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Search indexed NASA NTRS and DOE OSTI research on propulsion, heat transfer, battery materials and energy systems. Follow report and document links to the original sources.

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At least 163 records · Page 9
All sourcesNASA NTRSDOE OSTI
DOE OSTI2014

Particle concentration at planet-induced gap edges and vortices. I. Inviscid three-dimensional hydro disks

We perform a systematic study of the dynamics of dust particles in protoplanetary disks with embedded planets using global two-dimensional and three-dimensional inviscid hydrodynamic simulations. Lagrangian particles have been implemented into the magnetohydrodynamic code Athena with cylindrical coordinates. We find two distinct outcomes depending on the mass of the embedded planet. In the presence of a low-mass planet (8 M {sub ⊕}), two narrow gaps start to open in the gas on each side of the planet where the density waves are shocked. These shallow gaps can dramatically affect particle drift speed and cause significant, roughly axisymmetric dust depletion. On the other hand, a more massive planet (>0.1 M{sub J} ) carves out a deeper gap with sharp edges, which are subject to Rossby wave instability leading to vortex formation. Particles with a wide range of sizes (0.02 < Ωt{sub s} < 20) are trapped and settle to the midplane in the vortex, with the strongest concentration for particles with Ωt{sub s} ∼ 1. The dust concentration is highly elongated in the φ direction, and can be as wide as four disk scale heights in the radial direction. Dust surface density inside the vortex can be increased by more than a factor of 10{sup 2} in a very non-axisymmetric fashion. For very big particles (Ωt{sub s} >> 1) we find strong eccentricity excitation, in particular around the planet and in the vicinity of the mean motion resonances, facilitating gap openings there. Our results imply that in weakly turbulent protoplanetary disk regions (e.g., the {sup d}ead zone{sup )} dust particles with a very wide range of sizes can be trapped at gap edges and inside vortices induced by planets with M{sub p} < M{sub J} , potentially accelerating planetesimal and planet formation there, and giving rise to distinctive features that can be probed by ALMA and the Extended Very Large Array.

79 ASTRONOMY AND ASTROPHYSICS↗
DOE OSTI2014

Oblique shock breakout in supernovae and gamma-ray bursts. II. Numerical solutions for non-relativistic pattern speeds

Non-spherical explosions develop non-radial flows as the pattern of shock emergence progresses across the stellar surface. In supernovae, these flows can limit ejecta speeds, stifle shock breakout emission, and cause collisions outside the star. Similar phenomena occur in stellar and planetary collisions, tidal disruption events, accretion-induced collapses, and propagating detonations. We present two-dimensional, nested-grid Athena simulations of non-radial shock emergence in a frame comoving with the breakout pattern, focusing on the adiabatic, non-relativistic limit in a plane stratified envelope. We set boundary conditions using a known self-similar solution and explore the role of box size and resolution on the result. The shock front curves toward the stellar surface, and exhibits a kink from which weak discontinuities originate. Flow around the point of shock emergence is neither perfectly steady nor self-similar. Waves and vortices, which are not predominantly due to grid effects, emanate from this region. The post-shock flow is deflected along the stellar surface and its pressure disturbs the stellar atmosphere upstream of the emerging shock. We use the numerical results and their analytical limits to predict the effects of radiation transfer and gravity, which are not included in our simulations.

79 ASTRONOMY AND ASTROPHYSICS↗
DOE OSTI2015

THE EFFECT OF ANISOTROPIC VISCOSITY ON COLD FRONTS IN GALAXY CLUSTERS

Cold fronts—contact discontinuities in the intracluster medium (ICM) of galaxy clusters—should be disrupted by Kelvin-Helmholtz (K-H) instabilities due to the associated shear velocity. However, many observed cold fronts appear stable. This opens the possibility of placing constraints on microphysical mechanisms that stabilize them, such as the ICM viscosity and/or magnetic fields. We performed exploratory high-resolution simulations of cold fronts arising from subsonic gas sloshing in cluster cores using the grid-based Athena MHD code, comparing the effects of isotropic Spitzer and anisotropic Braginskii viscosity (expected in a magnetized plasma). Magnetized simulations with full Braginskii viscosity or isotropic Spitzer viscosity reduced by a factor f ∼ 0.1 are both in qualitative agreement with observations in terms of suppressing K-H instabilities. The rms velocity of turbulence within the sloshing region is only modestly reduced by Braginskii viscosity. We also performed unmagnetized simulations with and without viscosity and find that magnetic fields have a substantial effect on the appearance of the cold fronts, even if the initial field is weak and the viscosity is the same. This suggests that determining the dominant suppression mechanism of a given cold front from X-ray observations (e.g., viscosity or magnetic fields) by comparison with simulations is not straightforward. Finally, we performed simulations including anisotropic thermal conduction, and find that including Braginskii viscosity in these simulations does not significantly affect the evolution of cold fronts; they are rapidly smeared out by thermal conduction, as in the inviscid case.

