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This study involves a comparative analysis of the star formation rates (SFRs) of active galactic nucleus (AGN) galaxies and non-AGN galaxies and of the SFRs of type 1 and 2 AGNs. To carry out this investigation, we assembled a dataset consisting of 2677 X-ray AGNs detected by the XMM-Newton observatory and a control sample of 64 556 galaxies devoid of AGNs. We generated spectral energy distributions (SEDs) for these objects using photometric data from the DES, VHS, and AllWISE surveys, and we harnessed the CIGALE code to extract measurements for the (host) galaxy properties. Our dataset encompasses a diverse parameter space, with objects spanning a range of stellar masses from 9.5 < log [M*(M⊙)] < 12.0, intrinsic X-ray luminosities within 42 < log[LX,2−10 keV(erg s−1)] < 45.5, and redshifts between 0.3 < z < 2.5. To compare SFRs, we calculated the SFRnorm parameter, which signifies the ratio of the SFR of an AGN galaxy to the SFR of non-AGN galaxies sharing similar M* and redshift. Our analysis reveals that systems hosting an AGN tend to exhibit elevated SFRs compared to non-AGN galaxies, particularly beyond a certain threshold in LX. Notably, this threshold increases as we move toward more massive galaxies. Additionally, for AGN systems with the same LX, the magnitude of the SFRnorm decreases as we consider more massive galaxies. This suggests that in galaxies with an AGN, the increase in SFR as a function of stellar mass is not as prominent as in galaxies without an AGN. This interpretation finds support in the shallower slope that we identify in the X-ray star-forming main sequence in contrast to the galaxy main sequence. Employing CIGALE’s measurements, we classified AGNs into type 1 and type 2. In our investigation, we focused on a subset of 652 type 1 AGNs and 293 type 2 AGNs within the stellar mass range of 10.5 < log[M (M⊙)] < 11.5. Based on our results, type 1 AGNs display higher SFRs than type 2 AGNs, at redshifts below z < 1. However, at higher redshifts

The standard unification model of AGN assumes that optically obscured (Type 2) and unobscured (Type 1) can be explained with a clumpy structure of dust and gas - the torus - surrounding the central engine. For those AGN classified as intermediate types, the standard unification model assumes they are intermediate states of obscuration. However, this apparent change in extinction could be instead differences of other properties misinterpreted. These possible differences could be associated with the nuclear region of the AGN (a decreasing luminosity or BLR emission with intermediate class) or with properties of the host galaxy (an increasing luminosity or optical extinction). To shed light on this issue, we have studied a unique sample of 165 X-ray selected AGN drawn from the Bright Ultra-hard XMM-Newton Survey (BUXS). The sources span more than 3 orders of magnitude in X-ray luminosity, from ~1e42 erg/s to ~1e45 erg/s, and redshifts from ~0.06 to 0.75. Of these, 117 sources have been spectroscopically classified as type 1 (98% with intermediate classification) and 48 as type 2. Thanks to the high-quality multi-wavelength data available for all sample objects, we have been able to determine their obscuration properties, host galaxy properties and the effect of AGN luminosity on the BLR and torus properties. The uniform selection, large sample size and high optical spectroscopic classification completeness assure us the derived results are statistically robust. We have found a clear increase in the observed optical extinction with intermediate classification. The same trend was confirmed using X-ray obscuration. At the same time, we have not found differences between host galaxy optical obscuration. Neither significant changes between AGN luminosities or BLR emission have been detected for intermediate classes. However, 1.8-9/2.0 AGN seem to live in more luminous galaxies than 1.0-1.5 AGN. Based on our results, we can conclude that extinction is the main driver of the

XMM-Newton, a European Space Agency observatory, has been observing the X-ray, ultra-violet, and optical sky for 23 years. During this time, astronomy has evolved from mainly studying single sources to populations and from a single wavelength, to multi-wavelength/messenger data. We are also moving into an era of time domain astronomy. New software and methods are required to accompany evolving astronomy and prepare for the next-generation X-ray observatory, Athena. Here we present XMM2ATHENA, a program funded by the European Union's Horizon 2020 research and innovation program. XMM2ATHENA builds on foundations laid by the XMM-Newton Survey Science Centre (XMM-SSC), including key members of this consortium and the Athena Science ground segment, along with members of the X-ray community. The project is developing and testing new methods and software to allow the community to follow the X-ray transient sky in quasi-real time, identify multi-wavelength/messenger counterparts of XMM-Newton sources and determine their nature using machine learning. We detail here the first milestone delivery of the project, a new online, sensitivity estimator. We also outline other products, including the forthcoming innovative stacking procedure and detection algorithms, to detect the faintest sources. These tools will then be adapted for Athena and the newly detected/identified sources will enhance preparation for observing the Athena X-ray sky.

