Recent gravitational wave (GW) detections with LIGO/Virgo opened a new window on the Universe, unveiling the most violent catastrophic events in the cosmos. GW astronomy is just in its infancy, 3G detectors will extend our capabilities to observe colliding black holes and neutron stars from the ground, and the Laser Interferometer Space Antenna (LISA) and Pulsar Timing Arrays (PTAs) will offer...
The discovery of the gravitational wave transient GW170817 and its electromagnetic counterparts ushered in a new era of multi-messenger. astrophysics, in which both gravitational waves and light provide complementary views of the same source. These observations gave astronomers the unprecedented opportunity to probe the merger of two neutron stars, solving decade-long mysteries about the...
We exploit observations of the INTErnational Gamma-Ray Astrophysics Laboratory (INTEGRAL) to search for gamma-ray and hard X-ray emission associated with the gravitational wave events discovered during scientific runs of Advanced LIGO and Advanced Virgo. The highly eccentric orbit of INTEGRAL ensures high duty cycle, long-term stable background, and unobstructed view of the nearly entire sky....
Supermassive black hole binaries (SMBHB) are a natural outcome of the hierarchical mergers predicted by the $\Lambda$CDM cosmology, and promising sources of nanohertz continuous gravitational wave signals. However, their detection remains elusive. Since hard X-rays are produced in the innermost regions of active galactic nuclei, they are predicted to show the best signatures of SMBHB, namely a...
Fundamental properties of black hole X-ray binaries (BHXBs) are important in massive stellar evolution and high energy astrophysics. But, their astrometric properties have been reported for a handful of objects, because their transient behavior, faint optical counterparts and large distances (> 1 kpc) have made comprehensive astrometric investigations of BHXBs very challenging. Gaia has...
When a star is disrupted by a super-massive black hole (SMBH), the stellar debris returns to the black hole at a rate which exceeds the Eddington accretion rate in the majority of cases and can cause a large X-ray flare. The X-ray emission from the resultant thick disk, shares characteristics with that seen from highly-accreting, low black hole mass ($10^5$ to $10^7$ solar masses), AGN; namely...
XMM-Newton's large field of view and excellent sensitivity have resulted in hundreds of thousands of serendipitous X-ray detections, all publicly available in the latest version of the catalogue, 3XMM-DR8. Amongst these detections, many variable sources have been identified, including gamma-ray bursts, cataclysmic variables, supernova, magnetars, X-ray binaries and tidal disruption events. I...
Simultaneous O-IR / X-ray high-time resolution observations are one of the most powerful tools to study jets in Low-mass X-ray binareis. In this talk I present the latest results regarding fast-IR variabilty of the new black-hole transients which went in outburt between 2017 and today (e.g. MAXI J1535-571, MAXI J1820+070 and MAXI 1348-630). All these sources have been oberved in IR (K band)...
The heart of the Milky Way is a laboratory for high energy astrophysics, containing the Galactic supermassive black hole, thousands of X-ray point sources and prominent diffuse X-ray emission. I will review our knowledge of the present and past activity from the supermassive black hole as well as its relation to the recently discovered outflow connecting the central parsecs to the base of the...
Variable X-ray emission from the clouds of the Central Molecular Zone (CMZ) are attributed to the reflection of radiation emitted by the super-massive Black Hole of the Galaxy, Sgr A$^*$, during outbursts occurred in the recent (< 1000 yr) past.
Thanks to a detailed analysis of the XMM and Chandra data of the Galactic Center, based on the comparison of observed spectra and Monte Carlo...
I will review recent (and not so recent) results on accretion and ejection processes in X-ray binaries.
Characterization of X-ray binaries on the basis of their donor stars allow us to identify their parent stellar populations and measure directly their formation efficiency as function of their age. Combining this information with constraints on the nature of their compact objects allow us to measure the formation rate of compact objects and their demographics in different types of X-ray...
The sub-class of high mass X-ray binaries called Supergiant Fast X-ray Transients (SFXTs) shows flaring activity even outside outbursts, across more than four orders of magnitude in X-ray luminosity. We investigated these X-ray flares exploiting the XMM-Newton archival observations, taking advantage of the EPIC (0.2-12 keV) products made publicly available by the EXTraS project. Adopting the...