79 ASTRONOMY AND ASTROPHYSICS↗
DOE OSTI2015

Radio–X-ray synergy to discover and study jetted tidal disruption events

Observational consequences of tidal disruption of stars by supermassive black holes (SMBHs) can enable us to discover quiescent SMBHs, constrain their mass function, and study the formation and evolution of transient accretion disks and jet formation. A couple of jetted tidal disruption events (TDEs) have been recently claimed in hard X-rays, challenging jet models, which were previously applied to γ-ray bursts and active galactic nuclei. It is therefore of paramount importance to increase the current sample. In this paper, we find that the best strategy is not to use upcoming X-ray instruments alone, which will yield between several (eRosita) and a couple of hundred (Einstein Probe) events per year below redshift one. We rather claim that a more efficient TDE hunter will be the Square Kilometer Array (SKA) operating in survey mode at 1.4 GHz. It may detect up to several hundred events per year below z ∼ 2.5 with a peak rate of a few tens per year at z ≈ 0.5. Therefore, even if the jet production efficiency is not 100% as assumed here, the predicted rates should be large enough to allow for statistical studies. The characteristic TDE decay of t{sup −5/3}, however, is not seen in radio, whose flux emission is quite featureless. Identification therefore requires localization and prompt repointing by higher energy instruments. If radio candidates would be repointed within a day by future X-ray observatories (e.g., Athena- and LOFT-like missions), it will be possible to detect up to ≈400 X-ray counterparts, almost up to redshift 2. The shortcoming is that only for redshift below ≈0.4 will the trigger times be less than 10 days from the explosion. In this regard the X-ray surveys are better suited to probe the beginning of the flare, and are therefore complementary to SKA.

79 ASTRONOMY AND ASTROPHYSICS↗
DOE OSTI2015

Simulated photoevaporative mass loss from hot jupiters in 3D

Ionizing stellar photons heat the upper regions of planetary atmospheres, driving atmospheric mass loss. Gas escaping from several hot, hydrogen-rich planets has been detected using UV and X-ray transmission spectroscopy. Because these planets are tidally locked, and thus asymmetrically irradiated, escaping gas is unlikely to be spherically symmetric. In this paper, we focus on the effects of asymmetric heating on local outflow structure. We use the Athena code for hydrodynamics to produce 3D simulations of hot Jupiter mass loss that jointly model wind launching and stellar heating via photoionization. Our fiducial planet is an inflated, hot Jupiter with radius R{sub p}=2.14R{sub Jup} and mass M{sub p}=0.53M{sub Jup}. We irradiate the initially neutral, atomic hydrogen atmosphere with 13.6 eV photons and compute the outflow’s ionization structure. There are clear asymmetries in the atmospheric outflow, including a neutral shadow on the planet’s nightside. Given an incident ionizing UV flux comparable to that of the Sun, we find a steady-state mass loss rate of ∼2×10{sup 10} g s{sup −1}. The total mass loss rate and the outflow substructure along the substellar ray show good agreement with earlier 1D models, for two different fluxes. Our 3D data cube can be used to generate the outflow’s extinction spectrum during transit. As a proof of concept, we find absorption of stellar Lyα at Doppler-shifted velocities of up to ±50 km s{sup −1}. Our work provides a starting point for further 3D models that can be used to predict observable signatures of hot Jupiter mass loss.

