Search

Understanding and modelling astrophysical plasmas on atomic levels while taking into account various assumptions (for example, collisional ionisation equilibrium or photoionisation equilibrium) became essential with the progress of high-resolution X-ray spectroscopy. In order to prepare for the upcoming X-ray spectroscopy missions such as XRISM or Athena, the plasma codes with their models and the atomic databases need to be up to date and accurate. One such update for the plasma code SPEX is presented in this paper where we focus on the radiative loss due to collisional excitation in the low-density, optically thin regime. We also update the atomic data for neutral hydrogen and include the contribution of the dielectronic recombination. With all these updates being implemented in SPEX we finally present the new cooling curve. We include the comparison to other plasma codes (MEKAL, APEC, Cloudy) and other atomic databases (CHIANTI, ADAS). We show how the updated cooling impacts the stability curve for photoionised plasmas and find a new stable branch., 17 pages, 13 figures, 6 tables, accepted for publication in Astronomy & Astrophysics

Previous X-ray studies of the Perseus Cluster, consisting of 85 Suzaku pointings along eight azimuthal directions, revealed a particularly steep decrease in the projected temperature profile near the virial radius (~r200) towards the northwest (NW). To further explore this shock candidate, another 4 Suzaku observations on the NW edge of the Perseus Cluster have been obtained. These deeper data were designed to provide the best possible control of systematic uncertainties in the spectral analysis. Using the combined Suzaku observations, we have carefully investigated this interesting region by analyzing the spectra of various annuli and extracting projected thermodynamic profiles. We find that the projected temperature profile shows a break near r200, indicating a shock with M = 1.9+-0.3. Corresponding discontinuities are also found in the projected emission measure and the density profiles at the same location. This evidence of a shock front so far away from the cluster center is unprecedented, and may provide a first insight into the properties of large-scale virial shocks which shape the process of galaxy cluster growth., 12 pages, 6 figures, accepted by A&A

Knowledge of X-ray shock and radio relic connection in merging galaxy clusters has been greatly extended in terms of both observation and theory over the last decade. ZwCl 2341+0000 is a double-relic merging galaxy cluster; previous studies have shown that half of the S relic is associated with an X-ray surface brightness discontinuity, while the other half not. The discontinuity was believed to be a shock front. Therefore, it is a mysterious case of an only partial shock-relic connection. By using the 206.5 ks deep Chandra observations, we aim to investigate the nature of the S discontinuity. Meanwhile, we aim to explore new morphological and thermodynamical features. In addition, we utilize the GMRT and JVLA images to compute radio spectral index (SI) maps. In the deep observations, the previously reported S surface brightness discontinuity is better described as a sharp change in slope or as a kink, which is likely contributed by the disrupted core of the S subcluster. The radio SI maps show spectral flattening at the SE edge of the S relic, suggesting that the location of the shock front is 640 kpc away from the kink. We update the radio shock Mach number to be $2.2\pm0.1$ and $2.4\pm0.4$ for the S and N radio relics, respectively, based on the injection SI. We also put a 3 sigma lower limit on the X-ray Mach number of the S shock to be >1.6. Meanwhile, the deep observations reveal that the N subcluster is in a perfect cone shape, with a ~400 kpc linear cold front on each side. This type of conic subcluster has been predicted by simulations but is observed here for the first time. It represents a transition stage between a blunt-body cold front and a slingshot cold front. Strikingly, we found a 400 kpc long gas trail attached to the apex of the cone, which could be due to the gas stripping. In addition, an over-pressured hot region is found in the SW flank of the cluster., 16 pages, 10 figures. Accepted by A&A. The abstract on arXiv has been shorten to meet the word limit

We present an X-ray spectral analysis using XMM-Newton/EPIC observations (∼100 ks) of the merging galaxy cluster Abell 3365 (z = 0.093). Previous radio observations suggested the presence of a peripheral elongated radio relic to the east and a smaller radio relic candidate to the west of the cluster center. We find evidence of temperature discontinuities at the location of both radio relics, indicating the presence of a shock with a Mach number of ℳ = 3.5 ± 0.6 towards the east and a second shock with ℳ = 3.9 ± 0.8 towards the west. We also identify a cold front at r ∼ 1.6′ from the X-ray emission peak. Based on the shock velocities, we estimate that the dynamical age of the main merger along the east-west direction is ∼0.6 Gyr. We find that the diffusive shock acceleration scenario from the thermal pool is consistent with the electron acceleration mechanism for both radio relics. In addition, we studied the distribution of the temperature, iron (Fe) abundance, and pseudo-entropy along the merging axis. Our results show that remnants of a metal-rich cool-core can partially or entirely survive after the merging activity. Finally, we find that the merger can displace the metal-rich and low entropy gas from the potential well towards the cold front, as has been suggested via numerical simulations.

Context: Chandra observations of the Abell 3411-3412 merging system have revealed an outbound bullet-like sub-cluster in the northern part and many surface brightness (SB) edges at the southern periphery, where multiple diffuse sources are also reported from radio observations. Notably, a south-eastern radio relic associated with fossil plasma from a radio galaxy and with a detected X-ray edge provides direct evidence of shock re-acceleration. The properties of the reported X-ray edges have yet to be constrained from a thermodynamic view. Aims: We use the XMM-Newton and Suzaku observations to reveal the thermodynamical nature of the reported re-acceleration site and other X-ray edges. Meanwhile, we aim to investigate the temperature profile in the low-density outskirts with Suzaku data. Methods: We perform both imaging and spectral analysis to measure the density jump and the temperature jump across multiple known X-ray SB discontinuities. We present a new method to calibrate the XMM-Newton soft proton background. Archival Chandra, Suzaku, and ROSAT data are used to estimate the cosmic X-ray background and Galactic foreground levels with improved accuracy compared to standard blank sky spectra. Results: At the south-eastern edge, both XMM-Newton and Suzaku's temperature jumps point to a $\mathcal{M}\sim1.2$ shock, which agrees with result from SB fits with Chandra, and supports the re-acceleration scenario at this shock front. The southern edge shows a more complex scenario, where a shock and the presence of stripped cold material may coincide. The Suzaku temperature profiles in the southern low density regions are marginally higher than the typical relaxed cluster temperature profile. The measured value $kT_{500}=4.84\pm0.04\pm0.19$ keV with XMM-Newton and $kT_{500}=5.17\pm0.07\pm0.13$ keV with Suzaku are significantly lower than previously inferred from Chandra., 19 pages, 11 figures (+8 in appendix), 7 tables (+3 in appendix). Accepted for publication in A&A

