and Constraining a Noise Floor

Abstract The James Webb Space Telescope’s (JWST) NIRSpec instrument will unveil the nature of exoplanet atmospheres across the wealth of planet types, from temperate terrestrial worlds to ultrahot Jupiters. In particular, the 0.6–5.3 μm PRISM mode is especially well suited for efficient spectroscopic exoplanet observations spanning a number of important spectral features. We analyze a lab-measured NIRSpec PRISM mode Bright Object Time Series observation from the perspective of a JWST user to understand the instrument performance and detector properties. We create two realistic transiting exoplanet time-series observations by performing injection-recovery tests on the lab-measured data to quantify the effects of real instrument jitter, drift, intrapixel sensitivity variations, and 1/f noise on measured transmission spectra. By fitting the time-series systematics simultaneously with the injected transit, we can obtain more realistic transit-depth uncertainties that take into account noise sources that are currently not modeled by traditional exposure time calculators. We find that sources of systematic noise related to intrapixel sensitivity variations and point-spread function motions are apparent in the data at the level of a few hundred ppm but can be effectively detrended using a low-order polynomial with detector position. We recover the injected spectral features of GJ 436 b and TRAPPIST-1 d and place a 3σ upper limit on the detector noise floor of 14 ppm. We find that the noise floor is consistent with <10 ppm at the 1.7σ level, which bodes well for future observations of challenging targets with faint atmospheric signatures.

Wind properties of Milky Way and SMC massive stars: empirical Z dependence from cmfgen models

ABSTRACT Detailed knowledge about stellar winds and evolution at different metallicities is crucial for understanding stellar populations and feedback in the Local Group of galaxies and beyond. Despite efforts in the literature, we still lack a comprehensive, empirical view of the dependence of wind properties on metallicity (Z). Here, we investigate the winds of O and B stars in the Milky Way (MW) and Small Magellanic Cloud (SMC). We gathered a sample of 96 stars analysed by means of the nlte code cmfgen. We explored their wind strengths and terminal velocities to address the Z dependence, over a large luminosity range. The empirical wind–luminosity relation (WLR) obtained updates and extends previous results in the literature. It reveals a luminosity and Z dependence, in agreement with the radiatively driven wind theory. For bright objects (log L/L⊙ ≳ 5.4), we infer that $\dot{M} \sim Z^{0.5-0.8}$. However, this dependence seems to get weaker or vanish at lower luminosities. The analysis of the terminal velocities suggests a shallow Zn dependence, with n ∼ 0.1−0.2, but it should be confirmed with a larger sample and more accurate V∞ determinations. Recent results on SMC stars based on the PoWR code support our inferred WLR. On the other hand, recent bow-shocks measurements stand mostly above our derived WLR. Theoretical calculations of the WLR are not precise, specially at low L, where the results scatter. Deviations between our results and recent predictions are identified to be due to the weak wind problem and the extreme terminal velocities predicted by the models. The Z dependence suggested by our analysis deserves further investigations, given its astrophysical implications.

A SPHERE survey of self-shadowed planet-forming disks

To date, nearly two hundred planet-forming disks have been imaged at high resolution. Our propensity to study bright and extended objects does, however, bias our view of the disk demography. In this work, we aim to help alleviate this bias by analyzing fifteen disks targeted with VLT/SPHERE that look faint in scattered light. Sources were selected based on a low far-infrared excess from the spectral energy distribution. The comparison with the ALMA images available for a few sources shows that the scattered light surveyed by these datasets is only detected from a small portion of the disk extent. The mild anticorrelation between the disk brightness and the near-infrared excess demonstrates that these disks are self-shadowed: the inner disk rim intercepts much starlight and leaves the outer disk in penumbra. Based on the uniform distribution of the disk brightness in scattered light across all spectral types, self-shadowing would act similarly for inner rims at a different distance from the star. We discuss how the illumination pattern of the outer disk may evolve with time. Some objects in the sample are proposed to be at an intermediate stage toward bright disks from the literature, with either no shadow or with signs of azimuthally confined shadows.

