Abstracts

The transient blackhole candidate Maxi J1803-298, discovered during a 2021 outburst, is known to show multiple recurrent dips in its X-ray lightcurves while the outburst lasted. The dipping intervals were especially prominent during the hard/hard-intermediate states with recurring periods of about 7hrs. We report results for the broadband X-ray spectral analysis of the source. Our analysis reveals the source to be rapidly rotating and observed close to edge-on. Furthermore, we detected absorption line features in several of the source spectra at ~6.6keV, ~6.7keV, ~7.2keV and ~7.9keV. These lines have been known to be signatures of equatorial accretion disk winds. Joint fitting of the persistent and dip spectra suggests that blobs of obscuring materials passing along our line of sight close to the disk plane are plausibly responsible for the lightcurve dips.

Because of convective and rotational motions, cool stars generate strong magnetic fields, which extend outward to several stellar radii. These magnetic fields produce a wide range of magnetic phenomena in the stellar atmospheres. In particular, they heat and confine hot coronal plasmas, and, in young stars, they play a crucial role in the mass accretion mechanism. Since both coronal plasma and plasma heated in the accretion process are strong X-ray emitters, their physical conditions can be accurately probed by high resolution X-ray spectroscopy. In this talk I will present recent findings on magnetic phenomena occurring in the atmospheres of cool stars. I will also discuss the potential advances that will be made possible by future high spectral resolution X-ray missions.

Centaurus-A, as the nearest radio galaxy to Earth, offers a unique opportunity to study a wide range of astrophysical processes, such as high-energy gamma emissions, dust clouds, jet properties, star formation, and accretion and outflows from the galactic nucleus. Centaurus-A has been studied at a variety of wavelengths, but due to its high emissivity at radio frequencies, the vast majority of research has been done at shorter wavelengths. Its massive north-south radio lobes are especially intriguing because they have only been briefly explored in the X-ray spectrum. We present a statistical analysis of the properties of the identified sources and compile a catalogue of point-like sources from Chandra X-ray observations in five Suzaku collocated areas in these northern and southern lobes. The preliminary inventory of point-like sources is compiled by first calibrating and processing archived ACIS-I data using the Caldb-4.10.2 calibration database and using Wavdetect point source detection algorithm which is then cross-matched with CAT-Wise and Gaia DR3 catalogues in various energy bands to produce a catalogue with the broadest spectral coverage possible. The hardness ratios, spectral fitting, and light curve analysis for intra-observational variability that were discovered then provide us with a better understanding of the physical properties of these objects, which may help improve current theoretical models of X-ray emissions in radio galaxies.

Atomic databases used by collisional and photoionization plasma codes usually comprise atomic data of various different sources. While it is widely known that these data are subject to uncertainties, quantitative estimates of these uncertainties remain challenging. Moreover, the propagation of these uncertainties and their effect on observable spectral features is even more difficult. Here we present an alternative approach to quantifying systematic model uncertainties that is based on comparison of statistically high-quality observational data with those plasma models. We use archival Chandra/HETG data of the Seyfert I galaxy NGC 3783 to test the hypothesis that the residual discrepancies from fitting the photoionized plasma code xstar/warmasb to high statistical quality spectra are entirely due to systematic uncertainties in the atomic data. We compare our approach with Monte-Carlo based uncertainty estimates published for other spectral codes and discuss their implementation into common X-ray data analysis packages.

O star wind mass-loss rates are a key quantity for the study of stellar evolution, ISM feedback, and core collapse supernova physics. The X-rays themselves are produced by shock heating in the unstable, radiation-driven winds and high-resolution X-ray spectroscopy provides key information not just about the shock physics and X-ray production but also about the bulk wind properties. High resolution X-ray spectroscopy provides two complementary diagnostics of this important quantity -- one via resolved X-ray emission line profile shapes and the other via the broadband modeling of soft-X-ray attenuation. Results over the last decade confirm lower-than expected mass-loss rates of O supergiants and provide also a new diagnostic of wind clumping. More recent and surprising results show that the wind column density, and perhaps therefore the mass-loss rate, of the O supergiant zeta Puppis has changed over the past 20 years.

The hot circumgalactic medium (CGM) is often assumed to consist of a single virialized phase with isotropic density distribution and solar-like chemical composition. Thanks to the high spectral resolution of the grating facilities of Chandra and XMM-Newton, we can probe multiple transitions (e.g., K$\alpha$ and K$\beta$) of multiple ions (He-like and H-like) of multiple metals, and verify/refute those assumptions. We probe the hot CGM of the Milky Way using $z=0$ absorption lines of carbon, nitrogen, neon, magnesium, silicon, and iron in addition to the most common tracer oxygen, in the grating spectra of QSOs toward extragalactic ($|b|>20^\circ$) direction. We have discovered a super-virial $10^7$\,K phase and a sub-virial 10$^{5.5}$\,K phase coexisting with the well-known virialized $10^6$\,K phase along multiple high S/N individual sightlines and stacking of low S/N sightlines. The chemical composition of these phases is non-solar, with inhomogeneous abundance ratios of light elements and $\alpha$/Fe enhancement among phases. We also find the non-thermal line-broadening to be significantly non-zero in the virial and super-virial phases, indicating the presence of micro-turbulence in the hot CGM. The $>$order-of-magnitude scatter in the column densities of the virialized CGM across the sky contradicts the assumption of geometrically symmetric density models. The structure-function of column densities grows with angular scale at a power-law slope of $5.8\pm1.9$, exhibiting a $>2\sigma$ stronger scale-dependence than Kolmogorov-like slope of 5/3, and the structure-function saturates at 25--40$^\circ$, indicating large-scale turbulence in the hot CGM. Thus, the simplified picture of the hot CGM is clearly ruled out. For a galaxy like the Milky Way, these are exciting and perplexing results, because the super-virial phase, detailed chemistry, and turbulence from small to large scale are uncharted territories in most theories of galaxy evolution.

Absorption lines in the X-ray spectra of X-ray binaries were first detected more than two decades ago with ASCA. Only one year later, the timely launch of the X-ray observatories Chandra and XMM-Newton, equipped with high energy gratings, enabled to expand such discovery to additional sources and to emission lines and P-Cygni profiles, indicating the presence of a rich variety of atmospheres and winds and opening new avenues for understanding accretion/ejection processes around neutron stars and black holes.
In this talk, I will review the past observations and what we have learnt from them and the capability of upcoming instrumentation such as the Resolve calorimeter aboard XRISM to answer the still standing questions.

Near the supermassive black hole (SMBH), X-rays are produced and subsequently reprocessed by the gas and dust surrounding the active galactic nucleus (AGN), offering insights into the surrounding matter. Utilizing the RefleX platform, an X-ray spectra-generating ray-tracing code (Paltani & Ricci, 2017), we have devised two novel X-ray spectra models with more intricate and lifelike geometries than presently available models. The first model incorporates a toroidal dusty element, along with a polar medium perpendicular to the SMBH's rotational plane. For the second model, we leverage RefleX's ability to manage intricate geometries, and include not only the torus and polar medium, but also the accretion disk and broad-line region. In my presentation, I will introduce these new table models and provide an in-depth explanation of their configurations. High-resolution spectroscopy can take advantage of new complex models that implement more realistic geometries especially as high-resolution X-ray instruments like the one on XRISM emerge, complex models will become increasingly vital in the years ahead.

