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We investigate the X-ray variability properties of Seyfert 1 Galaxies belonging to the BAT AGN Spectroscopic Survey (BASS). The sample includes 151 unobscured (N H < 1022 cm−2) AGNs observed with XMM–Newton for a total exposure time of ∼27 ms, representing the deepest variability study done so far with high signal-to-noise XMM–Newton observations, almost doubling the number of observations analysed in previous works. We constrain the relation between the normalized excess variance and the 2–10 keV AGN luminosities, black hole masses, and Eddington ratios. We find a highly significant correlation between |$\sigma _{\rm NXS}^2$|  and M BH , with a scatter of ∼0.85 dex. For sources with high L 2–10 this correlation has a lower normalization, confirming that more luminous (higher mass) AGNs show less variability. We explored the |$\sigma _{\rm NXS}^2$|  versus M BH relation for the sub-sample of sources with M BH estimated via the 'reverberation mapping' technique, finding a tighter anticorrelation, with a scatter of ∼0.65 dex. We examine how the |$\sigma _{\rm NXS}^2$|  changes with energy by studying the relation between the variability in the hard (3–10 keV) and the soft (0.2–1 keV)/medium (1–3 keV) energy bands, finding that the spectral components dominating the hard energy band are more variable than the spectral components dominating in softer energy bands, on time-scales shorter than 10 ks. [ABSTRACT FROM AUTHOR]

Changing-look (CL) AGN are unique probes of accretion onto supermassive black holes (SMBHs), especially when simultaneous observations in complementary wavebands allow investigations into the properties of their accretion flows. We present the results of a search for CL behaviour in 412 Swift -BAT detected AGN with multiple epochs of optical spectroscopy from the BAT AGN Spectroscopic Survey (BASS). 125 of these AGN also have 14–195  keV ultra-hard X-ray light curves from Swift -BAT which are contemporaneous with the epochs of optical spectroscopy. Eight CL events are presented for the first time, where the appearance or disappearance of broad Balmer line emission leads to a change in the observed Seyfert type classification. Combining with known events from the literature, 21 AGN from BASS are now known to display CL behaviour. Nine CL events have 14–195  keV data available, and five of these CL events can be associated with significant changes in their 14–195  keV flux from BAT. The ultra-hard X-ray flux is less affected by obscuration and so these changes in the 14–195 keV band suggest that the majority of our CL events are not due to changes in line-of-sight obscuration. We derive a CL rate of 0.7–6.2 per cent on 10–25 yr time-scales, and show that many transitions happen within at most a few years. Our results motivate further multiwavelength observations with higher cadence to better understand the variability physics of accretion onto SMBHs. [ABSTRACT FROM AUTHOR]

The galaxy cluster Abell 3733 (A3733) is a very suitable candidate in addressing dynamical processes throughout galaxy cluster mergers. This study shows structural analysis results of A3733 (z  = 0.038) based on X-ray and optical data. According to X-ray luminosity map, A3733 hosts two sub-structures separated in the sky by 0.25 Mpc, and the two distinct clumps are located in the East (A3733E) and the West (A3733W) directions. Both sub-structures are centred on two different brightest cluster galaxies (BCGs), and the X-ray and optical centroids of both BCGs substantially coincide with each other. The intracluster medium (ICM) temperatures of the sub-structures are estimated to be 2.79 keV for A3733E and 3.28 keV for A3733W. Both sub-structures are found to be hosting cool central gas (kT ∼ 1.5–2.5 keV) surrounded by hotter gas (kT ∼ 3.0–3.5 keV). Besides, the X-ray concentration parameters are found to be c ∼ 0.3 for each sub-structure. These results indicate the existence of cool centres for both sub-structures. The optical density map reveals a crowded galaxy population within the vicinity of A3733W. The high probable (per cent 88.2) dynamical binding model of A3733 suggests that the cores of sub-structures have a 3D separation of 0.27 Mpc and will collide in 0.14 Gyr with the relative in-falling velocity of 1936 km s−1. As a conclusion, this study demonstrates some evidence suggesting that the A3733 system is in the pre-merger state. [ABSTRACT FROM AUTHOR]

We present structural analysis results of Abell 0141 (z = 0.23) based on X-ray data. The X-ray luminosity map demonstrates that Abell 0141 (A0141) is a bimodal galaxy cluster, which is separated on the sky by ~0.65 Mpc with an elongation along the north-south direction. The optical galaxy density map also demonstrates this bimodality. We estimate sub-cluster ICM temperatures of 5.17+0.20 -0.19 keV for A0141N and 5.23+0.24 -0.23 keV for A0141S. We obtain X-ray morphological parameters w = 0.034 ± 0.004, c = 0.113 ± 0.004, and w = 0.039 ± 0.004, c = 0.104 ± 0.005 for A0141N and A0141S, respectively. The resulting X-ray morphological parameters indicate that both sub-clusters are moderately disturbed non-cool core structures. We find a slight brightness jump in the bridge region, and yet, there is still an absence of strong X-ray emitting gas between sub-clusters.We discover a significantly hotspot (~10 keV) between sub-clusters, and a Mach number M = 1.69+0.40 -0.37 is obtained by using the temperature jump condition. However, we did not find direct evidence for shock-heating between subclusters. We estimate the sub-clusters' central entropies as K0 > 100 keV cm2, which indicates that the sub-clusters are not cool cores. We find some evidence that the system undergoes an off-axis collision; however, the cores of each sub-clusters have not yet been destroyed. Due to the orientation of X-ray tails of sub-clusters, we suggest that the northern sub-cluster moves through the south-west direction, and the southern cluster moves through the north-east direction. In conclusion, we are witnessing an earlier phase of close core passage between sub-clusters.. [ABSTRACT FROM AUTHOR]