Versatile monarch butterflies can switch navigation strategy

While the logistics of international travel remain off-putting as the Covid-19 pandemic ebbs and flows, creatures that routinely circumnavigate oceans and continents have continued undaunted. Arctic terns are still smashing long distance records while wildebeest move en masse in colossal herds. But the sovereign of the multigenerational migration has to be the monarch butterfly. Each spring, the original pioneers depart their overwintering grounds in Mexico for their Canadian summer home, yet it is their great-great-great-grandchildren that return ∼8 months later. ‘To keep a constant direction over this enormous distance, these animals rely on the sun for orientation’, says Myriam Franzke from the University of Wuerzburg, Germany. However, when the insects near their final destination, they may switch to other forms of guidance to select their ultimate landing site. Yet, no one had tested whether monarch butterflies can use other forms of navigation, beyond being directed by the sun, so Franzke, Christian Kraus, Maria Gayler, Keram Pfeiffer and Basil el Jundi, from the University of Wuerzburg, with David Dreyer from Lund University, Sweden, teamed up to test out the insect's homing instinct.‘We ordered the butterfly pupae from Costa Rica where they were raised in captivity’ says el Jundi, recalling that the adults began emerging from their chrysalises 3 days after their arrival in Germany. ‘It is always a remarkable moment when the small chrysalises turn into colourful butterflies with large wings’, says Franzke. Next, the team gently tethered individual butterflies at the centre of a cylindrical flight arena, allowing the insects to swivel in any direction as they took to the wing. Then, the scientists tested which directions the insects selected when they illuminated LEDs lining the wall of the arena, providing the insects with different views.Switching off three LED columns to show a 4 cm wide vertical dark band against a bright background, the team filmed the butterflies’ manoeuvres for 8 min, switching the position of the bar to the opposite side of the arena from time to time to make sure that the insects were still paying attention. Although the butterflies took hardly any notice of the bar initially, swivelling continually in different directions, by the end they were occasionally holding a steady direction toward one edge of the bar, before veering off again.In contrast, the monarchs seemed far more fixated by a bright vertical bar against a dark background. Some flew directly toward the light for the full 8 min, only switching direction when the bar shifted spontaneously to the other side of the arena: they were definitely attracted to the bright object. But how would the insects fare when the team presented them with a single illuminated green LED, which the butterflies mistake for the sun?This time, the insects set a bearing relative to the fake sun and tended to keep to that path, rotating through 180 deg each time the simulated sun jumped to the other side of the arena. They were using the bright light as a compass guiding their choice of direction, as if they were dispersing toward Canada or returning to Mexico to overwinter. And when the researchers alternated the bright vertical bar with the simulated sun, the butterflies flew persistently toward the bar, but switched direction and set a bearing when the fake sun flashed into view.‘[Monarch] butterflies can switch between compass orientation and attraction’, says el Jundi, and the team suspects that the insects depend on specialised guidance circuits in the brain when navigating over long distances by the sun, but have the ability to switch with ease and simply gravitate toward an object when close to home.

Modeling Buried Object Brightness and Visibility for Ground Penetrating Radar

Comparing the observed brightness of various buried objects is a straightforward way to characterize the performance of a ground penetrating radar (GPR) system. However, a limitation arises. A simple comparison of buried object brightness values does not disentangle the effects of the GPR system itself from the system's operating environment and the objects being observed. Therefore, with brightness values exhibiting an unknown synthesis of systemic, environmental, and object factors, GPR system analysis becomes a convoluted affair. In this work, we use an experimentally collected dataset of over 25,000 object observations from five different multi-static radar arrays to develop models of buried object brightness and control for these various effects. Our modeling efforts provide a means for quantifying the relative brightness of GPR systems, the objects they detect, and the physical properties of those objects which influence observed brightness. To evaluate the models' performance on new object observations, we repeatedly simulate fitting them to half the dataset and predicting the observed brightness values of the unseen half. Additionally, we introduce a method for estimating the probability that individual observations constitute a visible object, which aids in failure analysis, performance characterization, and dataset cleaning.