Chandra's arc-second spatial resolution, combined with the spectral sensitivity of its transmission gratings, make it an excellent instrument to study young supernovae (SNe), months to years after outburst. We illustrate this with Chandra high-resolution spectroscopy of SN 1996cr, a nearby Type IIn SN with an X-ray and radio lightcurve that was increasing with time for several years, a relatively rare event. We obtained a 480 ks HETG observation of SN 1996cr in 2009, arguably one of the highest resolution spectra of a young supernova. Coupled with HETG exposures in 2000 and 2004, and other lower signal-to-noise exposures, the data enable us to resolve spectrally the velocity profiles of Ne, Mg, Si, S, and Fe emission lines, explore possible geometrical models to describe the line profiles, provide new insights into the SN morphology, and monitor the line evolution as a tracer of the ejecta-circumstellar medium (CSM) interaction. Comparing the Si and Fe line profiles allows us to demonstrate that a polar geometry with two distinct opening angle configurations and internal obscuration can successfully reproduce all of the observed line profiles. Numerical hydrodynamic simulations, combined with synthetic spectral calculations and comparison to the high-resolution spectra, enable us to excavate the SN environment, trace the evolution of the shock wave within the CSM, and hone in on the SN progenitor. We note that this spectrum provides a good example of what the next generation of high-resolution X-ray observatories could accomplish for hundreds of nearby SNe.

Half of all clusters of galaxies have a cool core in which the temperature drops inward and the density rises as expected from a cooling flow. Over 20 years ago, High Resolution XMM RGS Spectra showed little evidence for the cooling flow continuing below 1 keV at the rates inferred from higher temperatures. We have now re-examined the RGS spectra of over 20 clusters and groups and 4 early-type galaxies and find that an intrisically-absorbed (HIdden Cooling Flow) model allows for significant continuous mass cooling rates to 0.1 keV and below at the level of 15-50% of the expected rates from above 1 keV. The rates range from 1-20 Msun/yr in groups to 15 -100 in regular clusters. Several highly luminous clusters have mass cooling rates of 1000 Msun/yr or more. Where available the Far Infrared flux is compatible with that expected from X-ray absorption. AGN feedback can account for 50-85% of the reduction in mass cooling rates but the remainder is significant. We discuss these results and outline the possible fate of the cooled gas, including Very Cold Gas Clouds, Low- Mass Star Formation, outward dragging by rising bubbles and non-luminous swallowing by the central black hole.

The AtomDB database is a large collection of atomic data and a series of models which allow modeling of X-ray emitting plasma. We have been expanding the database by including a range of new data, in particular for the dielectronic recombination process, which will provide accurate wavelengths and energies for large range of lines covering a wide range of processes. These lines form a powerful, hitherto unexploited, diagnostic of non-equilibrium ionization in spectra with sufficient resolution to resolve them, covering a wide range of temperatures. We discuss the new data and it’s application to plasmas such as supernovae and accreting stars. In addition we will introduce new models relevant to high resolution plasmas such as updates to the AtomDB charge exchange model (ACX), and the new resonant scattering model.

Accretion disks in BH XRBs often exhibit two seemingly disconnected phenomena in X-ray spectra; disk reflection and powerful disk winds. The physical parameters associated with disks, such as "inclination" and "density", can be constrained by reflection spectroscopy primarily in hard X-ray band. In recent years, disks in a number of the transient BH XRBs (e.g. MAXI J1348-630, EXO 1846-031, MAXI J1631-479, Swift J1658.2-4242) are found to be non-equatorial (theta ~ 10deg-40deg) with high density (n [cm^{-3}] ~ 1e19-1e21). Interestingly, these sources also show near-relativistic absorption lines (v/c ~ 0.05-0.1) in the Fe K band implying the presence of non-equatorial massive fast outflows. We propose in this work a novel approach to independently constrain the disk inclination and density by utilizing the disk-wind model where the wind column density gives a measure for disk density for a given inclination. In this framework, reflection (Compton hump) and fast wind (absorption) can independently provide, as synergistic tools, two diagnostics to probe disks. An exhaustive multi-epoch NuSTAR spectral analysis shows that two different methods, being complement to each other, successfully yield a broad agreement. However, given the complex absorbers identified only at CCD resolution, we demonstrate that high-resolution data from Chandra/HETGS and XRISM/Resolve could further shed light on the otherwise concealed spectral structures and better constrain the disk property of these systems.

We present a detailed analysis of the 2+ Ms HETG spectrum of the magnetic massive star theta^1 Orionis C. This O7 V star is an oblique magnetic rotator with a rotation period of 15.42 days. The spectra were extracted from archival and Chandra Very Large Program observations of the Trapezium cluster (PI: Schulz). The set of 68 HEG and MEG spectra were fit together, and grouped into phase bins to look for rotational modulation of several key line parameters including line width and line flux in emission lines ranging from Fe XXV to O VIII. We show that Voigt line profiles are needed to fit most lines. The line complexes were analyzed in two ways. We first fit all bright lines in a complex with Voigt profiles and a smooth continuum. We then fit only diagnostically important lines, modeling the remaining lines and pseudo-continuum with a multi-temperature APED model. This latter analysis allowed us to account for contamination from satellite lines. This proved especially helpful for measuring the f/i ratios of the He-like lines of Ne IX, Mg XI, Si XIII and S XV. We also present high-resolution 3D magnetohydrodynamic simulations of the magnetically confined wind shocks on theta^1 Ori C. We use a new CubeSphere code with a full energy equation to account for shock heating, radiative cooling, and inverse Compton cooling. We describe the dynamics of the wind shocks and compare the simulated emission-measure distributions with those extracted from our HETG data analysis. In particular we show that most hotter lines like Si XIV are formed in the magnetically confined wind shocks, while some cooler lines like O VIII are most likely formed in embedded wind shocks. The 3D simulations allow us to show that much of the observed rotational modulation is produced by variations of the line-of-sight absorption in the overlying cool wind.

In this work we present an overview of the most important advancements that can be achieved through high-resolution X-ray spectroscopy of accreting compact objects accreting compact objects such as black holes and neutron stars. We will focus on the X-ray reflection spectroscopy technique, which has proven to be an ideal diagnostic tool for understanding the state and composition of the accretion flow and to probe the space-time near the compact object distorted by the strong gravitational field. Key examples will be discussed, such as accurate constraints of the disk inner radius, and its impact in the measurements black hole spin and neutron star radii; the obscuration of the central X-ray emission by the disk’s outer edge, and its effect in constraining the inner disk inclination; the precise detection of disk returning radiation due to strong light bending effects as a probe of relativistic effects; and the characterization of high-density plasma effects in the atomic features observed in the X-ray spectrum.

Understanding feedback and feeding processes of super-massive black holes at the centre of Active Galactic Nuclei (AGN) is crucial for our understanding of the concurrent evolution of galaxies and black holes. X-ray spectroscopy is the tool to probe the innermost regions of the accretion flow, as well as strong sub-relativistic outflows ejected in the innermost ~100 pc from the event horizon, and that could be the carrier of the so far elusive “AGN feedback mechanism”. In my talk, I will review the spectacular advancements that high-resolution spectroscopic measurements with the grating systems on board Chandra and XMM-Newton have achieved on the dynamics and physics of the gas in the nuclear environment, as well as the exciting prospective the measurements with the micro-calorimeters on board XRISM and NewAthena will enable. As a bonus, these studies allow one to get significantly more reliable constraints on the distribution of super-massive black hole spins in the local Universe, a “fossil remnant” of host galaxy evolution.