We report the detection of pulsations from the archetypal ultraluminous X-ray source (ULX) NGC 1313 X-2. Acceleration searches reveal sinusoidal pulsations in segments of two out of six new observations of this object, with a period of $\sim 1.5$ s and a pulsed fraction of $\sim 5\%$. We demonstrate that the moderate significances of the individual detections are unlikely to originate in...
Ultraluminous X-ray sources (ULXs) are extragalactic X-ray emitters located off-center of their host galaxy and with a luminosity in excess of a few $10^{39}$ erg/s, if emitted isotropically. The discovery of periodic modulation revealed that in some ULXs the accreting compact object is a neutron star (NS), indicating luminosities substantially above their Eddington limit. The most extreme...
Observational studies of Ultraluminous X-ray Sources (ULXs, L > 1e39 erg/s) have taken on greater siginficance since the discovery that this population is (primarily) made up of X-ray binaries accreting at super-Eddington rates, a result that has been spectacularly confirmed with the detection of coherent pulsations from a growing number of ULXs (requiring neutron star accretors, despite...
Accretion is known to occur at rates far in excess of the classical Eddington limit in the local and distant Universe alike. In our Galaxy we are provided with a view of such accretion in the form of the extreme binary SS433, observations of which tell us that mass-loaded outflows and persistent collimated jets are associated features which redistribute energy and matter into the local...
Powerful accretion processes around black holes (BH) in X-ray binaries or AGN give birth to High energy emission from UV to X-rays/gamma-rays. While the BHs strongly differ in terms of mass in these objects, their close environment shows clear similarities with the presence of (1) an optically thick accretion disk, (2) a hot plasma (the so-called corona) producing hard X-rays through...
In high mass X-ray binaries (HMXBs), the black hole or neutron star accretes matter from the wind of a massive supergiant companion: the stellar wind drives changes in the accretion and thus the system’s X-ray emission. But the interaction of this emission with the wind material can also be used to study the wind itself, in particular its geometry, porosity (or clumpiness), mass-loss rate and...
Hercules X-1 is one of the best studied accreting neutron star X-ray binaries with a wealth of archival X-ray data. It is well-known for the various time periods in its system: a 35-day period of high, low and short-on flux states, likely caused by a precessing warped accretion disc, a 1.7 day orbital period and a 1.2 sec pulsation period of a neutron star with a ∼10^12 G magnetic field. I...
In the local Universe, it is observed that the X-ray luminosity ($L_X$) of HMXB populations is correlated with the host galaxy’s star formation rate (SFR). Recent X-ray studies of high-redshift galaxies find a positive evolution of this correlation with redshift. This trend is attributed to the formation of more luminous HMXBs in lower metallicity ($Z$) environments, as predicted by binary...
Supernovae are one of the most energetic explosion events in the universe, with the human detectability not only in electromagnetic wave but also neutrino and possibly gravitational wave. They also play the main role of chemical evolution of the universe. On the other hand, the explosion mechanism in detail is still unclear. We will summarize recent X-ray observations of remnants of supernovae...
Type IIn supernovae (SNe) are characterized by narrow lines on a broad base in their optical spectrum. A wide diversity in their lightcurves, and in SNe that exhibit IIn features, has greatly complicated the task of identifying their progenitors. IIns have the highest X-ray luminosity of all SN classes, and are observable in X-rays decades after explosion. Many of the lightcurves tend to fall...
Cataclysmic variables (CVs; interacting binaries in which a white dwarf accretes matter from a Roche-lobe filling donor on or near the main sequence) and symbiotic stars (white dwarf-red giant binaries) are excellent laboratories in which to study accretion physics, without having to worry about relativistic effects. Their fluxes are high enough to enable detailed X-ray and multiwavelength...
Galaxy clusters are the ideal locations to study the interplay between active galactic nuclei, hot and cold baryons, dark matter and cluster mergers. X-ray observations are very powerful to study these physical processes, as they let us directly see the hot baryons, the dominant baryonic component. I will review what deep X-ray observations have shown us about feedback in the cores of galaxy...