79 ASTRONOMY AND ASTROPHYSICS↗
DOE OSTI2015

Magnetohydrodynamic-particle-in-cell method for coupling cosmic rays with a thermal plasma: application to non-relativistic shocks

We formulate a magnetohydrodynamic-particle-in-cell (MHD-PIC) method for describing the interaction between collisionless cosmic ray (CR) particles and a thermal plasma. The thermal plasma is treated as a fluid, obeying equations of ideal MHD, while CRs are treated as relativistic Lagrangian particles subject to the Lorentz force. Backreaction from CRs to the gas is included in the form of momentum and energy feedback. In addition, we include the electromagnetic feedback due to CR-induced Hall effect that becomes important when the electron–ion drift velocity of the background plasma induced by CRs approaches the Alfvén velocity. Our method is applicable on scales much larger than the ion inertial length, bypassing the microscopic scales that must be resolved in conventional PIC methods, while retaining the full kinetic nature of the CRs. We have implemented and tested this method in the Athena MHD code, where the overall scheme is second-order accurate and fully conservative. As a first application, we describe a numerical experiment to study particle acceleration in non-relativistic shocks. Using a simplified prescription for ion injection, we reproduce the shock structure and the CR energy spectra obtained with more self-consistent hybrid-PIC simulations, but at substantially reduced computational cost. We also show that the CR-induced Hall effect reduces the growth rate of the Bell instability and affects the gas dynamics in the vicinity of the shock front. As a step forward, we are able to capture the transition of particle acceleration from non-relativistic to relativistic regimes, with momentum spectrum f(p)∝p{sup −4} connecting smoothly through the transition, as expected from the theory of Fermi acceleration.

79 ASTRONOMY AND ASTROPHYSICS↗
DOE OSTI2014

AN ALGORITHM FOR RADIATION MAGNETOHYDRODYNAMICS BASED ON SOLVING THE TIME-DEPENDENT TRANSFER EQUATION

We describe a new algorithm for solving the coupled frequency-integrated transfer equation and the equations of magnetohydrodynamics in the regime that light-crossing time is only marginally shorter than dynamical timescales. The transfer equation is solved in the mixed frame, including velocity-dependent source terms accurate to O(v/c). An operator split approach is used to compute the specific intensity along discrete rays, with upwind monotonic interpolation used along each ray to update the transport terms, and implicit methods used to compute the scattering and absorption source terms. Conservative differencing is used for the transport terms, which ensures the specific intensity (as well as energy and momentum) are conserved along each ray to round-off error. The use of implicit methods for the source terms ensures the method is stable even if the source terms are very stiff. To couple the solution of the transfer equation to the MHD algorithms in the ATHENA code, we perform direct quadrature of the specific intensity over angles to compute the energy and momentum source terms. We present the results of a variety of tests of the method, such as calculating the structure of a non-LTE atmosphere, an advective diffusion test, linear wave convergence tests, and the well-known shadow test. We use new semi-analytic solutions for radiation modified shocks to demonstrate the ability of our algorithm to capture the effects of an anisotropic radiation field accurately. Since the method uses explicit differencing of the spatial operators, it shows excellent weak scaling on parallel computers.

79 ASTRONOMY AND ASTROPHYSICS↗
DOE OSTI2024

Adaptive mesh refinement in binary black holes simulations

Abstract We discuss refinement criteria for the Berger–Rigoutsos (block-based) refinement algorithm in our numerical relativity code GR-Athena++ in the context of binary black hole (BBH) merger simulations. We compare three different strategies: the ‘box-in-box’ approach, the ‘sphere-in-sphere’ approach and a local criterion for refinement based on the estimation of truncation error of the finite difference scheme. We extract and compare gravitational waveforms using the three different mesh refinement methods and compare their accuracy against a calibration waveform and demonstrate that the sphere-in-sphere approach provides the best strategy overall when considering computational cost and the waveform accuracy. Ultimately, we demonstrate the capability of each mesh refinement method in accurately simulating gravitational waves from BBH systems—a crucial aspect for their application in next-generation detectors. We quantify the mismatch achievable with the different strategies by extrapolating the gravitational wave mismatch to higher resolution.