X-ray satellite lines are a reliable diagnostic of the electron temperature in plasmas in the lab and the Sun’s atmosphere but have not been used in massive stars. The recent deep exposure with the Chandra X-ray Observatory on the prototypical O-type supergiant zeta Puppis provides the first chance do so. I will discuss what satellite lines are, and their capabilities as either a direct measure of the temperature of a plasma or a way to test differential emission measure models for non-isothermal plasmas. The X-ray emitting plasmas of zeta Puppis fall in this latter category, allowing us to test the predictions of the differential emission measure model used by Huenemoerder et al. (2020). In doing so, we find evidence for affirmation of the X-ray emitting plasma being in a state of collisional ionization equilibrium and reject the alternative plasma state called Pollock’s paradigm.

The soft X-ray band (0.1-10keV) has great diagnostic value for studying energetic astrophysical environments: highly charged ions of astrophysically abundant elements imprint their characteristic spectral signatures on this band. These signatures serve as diagnostics for plasma parameters such as elemental abundances, temperature, density, and velocities of the material in the environment of these sources for a wide range of parameter space. High-resolution X-ray spectroscopy, such as provided by the Chandra and XMM-Newton gratings, as well as Hitomi-SXS and XRISM-Resolve and instruments on future observatories, provide us with a detailed view of these signatures, which in turn help us to understand the physics controlling the energetic processes in these sources. However, in order to correctly interpret these plasma diagnostics, it is crucial to know the underlying atomic physics to high accuracy as well as understand the uncertainty of our reference data. Laboratory astrophysics allows us to both benchmark and improve these atomic data and the plasma models using them. I will show examples that highlight both the need for and the solutions provided by laboratory astrophysics. This work was supported by LLNL under Contract DE-AC52-07NA27344 and by NASA grants to LLNL and NASA/GSFC.

We present a detailed X-ray spectral study of the high energy peaked blazar MKN 421 using the simultaneous broadband observations from the LAXPC and SXT instruments on-board the AstroSat satellite. In order to investigate the spectral properties of the source, we used the method of time resolved spectral analysis by dividing the total observation time into time-segments of 10 ksecs and then by fitting each segment with synchrotron emission of particle density from logparabola model. In each time-segment, we fitted the observed broadband X-ray spectrum. The X-ray spectrum of Mkn 421 showing significant spectral curvature is usually described by log-parabola model, however, the model fails to give the information of underlying physical parameters as the exact relationship of model parameters with the underlying physical quantities is not clear. Therefore in order to obtain the information of underlying physical parameters, we reproduce the X-ray spectrum with a analytical models viz. energy-dependent acceleration(EDA) model. On comparing the goodness of the fit of synchrotron convolved logparabola model with the EDA model, we noted that both the models provided nearly equally good fit to the broadband spectrum, though EDA model is comparatively better. Moreover, we studied the correlation between EDA model parameters (norm, ψ, κ) and the observed quantities using the Spearman rank correlation method. A significant anti-correlation is observed between ψ and κ with r_s = -0.82(P_{rs}= 1.69 ×10 -9) and similar anti correlation is also obtained for the case of κ and norm r_s = -0.86 (P_{rs} = 3.5 × 10-11). The above obtained correlation results between fit parameters for the case of EDA model are consistent with the definition. Which refer that the model is more appropriate for reproducing the X-ray spectrum of Mkn 421.

After being inactive for two decades, 4U 1543-47 experienced its most intense outburst in 2021. During its decay phase, AstroSat conducted nine observations of the source spanning from July 1 st to September 26 th , 2021. The first three observations were performed with an offset of 40 ′ with AstroSat/LAXPC, while the remaining six were on-axis observations. We provide a detailed spectral analysis of the source throughout the entire observation period while it was in the High/Soft state. A disk-dominated spectrum with a steep high-energy tail (power-law index ≥ 2.5) and a high temperature (∼0.84 keV) of the inner disk was observed for the source. Through the application of non-relativistic and relativistic models to the disk continuum, we determined that the inner radius was truncated at a significant value of >10Rg. Along with the disk truncation, a robust correlation between the accretion rate and the inner disk radius was observed.

Chandra's high-resolution spectral capability, along with high angular resolution, has led to major advances in the study of hot plasmas in massive star winds. Winds and other bulk motions in single (magnetic or non-magnetic) and binary massive stars are typically fast at 1000 km/s and more, making their emission lines ideal for resolving with Chandra. Resolved lines connect to the spatial distribution of hot gas in single-star winds, colliding winds, and magnetically channeled flow. The ability to spectrally distinguish the He-like f-i-r triplet lines provides an important diagnostic for locating hot plasma due to level-pumping effects by virtue of the star's strong UV radiation. The line profile shapes have likewise proven critical for the mapping exercise. We review the varieties of line profile shapes resulting from common stellar wind model assumptions and influences (e.g., wind photoabsorption, porosity, and line optical depth). We also review what resolved f-i-r components have to offer from future high-resolution instrumentation.

High-resolution spectra of weak sources pose unique challenges to the usual way spectral analysis is done. Both sparsity as well as background cause difficulties in robust estimations of fluxes and upper limits. I will discuss example cases based on Chandra and Hitomi data.

X-ray binaries have been studied for many years, but there are still open questions regarding different stages in their evolution. Since they show dramatic changes over short time periods, there are only a handful of clear outflow observations, especially in the X-ray band. One exceptional outflow was observed in the transient stellar black hole GRO J1655-40 during its 2005 outburst. The spectrum features deep absorption lines from many elements, including less abundant ones. In this work, we measure the different element abundances, and constrcut an AMD for an XRB for he first time. Precise measurement of the lines indicates there is significant saturation, making the column density inferred directly from the lines an underestimation. By using the equivalent width measurement and theoretical curve of growth we infer an ionic column density from each resolved line. For each hydrogen-like ion, there are measurements from the Lyman-alpha line, as well as the Lyman-beta, gamma and delta lines when resolved in the spectrum. Comparing the ionic column density of all elements to the sulfur column density provides an abundance measurement of the elements in the outflow. Considering the ionic column density enables us to construct an absorption measure distribution. From the absorption measure distribution, the density profile of the wind can be derived and provide more insight into the physical wind launching mechanism.

Accretion disk winds were first discovered in X-ray binaries (XRBs) more than two decades ago. Nowadays, they appear ubiquitous in the soft states of high inclination black hole and neutron star XRBs as well as in the highly accreting ultraluminous X-ray sources. These outflows have potential to carry away a significant fraction of the originally accreting material. They can thus affect the matter transfer and the long-term evolution of XRBs. In some cases, these outflows can additionally carry enough kinetic power to significantly influence the neighborhoods of XRBs.
Despite the recent detections of ionized winds in many individual XRBs, much is still unknown about the physics of these phenomena, including their launching mechanisms. In my talk, I will review the recent results on disk winds in XRBs using high-resolution X-ray spectroscopy. I will particularly focus on the most extreme class of XRBs – the highly accreting ultraluminous X-ray sources and their powerful relativistic outflows. I will also present our recent study of Hercules X-1, a neutron star XRB with a nearly edge-on, warped and precessing accretion disk. The disk precession allows us to uniquely sample the vertical structure of its disk wind, and thus create a 2D map of the wind properties.
Finally, I will conclude by presenting an overview of the capabilities of the upcoming XRISM high-resolution X-ray observatory and describe how it will revolutionize our understanding of disk winds in XRBs.