Determine the flux sensitivity in a given energy band for a given instrument of the Athena X-ray mission as a function of exposure time. The simulations can be done either running the jupyter notebook from the command line or executing (cell-by-cell) the jupyter-notebook Athena_Xray_flux_vs_expTime.ipynb. The steps followed are: 1. Importing libraries 2. Defining input parameters, derived parameters and Xspec parameters 3. Gettting background count rate in the reference band normalized to the source area 4. Determining counts, flux (cgs units; erg cm-2 s-1), confusion flux (cgs), optimum extraction flux (cgs) & optimum extraction radius (arcsec) in the reference band over a loop of exposure times 5. Output file with results: the information provided by the output file comprises: Time_s, Flux_cgs, Flux_confusion_cgs, FluxOptimumExtraction cgs & RadiusOptimumExtraction_arcsec 6. Plotting limiting sensitivity vs exposure time.

A complete census of Active Galactic Nuclei (AGN) is a prerequisite for understanding the growth of supermassive black holes across cosmic time. A significant challenge toward this goal is the whereabouts of heavily obscured AGN that remain uncertain. This paper sets new constraints on the demographics of this population by developing a methodology that combines X-ray spectral information with priors derived from multiwavelength observations. We select X-ray AGN in the Chandra COSMOS Legacy survey and fit their $2.2-500\mu m$ spectral energy distributions with galaxy and AGN templates to determine the mid-infrared ($6\mu m$) luminosity of the AGN component. Empirical correlations between X-ray and $6\mu m$ luminosities are then adopted to infer the intrinsic accretion luminosity at X-rays for individual AGN. This is used as prior information in our Bayesian X-ray spectral analysis to estimate physical properties, such as line-of-sight obscuration. Our approach breaks the degeneracies between accretion luminosity and obscuration that affect X-ray spectral analysis, particularly for the most heavily obscured (Compton-Thick) AGN with low photon counts X-ray spectra. The X-ray spectral results are then combined with the selection function of the Chandra COSMOS Legacy survey to derive the AGN space density and a Compton-Thick fraction of $21.0^{+16.1}_{-9.9}\%$ at redshifts $z<0.5$. At higher redshift, our analysis suggests upper limits to the Compton-Thick AGN fraction of $\la 40\%$. These estimates are at the low end of the range of values determined in the literature and underline the importance of multiwavelength approaches for tackling the challenge of heavily obscured AGN demographics.

In this paper we explore the scientific synergies between Athena and some of the key multi-messenger facilities that should be operative concurrently with Athena. These facilities include LIGO A+, Advanced Virgo+ and future detectors for ground-based observation of gravitational waves (GW), LISA for space-based observations of GW, IceCube and KM3NeT for neutrino observations, and CTA for very high energy observations. These science themes encompass pressing issues in astrophysics, cosmology and fundamental physics such as: the central engine and jet physics in compact binary mergers, accretion processes and jet physics in Super-Massive Binary Black Holes (SMBBHs) and in compact stellar binaries, the equation of state of neutron stars, cosmic accelerators and the origin of Cosmic Rays (CRs), the origin of intermediate and high-Z elements in the Universe, the Cosmic distance scale and tests of General Relativity and the Standard Model. Observational strategies for implementing the identified science topics are also discussed. A significant part of the sources targeted by multi-messenger facilities is of transient nature. We have thus also discussed the synergy of Athena with wide-field high-energy facilities, taking THESEUS as a case study for transient discovery. This discussion covers all the Athena science goals that rely on follow-up observations of high-energy transients identified by external observatories, and includes also topics that are not based on multi-messenger observations, such as the search for missing baryons or the observation of early star populations and metal enrichment at the cosmic dawn with Gamma-Ray Bursts (GRBs).