Accurate chemical abundance measurements of X-ray emitting atmospheres pervading massive galaxies, galaxy groups, and clusters provide essential information on the star formation and chemical enrichment histories of these large scale structures. Although the collisionally ionised nature of the intracluster medium (ICM) makes these abundance measurements relatively easy to derive, underlying spectral models can rely on different atomic codes, which brings additional uncertainties on the inferred abundances. Here, we provide a simple, yet comprehensive comparison between the codes SPEXACT v3.0.5 (cie model) and AtomDB v3.0.9 (vapec model) in the case of moderate, CCD-like resolution spectroscopy. We show that, in cool plasmas ($kT \lesssim 2$ keV), systematic differences up to $\sim$20% for the Fe abundance and $\sim$45% for the O/Fe, Mg/Fe, Si/Fe, and S/Fe ratios may still occur. Importantly, these discrepancies are also found to be instrument-dependent, at least for the absolute Fe abundance. Future improvements in these two codes will be necessary to better address questions on the ICM enrichment., 6 pages, 2 figures, accepted for publication in Astron. Nachr. Additional material can be found here: https://github.com/mernier/SPEX_XSPEC

X-ray measurements find systematically lower Fe abundances in the X-ray emitting haloes pervading groups ($kT\lesssim1.7$ keV) than in clusters of galaxies. These results have been difficult to reconcile with theoretical predictions. However, models using incomplete atomic data or the assumption of isothermal plasmas may have biased the best fit Fe abundance in groups and giant elliptical galaxies low. In this work, we take advantage of a major update of the atomic code in the spectral fitting package SPEX to re-evaluate the Fe abundance in 43 clusters, groups, and elliptical galaxies (the CHEERS sample) in a self-consistent analysis and within a common radius of 0.1$r_{500}$. For the first time, we report a remarkably similar average Fe enrichment in all these systems. Unlike previous results, this strongly suggests that metals are synthesised and transported in these haloes with the same average efficiency across two orders of magnitude in total mass. We show that the previous metallicity measurements in low temperature systems were biased low due to incomplete atomic data in the spectral fitting codes. The reasons for such a code-related Fe bias, also implying previously unconsidered biases in the emission measure and temperature structure, are discussed., 6 pages, 4 figures, accepted for publication in MNRAS Letters

The CHEERS (CHEmical enrichment reflection grating spectrometer sample) observations of clusters of galaxies with XMM-Newton have shown to be valuable to constrain the chemical evolution of the universe. The soft X-ray spectrum contains lines of the most abundant metals from N to Ni, which provide relatively accurate abundances that can be compared to supernova enrichment models. The accuracy of the abundances is currently limited by systematic uncertainties introduced by the available instruments and uncertainties in the modeling of the spectra, which are of the order of 20–30%. We discuss the possible gain of extending the current samples at low and high redshift. We conclude that expanding the samples would be expensive in terms of exposure time, but will not yield significantly improved results, because the current samples already reach the systematic limits. New instrumentation, like Astro-H2 and ATHENA, as well as improvements to the atomic databases, are needed to make significant advances in this field.

The high-resolution X-ray spectrum of the Perseus galaxy cluster observed with the Hitomi satellite challenges astrophysical collisional ionized plasma models that are widely used in the community. Although Hitomi spun out of control, several Hitomi-level missions have been proposed and some funded. The spectrometers aboard these future missions have a broader energy range and/or a higher spectral resolution to achieve different scientific goals. Accurate plasma models and atomic data are crucial for plasma diagnostics of high-quality spectra. Here, we present a few cases where improvement of plasma diagnostics will be decisive to better understand celestial bodies and their physical processes at play. We focus on collisional ionized and photoionized astrophysical plasmas in the context of developments of plasma models, as well as current and future generations of spectrometers., 10 pages, 3 figures, JINST accepted

We present XMM-Newton/EPIC observations of six merging galaxy clusters and study the distributions of their temperature, iron (Fe) abundance and pseudo-entropy along the merging axis. For the first time, we focus simultaneously, and in a comprehensive way, on the chemical and thermodynamic properties of the freshly collided intracluster medium (ICM). The Fe distribution of these clusters along the merging axis is found to be in good agreement with the azimuthally-averaged Fe abundance profile in typical non-cool-core clusters out to $r_{500}$. In addition to showing a moderate central abundance peak, though less pronounced than in relaxed systems, the Fe abundance flattens at large radii towards $\sim$0.2-0.3 $Z_\odot$. Although this shallow metal distribution is in line with the idea that disturbed, non-cool-core clusters originate from the merging of relaxed, cool-core clusters, we find that in some cases, remnants of metal-rich and low entropy cool cores can persist after major mergers. While we obtain a mild anti-correlation between the Fe abundance and the pseudo-entropy in the (lower entropy, $K$ = 200-500 keV cm$^2$) inner regions, no clear correlation is found at (higher entropy, $K$ = 500-2300 keV cm$^2$) outer radii. The apparent spatial abundance uniformity that we find at large radii is difficult to explain through an efficient mixing of freshly injected metals, particularly in systems for which the time since the merger is short. Instead, our results provide important additional evidence in favour of the early enrichment scenario - in which the bulk of the metals are released outside galaxies at $z$ > 2-3 - and extend it from cool-core and (moderate) non-cool-core clusters to a few of the most disturbed merging clusters as well. These results constitute a first step towards a deeper understanding of the chemical history of merging clusters., Accepted for publication in A&A, 21 pages with 17 figures and 19 tables

We present an X-ray spectral analysis of the nearby double radio relic merging cluster Abell 3376 ($z$ = 0.046), observed with the $Suzaku$ XIS instrument. These deep ($\sim$360 ks) observations cover the entire double relic region in the outskirts of the cluster. These diffuse radio structures are amongst the largest and arc-shaped relics observed in combination with large-scale X-ray shocks in a merging cluster. We confirm the presence of a stronger shock (${\cal M}_{\rm{W}}$ = 2.8 $\pm~0.4$) in the western direction at $r\sim26$', derived from a temperature and surface brightness discontinuity across the radio relic. In the East, we detect a weaker shock (${\cal M}_{\rm{E}}$ = 1.5 $\pm~0.1$) at $r\sim8$', possibly associated to the 'notch' of eastern relic, and a cold front at $r\sim3$'. Based on the shock speed calculated from the Mach numbers, we estimate that the dynamical age of the shock front is $\sim$0.6 Gyr after core passage, indicating that Abell 3376 is still an evolving merging cluster and that the merger is taking place close to the plane of the sky. These results are consistent with simulations and optical and weak lensing studies from the literature., Accepted for publication in A&A, 15 pages, 19 figures, 11 tables