The Sunyaev-Zeldovich effect provides an observational window to the intracluster medium, which is complementary to X-ray observations, and over the last few years has proved to be a mature technique to efficiently detect galaxy clusters. For instance, the Planck survey has mapped the whole microwave sky, detecting almost 2000 candidate massive clusters up to z~1, performing the first all-sky...
Mergers between galaxy clusters drive weak shock fronts into the intracluster medium, capable of both heating the gas and accelerating relativistic particles. Measurements of the high temperature gas and non-thermal inverse Compton (IC) emission that result from these shocks most benefit from sensitive observations at hard X-ray energies. NuSTAR observations of the Bullet cluster, Abell...
X-ray observations of the outskirts of galaxy clusters show that the entropy of the intracluster medium (ICM) in the virialization region is generally less than what is expected based on purely gravitational structure formation. Possible explanations include electron/ion non-equilibrium, accretion shocks that weaken during cluster formation, and the presence of unresolved cool gas clumps. ...
In the process of cluster formation, giant shock waves are driven in the intra-cluster medium (ICM) leaving remarkable imprints in the X-ray emitting gas. The detection of these fronts is complicated as shocks are generally located in the cluster outskirts, where the count statistics is low. In the very recent years, the number of merger shocks observed increased thanks to deep observations...
Galaxy groups are arguably the most important environment for our understanding of galaxy evolution, AGN feedback and the development of the hot intergalactic medium (IGM). Previous studies of groups in the nearby universe have either used optically-selected samples to examine galaxy populations, or X-ray selected samples (from the Rosat All-Sky Survey) to examine IGM properties. While these...
Galaxy clusters are dark-matter dominated systems enclosed in a volume that is a high-density microcosm of the rest of the universe. Clusters are thus excellent laboratories for probing the physics of the gravitational collapse of dark matter and baryons. As cluster growth and evolution depend on the underlying cosmology, their number density as a function of mass and redshift, spatial...
The study of the formation of galaxy clusters is incomplete without connecting measurements of clusters at low redshifts to their progenitor structures in the early universe. New surveys are now finding significant numbers of these cluster progenitors at z > 2 with relative ease. While some of these are associated with powerful active galaxies (radio galaxies and quasars) that are good...
A hot plasma is the dominant phase of the ISM of early-type galaxies. Its origin can reside in stellar mass losses, residual gas from the formation epoch, and accretion from outside. Its evolution is linked to the dynamical structure of the host galaxy, to the supernova and AGN feedback heating, and to the (late-epoch) star formation. Observations with XMM-Newton and Chandra have now...
Impending surveys from facilities such as e-Rosita, SPT-3G and Euclid will revolutionize cluster cosmology by yielding samples with $>10^{5}$ galaxy clusters, producing an exquisitely detailed 10 Gyr picture of cluster formation. In this new era of precision cluster cosmology dynamically relaxed clusters occupy a special role, enabling a reliable deprojection of ICM properties and reduced...
The hot ISM in early type galaxies (ETGs) plays a crucial role in understanding their formation and evolution. The structural features of the hot gas identified by Chandra and XMM-Newton observations point to key evolutionary mechanisms, (e.g., AGN and stellar feedback, merging history). In our X-ray Galaxy Atlas project, we systematically analyzed the archival Chandra (XMM-Newton) data of 70...
Galaxy cluster are the largest bound structures in the Universe. The formed recently, at z~2, and since then they have been growing through accretion of matter from the cosmic web in their outskirts. X-ray follow up observations of SZ selected clusters offer a unique opportunity to study the faint outskirts of these objects. The South Pole Telescope (SPT) 2500d survey detected hundreds of...
I will first review the baryon census in the local Universe and show that serious missing-mass problems are present at all scales. I will then present the possible solutions offered by hydro-dynamical simulations for the formation of structures, and show how theory reconciles these different-scale problems in the framework of a single missing-baryon problem. I will review the history of the...