The novel hot component of the Circumgalactic Medium (CGM) of the Milky Way was detected in two individual lines of sight toward the blazar 1ES 1553+113 and toward Mrk 421. We present our results obtained by stacking 46 lines of sight with Chandra ACISSHETG (10 Ms of exposure time) and 9 lines of sight with ACISSLETG (1 Ms of exposure time) spread across the sky with aim to study the CGM hot component. We focused on the spectral range 4 - 8 Å, studying in absorption the presence of highly ionized metals arising in this gas phase. We confirmed the presence of this hot phase by detecting transitions of SiXIV Kα (total significance of 6σ, and total column density of 1.50 ± 0.44 x 10^16 cm-2) and, for the first time, SXVI Kα (total significance of 4.8σ, and total column density of 0.87 ± 0.16 x 10^16 cm-2) in the rest frame of our Galaxy. Our results indicate that this newly discovered hot component of the CGM spreads throughout the halo and might contribute significantly to the problem of the missing baryon and metals in the Milky Way.

Thanks to the high resolution and high-throughput of Chandra and XMM-Newton, photoionised gas around powerful X-ray sources has been extensively studied since early 2000s. This led to the discovery of the ubiquitous presence of outflows in accreting systems and, in turn, revealed a wealth of information on the ionising sources. However, current photoionisation codes usually assume time-equilibrium and, thus, cannot self-consistently model the gas response to a time-variable (or transient) ionising source, as in most of the astrophysical systems, and leads to incorrect results when fitting their X-ray spectra. Moreover, gas density and distance are degenerate at equilibrium and, thus, the outflows energy and mass rates can be determined only with order-of-magnitude uncertainties. To maximise the scientific return of current X-ray telescopes, and get ready for the incoming XRISM mission, we developed one of the first Time Evolving Photo-Ionisation Device (TEPID), which follows the gas ionisation in response to a (time-varying) luminosity source and performs a first-order radiative transfer. The code is highly flexible and can model any astrophysical scenario, from variable AGNs to GRBs and diffuse nebulae. We are now analysing archival grating and CCD observations of time-variable AGN absorbers, with a particular focus on those that will be observed in the Performance Verification phase of XRISM.

The upcoming XRISM (2023) and proposed AXIS (2030s) missions are expected to provide high-spectral and -spatial resolution observations of Supernova remnants that will challenge conventional gradient-based approaches to optimization in the modelling of these sources. This talk will discuss the use of archival Chandra data in the development of XFit: a multi-objective global optimization algorithm whose primary objectives include exploring families of degenerate solutions in the parameter spaces of models as well as searching for previously unseen emission lines.

Each supernova (SN) injects around 10^51 ergs into the interstellar medium (ISM) shaping the chemical, thermal and dynamic evolution of the ISM. Thereby SNe are shocking and heating the gas. A good fraction of the injected energy is subsequently lost by radiative cooling. However, the fate of the emitted cooling photons is usually neglected in simulations as the surrounding ISM is treated to be optically thin with respect to it. This makes the high-resolution simulations quite unphysical. As for the real observations of SN remnants (SNRs): with the growing ability of X-ray imaging spectroscopy, we can define the pixel-by-pixel based parameters (such as plasma temperature, ionisation state and abundance of different elements). Adding to these polarisation images (e.g. currently from IXPE) we can also study the nature of the magnetic fields and turbulence as well. Thus, right now we need more realistic simulations of SNRs.
 We present state-of-the-art (magneto-)hydrodynamic simulations of SN explosion in the inhomogeneous environment using the FLASH code which considers radiative cooling from the SN event. Radiative cooling is calculated on the fly and fully consistent with the radiation transfer, X-ray physics and chemistry modules of the code. We calculate synthetic maps of the simulated SN remnant in several X-ray energy bands (e.g. Chandra energy bands in the range 0.1-10 keV) as well as for selected iron lines. Therefore, synthetic X-ray maps provide unique information about the physics of shock/cloud interaction, general morphology of the remnants, and enhanced magnetic field as well as a better comparison (and prediction) for SNRs observations

The neutron star low-mass X-ray binary SWIFT J1749.4-2807 is an accreting millisecond X-ray pulsar. (AMXP) which underwent a 2-week-long outburst in 2021. We conducted a thorough analysis of all the available X-rays observations, including XMM-Newton, NICER and NuSTAR. The outburst was relatively faint, reaching at the peak only about 1% of the Eddington luminosity and the system was found in the hard state, as typically observed for AMXPs. The significant detection of a blue-shifted Fe XXVI absorption line at ~7 keV indicates weakly relativistic X-ray disc winds, which are typically absent in the hard state of X-ray binaries. The detection of these winds defies typical paradigms of disc winds formation in X-ray binaries and may imply the existence of propeller-driven outflows. I will discuss the discovery in the context of unexpected disc winds and powerful outflows in AMXPs, potentially shedding light on the role of the rapidly spinning magnetic field in powering them.

The bulge of M 31 was observed over a span of a year with the Chandra High Energy Transmission Grating Spectrometer (HETGS) in nine separate observations of about 75 ks each. Over 50 sources were observed with 1,000 or more counts in the high resolution spectra. We will present a summary of spectral features including edges, absorption columns, and emission lines.

Outflowing winds link the supermassive black holes at the heart of AGN to their host galaxies. Determining the physical properties and energetics of AGN winds, and how they are launched and driven, are important for understanding their impact on their environment. Different kinds of ionized outflows, with distinct characteristics, have been found in AGN. The formation of these various outflows, and their relations to each other, are uncertain. High-resolution X-ray and UV spectroscopy is a crucial tool to advance our understanding of the nature and origin of AGN outflows. I review results from recent studies on the multi-phase structure of AGN outflows. I discuss how spectral variability is a powerful diagnostic tool to probe the uncertain parameters of AGN winds. By deciphering their variability and constructing their ionization and kinematic structure, new insights are gained on the formation of AGN outflows.

At the dawn of the high-energy astrophysics era, the origin of the bright, extended X-ray emission seen towards clusters and groups of galaxies was debated. The advent of dedicated space observatories established that these systems shine in X-rays via thermal bremsstrahlung and line emission from a hot (10^7-10^8 K), magnetized, collisionally ionized medium permeating them. However, radio wavelength detections of diffuse synchrotron radiation from relativistic electrons in some systems implies the existence of a non-thermal component that should also boost cosmic microwave background (CMB) photons up to X-ray energies. So far, such inverse-Compton (IC) emission had not been unambiguously detected on cluster/group scales. In this talk, we report and discuss a robust (4.6σ) detection of X-ray IC emission in a large-scale gravitationally bound system—the group of galaxies MRC 0116+111. This detection provides a unique unbiased estimate of (1.9 ± 0.3) μG of the volume-average magnetic field intensity within this group. We will discuss the robustness of this measurement and explore how its unrivaled accuracy is a pre-requisite for a realistic understanding of processes underlying the magnetic genesis within the largest gravitationally bound structures in our Universe.