En esta sesión daremos respuesta a los interrogantes acerca del sistema solar: ¿cómo y cuándo se formó?, ¿cuál fue y será su evolución?, ¿cuáles son sus principales integrantes?, ¿cuál es el papel del sol? Se brindará la oportunidad de tener un primer contacto con la astronomía de la mano de los mejores astrónomos y astrónomas. Existe la posibilidad añadida de una actividad de visualización de realidad virtual (solo en modalidad presencial y si hay suficientes móviles disponibles).

Transition Edge Sensors detector devices, like the core of the X-IFU instrument that will be on-board the Athena X-ray Observatory, produce current pulses as a response to the incident X-ray photons. The reconstruction of these pulses has been traditionally performed by means of a triggering algorithm based on the derivative signal overcoming a threshold (detection) followed by an optimal filtering (to retrieve the energy of each event). However, when the arrival of the photons is very close in time, the triggering algorithm is incapable of detecting all the individual pulses which are thus piled-up. In order to improve the efficiency of the detection and energy-retrieval process, we study here an alternative approach based on Machine Learning techniques to process the pulses. For this purpose, we construct and train a series of Neural Networks (NNs) not only for the detection but also for the recovering of the arrival time and the energy of simulated X-ray pulses. The data set used to train the NNs consists of simulations performed with the sixte/xifusim software package, the Athena/X-IFU official simulator. The performance of our NN classification clearly surpasses the detection performance of the classical triggering approach for the full range of photon energy combinations, showing excellent metrics and very competitive computing efficiency. However, the precision obtained for the recovery of the energy of the photons cannot currently compete with the standard optimal filtering algorithm, despite its much better computing efficiency.

We present a machine learning model to classify active galactic nuclei (AGNs) and galaxies (AGN-galaxy classifier) and a model to identify type 1 (optically unabsorbed) and type 2 (optically absorbed) AGN (type 1/2 classifier). We test tree-based algorithms, using training samples built from the X-ray Multi-Mirror Mission–Newton (XMM–Newton) catalogue and the Sloan Digital Sky Survey (SDSS), with labels derived from the SDSS survey. The performance was tested making use of simulations and of cross-validation techniques. With a set of features including spectroscopic redshifts and X-ray parameters connected to source properties (e.g. fluxes and extension), as well as features related to X-ray instrumental conditions, the precision and recall for AGN identification are 94 and 93 per cent, while the type 1/2 classifier has a precision of 74 per cent and a recall of 80 per cent for type 2 AGNs. The performance obtained with photometric redshifts is very similar to that achieved with spectroscopic redshifts in both test cases, while there is a decrease in performance when excluding redshifts. Our machine learning model trained on X-ray features can accurately identify AGN in extragalactic surveys. The type 1/2 classifier has a valuable performance for type 2 AGNs, but its ability to generalize without redshifts is hampered by the limited census of absorbed AGN at high redshift.

Con esta charla pretendemos acercar el papel de la mujer en la ciencia a través de personajes femeninos en el cine y la televisión. Mostraremos también la variedad de disciplinas en las que hay presencia de científicas y podremos reflexionar también sobre los estereotipos que rodean la labor del personal investigador, especialmente de las mujeres.

[EN] We have studied the capacity of the current and future X-ray observatories to detect Compton Thick AGN, heavily obscured and key to understand the formation and evolution of aalaxies. To achieve it we used a samole of 91 AGN selected in the mid-infrared., [ES] Se estudió la capacidad de los observatorios en rayos X actuales y futuros para detectar los AGNs Compton Thick, muy oscurecidos y clave para entender la formación y evolución de las galaxias. Para ello se uso una muestra de 91 AGNs seleccionados en el infrarrojo medio.

[EN] Obscured active galactic nuclei (AGNs) are a key ingredient in galaxy formation and evolution models. X-rays, thanks to their high penetration power, remain the most efficient method to detect and characterize them. In this work we propose to develop an automatic method to derive the redshift to these AGNs based on X-ray spectroscopy. Thus, we take advantage of the fact that one of the most common spectral characteristics of these AGNs is the presence of a very intense fluorescence emission line of the iron FeK at energies between 6.4 and 6.9 keV. The method is based on the detection of emission peaks in the observed X-ray spectra, in principle associated with the FeK line. The improvement consists of filtering to reduce noise using fourier techniques. This improvement has been performed by using AGN Compton Thick simulations at various redshifts, luminosities and column densities., [ES] Los núcleos galácticos activos (AGNs) oscurecidos son un ingrediente clave en los modelos de formación y evolución de galaxias. Los rayos X, gracias a su alto poder de penetración, siguen siendo el método más eficiente para detectarlos y caracterizarlos. En este trabajo proponemos un método automático para derivar la distancia o el redshift a estos AGNs basado únicamente en espectroscopía en rayos X. De este modo aprovechamos que una de las características espectrales más común de estos AGN es la presencia de una línea muy intensa de emisión de fluorescencia del hierro FeK con energías entre 6.4 y 6.9 keV. El método se basa en la detección de picos de emisión en los espectros de rayos X observados, en principio asociados a dicha linea. La mejora consiste en un filtrado para reducir el ruido mediante técnicas de fourier. Esta mejora se ha realizado mediante el uso de simulaciones de AGNs Compton Thick a varios redshift, luminosidades y densidades columna.