The hot intracluster medium (ICM) pervading galaxy clusters and groups is rich in metals, which were synthesised by billions of supernovae and have accumulated in cluster gravitational wells for several Gyrs. Since the products of both Type Ia and core-collapse supernovae - expected to explode over different time scales - are found in the ICM, constraining accurately the chemical composition these hot atmospheres can provide invaluable information on the history of the enrichment of large-scale structures. Recently, Hitomi observations reported solar abundance ratios in the core of the Perseus cluster, in tension with previous XMM-Newton measurements obtained for 44 cool-core clusters, groups, and massive ellipticals (the CHEERS sample). In this work, we revisit the CHEERS results by using an updated version of the spectral code used to fit the data (SPEXACT v3), the same as was used to obtain the Hitomi measurements. Despite limitations in the spectral resolution, the average Cr/Fe and Ni/Fe ratios are now found to be remarkably consistent with unity and in excellent agreement with the Hitomi results. Our updated measurements suggest that the solar composition of the ICM of Perseus is a very common feature in nearby cool-core systems., 6 pages, 4 figures, accepted for publication in MNRAS Letters

著者人数: 13名, Accepted: 2017-03-01, 資料番号: SA1170080000

We present significantly improved measurements of turbulent velocities in the hot gaseous halos of nearby giant elliptical galaxies. Using deep XMM-Newton Reflection Grating Spectrometer (RGS ) observations and a combination of resonance scattering and direct line broadening methods, we obtain well bounded constraints for 13 galaxies. Assuming that the turbulence is isotropic, we obtain a best fit mean 1D turbulent velocity of ~110 km/s. This implies a typical 3D Mach number ~0.45 and a typical non-thermal pressure contribution of ~6 per cent in the cores of nearby massive galaxies. The intrinsic scatter around these values is modest - consistent with zero, albeit with large statistical uncertainty - hinting at a common and quasi-continuous mechanism sourcing the velocity structure in these objects. Using conservative estimates of the spatial scales associated with the observed turbulent motions, we find that turbulent heating can be sufficient to offset radiative cooling in the inner regions of these galaxies (, Submitted to MNRAS, comments are welcome

We present some recent highlights and prospects for the study of hot astrophysical plasmas. Hot plasmas can be studied primarily through their X-ray emission and absorption. Most astrophysical objects, from solar system objects to the largest scale structures of the Universe, contain hot gas. In general we can distinguish collisionally ionised gas and photoionised gas. We introduce several examples of both classes and show where the frontiers of this research in astrophysics can be found. We put this also in the context of the current and future generation of X-ray spectroscopy satellites. The data coming from these missions challenge the models that we have for the calculation of the X-ray spectra., 12 pages, 6 figures, 2nd European Conference on Plasma Diagnostics, 18-21 April 2017, Bordeaux; to appear in JINST

著者人数: 20名, Accepted: 2017-07-16, 資料番号: SA1170131000

Metals play a fundamental role in ICM cooling processes in cluster cores through the emission of spectral lines. But when and how were these metals formed and distributed through the ICM? The X-ray band has the unique property of containing emission lines from all elements from carbon to zinc within the 0.1–10 keV band. Using XMM-Newton, the abundances of about 11 elements are studied, which contain valuable information about their origin. Most elements were formed in type Ia and core-collapse supernovae, which have very different chemical yields. Massive stars and AGB stars also contribute by providing most of the carbon and nitrogen in the ICM. Because feedback processes suppress star formation in the cluster centre, the element abundances allow us to directly probe the star formation history of the majority of stars that are thought to have formed between z = 2–3. The spatial distribution in the core and the evolution with redshift also provide information about how these elements are transported from the member galaxies to the ICM. I review the current progress in chemical enrichment studies of the ICM and give an outlook to the future opportunities provided by XMM-Newton's successors, like Astro-H. (© 2013 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim)

Pulsars emit low-frequency radio waves through to high-energy gamma-rays that are generated anywhere from the surface out to the edges of the magnetosphere. Detecting correlated mode changes in the multi-wavelength emission is therefore key to understanding the physical relationship between these emission sites. Through simultaneous observations, we have detected synchronous switching in the radio and X-ray emission properties of PSR B0943+10. When the pulsar is in a sustained radio 'bright' mode, the X-rays show only an un-pulsed, non-thermal component. Conversely, when the pulsar is in a radio 'quiet' mode, the X-ray luminosity more than doubles and a 100%-pulsed thermal component is observed along with the non-thermal component. This indicates rapid, global changes to the conditions in the magnetosphere, which challenge all proposed pulsar emission theories., Paper published in Science including supplementary material

We extend our previous study of the cool gas responsible for the emission of O $\tiny \text{VII}$ X-ray lines in the cores of clusters and groups of galaxies. This is the coolest X-ray emitting phase and connects the 10 000 K H $\alpha$ emitting gas to the million degree phase, providing a useful tool to understand cooling in these objects. We study the location of the O $\tiny \text{VII}$ gas and its connection to the intermediate Fe $\tiny \text{XVII}$ and hotter O $\tiny \text{VIII}$ phases. We use high-resolution X-ray grating spectra of elliptical galaxies with strong Fe $\tiny \text{XVII}$ line emission and detect O $\tiny \text{VII}$ in 11 of 24 objects. Comparing the O $\tiny \text{VII}$ detection level and resonant scattering, which is sensitive to turbulence and temperature, suggests that O $\tiny \text{VII}$ is preferably found in cooler objects, where the Fe $\tiny \text{XVII}$ resonant line is suppressed due to resonant scattering, indicating subsonic turbulence. Although a larger sample of sources and further observations is needed to distinguish between effects from temperature and turbulence, our results are consistent with cooling being suppressed at high turbulence as predicted by models of active galactic nuclei feedback, gas sloshing and galactic mergers. In some objects, the O $\tiny \text{VII}$ resonant-to-forbidden line ratio is decreased by either resonant scattering or charge exchange boosting the forbidden line, as we show for NGC 4636. Charge exchange indicates interaction between neutral and ionized gas phases. The Perseus cluster also shows a high Fe $\tiny \text{XVII}$ forbidden-to-resonance line ratio, which can be explained with resonant scattering by low-turbulence cool gas in the line of sight., This work is based on observations obtained with XMM–Newton, an ESA science mission funded by ESA Member States and USA (NASA). We also acknowledge support from ERC Advanced Grant Feedback 340442 and new data from the awarded XMM–Newton proposal ID 0760870101. YYZ acknowledges support by the German BMWi through the Verbundforschung under grant 50OR1506.