Webb telescope goes into space

Webb telescope goes into space

Cloud Detection for Pleiades and SPOT 6/7 Imageries Using Modified K-means and Deep Learning

<p class='IJASEITAbtract'>Cloud detection is one of the important stages in optical remote sensing activities as the cloud's existence interferes with the works. Many methods have been developed to detect the cloud, but it is still a few methods for high-resolution images, which mostly have limited multispectral bands. In this paper, a novel method of cloud detection for the images is proposed by integrating an unsupervised algorithm and deep learning. This method has three main steps: (1) pre-processing; (2) segmentation using modified K-means; and (3) cloud detection using CNN. In the segmentation step, an unsupervised algorithm, K-means is modified and used to divide pixels values into k clusters. Our modified K-means method can separate thin clouds from relative bright objects in gray clusters that will be grouped into potential cloud pixels. Afterward, a design of convolutional neural network (CNN) is used to extract the multi-scale features from each cluster and classify them into two classes: (1) cloud, which consists of thin cloud and thick cloud, and (2) non-cloud. The potential cloud area from the first step is used for guiding the result of CNN to provide accurate cloud areas. Several Pleiades and SPOT 6/7 images were used to test the reliability of the proposed method. As a result, our modified K-means has an improvement to increase the accuracy of the results. The results showed that the proposed method could detect cloud and non-cloud accurately and has the highest accuracy of the results compared to the other methods.

Research on performances of back-illuminated scientific CMOS for astronomical observations

To evaluate performances of a back-illuminated scientific CMOS (sCMOS) camera for astronomical observations, comparison tests between Andor Marana sCMOS and Andor iKon-L 936 CCD cameras were conducted in a laboratory and on a telescope. The laboratory tests showed that the readout noise of the sCMOS camera is about half lower, the dark current is about 17 times higher, the dynamic range is lower in the 12-bit setting and higher in the 16-bit setting, and the linearity and bias stability are comparable relative to those of the CCD camera. In field tests, we observed the open cluster M67 with the sCMOS and CCD cameras on a 60 cm telescope. Unlike the CCD camera, the sCMOS camera has a dual-amplifier architecture. Since a 16-bit image of the sCMOS camera is composed of two 12-bit images sampled with 12-bit high gain and low gain amplifiers simultaneously, it is not real 16-bit output data. The evaluation tests indicated that the dual-amplifier architecture of the sCMOS camera leads to a decline of photometric stability by about six times around specific pixel counts. For photometry of bright objects with similar magnitudes that require high frame rates, the sCMOS camera under 12-bit setting is a good choice. Therefore, the sCMOS camera is fitted with survey observations of variable objects requiring short exposure times, mostly less than 1 s, and high frame rates. It also satisfies the requirements for an offset guiding instrument owing to its high sensitivity, high temporal resolution and high stability.

Region Adaptive Single Image Dehazing.

Image haze removal is essential in preprocessing for computer vision applications because outdoor images taken in adverse weather conditions such as fog or snow have poor visibility. This problem has been extensively studied in the literature, and the most popular technique is dark channel prior (DCP). However, dark channel prior tends to underestimate transmissions of bright areas or objects, which may cause color distortions during dehazing. This paper proposes a new single-image dehazing method that combines dark channel prior with bright channel prior in order to overcome the limitations of dark channel prior. A patch-based robust atmospheric light estimation was introduced in order to divide image into regions to which the DCP assumption and the BCP assumption are applied. Moreover, region adaptive haze control parameters are introduced in order to suppress the distortions in a flat and bright region and to increase the visibilities in a texture region. The flat and texture regions are expressed as probabilities by using local image entropy. The performance of the proposed method is evaluated by using synthetic and real data sets. Experimental results show that the proposed method outperforms the state-of-the-art image dehazing method both visually and numerically.

