We present X-ray and Optical/IR observational analysis for J163331.6-445727 — a newly discovered Symbiotic X-ray Binary (SyXB) system in the far Norma Arm. In our search for new X-ray binaries (XBs) in the 4XMM catalog J163331.6-445727 was selected among other XB candidates using machine learning technique. To establish its nature we analyzed archival data of XMM-Newton and carried out a dedicated pointed X-ray observation with the Mikhail Pavlinsky ART-XC telescope on board the SRG mission and optical spectroscopic observations with the Robert Stobie Spectrograph on SALT. X-ray data allowed us to reveal in J163331.6-445727 coherent X-ray pulsations with the period of ≃ 1552 s. The optical counterpart is a reddened (A_V ≍ 5.5^mag) giant star of the K3-3.5III spectral type at a distance of ≍ 6.5 kpc. According to the presence of the pulsations, hardness of X-ray spectrum and optical companion type, we conclude that J163331.6-445727 belongs to a rare class of distant SyXB systems.

With rapid improvements in the assembly of large samples of galaxy clusters, we are approaching the ability to study clusters at z ≳ 2. Evolutionary studies comparing these distant clusters to the clusters in our local Universe depend heavily on the reliability of low-redshift cluster samples, most of which are subject to X-ray selection effects, biasing them to relaxed, cool-core clusters. Here, we introduce the Cluster Evolutionary Reference Ensemble at Low-z (CEREAL) sample, composed of Chandra X-ray observations of 169 galaxy clusters that have been selected from the Planck Sunyaev─Zel'dovich catalog. CEREAL has a simple and well-understood selection function, spans an order of magnitude in mass at z ∼ 0.15, and has uniform, high-resolution X-ray follow-up. We present the full sample and provide results based on X-ray surface brightness properties, finding significantly more non-cool-core systems than in X-ray-selected samples. We use surface brightness concentration (c_SB) as a proxy for cool-core strength and centroid shift (w) to measure dynamical state. Over the full sample, we find a cool-core (c_SB > 0.075) fraction of 0.39−0.04+0.04 , a strong cool-core (c_SB > 0.155) fraction of 0.13−0.03+0.03 , and a dynamically relaxed (w < 0.01) fraction of 0.42−0.04+0.04 . We find no mass dependence in the fraction of clusters that appear relaxed or have cool cores. We quantify the rarity of X-ray-bright central point sources (L_{nuc, 2−10 keV} > 10⁴³ erg s⁻¹), finding them to be intrinsically rare ( 0.7−0.5+1.2 % of massive, low-z clusters) with a notable increase in occurrence rate at the centers of cool cores.

The evolutionary classification of molecular clumps, crucial for understanding star formation, is commonly based on human-assigned categories derived from infrared (IR) emission and well-established morphological criteria. However, due to ambiguous signatures, distance uncertainties or heavily obscured IR emission, a significant fraction of sources often remains unclassified. This work demonstrates the capability of machine learning (ML) as a complementary, data-driven approach to automate the identification and classification of these clumps using data from the MALT90 survey, complemented by Spitzer IR photometry. We applied unsupervised clustering with HDBSCAN on molecular line intensities, revealing distinct groupings that correspond to evolutionary stages. Using only five molecular lines (HCO$^+$, HNC, N$_2$H$^+$, HCN, C$_2$H), we identified stable clusters of protostars and regions without active star formation, driven primarily by C$_2$H and N$_2$H$^+$ emission. Incorporating H$^{13}$CO$^+$ gave rise to a distinct UV-dominant cluster, tracing more evolved regions. Infrared properties appeared as non-significant features implying that envelopes of clumps with different masses are similar in their global infrared characteristics. We then employed supervised learning to classify clumps with previously uncertain categories and provided classifications for 522 objects, predominantly as regions without active star formation. Our results show that ML techniques can effectively uncover intrinsic evolutionary structures in complex astrochemical data and assign categories to uncertain sources, providing a powerful, data-driven complement to traditional methods.

The Galactic microquasar SS 433 and the radio nebula W50 surrounding it present a prototypical example of a hyper-Eddington binary system shaping its ambient interstellar medium via energetic outflows. In this paper, we present X-ray observations of the SS 433/W50 complex by the eROSITA telescope onboard the SRG space observatory. These data provide images of the entire nebula characterized by a very large dynamic range and allow spectral analysis of the diffuse X-ray emission. In particular, these data illustrate a close connection between the thermal and non-thermal components of W50 on scales ranging from sub-parsecs, represented by narrow X-ray bright filaments, to the entire extent of ≳ 100 pc of the nebula. These data also allowed us to fully characterize a pair of nearly symmetric, sharp-edged, elongated structures aligned with the orbital axis of the binary system, which lack radio counterparts but are prominent in very-high-energy gamma-ray emission. The resulting multifaceted picture of the interaction between energetic outflows and the surrounding medium paves the way for future focused multiwavelength observations and dedicated numerical simulations.

The Perseus cluster (Abell 426) is a nearby massive galaxy cluster that spans several degrees. We combined SRG/eROSITA, XMM-Newton, and Chandra data to get a complete coverage of this cluster in X-rays up to R_200c and beyond, although at the largest radii, spatial nonuniformities of the X-ray sky background and foreground dominate. While the Perseus central part represents a canonical cool-core structure with clear signs of active galactic nucleus (AGN) feedback, the outskirts, in turn, serve as a convincing example of a merger-perturbed system. X-ray data suggest that IC310 is the main galaxy of a subcluster that merged with Perseus over the past ∼4 Gyr. Overall, this configuration resembles the merger between the Coma cluster and the NGC 4839 group. It is statistically more likely to find a merging group near the apocenter of its orbit. Therefore, it is not surprising that IC310 in Perseus has a small velocity relative to the main cluster, similarly to NGC 4839 in Coma. Perseus also hosts a high-velocity radio galaxy, NGC 1265, whose line-of-sight (LOS) velocity is almost twice the virial velocity of the main cluster. It is known for its spectacular radio tail. Unless NGC 1265 has been accelerated by a time-variable potential associated with the merger, it has to move almost along the line of sight through the entire cluster, which would be a rare, but not a truly exceptional, configuration. Both galaxies, IC310 and NGC 1265, have remarkable radio tails with sharp bends that are reminiscent of a "snake biting its tail". We speculate that these curious shapes are natural consequences of their different orbits in Perseus. For IC310, the proximity to the apocenter and the reversal of its radial velocity might play a role. For NGC 1265, the nearly LOS motion coupled with the gas motions in the merging system might be important.