The X-ray spectra of supernova remnants (SNRs) often exhibit prominent emission lines that can be used to diagnose the physical conditions in an SNR plasma. In lower-resolution spectra, commonly observed lines, like the components of H- and He-like Kα triplets, as well as lines in the Fe-L complex, can appear blended. With sufficiently precise high-resolution X-ray spectroscopy, these individual lines may be resolved, and previously obscured faint lines from trace elements may become detectable. Precise measurements of the widths, shapes, and intensities of these lines reveal the temperature, ionization state, elemental abundances, and velocity of the X-ray emitting plasma. Evaluation of these properties helps to constrain models of the progenitor SN explosion mechanism, the age and distance to an SNR, and its dynamical 3D evolution. I will discuss new findings garnered from SNR studies that utilized high-resolution X-ray grating spectrometers on board Chandra and XMM-Newton, and the challenges of using these dispersed spectra to study extended sources like SNRs. One of the exciting new tools in X-ray spectroscopy is the microcalorimeter, which produces non-dispersive high-resolution spectra. Microcalorimeters have been employed in the short-lived Hitomi satellite and its successor, the upcoming X-Ray Imaging and Spectroscopy Mission. New telescopes under development like the Advanced Telescope for High Energy Astrophysics and proposed telescopes like the Lynx X-ray Observatory may be launched in the 2030s, and are planned to feature advanced microcalorimeter detectors. I will discuss the potential of these new detectors, which are designed to have both the spectral resolution of current gratings spectrometers and the spatial resolution of CCD detectors, in the context of SNR observations.

When the XRISM X-ray observatory begins operations later this year, it will provide an unprecedented combination of high spectral resolution, large collecting area, and broad-band X-ray coverage, enabling new insights into many areas of astrophysics. The capability to precisely measure line-of-sight motion in spatially resolved regions promises to transform the study of galaxy clusters, allowing direct measurements of ICM bulk motions and turbulent velocity within and away from the cluster core. These measurements in turn will place interesting constraints on the non-thermal pressure support in relaxed clusters, with implications for cosmologically important X-ray mass estimates. I will describe the initial observing campaign designed to perform these measurements, which will serve as a benchmark for future XRISM observations to expand the sample of clusters with direct ICM velocity measurements.

Novae are explosive nuclear fusion events taking place on the surface of a White Dwarf star, and the required hydrogen-rich burning fuel is obtained by previous accretion from a companion star. The energy is initially released in the form of high-energy radiation, but dense absorbing material converts it to kinetic energy (expansion of ejecta) and lower-energy radiation. The lower-energy radiation escapes into space at a pseudo photosphere whose radius and effective temperature depend on the optical depth of and path through the material between the bottom burning layers and where the opacity drops to tau~1. The radiation transport zones are not in hydrostatic equilibrium (like in stars), and the appearance of a nova changes continuously, initially bright in the visible leading to discovery, usually by optical observers from the ground. This continuous shift of the Spectral Energy Distribution (SED) terminates at Teff of a few 10^5K, observable as a super-soft X-ray spectrum (Wien tail at ~1-2keV), and the nova radiations this emission until the hydrogen reservoir is converted to helium. High-resolution spectroscopy of this super-soft emission revealed bright continua spectra with absorption lines whose depth scales with abundances and whose blue-shifts reveal the expansion velocity of ejecta. There is also a class of permanent Super-Soft-Sources (SSS) which obtain the fuel from the companion star at the same rate as it is burnt. In this review talk, I will demonstrate a surprisingly large degree of diversity of SSS spectra. For example, some are modulated with short-term quasi-periodic oscillations, some have with flat others very deep absorption lines, some are dominated by emission lines. All these observational properties are only observable in high spectral resolution and give important information, e.g. about the system orientation or the absorption behaviour of the overlying material.

The amount of baryons hosted in the disks of galaxies is lower than expected based on the mass of their dark-matter halos and the fraction of baryon-to-total matter in the universe, giving rise to the so called galaxy missing-baryon problem. It has been suggested, that the galaxy missing baryons may hide in a hot gaseous phase of the circum-galactic medium, possibly near the halo virial temperature. Here we report the first direct high-statistical-significance (5.3-6.2 sigma) detection of Ovii and Nvi absorption in the stacked XMM-Newton and Chandra spectra of three quasars. We show that these absorbers trace hot medium in the X-ray halo of these systems, at logT(in k) ~ 5.88-6.1 K. We estimate a mass of the X-ray halo M(hot-CGM) ~ (1.4-1.6)x1e11 Msun, corresponding, for these systems, to a galaxy missing baryon fraction xi = M(hot-CGM)/M(missing) ~ 0.99-1.13 and thus closing the galaxy baryon census in typical L* galaxies. Our measurements contribute significantly to the solution of the long-standing galaxy missing baryon problem and to the understanding of the continuous cycle of baryons in-and-out of galaxies throughout the life of the universe.

Identifying trends between observational data and the range of physical parameters of massive stars is a critical step to the still-elusive full understanding of the source, structure, and evolution of X-ray emission from the stellar winds, requiring a substantial sample size and systematic analysis methods. The Chandra data archive as of 2022 contains 37 high resolution spectra of O, B, and WR stars, observed with the Chandra/HETGS and of sufficient quality to fit the continua and emission line profiles. Using a systematic approach to the data analysis, we explore morphological trends in the line profiles (i.e., O, Ne, Mg, Si) and find that the centroid offsets of resolved lines versus wavelength can be separated in three empirically-defined groups based on the amount of line broadening and centroid offset. Using \ion{Fe}{17} (15.01 \AA, 17.05 \AA) and \ion{Ne}{10} $\alpha$ (12.13 \AA) lines which are prevalent among the sample stars, we find a well-correlated linear trend of increasing Full Width Half Maximum (FWHM) with faster wind terminal velocity. The H-like/He-like total line flux ratio for strong lines displays different trends with spectral class depending on ion species. Some of the sources in our sample have peculiar properties (e.g., magnetic and $\gamma$Cas-analogue stars) and we find that these sources stand out as outliers from more regular trends. Finally, our spectral analysis is presented summarily in terms of X-ray spectral energy distributions in specific luminosity for each source, plus tables of line identifications and fluxes.

The Milky Way resides in a gaseous halo made up of hot and tenuous plasma. It is important to understand the physics of this gas, because of its impact on the Galaxy and because it is an analog of halos of external galaxies, which are currently challenging to probe.
In this talk we present an absorption study of the hot Milky Way halo towards radiatively efficient and feature-rich AGN NGC 4051 with 1 Ms Chandra HETG observations across two epochs, 8 years apart. In contrast to typically used featureless blazars, modeling Milky Way absorption here requires de-blending the signal from AGN absorption. We achieve this by using an agnostic Bayesian framework and modeling Milky Way and AGN absorption fully self-consistently, using all of the data available (i.e. not focusing on individual lines). Critically, we do not fix the AGN model (nor any other parameters), accounting for correlations in model parameters, which results in unbiased measurements and uncertainties.
We obtain measurements of the temperature, column density, velocity structure, line broadening, and metallicity of the Milky Way hot halo, as well as its evolution over an 8 year period. Crucially, we also place a statistically robust constraint on the number of absorption components required to fit these high S/N high resolution spectra, avoiding overfitting.
The main advantage of our approach is that it allows us now to use the deepest, highest S/N spectra ever taken with Chandra to map the structure of the Milky Way halo towards multiple sightlines across many visits, which is important because Chandra HETG remains the highest resolution X-ray spectrograph.