For years, detection of cosmic filaments has been an elusive target for observers. Although predicted by simulations and seen in the distribution of galaxies for decades, only a few statistically significant measurements of the diffuse web have been made, particularly in the X-ray regime. However, in a very deep (2.4 Ms) observation with Chandra around the cluster Abell 133 (z=0.055), we...
The missing baryon and missing metals problems are the two major challenges for galaxy formation. The missing matter most likely resides in the warm-hot (10$^{5-7}$ K) medium beyond galaxies. Hot outflows driven by supernovae carry the majority of energy and metals, providing a natural solution to these problems. X-ray emission from hot corona around spiral galaxies, observed by XMM-Newton and...
Surface brightness fluctuation analysis has become a new frontier in studying cosmic X-ray background (CXB) due its ability to disentangle contributions of different CXB components via their different angular correlation properties and energy spectra. This analysis can be utilized to search for contribution of low surface brightness objects, such as faint and distant cluster of galaxies and...
X-ray emission from AGN is believed to be produced via Comptonization of optical/UV seed photons emitted by the accretion disk, up-scattered by hot electrons in a corona surrounding the black hole. A critical compactness vs. temperature threshold is predicted above which any increase in the source luminosity would generate positron-electron pairs rather than continue heating the coronal...
Outflows from active galactic nuclei are found over a broad range of distances from the supermassive black hole and with a large range of velocities. The so-called "warm absorbers" cover a broad range of ionization parameters but at modest velocities of a few hundred to thousand km/s and relatively modest column densities of typically less than 1% of the Thomson depth. On the other extreme,...
The observed overlap between soft X-ray emission and the NLR in obscured AGN is commonly interpreted as evidence for a constant gas pressure multiphase medium. Radiation pressure compression (RPC) also leads to a density distribution, since a gas pressure (hence density) gradient must arise within each cloud to counteract the ionizing radiation pressure. RPC leads to a well-defined ionization...
Water megamaser emission is powerful in tracing the inner region of active nuclei, mapping accretion disks and providing important clues on their absorption properties. From the broad band X-ray spectra of AGN it is possible to estimate the intrinsic power of the central engine and the obscuring column density. The synergy between X-ray and water maser studies allows to tackle the AGN inner...
In the past decade, spectral-timing measurements of accreting black holes have revealed reverberation light travel echoes between the X-ray emitting corona, and the accretion disc. Together, XMM-Newton, NuSTAR, Swift and NICER have measured light echoes from size scales ranging from the broad line region down to the ISCO. In this talk, I will give an overview of the progress over the past...
Recent observing campaigns revealed the occurrence of “obscured states” in a few Seyfert galaxies, produced by streams of outflowing, lowly ionized gas, partially eclipsing the X-ray source. These events appear to be transient, temporarily modifying the X-ray properties of the source. The increasing number of detections suggests this might be a common phenomenon. It is therefore important to...
Several AGN have shown UV/optical variability lagging behind the X-ray emission by a few days. The simplest and most straightforward interpretation is that the variable X-ray flux from the corona illuminates the accretion disc below where it is partially reflected and observed as fast X-ray reverberation signal, and partially absorbed and thermalised in the disc, which produces a slow UV and...
We present current X-ray observations and simulations showing how gravitational lensing is used to infer the structure near the event horizons of black holes, constrain the spin of the supermassive black hole and its evolution over cosmic time and test general relativity in the strong-gravity regime.
We also show how these observations can be expanded to a statistically large sample of z =...
AGN radiative feedback, driven by radiation pressure on dust, is a key physical mechanism connecting the accreting black hole to its surrounding environment. The actual importance of radiative feedback can be observationally tested by analysing how X-ray-selected AGN samples populate the so-called "NH-lambda plane", defined by the column density versus the Eddington ratio. A "forbidden" region...
We report results from a series of X-ray observations of a local galactic core whose long-term properties over the course of the past ten years are consistent with a long-lived tidal disruption event. A new spectacular phenomenon is occurring in this system 2018 December onwards, when XMM-Newton has discovered massive, repeating X-ray flares. During these "quasi-periodic eruptions" (or QPEs)...