We present the results of $Suzaku$ and $XMM-Newton$ X-ray observations of the cluster pair 1E2216.0-0401 and 1E2215.7-0404. We discover an X-ray bridge between the clusters. $Suzaku$ and $XMM-Newton$ observations revealed that each cluster hosts gas with moderate temperature of $kT_{1E2216.0-0401}=$4.8$\pm$0.1 keV and $kT_{1E2215.7-0404}=$5.8$\pm$0.2 keV, respectively. On the other hand, the bridge region shows a remarkably high temperature ({\it kT}=6.6$\pm$0.5 keV). Furthermore, at the position of the bridge, we detected an enhancement in the wavelet-decomposed soft-band (0.5-4.0 keV) $XMM-Newton$ image at 3 sigma significance, this is most likely due to a compression of the intracluster medium (ICM) as a consequence of the merging activity. This X-ray intensity and temperature enhancement are not consistent with those expected from a late phase, but are in agreement with the predictions by numerical simulations of an early phase merger. From the temperature jump at the location of the bridge, the Mach number is estimated to be ${\cal M}=1.4\pm0.1$, which corresponds to a shock propagation velocity of about 1570 km/s. From the shock properties, we estimate that core-passage will occur in 0.3-0.6 Gyr and that the age of the shock structure is 50--100 Myr. Based on the measured properties of the ICM at the bridge and estimation of timescales, we find indications for non-equilibrium ionization. We also discover possible diffuse radio emission located between the merging clusters. Combining the radio, X-ray, and optical image data, we speculate that the detected radio sources are most likely related to the merger event. Thus, 1E2216.0-0401 and 1E2215.7-0404 is a new example of an early phase cluster merger with remarkable characteristics., 5 pages, 3 figures, accepted for publication in A&A Letters

Event: SPIE Astronomical Telescopes + Instrumentation, 2016, Edinburgh, United Kingdom., We present the design of tessim, a simulator for the physics of transition edge sensors developed in the framework of the Athena end to end simulation effort. Designed to represent the general behavior of transition edge sensors and to provide input for engineering and science studies for Athena, tessim implements a numerical solution of the linearized equations describing these devices. The simulation includes a model for the relevant noise sources and several implementations of possible trigger algorithms. Input and output of the software are standard FITS- files which can be visualized and processed using standard X-ray astronomical tool packages. Tessim is freely available as part of the SIXTE package (http://www.sternwarte.uni-erlangen.de/research/sixte/)., This work made use of ISIS functions (ISISscripts) provided by ECAP/Remeis observatory and MIT (http://www.sternwarte.uni-erlangen.de/isis/). We thank J.E. Davis for the development of the SLXfig module, which was used to create all gures in this paper. JW, TB, and TD acknowledge funding by the Deutsches Zentrum f ur Luft- und Raumfahrt contract 50QR1402. MTC and BC acknowledge nancial support by MINECO through grant ESP2014-53672-C3-1-P.

Ultra-compact X-ray binaries consist of a neutron star or black hole that accretes material from a white dwarf-donor star. The ultra-compact nature is expressed in very short orbital periods of less than 1 hour. In the case of 4U 0614+091 oxygen-rich material from a CO or ONe white dwarf is flowing to the neutron star. This oxygen-rich disc can reflect X-rays emitted by the neutron star giving a characteristic emission spectrum. We have analyzed high-resolution RGS and broad band EPIC spectra of 4U 0614+091 obtained by the XMM-Newton satellite. We detect a broad emission feature at ~0.7 keV in both instruments, which cannot be explained by unusual abundances of oxygen and neon in the line of sight, as proposed before in the literature. We interpret this feature as O VIII Lyalpha emission caused by reflection of X-rays off highly ionized oxygen, in the strong gravitational field close to the neutron star.

Clusters of galaxies are the largest gravitationally bounded structures in the Universe dominated by dark matter. We review the observational appearance and physical models of plasma structures in clusters of galaxies. Bubbles of relativistic plasma which are inflated by supermassive black holes of AGNs, cooling and heating of the gas, large scale plasma shocks, cold fronts, non-thermal halos and relics are observed in clusters. These constituents are reflecting both the formation history and the dynamical properties of clusters of galaxies. We discuss X-ray spectroscopy as a tool to study the metal enrichment in clusters and fine spectroscopy of Fe X-ray lines as a powerful diagnostics of both the turbulent plasma motions and the energetics of the non-thermal electron populations. The knowledge of the complex dynamical and feedback processes is necessary to understand the energy and matter balance as well as to constrain the role of the non-thermal components of clusters., 55 pages, 24 pages

MACHO-96-BLG-5 was a microlensing event observed toward the bulge of the Galaxy with an exceptionally long duration of ~970 days. The microlensing parallax fit parameters were used to estimate a lens mass M = 6 M☉, corresponding to a distance d in the range 0.5-2 kpc. The upper limit on the absolute brightness for main-sequence stars of the same mass is less than 1 L☉, so the lens is a good black hole candidate. Such a black hole would accrete from the interstellar medium, thereby emitting in the X-ray band. Here we report the analysis of a deep XMM-Newton observation toward the MACHO-96-BLG-5 lens position. Only an upper limit (99.8% confidence level) to the X-ray flux from the lens position, 9.10 × 10-15 to 1.45 × 10-14 ergs cm-2 s-1 in the 0.2-10 keV energy band, is obtained, allowing us to constrain the putative black hole's accretion parameters.