Robust Single-Image Dehazing

This paper proposes a new single-image dehazing method, which is an important preprocessing step in vision applications to overcome the limitations of the conventional dark channel prior. The dark channel prior has a tendency to underestimate transmissions of bright regions or objects that can generate color distortions during the process of dehazing. In order to suppress the distortions in a large sky area or a bright white object, the sky probabilities and the white-object probabilities calculated in the non-sky area are proposed. The sky area is detected by combining the advantages of a region-based and a boundary-based sky segmentation in order to consider various sky shapes in road scenes. The performance of the proposed methods is evaluated using synthetic and real-world datasets. When compared to conventional methods in the reviewed literature, the proposed method produces significant improvements concerning visual and numerical criteria.

A New Catalog of Asymptotic Giant Branch Stars in Our Galaxy

Abstract We present a new catalog of 11,209 O-rich asymptotic giant branch (AGB) stars and 7172 C-rich AGB stars in our Galaxy, identifying more AGB stars in the bulge component and considering more visual carbon stars. For each object, we cross-identify the Infrared Astronomical Satellite (IRAS), AKARI, Midcourse Space Experiment, Wide-field Infrared Survey Explorer (WISE), Two-Micron All-Sky Survey, and American Association of Variable Star Observers counterparts. We present the new catalog in two parts: one is based on the IRAS PSC for brighter or more isolated objects; the other one is based on the ALLWISE source catalog for less bright objects or objects in crowded regions. We present various infrared two-color diagrams (2CDs) for the sample stars. We find that the theoretical dust shell models can roughly explain the observations of AGB stars on the various IR 2CDs. We investigate IR properties of SiO and OH maser emission sources in the catalog. For Mira variables in the sample stars, we find that the IR colors get redder for longer pulsation periods. We also study infrared variability of the sample stars using the WISE photometric data in the last 12 yr: the ALLWISE multiepoch data and the Near-Earth Object WISE Reactivation 2021 data release. We generate light curves using the WISE data at W1 and W2 bands and compute the Lomb–Scargle periodograms for all of the sample stars. From the WISE light curves, we have found useful variation parameters for 3710 objects in the catalog, for which periods were either known or unknown in previous works.

Molecular Gas in a Gravitationally Lensed Galaxy Group at z = 2.9

Abstract Most molecular gas studies of z &gt; 2.5 galaxies are of intrinsically bright objects, despite the galaxy population being primarily normal galaxies with less extreme star formation rates. Observations of normal galaxies at high redshift provide a more representative view of galaxy evolution and star formation, but such observations are challenging to obtain. In this work, we present Atacama Large Millimeter/submillimeter Array 12CO(J = 3 → 2) observations of a submillimeter selected galaxy group at z = 2.9, resulting in spectroscopic confirmation of seven images from four member galaxies. These galaxies are strongly lensed by the MS 0451.6-0305 foreground cluster at z = 0.55, allowing us to probe the molecular gas content on levels of 109–1010 M ⊙. Four detected galaxies have molecular gas masses of (0.2–13.1) × 1010 M ⊙, and the nondetected galaxies have inferred molecular gas masses of &lt;8.0 × 1010 M ⊙. We compare these new data to a compilation of 546 galaxies up to z = 5.3, and find that depletion times decrease with increasing redshift. We then compare the depletion times of galaxies in overdense environments to the field-scaling relation from the literature, and find that the depletion time evolution is steeper for galaxies in overdense environments than for those in the field. More molecular gas measurements of normal galaxies in overdense environments at higher redshifts (z &gt; 2.5) are needed to verify the environmental dependence of star formation and gas depletion.