Mid- and far-infrared (IR) photometric and spectroscopic observations are fundamental to a full understanding of the dust-obscured Universe and the evolution of both star formation and black hole accretion in galaxies. In this work, using the specifications of the SPace Infrared telescope for Cosmology and Astrophysics (SPICA) as a baseline, we investigate the capability to study the dust-obscured Universe of mid- and far-IR photometry at 34 and 70 µm and low-resolution spectroscopy at 17−36 µm using the state-of-the-art SpectroPhotometric Realisations of Infrared-selected Targets at all-z (SPRITZ) simulation. This investigation is also compared to the expected performance of the Origins Space Telescope and the Galaxy Evolution Probe. The photometric view of the Universe of a SPICA-like mission could cover not only bright objects (e.g. LIR > 1012 L) up to z = 10, but also normal galaxies (LIR < 1011 L) up to z ∼ 4. At the same time, the spectroscopic observations of such mission could also allow us to estimate the redshifts and study the physical properties for thousands of star-forming galaxies and active galactic nuclei by observing the polycyclic aromatic hydrocarbons and a large set of IR nebular emission lines. In this way, a cold, 2.5-m size space telescope with spectro-photometric capability analogous to SPICA, could provide us with a complete three-dimensional (i.e. images and integrated spectra) view of the dust-obscured Universe and the physics governing galaxy evolution up to z ∼ 4.

We use the SPace Infrared telescope for Cosmology and Astrophysics (SPICA) project as a template to demonstrate how deep spectrophotometric surveys covering large cosmological volumes over extended fields (1-15 deg(2)) with a mid-IR imaging spectrometer (17-36 mu m) in conjunction with deep 70 mu m photometry with a far-IR camera, at wavelengths which are not affected by dust extinction can answer the most crucial questions in current galaxy evolution studies. A SPICA-like mission will be able for the first time to provide an unobscured three-dimensional (3D, i.e. x, y, and redshift z) view of galaxy evolution back to an age of the universe of less than similar to 2 Gyrs, in the mid-IR rest frame. This survey strategy will produce a full census of the Star Formation Rate (SFR) in the universe, using polycyclic aromatic hydrocarbons (PAH) bands and fine-structure ionic lines, reaching the characteristic knee of the galaxy luminosity function, where the bulk of the population is distributed, at any redshift up to z similar to 3.5. Deep follow-up pointed spectroscopic observations with grating spectrometers onboard the satellite, across the full IR spectral range (17-210 mu m), would simultaneously measure Black Hole Accretion Rate (BHAR), from high-ionisation fine-structure lines, and SFR, from PAH and low- to mid-ionisation lines in thousands of galaxies from solar to low metallicities, down to the knee of their luminosity functions. The analysis of the resulting atlas of IR spectra will reveal the physical processes at play in evolving galaxies across cosmic time, especially its heavily dust-embedded phase during the activity peak at the cosmic noon (z similar to 1-3), through IR emission lines and features that are insensitive to the dust obscuration.

