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Observations of scattered X-rays from the Central Molecular Zone suggest that Sagittarius A* was much more active in the past, and moreover provide an approximate map of the location of the illuminated molecular clouds in the Galactic Centre.

A magnetic halo featuring coherent magnetized ridges several kiloparsecs above and below the Galactic Disk, and a gamma-ray counterpart, are revealed. They probably arise from outflows that are driven by star-forming regions in the Galactic Disk, 3–5 kiloparsecs from the Galactic Centre.

The Hot Universe Baryon Surveyor (HUBS) is a proposed space-based X-ray telescope for detecting X-ray emissions from the hot gas content in our universe. With its unprecedented spatially-resolved high-resolution spectroscopy and large field of view, the HUBS mission will be uniquely qualified to measure the physical and chemical properties of the hot gas in the interstellar medium, the circumgalactic medium, the intergalactic medium, and the intracluster medium. These measurements will be valuable for two key scientific goals of HUBS, namely to unravel the AGN and stellar feedback physics that governs the formation and evolution of galaxies, and to probe the baryon budget and multi-phase states from galactic to cosmological scales. In addition to these two goals, the HUBS mission will also help us solve some problems in the fields of galaxy clusters, AGNs, diffuse X-ray backgrounds, supernova remnants, and compact objects. This paper discusses the perspective of advancing these fields using the HUBS telescope.

Magnetic halos of galaxies are crucial for understanding galaxy evolution, galactic-scale outflows and feedback from star formation activity. Identifying the magnetized halo of the Milky Way is challenging because of the potential contamination from foreground emission arising in local spiral arms. In addition, it is unclear how our magnetic halo is influenced by recently revealed large-scale structures such as the X-ray-emitting eROSITA Bubbles detected by the extended Roentgen Survey with an Imaging Telescope Array (eROSITA). Here we report the identification of several kiloparsec-scale magnetized structures on the basis of their polarized radio emission and their gamma-ray counterparts, which can be interpreted as the radiation of relativistic electrons in the Galactic magnetic halo. These non-thermal structures extend far above and below the Galactic plane and are spatially coincident with the thermal X-ray emission from the eROSITA Bubbles. The morphological consistency of these structures suggests a common origin, which can be sustained by Galactic outflows driven by active star-forming regions located in the Galactic Disk at 3–5 kpc from the Galactic Centre. These results reveal how X-ray-emitting and magnetized halos of spiral galaxies can be related to intense star formation activities and suggest that the X-shaped coherent magnetic structures observed in their halos can stem from galactic outflows. A magnetic galactic halo featuring coherent ridges several kiloparsecs above and below the Galactic Disk has been detected in multi-wavelength observations. The halo is probably a consequence of outflows driven by active star-forming regions in the disk.

Observational signatures of accretion disc winds have been found in a significant number of low-mass X-ray binaries at either X-ray or optical wavelengths. The 2015 outburst of the black hole transient V404 Cygni provided a unique opportunity for studying both types of outflows in the same system. We used contemporaneous X-ray (Chandra Observatory) and optical (Gran Telescopio Canarias, GTC) spectroscopy, in addition to hard X-ray light curves (INTEGRAL). We show that the kinetic properties of the wind, as derived from P-Cyg profiles detected in the optical range at low hard X-ray fluxes and in a number of X-ray transitions during luminous flares, are remarkably similar. Furthermore, strictly simultaneous data taken at intermediate hard X-ray fluxes show consistent emission line properties between the optical and the X-ray emission lines, which most likely arise in the same accretion disc wind. We discuss several scenarios to explain the properties of the wind, favouring the presence of a dynamic, multi-phase outflow during the entire outburst of the system. This study, together with the growing number of wind detections with fairly similar characteristic velocities at different wavelengths, suggest that wind-type X-ray binary outflows might be predominantly multi-phase in nature.

