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Athena papers

Athena papers

"Athena X-IFU synthetic observations of galaxy clusters to probe the chemical enrichment of the Universe", by E. Cucchetti et al.


E.Cuccheti

By Edoardo Cucchetti (IRAP, Toulouse, France)

What are we made of? Most of the atoms and elements we know of are formed within stars, either during their life (winds) or during powerful end-of-life phenomena called supernovae. In fact, different mechanisms of metal creation exist in the Universe and elements were not formed evenly during its history. To investigate this chemical enrichment, one must look in the X-rays at the hot gas within clusters of galaxies – the intra cluster medium (ICM) – which is continuously enriched through time by the billions of stars contained in its galaxies. However, to perform meaningful studies of the enrichment through cosmic time, a combination of a high-resolution spatially-resolved spectroscopy and a large telescope collective area is required. For this reason, the Athena/X-IFU will be the breakthrough instrument to investigate metal formation and circulation in the Universe.

In this paper, we tested the power of the X-IFU to fulfil this specific science objective. Using a set of simulated clusters derived from hydrodynamical simulations, we performed synthetic observations of this sample of objects through time, up to a redshift z=2 (10.4 billion years ago) with a completely realistic set-up (including e.g., background, instrumental effects). We demonstrated that with routine 100 ks observations, the X-IFU will be able to study the enrichment with unprecedented accuracy out to the outskirts of the clusters and provide solid answers to the origin of their metal content.

This work is paramount in the Athena context, as it shows the power of the mission in answering some of the key astrophysical questions of our time. It also serves as a feasibility study of the X-IFU, consolidating the current design and the need for spatially-resolved high-resolution spectroscopy.

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"On obtaining neutron-star mass and radius constraints from quiescent low-mass X-ray binaries in the Galactic plane", by A. Marino et al.

1806MarinoetalBy Alessio Marino (Università degli Studi di Palermo, Palermo, Italy)

Analysing spectra of quiescent Low Mass X-Ray Binaries (LMXBs) hosting Neutron Stars (NSs) is one of the main techniques for measuring the mass and/or the radius of NSs and, in turn, constrain the Equation of state of ultra-dense matter. However, the precision and the power of these constraints are heavily related to the quality of the spectra. Furthermore, several biases affect the results obtained with this method, in particular, the uncertainty in the distance, the possibility of missing the presence of a power-law component in the spectrum and the evidence that a small variation in the energy range over which the spectrum is extracted might change significantly the results of the fits. As shown in this paper, these biases and limitations could be partially overcome with ESA's Athena mission.

We simulated spectra of two LMXBs hosting Neutron Stars, 4U 1608-52 and EXO 0748-676, based on Chandra archival observations and compared the simulated with the “original” spectra. In the case of 4U 1608-52, while the quality of the Chandra spectrum is too poor to give valuable constraints on the mass and/or the radius of the NS, a fit with a composite quasi-thermal plus power-law model performed on the simulated Athena spectrum results in precise outcomes (relative errors of 0,01-0,001%). On the other hand, the Chandra spectral analysis of EXO 0748-676 is not only limited by the statistics, but also by the energy range dependence, which is apparent analysing a 0.3-10 keV and a 0.5-10 keV spectrum; a simulated single Athena spectrum of the source is, on the contrary, unaffected by the change in the energy range. These results show how in the Athena era the search for constraints on the equation of state of ultra-dense matter via NS radius and mass measurements might receive a considerable boost, although without precise distance measurements an uncertainty associated with the range of plausible distances of the source must be taken into account.

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"Measuring turbulence and gas motions in galaxy clusters via synthetic Athena X-IFU observations", by M. Roncarelli et al.

MRoncarelli

 

The X-IFU that will be on board of Athena will allow a major breakthrough in our understanding of the physics of galaxy clusters. Besides thermodynamics quantities, such as density and temperature, that are already measurable by current X-ray instruments, the X-IFU will unveil the kinematics of the intracluster medium, mapping gas velocity and velocity dispersion by studying the emission lines of heavy elements. 

In this work, it is simulated a set of realistic X-IFU observation of galaxy clusters with the injection of turbulent motions, to test the accuracy of the X-IFU to recover and map their internal kinematics. It is shown that the X-IFU will be able to map kinematic quantities with great accuracy. This will open the possibility not only to measure intracluster turbulence but also to observe galaxy clusters rotation and the accretion of matter from the large-scale structure of the Universe with unprecedented detail.
 

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"The Performance of the Athena X-ray Integral Field Unit at Very High Count Rates", by P. Peille

Peille XIFU JLTPAbstract: "The Athena X-ray Integral Field Unit (X-IFU) will operate at 90 mK a hexagonal matrix of 3840 Transition Edge Sensor pixels providing spatially resolved high-resolution spectroscopy (2.5 eV FWHM up to 7 keV) between 0.2 and 12 keV. During the observation of very bright X-ray sources, the X-IFU detectors will receive high photon rates going up to several tens of counts per second per pixel and hundreds per readout channel, well above the normal operating mode of the instrument. In this paper, we investigate through detailed end-to-end simulations the performance achieved by the X-IFU at the highest count rates. Special care is notably taken to model and characterize pulse processing limitations, readout-chain saturation effects, as well as the non-Gaussian degradation of the energy redistribution from crosstalk at the focal plane level (both thermal and electrical). Overall, we show that the instrument performance should safely exceed the scientific requirements, and in particular that more than 50 % throughput at 1 Crab in the 5–8 keV band can be achieved with better than 10 eV average resolution with the use of a Beryllium filter, enabling breakthrough science in the field of bright sources."

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Papers related with Athena

Your Athena related publications: Please inform us about your Athena related publications. They will posted in our web site and in the Athena social media.

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Overview papers

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Athena mission proposal and white paper

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Athena supporting papers

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