We use the SPace Infrared telescope for Cosmology and Astrophysics (SPICA) project as a template to demonstrate how deep spectrophotometric surveys covering large cosmological volumes over extended fields (1–15 deg2) with a mid-IR imaging spectrometer (17–36 µm) in conjunction with deep photometry with a far-IR camera, at wavelengths which are not affected by dust extinction can answer the most crucial questions in current galaxy evolution studies. A SPICA-like mission will be able for the first time to provide an unobscured three-dimensional (3D, i.e. x, y, and redshift z) view of galaxy evolution back to an age of the universe of less than ∼ 2 Gyrs, in the mid-IR rest frame. This survey strategy will produce a full census of the Star Formation Rate (SFR) in the universe, using polycyclic aromatic hydrocarbons (PAH) bands and fine-structure ionic lines, reaching the characteristic knee of the galaxy luminosity function, where the bulk of the population is distributed, at any redshift up to z ∼ 3.5. Deep follow-up pointed spectroscopic observations with grating spectrometers onboard the satellite, across the full IR spectral range (17–210 µm), would simultaneously measure Black Hole Accretion Rate (BHAR), from high-ionisation fine-structure lines, and SFR, from PAH and low- to mid-ionisation lines in thousands of galaxies from solar to low metallicities, down to the knee of their luminosity functions. The analysis of the resulting atlas of IR spectra will reveal the physical processes at play in evolving galaxies across cosmic time, especially its heavily dust-embedded phase during the activity peak at the cosmic noon (z ∼ 1–3), through IR emission lines and features that are insensitive to the dust obscuration.

In the black hole (BH)–galaxy co-evolution framework, most of the star formation (SF) and the BH accretion are expected to take place in highly obscured conditions. The large amount of gas and dust absorbs most of the UV-to-soft-X radiation and re-emits it at longer wavelengths, mostly in the IR. Thus, obscured active galactic nuclei (AGN) are very difficult to identify in optical or X-ray bands but shine bright in the IR. Moreover, X-ray background (XRB) synthesis models predict that a large fraction of the yet-unresolved XRB is due to the most obscured (Compton thick, CT: NH ≥ 1024 cm−2) of these AGN. In this work, we investigate the synergies between putative IR missions [using SPace Infrared telescope for Cosmology and Astrophysics (SPICA), proposed for European Space Agency (ESA)/M5 but withdrawn in 2020 October, and Origins Space Telescope, OST, as ‘templates’] and the X-ray mission Athena (Advanced Telescope for High ENergy Astrophysics), which should fly in early 2030s, in detecting and characterising AGN, with a particular focus on the most obscured ones. Using an XRB synthesis model, we estimated the number of AGN and the number of those which will be detected in the X-rays by Athena. For each AGN, we associated an optical-to-Far InfraRed (FIR) spectral energy distribution (SED) from observed AGN with both X-ray data and SED decomposition and used these SEDs to check if the AGN will be detected by SPICA-like or OST at IR wavelengths. We expect that, with the deepest Athena and SPICA-like (or OST) surveys, we will be able to photometrically detect in the IR more than 90% of all the AGN (down to L2−10keV ∼ 1042 erg s−1 and up to z ∼ 10) predicted by XRB synthesis modeling, and we will detect at least half of them in the X-rays. The spectroscopic capabilities of the OST can provide ≈51 000 and ≈3 400 AGN spectra with R = 300 at 25–588µm in the wide and deep surveys, respectively, the last one up to z ≈ 4. Athena will be extremely powerful in detecting and dis

[Aims]: to detect and to reconstruct the pulses that X-ray photons produce at TES (Transition Edge Sensor) detectors (like the one in the Athena/X-IFU instrument), using Deep Learning techniques. The dataset used contains simulations performed with the Athena official simulator SIXTE., [Methods]: We construct and train a Convolution Neural Network (CNN) to differentiate between single, double and triple pulses. We use a hyper-parameter bayesian optimization to select the optimal CNN architecture., [Results]: we present the results of our CNN classification over 15,000 simulated pulses achieving excellent performance metrics.

The Athena X-ray Observatory, to be launched in the early 2030s, is designed to implement the Hot and Energetic Universe science theme. The X-ray Integral Field Unit (X-IFU) proposed for the Athena mission is a cryogenic imaging spectrometer, offering spatially-resolved high-spectral resolution X-ray spectroscopy over a 5 arcminute equivalent diameter field of view. In this project, we aim to detect and reconstruct the X-ray pulses that will be detected by the X-IFU instrument using Deep Learning techniques over a dataset of simulations with SIXTE (a software package for X-ray telescope observation simulations). We construct and train a Convolution Neural Network (CNN) to differentiate between single, double and triple pulses (i.e., detections with one, two or three pulses in the same record, respectively). We use a hyper-parameter bayesian optimization to select the best CNN architecture. Finally, we present the results of our CNN classification on a test set of simulated pulses, covering all the possible cases in terms of energy ranges and pulse distances, achieving excellent performance metrics.