We present here a study of chemical abundances in the giant elliptical galaxy M 87 using high-resolution spectra obtained with the Reflection Grating Spectrometers during two deep XMM-Newton observations. While we confirm the two-temperature structure of the inter-stellar medium (ISM) in M 87, we also show that a continuous temperature distribution describes the data equally well. The high statistics allows us, for the first time, to determine relatively accurate abundance values also for carbon and nitrogen. The comparison of the abundance ratios of C, N, O and Fe in the ISM of M 87 with those in the stellar population of our Galaxy shows that the relative contribution of core-collapse supernovae to the enrichment of the ISM in M 87 is significantly less than in the Milky Way and indicates that the enrichment of the ISM by iron through Type Ia supernovae and by carbon and nitrogen is occurring in parallel. This suggests that the main source of carbon and nitrogen in M 87 are the low- and intermediate-mass asymptotic giant branch stars. From the oxygen to iron abundance ratio in the hot gas we estimate that the relative number of core collapse and type Ia supernovae contributing to the enrichment of the ISM in the core of M 87 is ~60% and ~40% respectively. The spatial distributions of iron and oxygen are different. While the oxygen abundance distribution is flat the iron abundance peaks in the core and has a gradient throughout the ~4' wide field of view of the instrument, suggesting an early enrichment by core-collapse supernovae and a continuous contribution of type Ia supernovae., Accepted for publication in A&A

Using the mosaic of six XMM-Newton observations, we study the hydrodynamic state of the A3562, a cluster in the center of the Shapley Supercluster. The X-ray image reveals a sharp surface brightness gradient within the core of A3562, a 200 kpc ridge extending to the south-west. A nearby group, SC1329-313, imaged within this program also exhibits a tail aligned with the ridge. Study of the pressure and entropy identified the ridge with a 40% pressure enhancement. An associated Mach number of 1.15 relative to a polytropic sound speed for a 5 keV plasma requires the velocity of the group to be 1400 km/s, while the projected velocity difference between the cluster and the group amounts to 1200-1500 km/s. Apparent disruption of the group, if attributed to the ram pressure, also requires the velocity of the group in the cluster frame to amount to 1700+/-150 km/s. The sharp surface brightness gradient at the center is identified with a contact discontinuity, which together with dove tails in the the large-scale entropy distribution reveals a sloshing of the BCG in response to the passage of the SC1329-313 group. Using the extent of the low-entropy tails in A3562 we estimate the amplitude of sloshing motion to be 200/h_70 kpc and the oscillation frequency 1 Gyr., Comment: ApJ in press, 10 pages

We present an XMM-Newton mosaic observation of the hot (kT ∼ 6.5 keV) and nearby (z = 0.0881) relaxed cluster of galaxies A478. We derive precise gas density, gas temperature, gas mass and total mass profiles up to 12 � (about half of the virial radius R200). The gas density profile is highly peaked towards the center and the surface brightness profile is well fitted by a sum of three β-models. The derived gas density profile is in excellent agreement, both in shape and in normalization, with the published Chandra density profile (measured within 5 � of the center). Projection and PSF effects on the temperature profile determination are thoroughly investigated. The derived radial temperature structure is as expected for a cluster hosting a cooling core, with a strong negative gradient at the cluster center. The temperature rises from ∼2 keV up to a plateau of ∼6.5 keV beyond 2 � (i.e. r > 208 kpc = 0.1R200, R200 = 2.08 Mpc being the virial radius). From the temperature profile and the density profile and on the hypothesis of hydrostatic equilibrium, we derived the total mass profile of A478 down to 0.01 and up to 0.5 times the virial radius. We tested different dark matter models against the observed mass profile. The Navarro et al. (1997) model is significantly preferred to other models. It leads to a total mass of M200 = 1.1 × 10 15 Mfor a concentration parameter of c = 4.2 ± 0.4. The gas mass fraction increases slightly with radius. The gas mass fraction at a density contrast of δ = 2500 is fgas = 0.13 ± 0.02, consistent with previous results on similar hot and massive clusters. We confirm the excess of absorption in the direction of A478. The derived absorbing column density exceeds the 21 cm measurement by a factor of ∼2, this excess extending well beyond the cool core region. Through the study of this absorbing component and a cross correlation with infrared data, we argue that the absorption excess is of Galactic origin, rather than intrinsic to the cluster.

We report the results from a spatially resolved spectroscopy study with XMM-Newton on the relaxed cluster of galaxies Abell 478. From the EPIC data we extract a temperature profile and radial abundance profiles for Ne, Mg, Si, S, Ca, Fe and Ni. The abundance profiles follow the same trends as observed in other clusters. The spectra of the core of the cluster can be best fitted with a multi-temperature model. We argue that this multi-temperature behavior is mostly due to projection effects, because of the strong temperature gradient in the core. Contributions from other effects, for example, intrinsic temperature stratification cannot be fully excluded. For the first time we measure an underabundance of oxygen in the Galactic absorption component toward a cluster. The measured oxygen abundance in this absorber is about 0.5 times the solar oxygen abundance as determined by Anders & Grevesse (1989)., 9 pages. Accepted for publication in Astronomy & Astrophysics

Using the EPIC and RGS data from a deep (~200 ks) XMM-Newton observation, we investigate the temperature structure (kT and sigma_T ) and the abundances of 9 elements (O, Ne, Mg, Si, S, Ar, Ca, Fe and Ni) of the intra-cluster medium (ICM) in the nearby (z=0.046) cool-core galaxy cluster Abell 4059. Next to a deep analysis of the cluster core, a careful modelling of the EPIC background allows us to build radial profiles up to 12' (~650 kpc) from the core. Probably because of projection effects, the temperature ICM is found not to be in single phase, even in the outer parts of the cluster. The abundances of Ne, Si, S, Ar, Ca and Fe, but also O are peaked towards the core. Fe and O are still significantly detected in the outermost annuli; suggesting that the enrichment by both type Ia and core-collapse SNe started in the early stages of the cluster formation. However, the particularly high Ca/Fe ratio that we find in the core is not well reproduced by the standard SNe yield models. Finally, 2-D maps of temperature and Fe abundance are presented and confirm the existence of a denser, colder, and Fe-rich ridge southwest of the core, previously observed by Chandra. The origin of this asymmetry in the hot gas of the cluster core is still unclear, but might be explained by a past intense ram-pressure stripping event near the central cD galaxy., Comment: 17 pages, 13 figures, accepted for publication in A&A

MACHO-96-BLG-5 was a microlensing event, observed towards the bulge of the Galaxy, with the exceptionally long duration of 970 days. The microlensing parallax fit parameters were used in the past in a likelihood analysis through which it has been possible to estimate both the distance and mass of the lens objects. This analysis has shown that the most likely mass for the MACHO-96-BLG-5 lens object is M=6+10-3 Sol with a distance in the range 0.5 kpc-2 kpc. The observed upper limits on the absolute brightness of main-sequence stars for this lens is less than 1 L_Sol so that it is a good black hole candidate. If it is so, then the black hole would accrete by interstellar medium thereby emitting in the X-ray band. Here, the analysis of a 100 ks XMM observation towards MACHO-96-BLG-5 lens position is reported. Only an upper limit to the X-ray flux from the black hole can been obtained from that deep observation allowing to costrain the black hole accretion parameter.