Accretion in active galactic nuclei (AGN) is accompanied by two modes of outflow: winds and jets. However, the connection between the winds, jets, and the accretion flows is not fully understood. I present the results of a recently-published paper (Mehdipour & Costantini 2019), where we have investigated the relation between the parameters of the ionised wind and the jet in a sample of...
The growing evidence for energy-conserving outflows in powerful and luminous AGN supports the idea that high-velocity X-ray winds launched from the accretion disc evolve after undergoing a shock with the ambient medium, with the ultimate effect to expel enough mass and energy so as to produce the so-called AGN feedback, often invoked in galaxy formation and evolution. This talk will present...
Almost twenty years of X-ray grating observations allowed us to characterize the multi-component ionized gas, outflowing from active galactic nuclei, with unprecedented accuracy. XMM-Newton combined with HST have been key in unveiling the secrets of outflowing winds.
Here I will show the results of our most recent multi-wavelength campaign on the narrow line Seyfert 1 IZw1 (230 ks with XMM...
I will review our understanding of the AGN as detected by the current suite of X-ray observatories. I will discuss the complementary parameter space from the broad swathe of extragalactic X-ray surveys undertaken to date. I will describe the types of AGN detected in these surveys, their overall properties and cosmic evolution. A key objective of this talk is to provide the context for many of...
From observations of active galactic nuclei (AGN) we may improve our understanding of the growth of black holes across cosmic time and their impact on their host galaxies, but observations alone may be limited by complex biases. Here I will present the results from modeling the whole AGN population while accounting for observational biases.
I will begin by showing that the Eddington ratio...
It has been claimed for decades that almost all galaxies in the local Universe host at their centre a super-massive black hole (SMBH) the mass of which appears to be tightly correlated with the stellar mass and the random motion ("velocity dispersion", sigma) of the stars of the host galaxy. In this talk I will first highlight that significant biases affect local black hole-galaxy...
The cosmological concordance model (ΛCDM) well accounts for a wealth of observations, from the existence of Cosmic Microwave background (CMB) to the discovery of the accelerated expansion of the universe from Type Ia supernovae. Yet, it assumes a still unknown form of dark energy and matter and some tensions arose recently as, for instance, the discovery of a >3σ discrepancy between the local...
The formation channels of Supermassive Black holes (SMBHs) seeds are currently debated, as are their accretion limits, growth and co-evolution with galaxies. Independent of these questions, we investigate the occurance of SMBH seeds with a simple generic framework. We consider that when halos outgrow a mass threshold, a fraction of them have formed black holes. Following the well-understood...
We are performing a systematic study of the the X-ray properties of the most luminous (L$_{bol}>10^{47}$ erg/s) quasars in the Universe spanning from optical- NIR- MIR-selected sources at z=2-3. These AGN exhibit widespread outflow signatures at all scales and they are the sources where we expect quasar feedback to manifests in full force. Hence they are in a transit phase, predicted in quasar...
Some AGN are known to be efficient producers of strong, relativistic jets which power the extended radio sources. Most spectacular in respect of powers and sizes are the radio sources associated with AGN hosted by giant elliptical galaxies. However even among them, the production of powerful jets is a very rare phenomenon and the unanswered question remains why it is so. Since relativistic...
Despite the importance of dual active galactic nuclei to wide-ranging astrophysical fields such as galaxy formation and gravitational waves, the rate of dual AGNs has yet to be accurately measured. However, the rate of dual AGNs can inform us of the role galaxy mergers play in triggering AGN, timescales for post-merger SMBHs to sink to the center of the potential well (or, the effectiveness of...
X-ray emission is an ubiquitous property of Active Galactic Nuclei and, being produced within a few gravitational radii from the supermassive black hole, can provide fundamental information about the structure and geometry of the circumnuclear material, as well as on the characteristics of the accretion flow. In my talk I will present recent studies of the obscuration and accretion properties...
An accurate assessment of the fraction of heavily obscured, "Compton-thick" AGN in the local Universe provides important insights into the composition and structure of AGN X-ray obscuration, as well as its connection with the evolution of supermassive black holes and their surrounding host galaxies. However, current estimates of the Compton-thick fraction vary dramatically between ~20-70%,...