20 Galactic and Magellanic Cloud novae have been observed with the X-ray gratings, most of them with the Chandra HETG or LETG. In addition, also 9 supersoft X-ray sources, related to novae because of shell hydrogen burning, have been observed with the Chandra LETG. Two of the novae were "recurrent novae" - with outbursts recurring on time scales of years - and they have been monitored in two different outbursts, allowing an interesting comparison between the eruptions. Two types of X-ray spectra are observed in novae: one is due to powerful shocks in the outflows, perhaps related to the gamma-ray emission or... perhaps not, and the second type is observed when the hydrogen burning white dwarf shrinks to almost pre-outburst dimensions and the surrounding ejecta became transparent to supersoft X-rays. Sometimes the spectra from the two different emitting sites are superimposed for an amount of time. We observed intricate and extremely interesting spectra, allowing us to throw light on a number of interesting phenomena, but we still have some unidentified lines. I will outline the highlights of this research that spans over 20 years.

Massive stars are important cosmic engines driving cosmic circuit of matter in star forming galaxies. Being born with masses above at least 8 solar, these stars dominate the cosmic supply chain of neutron stars and black holes. The advent of gravitational wave astronomy led to the renaissance of the massive star research. Among the most profound questions are the properties of stellar winds, especially in evolved stars short before their core collapse. Since the beginning of XXI century, high-resolution X-ray spectroscopy is among the key tools to study stellar winds. During all this time, Chandra and XMM-Newton operate in parallel with the Hubble Space Telescope (HST) which allows to measure high-resolution UV spectra of hot stars. Joint, UV and X-ray spectroscopy open a new window into the dynamic environment of stellar winds. At the same time, the theory advantages made in the last decade challenge previous paradigms and, by developing 3-D models, open new research avenues. I will review the recent advances in high-resolution spectroscopy of massive hot stars. The results of large and joint observing campaigns will be presented and discussed. I will also discuss future perspectives highlighting the continuous need for high-resolution X-ray spectroscopy of hot stars and their winds.

The first detection of X-ray wind signatures (mainly FeXXV/XXVI absorption lines between 6 and 8 keV) in Black Hole Low Mass X-ray Binaries (BHLMXBs) took place more than 20 years ago. In the last decade, it has become apparent that these winds are only detected in strongly inclined objects, hinting at them originating from the disk, although there is still no unequivocal evidence for a magnetic or thermal origin. On the other hand, most detections occur during the soft spectral state, for reasons yet to be fully understood. We present an update of the current state of wind detections in BHLMXBs, through the analysis of all available XMM-EPIC and Chandra-HETG data of all LMXBs currently classified as BH/BH candidates, from the BlackCAT and WATCHDOG catalogs. We will discuss the number of sources with statistically significant detections in the 6-8 keV band, the associated EWs, blueshifts and line ratios, and their correlation with inclination and spectral state. Following this, we will present preliminary comparisons with synthetic spectra of MHD accretion-ejection models.

X-ray cavities and radio lobes, inflated into the atmospheres of giant elliptical galaxies, groups and clusters by the relativistic jets emanating from central active galactic nuclei (AGN), play a crucial role in radio-mechanical AGN feedback. Studying their properties provides a powerful insight into the energetics of hot galactic atmospheres and allows to probe how the central AGN engines affect the surrounding intracluster medium (ICM). Moreover, for many sources, X-ray cavities represent the only remnant of past AGN activity, making them important probes of AGN feedback over cosmic time.
We will present Cavity Detection Tool (CADET), a machine learning pipeline, which has been trained to detect X-ray cavities from noisy Chandra images of early-type galaxies, groups and clusters. The pipeline can be used as a stand-alone script to automatically detect X-ray cavities for a number of systems as well as via a simple web interface. Detected X-ray cavities, when combined with deprojected pressure profiles, can be used to estimate the mechanical power of the AGN jet that inflated them. We will further present a comparison between mechanical jet powers derived from radio lobes and X-ray cavities detected by CADET for a sample of nearby radio galaxies.

Changes in neutral K$\alpha$ fluorescence lines and absorption column density, are often used as tracers of these changing physical conditions in X-ray binaries. These emission lines are ubiquitous to these systems and are powerful probes of the geometry and abundances of surrounding matter near the compact object. If the Compton optical depth of the medium is high ($>0.1$), the Fe K$\alpha$ photon at 6.4 \,keV can be further Compton scattered in the same medium and lose some energy ($\sim 156$\,eV for backscattered photons). Such scattered photons produce a shoulder at a lower energy, known as the Compton Shoulder and is most significant for the Fe K$\alpha$ line due to its high fluorescence yield. These Compton scattering features at high energies provide a sensitive diagnostic for physical conditions of matter irradiated by an X-ray source such as an accretion disk/stellar wind structure illuminated by a compact object and can currently be exclusively studied only by Chandra gratings. We discuss the relevance of these features in High Mass X-ray Binaries like IGR J16318-4848, GX 1+4, and OAO 1657-415 and the importance of such high-resolution spectral studies with XRISM.

The Orion Nebula Cluster (ONC) is an ideal astrophysical laboratory to study very young (< 0.5 - 2 Myr) stars. Being the nearest site of massive star formation and hosting a young high-mass near ZAMS stellar population, the core of the ONC is ideal for detailed spectroscopic studies of young embedded cluster stars. In 2003 the Chandra Orion Ultradeep Project (COUP) established global X-ray properties of the stellar populations with the ONC setting a true milestone in the X-ray studies of star forming regions. A Chandra Very Large Project (VLP) to re-observe the core of the ONC was carried out to boost the exposure with the Chandra High Energy Transmission Grating Spectrometer (HETGS) to 2.2 Msec. We have now completed a milestone step in the process of cluster confusion cleaning of HETGS spectra which allows us to release a first set of three dozen high resolution X-ray spectra from young massive, intermediate mass, and low mass stars. In this first release we determine line widths, line ratios, abundances, and column densities as part of a pilot paper. Besides the source table where we have 1st order spectra we present a zero order source detection table with stars that have not been observed during COUP. We also present an updated companion account to all high mass stars in the cluster. Higher order spectra are highlighted which have spectral resolving powers of 1500 to 500 from Mg to Ca providing us with a glimpse of what to expect from near future missions such as XRISM and Athena.

Interstellar dust is an important ingredient of the interstellar medium (ISM) of galaxies, as it appears in every stage of stellar evolution, from evolved stars and supernovae to protoplanetary disks. High-resolution X-ray spectroscopy is a powerful tool for studying interstellar dust mineralogy. X-ray absorption fine structures (XAFS) are oscillatory modulations observed near the X-ray photoelectric absorption edges, and their shape is the ultimate footprint of the dust chemical composition, size and lattice structure. In this presentation I will demonstrate the newest laboratory measurements of XAFS from astrophysical dust templates in the O K and Fe L photoabsorption edges (Psaradaki et al. 2020,2021), and their application to high-resolution X-ray spectra of a sample of bright Galactic X-ray sources. I will present recent results (Psaradaki et al. 2022) on dust mineralogy in the diffuse regions in our Galaxy using Chandra/HETGS and XMM-Newton/RGS observations. This study gave the most comprehensive view of the silicate mineralogy in the diffuse regions of ISM, through the X-ray energy band. We found that the Mg-rich amorphous pyroxene dust composition (Mg0.75Fe0.25SiO3), and metallic iron represents the bulk of the dust chemistry in the diffuse ISM. Finally, I will discuss the prospects of studying the dust grain chemistry in denser regions of the ISM through the XRISM performance verification phase (PV) target, GX 13+1.