The hot intra-cluster medium (ICM) is rich in metals, which are synthesized by supernovae (SNe) explosions and accumulate over time into the deep gravitational potential well of clusters of galaxies. Since most of the elements visible in X-rays are formed by type Ia (SNIa) and/or core-collapse (SNcc) supernovae, measuring their abundances gives us direct information on the nucleosynthesis products of billions of SNe since the epoch of the star formation peak (z ~ 2-3). In this study, we use the EPIC and RGS instruments onboard XMM-Newton to measure the abundances of 9 elements (O, Ne, Mg, Si, S, Ar, Ca, Fe and Ni) from a sample of 44 nearby cool-core galaxy clusters, groups, and elliptical galaxies. We find that the Fe abundance shows a large scatter (~20-40%) over the sample, within 0.2$r_{500}$ and, especially, 0.05$r_{500}$. Unlike the absolute Fe abundance, the abundance ratios (X/Fe) are quite uniform over the considered temperature range (~0.6-8 keV), and with a limited scatter. In addition to a unprecedented treatment of systematic uncertainties, we provide the most accurate abundance ratios measured so far in the ICM, including Cr/Fe and Mn/Fe that we firmly detect (>4{\sigma} with MOS and pn independently). We find that Cr/Fe, Mn/Fe and Ni/Fe, differ significantly from the proto-solar values. However, the large uncertainties in the proto-solar abundances prevent us from making a robust comparison between the local and the intra-cluster chemical enrichments. We also note that, interestingly, and despite the large net exposure time (~4.5 Ms) of our dataset, no line emission feature is seen around ~3.5 keV., Comment: 17 pages, 9 figures, accepted for publication in A&A

Trabajo presentado a la conferencia: "Space Telescopes and Instrumentation: Ultraviolet to Gamma Ray" celebrada en Amsterdam (Holanda) el 1 de julio de 2012.-- et al., One of the instruments on the Advanced Telescope for High-Energy Astrophysics (Athena) which was one of the three missions under study as one of the L-class missions of ESA, is the X-ray Microcalorimeter Spectrometer (XMS). This instrument, which will provide high-spectral resolution images, is based on X-ray micro-calorimeters with Transition Edge Sensor (TES) and absorbers that consist of metal and semi-metal layers and a multiplexed SQUID readout. The array (32 x 32 pixels) provides an energy resolution of < 3 eV. Due to the large collection area of the Athena optics, the XMS instrument must be capable of processing high counting rates, while maintaining the spectral resolution and a low deadtime. In addition, an anti-coincidence detector is required to suppress the particle-induced background. Compared to the requirements for the same instrument on IXO, the performance requirements have been relaxed to fit into the much more restricted boundary conditions of Athena. In this paper we illustrate some of the science achievable with the instrument. We describe the results of design studies for the focal plane assembly and the cooling systems. Also, the system and its required spacecraft resources will be given. © (2012) COPYRIGHT Society of Photo-Optical Instrumentation Engineers (SPIE). Downloading of the abstract is permitted for personal use only.

We aim to estimate the level of turbulence in the hot gas of elliptical galaxies using resonant scattering in Fe XVII lines. Using the RGS grating spectrometer aboard XMM-Newton, we measure the ratio between the Fe XVII lines at 15 A and 17 A in two deep observations of NGC 5044 and NGC 5813. The 15 A line has a large oscillator strength and is therefore sensitive to resonant scattering. We find a significant difference in the (I17.05+I17.10)/I15.01 line ratio between the two objects. The level of turbulence in NGC 5044 appears to be significantly higher than in NGC 5813, which could be explained by their spatial structures seen in Chandra images.

The physics of the coolest phases in the hot Intra-Cluster Medium (ICM) of clusters of galaxies is yet to be fully unveiled. X-ray cavities blown by the central Active Galactic Nucleus (AGN) contain enough energy to heat the surrounding gas and stop cooling, but locally blobs or filaments of gas appear to be able to cool to low temperatures of 10^4 K. In X-rays, however, gas with temperatures lower than 0.5 keV is not observed. Using a deep XMM-Newton observation of the cluster of galaxies Abell 2052, we derive 2D maps of the temperature, entropy, and iron abundance in the core region. About 130 kpc South-West of the central galaxy, we discover a discontinuity in the surface brightness of the hot gas which is consistent with a cold front. Interestingly, the iron abundance jumps from ~0.75 to ~0.5 across the front. In a smaller region to the North-West of the central galaxy we find a relatively high contribution of cool 0.5 keV gas, but no X-ray emitting gas is detected below that temperature. However, the region appears to be associated with much cooler H-alpha filaments in the optical waveband. The elliptical shape of the cold front in the SW of the cluster suggests that the front is caused by sloshing of the hot gas in the clusters gravitational potential. This effect is probably an important mechanism to transport metals from the core region to the outer parts of the cluster. The smooth temperature profile across the sharp jump in the metalicity indicates the presence of heat conduction and the lack of mixing across the discontinuity. The cool blob of gas NW of the central galaxy was probably pushed away from the core and squeezed by the adjacent bubble, where it can cool efficiently and relatively undisturbed by the AGN. Shock induced mixing between the two phases may cause the 0.5 keV gas to cool non-radiatively and explain our non-detection of gas below 0.5 keV., Comment: 11 pages, 9 figures, A&A, in press

We present radial profiles of the temperature and metallicity of the cluster of galaxies Abell 2052 obtained with XMM‐Newton. The temperature is rising from 2 keV in the core of the cluster up to ∼3 keV around 9′. The iron abundance profile as derived from single‐temperature models shows a dip in the center of the cluster. The dip turns into a peak when multi‐temperature models are used to fit the central 1′. This result is a dramatic example of so‐called ‘Fe bias’. The use of multi‐temperature models is necessary in this cluster to obtain accurate abundance values.