We summarise observations and our current understanding of the interstellar medium (ISM) in galaxies, which mainly consists of three phases: cold atomic or molecular gas and clouds, warm neutral or ionised gas, and hot ionised gas. These three gas phases form thermally stable states, while disturbances are caused by gravitation and stellar feedback in form of photons and shocks in stellar winds and supernovae. Hot plasma is mainly found in stellar bubbles, superbubbles, and Galactic outflows/fountains and is often dynamically unstable and is over-pressurised. In addition, in galactic nuclear regions, accretion onto the supermassive black hole causes enhanced star formation, outflows, additional heating, and acceleration of cosmic rays.

The history of supermassive black holes’ activity can be partly constrained by monitoring the diffuse X-ray emission possibly created by the echoes of past events propagating through the molecular clouds of their respective environments. In particular, using this method we have demonstrated that our Galaxy’s supermassive black hole, Sgr A⋆, has experienced multiple periods of higher activity in the last centuries, likely due to several short but very energetic events, and we now investigate the possibility of studying the past activity of other supermassive black holes by applying the same method to M31⋆. We set strong constraints on putative phase transitions of this more distant galactic nucleus but the existence of short events such as the ones observed in the Galactic center cannot be assessed with the upper limits we derived.

Collecting and analysing X-ray photons over either spatial or temporal scales encompassing varying optical depth values requires knowledge about the optical depth distribution. In the case of sufficiently broad optical depth distribution, assuming a single column density value leads to a misleading interpretation of the source emission properties, nominally its spectral model. We present a model description for the interstellar medium absorption in X-ray spectra at moderate energy resolution, extracted over spatial or temporal regions encompassing a set of independent column densities. The absorption model (named disnht) approximates the distribution with a lognormal one and is presented in table format. The solution table and source code are made available and can be further generalized or tailored for arbitrary optical depth distributions encompassed by the extraction region. The disnht absorption model presented and its generalized solution are expected to be relevant for present and upcoming large angular scale analyses of diffuse X-ray emission, such as the ones from the extended ROentgen Survey with an Imaging Telescope Array (eROSITA) and the future Athena missions.

The bulk of the FeKα emission detected in the central molecular zone (CMZ) is thought to be associated with reflection by the central molecular clouds of enhanced past emission from an external X-ray source, most likely Sgr A*. In order to follow the propagation of the reflected emission through the Galactic center (GC), we analyzed all XMM-Newton observations carried out from 2000 to 2012. Preliminary results indicate that while most of the regions that were bright at 6.4 keV in 2000–2001 have a significantly lower flux in 2012, a few other experienced a flux increase. We report for the first time a significant decrease of the FeKα emission in the Sgr C complex, supporting the reflection origin of the 6.4 keV emission detected in this region.

We report here on the results of the analysis of Chandra, XMM-Newton and NuSTAR recent observations of the Supergiant Fast X-ray Transient XTEJ1739-302. The source was caught in a low X-ray luminosity state, from a few \\(10^{31}\\) to \\(10^{34}\\) erg/s (0.5-10 keV). In particular, a very low X-ray luminosity was captured during an XMM-Newton observation performed in October 2022, at a few \\(10^{31}\\) erg/s (0.5-10 keV), never observed before in XTEJ1739-302. The XMM-Newton spectrum could be well fitted either by an absorbed, steep power law model (photon index of 3.5) or by a collisionally-ionized diffuse gas with a temperature of 0.7 keV, very likely produced by shocks in the supergiant donor wind. These observations covered different orbital phases, but all appear compatible with the low luminosity level expected from the orbital INTEGRAL light curve. The absorbing column density is variable in the range \\(10^{22}-10^{23}\\) cm\\(^{-2}\\). A broad-band X-ray spectrum could be investigated at \\(10^{34}\\) erg/s (0.5-30 keV) for the first time in XTEJ1739-302 with not simultaneous (but at similar orbital phases) Chandra and NuSTAR data, showing a power law spectral shape with a photon index of about 2.2 and an absorbing column density of $\\sim$$10^{23}\\( cm\\)^{-2}$. Remarkably, owing to the XMM-Newton observation, the amplitude of the X-ray variability has increased to five orders of magnitude, making XTEJ1739-302 one of the most extreme SFXTs.