X-ray observations of galaxy clusters have revealed the presence of spiraling features, particularly ~ 95% in cool core (CC) clusters. These features are believed to arise from the motion of the intracluster medium induced by mergers or other disturbances. While simulations of merging clusters have reproduced such features, their limitations (e.g., merging is rare in CC clusters) have prompted the investigation of alternative mechanisms. AGN feedback is one such mechanism, and its potential role in driving gas sloshing has been the focus of recent research. We present evidence of gas sloshing motion in a cosmic ray (CR) dominated AGN jet feedback simulation of galaxy clusters. Our magnetohydrodynamic simulation shows spiral-like features with a scale of ~100 kpc, consistent with some current X-ray observations of CC clusters. We investigated the results in various projections and compared them with real X-ray observations from Chandra and XMM Newton. Our findings suggest that AGN jet feedback can drive spiral like gas features in galaxy clusters. These findings have important implications for understanding the formation and evolution of galaxy clusters and the role of AGN feedback in shaping their properties. The high-resolution spectroscopy can reveal the natures of the motions in these systems, as well as the abundances of the gas.

While the field of X-ray spectral analysis has burgeoned over the last two decades, the intrinsic spectrum of targets has eluded astronomers; rather than observing the true spectrum, the observed spectrum is a convolution of the true spectrum with the instrumental response function. Using a class of neural networks known as a Recurrent Inference Machine (RIM), we have successfully deconvolved the source’s intrinsic spectrum from the instrumental response function for the first time. In his presentation, we will discuss the intricacies of fitting X-ray spectra, how RIMs can be used to deconvolve them, and the implications of this deconvolution to several domains of X-ray astronomy.

Eclipse and out-of-eclipse high-resolution X-ray spectra of Cen X-3 were extracted and analysed from two XMM-Newton observations. Properties of the emitting and absorbing matter were studied through the emission and absorption lines identified in its spectra. The level of counts above 20 Å was compatible with the X-ray background. RGS continuum was described with several collisional ionization equilibrium components for optically thin plasmas plus an absorption neutral gas. Emission lines from Si v, Mg xii, Mg xi, and Ne x were detected in the eclipse spectrum but seemed to be absent in the out-of-eclipse spectrum.

The origin of X-rays from the inner regions of our Galaxy, first discovered over 40 years ago, remains uncertain. There is now evidence for an excess of both hard (> 10 keV) and soft (< 10 keV) X-rays from both the Galactic Ridge and the Galactic Center. The Fe K-alpha emission complex is also seen in both regions. Multiple studies have postulated that accreting white dwarfs (WDs) are the dominant contributors to X-ray continuum and line emission from the Galactic Ridge and Galactic Center. I will briefly summarize how these studies strongly disagree on the mean mass of the accreting WDs, and even on whether the prevailing WDs are strongly magnetic. I will highlight how high-resolution X-ray spectroscopy can provide a unique insight into this long-standing mystery.

The study investigates Xray Transients in the nearby galaxy NGC 4552,which is an elliptical early type galaxy in the Virgo Cluster, using the datas obtained from Chandra telescope. We visually detected a total of 15 transients within the 4Re circle and 6 sources outside the 4Re circle.Visual identification is based on the on-off state of the xray sources.The spectrum and lightcurve for these 15 sources inside the 4Re circle is extracted. The extracted spectrum is fitted using single component models POWER-LAW and DISKBB and using the CFLUX we calculated flux value and error for these xray sources and calculated the luminosity value. The luminosity range for the detected sources vary from 10^37 to 10^40 erg/s,which is thereby satisfying the first criteria of Xray Transients which have luminosity limit of 10^36 erg/s. Then the upper limit for the undetected sources are calculated and the flux and luminosity range for those also calculated. On the basis of the classification of transients based on the luminosity, most of the Xray sources we detected are soft Xrays and are in LMXBs.

We have observed the ultracompact X-ray binary pulsar 4U 1626-67 for a time span over two decades starting before and continuing after the magnetic accretion torque reversal event in 2008 with tha Chandra X-ray Observatory High Energy Transmission Grating Spectrometer. Spectral fits to strong Ne and O emission disk lines with Keplerian profiles are interpreted as arising from the inner edge of the magnetically-truncated accretion disk. The absence of radiative recombination continua in the spectra and the shape of the observed disk lines are consistent with a hot collisionally ionized plasma with temperatures of the order of 10 MK at the inner edge of a truncated accretion disk. Furthermore, by using the inner disk radius from the disk line fits before and after the 2008 torque reversal event as a tracer we observe inner disk radii that are larger than the corotation radius during spin-down but smaller after the torque reversal as the pulsar began to spin faster. Monitoring of these disk ine properties for well over a decade past the torque reversal event in 2008 also shows that temperature of the collisionally ionized plasma region is very stable but also highly clumped allowing for coexistance of hot ionized and cool neutral matter. The data also provide details about system inclination, source distance, and abundance estimates that can be used to constrain the mass and constitution of the degenerate companion. We will provide a detailed picture of what the high energy emissions of this unique system are about. Finally, we extrapolate the current trend to estimate the date of the next torque reversal.

Winds driven by Active Galactic Nuclei (AGNs), represent one of the primary mechanisms by which a supermassive black hole interacts with its host galaxy. We study sub-relativistic winds observed in the Narrow Line Seyfert 1 Galaxy Mrk 110, which were detected as absorption lines in high-resolution X-ray spectra by the Reflection grating Spectrometer (RGS) on the XXM-Newton satellite. We identified at least two Ultra Fast Outflows (UFOs) in the spectra, with velocities of 45,900 km/s and 19,400 km/s, respectively. In addition, these UFOs exhibited a lower ionization state and column density than highly ionized UFOs that have been previously observed. Preliminary results on NuSTAR spectroscopy of Mrk 110 confirm the presence of a wind component from highly ionized Iron. Overall, our results provide further evidence of the high occurrence of stratified UFOs in NLSy1 galaxies.

Iron is the most abundant heavy element in the universe and plays a crucial role in spectroscopic research, particularly in understanding the properties of hot celestial plasmas. X-ray astronomers have faced a long-standing issue for over 40 years concerning the intensity ratio of two transitions in Fe XVII, which is critical for plasma diagnostics. The disagreement between state-of-the-art theory and observations has resulted in discrepancies in atomic data and spectral plasma models. Here I present new laboratory measurements obtained using electron beam ion traps and various spectrometers to determine the individual line formation processes contributing to Fe XVII transitions. Furthermore, I will demonstrate how this issue has been resolved at the PETRA III synchrotron facility by improving the resolving power and signal-to-noise ratio to an unprecedented level, resulting in an agreement between theory and experiment for the oscillator strengths of Fe XVII transitions. The new laboratory data will significantly enhance the accuracy of atomic data for plasma diagnostics, including measurements of electron temperature and density, element abundance, velocity turbulence, and plasma opacity.

Accurate measurement of X-ray source properties necessitates a comprehensive understanding of the X-ray background, particularly when studying faint and extended objects. Traditionally, we subtract the estimated X-ray background from nearby regions with no source emission or employ a blank-sky background. However, these estimates may not precisely reflect the true background in the data, in addition to the challenges in obtaining reliable statistical information from background-subtracted images. In this talk, I will introduce a novel approach for estimating X-ray background models that encompass various components, including foreground contamination, unresolved point sources, and particle-induced background. I will showcase the impressive performance achieved thus far with this method on Chandra data for regions devoid of resolved source emission, highlighting its ability to extract valuable information from extremely faint sources. This novel approach assumes greater significance for future X-ray missions with higher spectral resolution, such as XRISM, in order to ensure the generation of robust and accurate results for faint sources.