Astronomy & Astrophysics↗
DOE OSTI2018

Leveraging the checkpoint-restart technique for optimizing CPU efficiency of ATLAS production applications on opportunistic platforms

Data processing applications of the ATLAS experiment, such as event simulation and reconstruction, spend considerable amount of time in the initialization phase. This phase includes loading a large number of shared libraries, reading detector geometry and condition data from external databases, building a transient representation of the detector geometry and initializing various algorithms and services. In some cases the initialization step can take as long as 10-15 minutes. Such slow initialization has a significant negative impact on overall CPU efficiency of the production job, especially when the job is executed on opportunistic, often short-lived, resources such as commercial clouds or volunteer computing. In order to improve this situation, we can take advantage of the fact that ATLAS runs large numbers of production jobs with similar configuration parameters (e.g. jobs within the same production task). This allows us to checkpoint one job at the end of its configuration step and then use the generated checkpoint image for rapid startup of thousands of production jobs. By applying this technique we can bring the initialization time of a job from tens of minutes down to just a few seconds. In addition to that we can leverage container technology for restarting checkpointed applications on the variety of computing platforms, in particular of platforms different from the one on which the checkpoint image was created. We will describe the mechanism of creating checkpoint images of Geant4 simulation jobs with AthenaMP (the multi-process version of the ATLAS data simulation, reconstruction and analysis framework Athena) and the usage of these images for running ATLAS Simulation production jobs on volunteer computing resources (ATLAS@Home) and on Supercomputers.

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗
DOE OSTI2018

Achievable noise performance of spectroscopic prototype DEPFET detectors

A new generation of spectroscopic X-ray DEPFET detectors has been produced here in the course of the detector development for the Wide Field Imager (WFI) of Athena. These devices served to perform a detailed analysis of the noise composition, which was enabled by the development of appropriate test algorithms. A result of the analysis is the distinction of different components, which sum up to the total noise. In particular the contribution of shot noise, white noise and 1/f noise to the readout noise is determined as well as the signal noise caused by the generation of charge carriers. The resulting parametrization enables the adaptation and optimization of operation modes to given purposes. The studied prototype detectors included 64×64 pixels with a linear gate design and provided an excellent noise, below 1.6 e - ENC at a readout time faster than 10 μs/pixel and a temperature of -80 °C in rolling-shutter operation. This performance is enabled by an extended signal integration time. A further noise reduction is prevented by the signal noise, caused by charge carrier generation. In order to demonstrate the low noise properties of the DEPFET transistor, the measurement conditions were adapted and a noise of 0.95 e - ENC was measured at the expense of the sensor size—by operating only parts of the sensor in window mode—and dynamic range—by using the Al Kα line at about 1.49 keV for calibration.

47 OTHER INSTRUMENTATION↗
DOE OSTI2014

A NEW COSMOLOGICAL DISTANCE MEASURE USING ACTIVE GALACTIC NUCLEUS X-RAY VARIABILITY

We report the discovery of a luminosity distance estimator using active galactic nuclei (AGNs). We combine the correlation between the X-ray variability amplitude and the black hole (BH) mass with the single-epoch spectra BH mass estimates which depend on the AGN luminosity and the line width emitted by the broad-line region. We demonstrate that significant correlations do exist that allow one to predict the AGN (optical or X-ray) luminosity as a function of the AGN X-ray variability and either the Hβ or the Paβ line widths. In the best case, when the Paβ is used, the relationship has an intrinsic dispersion of ∼0.6 dex. Although intrinsically more disperse than supernovae Ia, this relation constitutes an alternative distance indicator potentially able to probe, in an independent way, the expansion history of the universe. With respect to this, we show that the new mission concept Athena should be able to measure the X-ray variability of hundreds of AGNs and then constrain the distance modulus with uncertainties of 0.1 mag up to z ∼ 0.6. We also discuss how our estimator has the prospect of becoming a cosmological probe even more sensitive than the current supernovae Ia samples by using a new dedicated wide-field X-ray telescope able to measure the variability of thousands of AGNs.

79 ASTRONOMY AND ASTROPHYSICS↗
DOE OSTI2021

Gravito-turbulence and dynamo in poorly ionized protostellar discs – I. Zero-net-flux case

In their early stages, protoplanetary discs are sufficiently massive to undergo gravitational instability (GI). This instability is thought to be involved in mass accretion, planet formation via gas fragmentation, the generation of spiral density waves, and outbursts. A key and very recent area of research is the interaction between the GI and magnetic fields in young protoplanetary discs, in particular whether this instability is able to sustain a magnetic field via a dynamo. We conduct 3D, stratified shearing-box simulations using two independent codes, PLUTO and Athena++, to characterize the GI dynamo in poorly ionized protostellar discs subject to ambipolar diffusion. We find that the dynamo operates across a large range of ambipolar Elssaser number Am (which characterizes the strength of ambipolar diffusion) and is particularly strong in the regime Am = 10–100, with typical magnetic to thermal energy ratios of order unity. The dynamo is only weakly dependent on resolution (at least for Am ≲ 100), box size, and cooling law. The magnetic field is produced by the combination of differential rotation and large-scale vertical roll motions associated with spiral density waves. Our results have direct implications for the dynamo process in young protoplanetary discs and possibly some regions of active galactic nucleus discs.