We study the physical properties of three clusters of galaxies, selected from a BeppoSAX Wide Field Camera (WFC) survey. These sources are identified as 1RXS J153934.7-833535, 1RXS J160147.6-754507, and 1RXS J081232.3-571423 in the ROSAT All-Sky Survey catalogue. We obtained XMM-Newton follow-up observations for these three clusters. We fit single and multi-temperature models to spectra obtained from the EPIC-pn camera to determine the temperature, the chemical composition of the gas and their radial distribution. Since two observations are contaminated by a high soft-proton background, we develop a new method to estimate the effect of this background on the data. For the first time, we present the temperature and iron abundance of two of these three clusters. The iron abundance of 1RXS J153934.7-33535 decreases with radius. The fits to the XMM-Newton and Chandra data show that the radial temperature profile within 3' towards the centre either flattens or lowers. A Chandra image of the source suggests the presence of X-ray cavities. The gas properties in 1RXS J160147.6-754507 are consistent with a flat radial distribution of iron and temperature within 2' from the centre. 1RXS J081232.3-571423 is a relatively cool cluster with a temperature of about 3 keV. The radial temperature and iron profiles suggest that 1RXS J153934.7-833535 is a cool core cluster. The Chandra image shows substructure which points toward AGN feedback in the core. The flat radial profiles of the temperature and iron abundance in 1RXS J160147.6-754507 are similar to the profiles of non-cool-core clusters., Comment: Accepted for publication in A&A, 8 pages, 8 figures; corrected typos, added data points on which fig 1 and 2 are based as comment to source file.

We compare the abundance ratios of carbon, nitrogen, oxygen, and iron in the inter-stellar medium (ISM) of M 87 with those in the stellar population of our Galaxy. The relative contribution of core-collapse supernovae to the enrichment of the ISM in M 87 is significantly lower than in the Milky Way. The abundance ratios indicate that the enrichment of the ISM by iron through Type Ia supernovae and by carbon and nitrogen is occurring in parallel. This suggests that the main sources of carbon and nitrogen in M 87 are the low- and intermediate-mass asymptotic giant branch stars.

Recently the first detections of highly ionised gas associated with two Warm-Hot Intergalactic Medium (WHIM) filaments have been reported. The evidence is based on X-ray absorption lines due to O VII and other ions observed by Chandra towards the bright blazar Mrk 421. We investigate the robustness of this detection by a re-analysis of the original Chandra LETGS spectra, the analysis of a large set of XMM-Newton RGS spectra of Mrk 421, and additional Chandra observations. We address the reliability of individual spectral features belonging to the absorption components, and assess the significance of the detection of these components. We also use Monte Carlo simulations of spectra. We confirm the apparent strength of several features in the Chandra spectra, but demonstrate that they are statistically not significant. This decreased significance is due to the number of redshift trials that are made and that are not taken into account in the original discovery paper. Therefore these features must be attributed to statistical fluctuations. This is confirmed by the RGS spectra, which have a higher signal to noise ratio than the Chandra spectra, but do not show features at the same wavelengths. Finally, we show that the possible association with a Ly-alpha absorption system also lacks sufficient statistical evidence. We conclude that there is insufficient observational proof for the existence of the two proposed WHIM filaments towards Mrk 421, the brightest X-ray blazar on the sky. Therefore, the highly ionised component of the WHIM still remains to be discovered., 13 pages, 4 figures, submitted to the Astrophysical Journal

Using a new long X-ray observation of the cluster of galaxies Sersic 159-03 with XMM-Newton, we derive radial temperature and abundance profiles using single- and multi-temperature models. The fits to the EPIC and RGS spectra prefer multi-temperature models especially in the core. The radial profiles of oxygen and iron measured with EPIC/RGS and the line profiles in RGS suggest that there is a dip in the O/Fe ratio in the centre of the cluster compared to its immediate surroundings. A possible explanation for the large scale metallicity distribution is that SNIa and SNII products are released in the ICM through ram-pressure stripping of in-falling galaxies. This causes a peaked metallicity distribution. In addition, SNIa in the central cD galaxy enrich mainly the centre of the cluster with iron. This excess of SNIa products is consistent with the low O/Fe ratio we detect in the centre of the cluster. We fit the abundances we obtain with yields from SNIa, SNII and Population-III stars to derive the clusters chemical evolution. We find that the measured abundance pattern does not require a Population-III star contribution. The relative contribution of the number of SNIa with respect to the total number of SNe which enrich the ICM is about 25-50%. Furthermore, we discuss the possible presence of a non-thermal component in the EPIC spectra. A potential source of this non-thermal emission can be inverse-Compton scattering between Cosmic Microwave Background (CMB) photons and relativistic electrons, which are accelerated in bow shocks associated with ram-pressure stripping of in-falling galaxies., 18 pages, 11 figures, Accepted for publication in Astronomy & Astrophysics

We present results from a new 120 ks XMM-Newton observation of the cluster of galaxies Sersic 159-03. In this paper we focus on the high-resolution X-ray spectra obtained with the Reflection Grating Spectrometer (RGS). The spectra allow us to constrain the temperature structure in the core of the cluster and determine the emission measure distribution as a function of temperature. We also fit the line widths of mainly oxygen and iron lines., Comment: 7 pages and 4 figures. Contribution to the proceedings of the COSPAR Scientific Assembly, session E1.2 "Clusters of Galaxies: New Insights from XMM-Newton, Chandra and INTEGRAL", july 2004, Paris (France). Accepted for publication in Advances in Space Research

We present here the results of a deep (130 ks) XMM-Newton observation of the cluster of galaxies 2A 0335+096. The deep exposure allows us to study in detail its temperature structure and its elemental abundances. We fit three different thermal models and find that the multi-temperature wdem model fits our data best. We find that the abundance structure of the cluster is consistent with a scenario where the relative number of Type Ia supernovae contributing to the enrichment of the intra-cluster medium is ~25%, while the relative number of core collapse supernovae is ~75%. Comparison of the observed abundances to the supernova yields does not allow us to put any constrains on the contribution of Pop III stars to the enrichment of the ICM. Radial abundance profiles show a strong central peak of both Type Ia and core collapse supernova products. Both the temperature and iron abundance maps show an asymmetry in the direction of the elongated morphology of the surface brightness. In particular the temperature map shows a sharp change over a brightness edge on the southern side of the core, which was identified as a cold front in the Chandra data. This suggests that the cluster is in the process of a merger with a subcluster. Moreover, we find that the blobs or filaments discovered in the core of the cluster by Chandra are, contrary to the previous results, colder than the ambient gas and they appear to be in pressure equilibrium with their environment., Comment: Accepted for publication in A&A, 19 pages