The AGN effect on host galaxies is an interesting topic that has been often discussed so far. The AGN is usually X-ray luminous, and thus X-ray irradiation by the AGN is unavoidable for its host galaxy. We report our recent study on X-ray-irradiated gas in the central ~100 pc of the Circinus galaxy (TK+19), a Compton-thick AGN host, at 10-pc resolution using Chandra and ALMA. Based on ~200...
The ability of the X-rays to penetrate and measure large columns of obscuring material is crucial to characterise the emission from the Active Galactic Nuclei (AGN), especially those with heavy obscuration and/or weak emission.
In this work we exploit the largest energy band available in the X-rays ($\sim$0.5-30 keV) to accurately assess the intrinsic power and obscuration for a sample of 30...
Through the years, AGN accretion theory has lagged behind with respect to the plethora of observational signatures driven by accretion onto supermassive black holes. For instance, the smoking gun of the disk-corona interplay in radiatively-efficient AGN is given by the correlation observed between monochromatic $\log L_{X}-\log L_{UV}$. Despite being used for decades (since the introduction of...
Studies of recent decades have led to the conclusion that there is an inextricable link between galaxies and the Supermassive Black Holes (SMBHs) located in their centre. However, it is still unclear how the activity of the SMBH affects the properties of the host galaxy. Furthermore, there is a scientific debate whether the absorption we observe in some AGN is a geometric effect or an...
Scaling relations are the most powerful astrophysical tools to set constraints to the physical mechanisms of astronomical sources and to infer properties for objects where they cannot be accessed directly. We have re-investigated one of these scaling relations using powerful type 1 Seyferts; the so-called X-ray variability plane (or mass-luminosity-timescale relation, McHardy et al. 2006)....
Determining the processes responsible for the initial formation and subsequent growth of the very first supermassive black holes, primarily taking place at very high redshifts (z>6), will be a major challenge for the next decade of X-ray astronomy and beyond. I will review what is currently known about black hole growth during this early period of cosmic time (from both an X-ray and...
Chandra and XMM-Newton showed that AGN existed in the early Universe (at z~7.5) and this challenges our understanding of SMBH formation. Chandra detected serendipitously only an handful of z>4-5 sources and the majority of the constrains on the nature of early Black holes come from Cosmic background fluctuations studies or stacking/follow up of Infrared selected sources. I will present recent...
More than 200 quasars (QSOs) with spectroscopic redshift z > 6 have been discovered so far.
Multi-wavelength observations showed that these objects are evolved systems with large black hole masses ($10^8−10^{10} M_{\odot}$), and that their broad-band spectral energy distributions (SEDs) and rest-frame UV spectra have not significantly evolved over cosmic time.
The formation of their Super...
With about 350 refereed papers published each year, XMM-Newton is one of the most successful scientific missions of ESA ever. The talk summarizes the status of the mission and introduces the main performance indicators, which characterize the scientific impact of the mission. The talk gives then an overview of recent research highlights, which are indicative of the main developments of current...
I will summarise Chandra’s scientific legacy during the first 20 years of operation. This includes key results across the full range of astrophysics enabled by Chandra’s unique spatial resolution, spectral resolution, broad dynamic range and longevity, as well as its’ major impact on our community. Looking forward to the next 10 years, I will summarise Chandra’s current status, and the rich...
The next generation of wide-area, sensitive X-ray surveys designed to map the hot and energetic Universe will be heralded by eROSITA (extended ROentgen Survey with an Imaging Telescope Array), the core instrument on the Russian-German Spektrum-Roentgen-Gamma (SRG) mission, successfully launched in July 2019. eROSITA will perform a deep survey of the entire X-ray sky, and will be about 30 times...
I discuss how several of the proposed models for space-time quantization predict an energy dependent speed for photons.
Although the predicted discrepancies with the general speed of light are minuscule, I discuss how it is possible to detect this intriguing signature of space-time granularity with a new concept of modular observatory for photons in the energy band from few keV to few MeV....