79 ASTRONOMY AND ASTROPHYSICS↗
DOE OSTI2022

Chandra measurements of gas homogeneity and turbulence at intermediate radii in the Perseus Cluster

ABSTRACT We present a Chandra study of surface brightness fluctuations in the diffuse intracluster medium of the Perseus Cluster. Our study utilizes deep, archival imaging of the cluster core as well as a new mosaic of 29 short $\, 5\,$-ks observations extending in eight different directions out to radii of $r_{500} \sim 2.2\, r_{2500}$. Under the assumption that the distribution of densities at a given radius is log-normally distributed, two important quantities can be derived from the width of the log-normal density distribution on a given spatial scale: the density bias, that is equal to the square root of the clumping factor C; and the one-component turbulent velocity, vk,1D. We forward-model all contributions to the measured surface brightness, including astrophysical and particle background components, and account for the Poisson nature of the measured signal. Measuring the distribution of surface brightness fluctuations in 1 arcmin2 regions, spanning the radial range $0.3\rm {-}2.2\, r_{2500}$ ($7.8\rm {-}57.3\,$ arcmin), we find a small to moderate average density bias of around $3{{\ \rm per\ cent}}$ at radii below $1.6\, r_{2500}$. We also infer an average turbulent velocity at these radii of V1D < 400 km s−1. Direct confirmation of our results on turbulent velocities inferred from surface brightness fluctuations should be possible using the X-ray calorimeter spectrometers to be flown aboard the XRISM and Athena observatories.

79 ASTRONOMY AND ASTROPHYSICS↗
DOE OSTI2022

Long-term general relativistic magnetohydrodynamics simulations of magnetic field in isolated neutron stars

ABSTRACT Strong magnetic fields play an important role in powering the emission of neutron stars. Nevertheless, a full understanding of the interior configuration of the field remains elusive. In this work, we present general relativistic magnetohydrodynamics (MHD) simulations of the magnetic field evolution in neutron stars lasting ${\sim } {880}\,$ms (∼6.5 Alfvén crossing periods) and up to resolutions of $0.1155\,$km using Athena++. We explore two different initial conditions, one with purely poloidal magnetic field and the other with a dominant toroidal component, and study the poloidal and toroidal field energies, the growth times of the various instability-driven oscillation modes, and turbulence. We find that the purely poloidal setup generates a toroidal field, which later decays exponentially reaching $1{{\ \rm per\ cent}}$ of the total magnetic energy, showing no evidence of reaching equilibrium. The initially stronger toroidal field setup, on the other hand, loses up to 20 per cent of toroidal energy and maintains this state till the end of our simulation. We also explore the hypothesis, drawn from previous MHD simulations, that turbulence plays an important role in the quasi-equilibrium state. An analysis of the spectra in our higher resolution setups reveals, however, that in most cases we are not observing turbulence at small scales, but rather a noisy velocity field inside the star. We also observe that the majority of the magnetic energy gets dissipated as heat increasing the internal energy of the star, while a small fraction gets radiated away as electromagnetic radiation.

79 ASTRONOMY AND ASTROPHYSICS↗
DOE OSTI2023

Magnetized rotating isothermal winds

ABSTRACT We consider the general problem of a Parker-type non-relativistic isothermal wind from a rotating and magnetic star. Using the magnetohydrodynamics code athena++, we construct an array of simulations in the stellar rotation rate Ω* and the isothermal sound speed cT, and calculate the mass, angular momentum, and energy loss rates across this parameter space. We also briefly consider the 3D case, with misaligned magnetic and rotation axes. We discuss applications of our results to the spin-down of normal stars, highly irradiated exoplanets, and to nascent highly magnetic and rapidly rotating neutron stars born in massive star core-collapse.