[Context]: The XMM-Newton Survey Science Centre Consortium (SSC) develops software in close collaboration with the Science Operations Centre to perform a pipeline analysis of all XMM-Newton observations. In celebration of the twentieth anniversary of the XMM-Newton launch, the SSC has compiled the fourth generation of serendipitous source catalogues, 4XMM., [Aims]: The catalogue described here, 4XMM-DR9s, explores sky areas that were observed more than once by XMM-Newton. These observations are bundled in groups referred to as stacks. Stacking leads to a higher sensitivity, resulting in newly discovered sources and better constrained source parameters, and unveils long-term brightness variations., [Methods]: The 4XMM-DR9s catalogue was constructed from simultaneous source detection on overlapping observations. As a novel feature, positional rectification was applied beforehand. Observations with all filters and suitable camera settings were included. Exposures with a high background were discarded. The high-background thresholds were determined through a statistical analysis of all exposures in each instrument configuration. The X-ray background maps used in source detection were modelled via an adaptive smoothing procedure with newly determined parameters. Source fluxes were derived for all contributing observations, irrespective of whether the source would be detectable in an individual observation., [Results]: The new catalogue lists the X-ray sources detected in 1329 stacks with 6604 contributing observations over repeatedly covered 300 square degrees in the sky. Most stacks are composed of two observations, the largest one comprises 352 observations. We find 288 191 sources of which 218 283 were observed several times. The number of observations of a source ranges from 1 to 40. Auxiliary products, like X-ray full-band and false-colour images, long-term X-ray light curves, and optical finding charts, are published as well., [Conclusions]: 4XMM-DR9s contains new detections and is considered a prime resource to explore long-term variability of X-ray sources discovered by XMM-Newton. Regular incremental releases, including new public observations, are planned.

In the era of new technologies, in the Department of Public Outreach of the Instituto de Física de Cantabria we have added to our more purely digital catalog various materials and activities from the “manual” era, for which IFCA staff have developed their better DIY skills. From a planetary system to a (dis) mountable black hole, through a cloud chamber or a gravitational table, never forgetting the infallible ©LEGO, the manual materials have surprisingly aroused the interest of our public and visitors of all ages encouraging, in addition, the interdisciplinarity and team work of the members of the different IFCA research groups. From the IFCA PO department we have been able to verify how these types of materials have a great acceptance and are frequently required because they provide a complementary, more classical vision of the physical phenomena that we show in our activities. This presentation takes a tour of the materials that we have developed at IFCA, from the manufacturing process to their use and enjoyment, and will try to convince the audience of the therapeutic nature of building and, that an image is worth a thousand words but it is worth more than two thousand words if you have a gadget next to it.

The Athena Community Office (ACO) supports ESA’s Athena Science Study Team (ASST) in its role as ”focal point for the interests of the broad scientific community”. The ACO is led by the Instituto de Física de Cantabria (CSIC-UC). Further ACO contributors are IRAP, MPE and the University of Geneva.

We present the X-ray spectra of 185 bright sources detected in the XMM-Newton deep survey of the Chandra Deep Field South with the three EPIC cameras combined. The 2–10 keV flux limit of the sample is 2 × 10−15 erg s−1 cm−2. The sources are distributed over a redshift range of z = 0.1−3.8, with 11 new X-ray redshift measurements included. A spectral analysis was performed using a simple model to obtain absorbing column densities, rest-frame 2–10 keV luminosities, and Fe K line properties of 180 sources at z > 0.4. Obscured AGN are found to be more abundant toward higher redshifts. Using the XMM-Newton data alone, seven Compton-thick AGN candidates were identified, which set the Compton-thick AGN fraction at ≃4%. An exploratory spectral inspection method with two rest-frame X-ray colours and an Fe line strength indicator was introduced and tested against the results from spectral fitting. This method works reasonably well to characterise a spectral shape and can be useful for a pre-selection of Compton-thick AGN candidates. We found six objects exhibiting broad Fe K lines out of 21 unobscured AGN of best data quality, implying a detection rate of ∼30%. Five redshift spikes, each with more than six sources, are identified in the redshift distribution of the X-ray sources. Contrary to the overall trend, the sources at the two higher redshift spikes, at z = 1.61 and z = 2.57, exhibit a puzzlingly low obscuration.