INTEGRAL regularly scans the Galactic plane to search for new objects and in particular for absorbed sources with the bulk of their emission above 10-20 keV. The first new INTEGRAL source was discovered on 2003 January 29, 0.5 degree from the Galactic plane and was further observed in the X-rays with XMM-Newton. This source, IGR J16318-4848, is intrinsically strongly absorbed by cold matter and displays exceptionally strong fluorescence emission lines. The likely infrared/optical counterpart indicates that IGR J16318-4848 is probably a High Mass X-Ray Binary neutron star or black hole enshrouded in a Compton thick environment. Strongly absorbed sources, not detected in previous surveys, could contribute significantly to the Galactic hard X-ray background between 10 and 200 keV., 6 pages, 4 figures (fig 1 quality lowered), accepted for publication in A&A letters (INTEGRAL special issue)

The interstellar and intra-cluster medium in giant elliptical galaxies and clusters of galaxies is often assumed to be in hydrostatic equilibrium. Numerical simulations, however, show that about 5-30% of the pressure in a cluster is provided by turbulence induced by, for example, the central AGN and merger activity. We aim to put constraints on the turbulent velocities and turbulent pressure in the ICM of the giant elliptical galaxies NGC 5044 and NGC 5813 using XMM-Newton RGS observations. The magnitude of the turbulence is estimated using the Fe XVII lines at 15.01 A, 17.05 A, and 17.10 A in the RGS spectra. At low turbulent velocities, the gas becomes optically thick in the 15.01 A line due to resonant scattering, while the 17 A lines remain optically thin. By comparing the (I(17.05)+I(17.10))/I(15.01) line ratio from RGS with simulated line ratios for different Mach numbers, the level of turbulence is constrained. The measurement is limited by systematic uncertainties in the atomic data, which are at the 20-30% level. We find that the line ratio in NGC 5813 is significantly higher than in NGC 5044. This difference can be explained by a higher level of turbulence in NGC 5044. The high turbulent velocities and the fraction of the turbulent pressure support of >40% in NGC 5044, assuming isotropic turbulence, confirm that it is a highly disturbed system, probably due to an off-axis merger. The turbulent pressure support in NGC 5813 is more modest at 15-45%. The (I(17.05)+I(17.10))/I(15.01) line ratio in an optically thin plasma, calculated using AtomDB v2.0.1, is 2 sigma above the ratio measured in NGC 5044, which cannot be explained by resonant scattering. This shows that the discrepancies between theoretical, laboratory, and astrophysical data on Fe XVII lines need to be reduced to improve the accuracy of the determination of turbulent velocities using resonant scattering., 11 pages, 5 figures, accepted for publication in A&A

The hot Intra-Cluster Medium (ICM) in clusters of galaxies is a very large repository of metals produced by supernovae. We aim to accurately measure the abundances in the ICM of many clusters and compare these data with metal yields produced by supernovae. Using the data archive of the XMM-Newton X-ray observatory, we compile a sample of 22 clusters. We fit spectra extracted from the core regions and determine the abundances of silicon, sulfur, argon, alcium, iron, and nickel. The abundances from the spectral fits are subsequently fitted to supernova yields determined from several supernova type Ia and core-collapse supernova models. We find that the argon and calcium abundances cannot be fitted with currently favoured supernova type Ia models. We obtain a major improvement of the fit, when we use an empirically modified delayed-detonation model that is calibrated on the Tycho supernova remnant. The two modified parameters are the density where the sound wave in the supernova turns into a shock and the ratio of the specific internal energies of ions and electrons at the shock. Our fits also suggest that the core-collapse supernovae that contributed to the enrichment of the ICM had progenitors which were already enriched. The Ar/Ca ratio in clusters is a good touchstone for determining the quality of type Ia models. The core-collapse contribution, which is about 50% and not strongly dependent on the IMF or progenitor metallicity, does not have a significant impact on the Ar/Ca ratio. The number ratio between supernova type Ia and core-collapse supernovae suggests that binary systems in the appropriate mass range are very efficient (~ 5-16%) in eventually forming supernova type Ia explosions., 13 pages, 10 figures, accepted for publication in A&A

We present the results from a new 120 ks XMM-Newton observation of Sersic 159-03. A previous XMM-Newton observation of this cluster shows the presence of a soft X-ray excess in the outer parts of the cluster, which is possibly connected to the interaction between the cluster and the gas from the surrounding filaments. We exploit the long exposure time to constrain the excess emission and discuss the relation to the warm-hot intergalactic medium. Furthermore, we show a high-resolution RGS spectrum of the core of the cluster and radial profiles from EPIC, which allow us to constrain the internal temperature structure and elemental abundances.

Herder, Jan-Willem den et al., ORIGIN is a proposal for the M3 mission call of ESA aimed at the study of metal creation from the epoch of cosmic dawn. Using high-spectral resolution in the soft X-ray band, ORIGIN will be able to identify the physical conditions of all abundant elements between C and Ni to red-shifts of z = 10, and beyond. The mission will answer questions such as: When were the first metals created? How does the cosmic metal content evolve? Where do most of the metals reside in the Universe? What is the role of metals in structure formation and evolution? To reach out to the early Universe ORIGIN will use Gamma-Ray Bursts (GRBs) to study their local environments in their host galaxies. This requires the capability to slew the satellite in less than a minute to the GRB location. By studying the chemical composition and properties of clusters of galaxies we can extend the range of exploration to lower redshifts (z-0.2). For this task we need a high-resolution spectral imaging instrument with a large field of view. Using the same instrument, we can also study the so far only partially detected baryons in the Warm-Hot Intergalactic Medium (WHIM). The less dense part of the WHIM will be studied using absorption lines at low redshift in the spectra for GRBs. The ORIGIN mission includes a Transient Event Detector (coded mask with a sensitivity of 0.4 photon/cm2/s in 10 s in the 5–150 keV band) to identify and localize 2000 GRBs over a five year mission, of which -65 GRBs have a redshift > 7. The Cryogenic Imaging Spectrometer, with a spectral resolution of 2.5 eV, a field of view of 30 arcmin and large effective area below 1 keV has the sensitivity to study clusters up to a significant fraction of the virial radius and to map the denser parts of the WHIM (factor 30 higher than achievable with current instruments). The payload is complemented by a Burst InfraRed Telescope to enable onboard red-shift determination of GRBs (hence securing proper follow up of high-z bursts) and also probes the mildly ionized state of the gas. Fast repointing is achieved by a dedicated ControlledMomentum Gyro and a low background is achieved by the selected low Earth orbit., The team likes to express its appreciation for the support of Astrium UK for the present study.