We study the dynamical structure of a bimodal galaxy cluster Abell 3653 at z = 0.1089 using optical and X-ray data. Observations include archival data from the Anglo-Australian Telescope, X-ray observatories XMM-Newton and Chandra. We draw a global picture for A3653 using galaxy density, X-ray luminosity and temperature maps. The galaxy distribution has a regular morphological shape at the 3 Mpc size. The galaxy density map shows an elongation in the east-west direction, which perfectly aligns with the extended diffuse X-ray emission. We detect two dominant groups around the two brightest cluster galaxies (BCGs). BCG1 (z = 0.1099) can be associated with the main cluster A3653E, and a foreground subcluster A3653W is concentrated at BCG2 (z = 0.1075). Both X-ray peaks are dislocated from the BCGs by ~35 kpc, which suggest an ongoing merger process. We measure the subcluster gas temperatures of 4.67 and 3.66 keV, respectively. Two-body dynamical analysis shows that A3653E and A3653W are very likely gravitationally bound (93.5 per cent probability). The highly favoured scenario suggests that the two subclusters have a mass ratio of 1.4 and are colliding close to the plane of sky (α = 17.61°) at 2400 km s-1, and will undergo core passage in 380 Myr. The temperature map also significantly shows a shock-heated gas (6.16 keV) between the subclusters, which confirms the supersonic infalling scenario. [ABSTRACT FROM AUTHOR]

In this work, we studied 10 nearby (z ≤ 0.038) galaxy clusters to understand possible interactions between hot plasma and member galaxies. A multi-band source detection was applied to detect point-like structures within the intra-cluster medium. We examined the spectral properties of a total of 391 X-ray point sources within each cluster's potential well. logN versus log S was studied in the energy range 2-10 keV to measure X-ray overdensities. Optical overdensities were also calculated to solve suppression/triggering phenomena for nearby galaxy clusters. X-ray and optical flux/luminosity properties (X/O, LX/LB and LX/LK) were investigated for optically identified member galaxies. The X-ray luminosities of our point sources were found to be faint [40.08 ≤ log (LX) ≤ 42.39 erg s-1]. The luminosity range of point sources reveals possible contributions to X-ray emission from low-luminosity active galactic nuclei, X-ray binaries and star formation. We estimated ~2 times higher X-ray overdensities from galaxies within galaxy clusters compared to fields. Our results demonstrate that optical overdensities are much higher than X-ray overdensities at a cluster's centre, whereas X-ray overdensities increase through the outskirts of clusters. We conclude that high pressure from a cluster's centre affects the balance of galaxies and they lose a significant amount of their fuel. As a result, the clustering process quenches the X-ray emission of the member galaxies. We also find evidence that the existence of X-ray bright sources within a cluster environment can be explained by two main phenomena: contributions from off-nuclear sources and/or active galactic nucleus (AGN) triggering caused by galaxy interactions rather than AGN fuelling. [ABSTRACT FROM AUTHOR]

AbstractThis study examined discretionary automation – the choice to engage optional, automated support. In a dynamic decision-making task, after manual and aided trials, participants chose whether to engage a machine learning decision aid. The aid improved performance but participants frequently disused automation and lagged in compliance. Experiment 2 forced greater evidence accumulation, improving compliance, automation use, and performance. Experiment 3 required an initial judgment coupled with subsequent evidence accumulation. This reduced automation use but retained higher levels of compliance and performance. Across experiments, trust in automation and self-confidence influenced use decisions, but task difficulty had little impact. Implications for human-automation systems are discussed. [ABSTRACT FROM AUTHOR]

This paper investigates the integration of multiple geometries present within a ReLU-based neural network. A ReLU neural network determines a piecewise affine linear continuous map, M , from an input space ℝ m to an output space ℝ n . The piecewise behavior corresponds to a polyhedral decomposition of ℝ m . Each polyhedron in the decomposition can be labeled with a binary vector (whose length equals the number of ReLU nodes in the network) and with an affine linear function (which agrees with M when restricted to points in the polyhedron). We develop a toolbox that calculates the binary vector for a polyhedra containing a given data point with respect to a given ReLU FFNN. We utilize this binary vector to derive bounding facets for the corresponding polyhedron, extraction of "active" bits within the binary vector, enumeration of neighboring binary vectors, and visualization of the polyhedral decomposition (Python code is available at https://github.com/cglrtrgy/GoL&#95;Toolbox). Polyhedra in the polyhedral decomposition of ℝ m are neighbors if they share a facet. Binary vectors for neighboring polyhedra differ in exactly 1 bit. Using the toolbox, we analyze the Hamming distance between the binary vectors for polyhedra containing points from adversarial/nonadversarial datasets revealing distinct geometric properties. A bisection method is employed to identify sample points with a Hamming distance of 1 along the shortest Euclidean distance path, facilitating the analysis of local geometric interplay between Euclidean geometry and the polyhedral decomposition along the path. Additionally, we study the distribution of Chebyshev centers and related radii across different polyhedra, shedding light on the polyhedral shape, size, clustering, and aiding in the understanding of decision boundaries., Competing Interests: The authors declare that the research was conducted in the absence of any commercial or financial relationships that could be construed as a potential conflict of interest., (Copyright © 2023 Liu, Caglar, Peterson and Kirby.)