The physical properties of the faint and extremely tenuous plasma in the filaments of the cosmic web remain one of the biggest unknowns in our story of large-scale structure evolution. The observations with nowadays missions still posses a big challenge. The most common techniques how to observe this medium are either in emission, or in absorption against very bright, point-like sources. In this talk I will focus on the warm-hot intergalactic medium (WHIM) and present yet another technique, which can be explored for now only in theory and with simulations, but it might serve as a complementary tool to explore the properties of the cosmic web with upcoming future X-ray missions. I will present how the cosmic web filaments, simulated with the cosmological hydrodynamical simulations Hydrangea, look like in OVII and OVIII absorption against diffuse extended sources, in particular, relaxed, nearby, massive cool core galaxy clusters. I show its spatial properties as well as its velocity structure in particular projections. I simulate the observations with Athena X-IFU and LEM, while taking into account the absorption from our Galaxy, and report on the significance of the detection of WHIM in OVII. I discuss the lower limit on the OVII and OVIII column densities that can still be observed with these instruments and provide a guide of where to look for WHIM on the sky with future missions.

We present the analysis of archival high-dispersion XMM-Newton and Chandra data of the symbiotic star CH Cyg. He-like triplets detected in the XMM-Newton RGS and Chandra HEG & MEG confirm the multi-temperature X-ray-emitting gas of this symbiotic star. These high-dispersion spectra are also used to estimate abundances of the X-ray-emitting gas in CH Cyg which are very similar to the reg giant companion. In combination with medium-resolution spectra we also study the variability detected through the Fe emission lines in the 6-7 keV energy range. We finally address the production of X-rays from this symbiotic star by reflection from a disk-like component.

Stellar and AGN feedback is thought to play an essential role in galaxy formation and evolution. However, much of the underlying astrophysics remains highly uncertain. A powerful tool for probing the astrophysics of feedback is X-ray spectroscopy. I'd like to review several recent studies based on spectroscopic data from the XMM-Newton grating instruments, focusing on X-ray diagnostics of charge exchange and AGN remnants in the interstellar medium, and demonstrate the unique insights that such studies can provide into the nature of diffuse X-ray emission and the workings of feedback in galactic ecosystems.

The interplay between accretion and ejection in active galactic nuclei (AGN) is crucial for understanding the evolution of the central supermassive black hole and the host galaxy. However, the physical mechanisms underlying these phenomena are not yet fully understood. Ultra-fast outflows (UFO) launched from the inner accretion disk can help probe this connection. In this study, we systematically investigate the UFO response to source variations in seven highly accreting narrow-line Seyfert 1 AGN through time- and flux-resolved spectroscopy of archival XMM-Newton observations, expanding the sample size from three to ten. Our results reveal that the UFO is faster during brighter states in four out of the seven sources, indicating radiatively-driven outflows. However, we do not observe any significant UFO response in the remaining three sources, likely due to their relatively stable nature or rapid variability, which constrains the density of UFOs. A comparison of the outflow response to the continuum in these sources with those found in the literature provides insight into the nature of ultra-fast outflows in high-accretion systems.

The accreting pulsar 4U1907-09 is one of ~35 high-mass X-ray binaries with known high magnetic field strengths. A detected cyclotron resonance scattering feature at ~19 keV leads to a field strength of ~2E12 G. The system consists of a slowly-rotating (~440 s) X-ray pulsar accreting from the stellar wind of an O8/9 supergiant. The X-ray pulsar is in a close (~8.37 d) elliptical orbit (e $\sim$ 0.28) around its donor. We conducted an analysis of four High Energy Transmission Grating observations with the Chandra X-ray Observatory for a total of ~140 ks and one NuSTAR observations for 78 ks, at different orbital phases, to probe the variation of the absorbing column around the orbit. We measure line fluorescence at Fe K and possibly Si K and other lower Z elements to study dense clumps in the wind of the pulsar's companion star. The details of the NuSTAR observation is used to determine the higher energy continuum beyond 10 keV.

Studying the structure and kinematics of AGN outflows with X-ray observations inform our understanding of black hole accretion and AGN feedback. I will present the four XMM-Newton/NuSTAR observations taken during the campaign, as part of an ongoing, intensive multi-wavelength monitoring program of the Seyfert 1 galaxy Mrk 817 by the AGN Space Telescope and Optical Reverberation Mapping 2 (AGN STORM 2) Project. One fortuitous observation taken during a bright flare reveals strong narrow absorption lines in the high-resolution gratings spectra. From these absorption features, we reveal that the obscurer is in fact a multi-phase ionized wind with an outflow velocity of ~5000 km/s, and for the first time find evidence for a lower ionization component of the same velocity in the simultaneous HST spectra. The three other XMM-Newton/NuSTAR observations, one with a simultaneous Chandra observation, show strong narrow emission lines from a more distant absorber.

Over the past two decades, X-ray observations played a pivotal role in understanding the physics of the most massive halos in the Universe. These observations have enabled measurements of the hot gas densities, temperatures, and abundances of heavy elements in many systems, allowing the studies of AGN feedback, physical processes behind structure formation, and cluster cosmology. The next fundamental frontier in the studies of hot halos is measuring gas velocities and detailed distributions of metals. A new X-ray observatory, X-ray Imaging and Spectroscopy Mission (XRISM), will revolutionize this field, observing extended sources with an unprecedented spectral resolution of 5-7 eV. I will briefly review the observational program for the first six months of the mission, focusing on direct, spatially-resolved velocity measurements in the intracluster medium, accurate metallicity measurements and search for rare elements, resonant scattering, and charge exchange processes. These novel observables will provide new insights into the physical mechanisms that connect supermassive black holes with their host galaxies. Potential challenges with data interpretation will be discussed, along with possible approaches to resolve them. Additionally, I will highlight the capabilities of an exciting X-ray mission concept, Line Emission Mapper (LEM), that will enable high-resolution spectroscopic studies of cluster outskirts (up to a virial radius and beyond) and extended hot halos around the Milky-Way mass galaxies.

The circumgalactic medium (CGM) is the multiphase gas surrounding galaxies and is the reservoir from which gas flows onto galaxies and into which stellar and active galactic nuclei feedback eventually deposit mass, momentum, and energy. The dominant portion of the CGM by mass is hot and emits in X-rays. The Line Emission Mapper (LEM) probe is an X-ray observatory that would have the capability to map the thermodynamic, chemical, and kinematic properties of the CGM. In this work, we analyze the velocity fields of the hot X-ray emitting CGM of Milky Way-mass disk galaxies with bubbles similar to that in the MW from the TNG50 simulation using synthetic LEM observations. These are characterized by inflows and outflows in directions perpendicular to the disk, as well as rotation of the CGM which is generally aligned with the rotation of the stellar disk. We investigate the properties of the X-ray line shapes which will be produced by CGM motions, which will be determined by the types of velocity fields in the CGM as well as the observed line of sight. We also determine the relationship between the velocity fields of the cold and hot gas components of the galaxies, and how this relationship could be probed with multi-wavelength observations. Our results show how X-rays can detect and analyze the flows of hot gas into and out of the CGM that drive the formation and ongoing evolution of galaxies.