Astronomy & Astrophysics↗
DOE OSTI2015

Gas density fluctuations in the Perseus Cluster: clumping factor and velocity power spectrum

X-ray surface brightness fluctuations in the core of the Perseus Cluster are analysed, using deep observations with the Chandra observatory. The amplitude of gas density fluctuations on different scales is measured in a set of radial annuli. It varies from 7 to 12 per cent on scales of ~10–30 kpc within radii of 30–220 kpc from the cluster centre. Using a statistical linear relation between the observed amplitude of density fluctuations and predicted velocity, the characteristic velocity of gas motions on each scale is calculated. The typical amplitudes of the velocity outside the central 30 kpc region are 90–140 km s -1 on ~20–30 kpc scales and 70–100 km s -1 on smaller scales ~7–10 kpc. The velocity power spectrum (PS) is consistent with cascade of turbulence and its slope is in a broad agreement with the slope for canonical Kolmogorov turbulence. The gas clumping factor estimated from the PS of the density fluctuations is lower than 7–8 per cent for radii ~30–220 kpc from the centre, leading to a density bias of less than 3–4 per cent in the cluster core. Uncertainties of the analysis are examined and discussed. Future measurements of the gas velocities with the Astro-H, Athena and Smart-X observatories will directly measure the gas density–velocity perturbation relation and further reduce systematic uncertainties in this analysis.

79 ASTRONOMY AND ASTROPHYSICS↗
DOE OSTI2018

Magnetothermal disc winds in X-ray binaries: poloidal magnetic fields suppress thermal winds

Magnetic, radiation pressure, and thermal driving are the three mechanisms capable of launching accretion disc winds. In X-ray binaries, radiation pressure is often not significant, as in many systems the luminosity is too low for driving due to continuum transitions yet too high for driving due to line transitions. This leaves thermal and magnetic driving as the contender launching mechanisms in these systems. Using ATHENA++, here we perform axisymmetric ideal MHD simulations that include radiative heating and cooling processes appropriate for Compton heated winds to show that the inclusion of magnetic fields into a thermally driven wind has the opposite effect of what one might expect: rather than provide a velocity boost, the thermal wind is suppressed in low-plasma beta regions where the field lines are strong enough to reshape the direction of the flow. Our analysis reveals that magneto-centrifugal launching is present but weak, while the reduction in wind velocity is not due to the change in gravitational potential through the magnetically imposed streamline geometry, but rather due to the increased flow tube area just above the surface of the disc, which is less conducive to acceleration. Finally, our results suggest that for magnetothermal wind models to be successful at producing fast dense outflows in low-mass X-ray binaries, the winds must be magnetically launched well within the Compton radius.

79 ASTRONOMY AND ASTROPHYSICS↗
DOE OSTI2018

Hitomi observations of the LMC SNR N 132 D: Highly redshifted X-ray emission from iron ejecta

Here, we present Hitomi observations of N 132 D, a young, X-ray bright, O-rich core-collapse supernova remnant in the Large Magellanic Cloud (LMC). Despite a very short observation of only 3.7 ks, the Soft X-ray Spectrometer (SXS) easily detects the line complexes of highly ionized S K and Fe K with 16–17 counts in each. The Fe feature is measured for the first time at high spectral resolution. Based on the plausible assumption that the Fe K emission is dominated by He-like ions, we find that the material responsible for this Fe emission is highly redshifted at ~800 km s –1 compared to the local LMC interstellar medium (ISM), with a 90% credible interval of 50–1500 km s –1 if a weakly informative prior is placed on possible line broadening. This indicates that the Fe emission arises from the supernova ejecta, and that these ejecta are highly asymmetric, since no blueshifted component is found. The S K velocity is consistent with the local LMC ISM, and is likely from swept-up ISM material. These results are consistent with spatial mapping that shows the He-like Fe concentrated in the interior of the remnant and the S tracing the outer shell. The results also show that even with a very small number of counts, direct velocity measurements from Doppler-shifted lines detected in extended objects like supernova remnants are now possible. Thanks to the very low SXS background of ~1 event per spectral resolution element per 100 ks, such results are obtainable during short pointed or slew observations with similar instruments. This highlights the power of high-spectral-resolution imaging observations, and demonstrates the new window that has been opened with Hitomi and will be greatly widened with future missions such as the X-ray Astronomy Recovery Mission (XARM) and Athena.

79 ASTRONOMY AND ASTROPHYSICS↗