We present the concept of a future Japan-lead X-ray medium-class mission, FORCE (Focusing On Relativistic universe and Cosmic Evolution). FORCE is characterized by broadband (1-80 keV) X-ray imaging spectroscopy with high angular resolution (<15"). The sensitivity above 10 keV will be 10 times higher than that of any previous hard X-ray missions. FORCE will trace the cosmic formation history...
We have invented a new type of X-ray interferometers, MIXIM, which simply consists of a grating (multiple slits) and a pixel detector. This configuration provides X-ray images as multiple slit camera can do. If we employ a grating of a pitch d of 5micrometer, and opening fraction f of 0.2 separated from the detector by the distance z of 50cm, we expect the image width of 0.4’’. It suggests...
Athena (The Advanced Telescope for High Energy Astrophysics) is a next-generation X-ray observatory to address the Hot and Energetic Universe science theme, selected by ESA as the second large mission of the Cosmic Vision program. The driving science of the mission is to understand the formation and evolution of hot gas structures in the Universe, and the growth and evolution of supermassive...
X-Ray Imaging and Spectroscopy Mission (XRISM) is the mission to resume high resolution X-ray spectroscopy with imaging once realized but unexpectedly terminated by a mishap of Hitomi. This innovative, JAXA-led international project being developed in collaboration with NASA, ESA, and other world wide partners, focuses on large scale flows of energy and matter in the universe with the...
Almost half a century will have passed since the first satellite experiment to attempt to measure the polarization of non-solar X-ray sources, the Bragg crystal polarimeter aboard the Orbiting Solar Observatory number 8, was performed. NASA’s Small Explorer Mission, the Imaging X-ray Polarimetry Explorer (IXPE), which I have the privilege to be the Principal Investigator of, is scheduled for...
The Transient High-Energy Sky and Early Universe Surveyor (THESEUS) is a space mission concept currently under Phase A study by ESA as candidate M5 mission, aiming at exploiting Gamma-Ray Bursts for investigating the early Universe and at providing a substantial advancement of multi-messenger and time-domain astrophysics. Through an unprecedented combination of X-/gamma-rays monitors, and...
There is strong evidence for a link between the growth of supermassive black holes (SMBHs) and their host galaxies. Active galactic nuclei (AGN) powered by accretion onto SMBHs release a huge amount of energy in the surrounding medium in the form of radiation, winds and jets. This phenomenon also known as AGN feedback has been invoked to regulate the growth of SMBHs and their host galaxies as...
This talk will summarize the status of and prospects for future NASA X-ray astronomy missions. Although there is only one NASA X-ray astronomy mission currently under development (the Imaging X-ray Polarimetry Explorer), there are several promising candidates for selection over the next 2-3 years through NASA’s Small and mid-sized Explorer (SMEX and MIDEX) solicitations, including Arcus and...
The enhanced X-ray Timing and Polarimetry (eXTP), a large international space science mission led by China with major contributions from many European countries and other international partners, is designed to study fundamental physics under extreme conditions of density, gravity and magnetism. eXTP will carry two sets of focusing X-ray telescopes for spectroscopy (9 telescopes) and...
Andrea Comastri, Chryssa Kouveliotou (chairs)
Pepi Fabbiano, Fabrizio Fiore, Poshak Gandhi, Colin Norman, Aurora Simoniescu
Most active galactic nuclei are seen through thick circum-nuclear gas and dust. Also, these column densities vary on time scales of days to years, indicating that the obscurer is made from clumps. We present the first clumpy obscurer model that reproduces eclipse events and column density distributions. We developed a new, open-source Monte Carlo code, XARS, to X-ray illuminate arbitrary...
Accretion onto a Black Hole seems to be a universal phenomena: it occurs in Black Holes of all masses, from galactic X-ray Binaries with stellar mass Black Holes, to extragalactic Active Galactic Nuclei harboring Supermassive Black Holes. A question naturally arises in this context: is the nature of the accretion onto Black Holes also universal across the mass range? In this work, we extend...
We present X-ray spectra spanning 18 years of evolution for SN1996cr, one of the five nearest (~4 Mpc) SNe detected in the modern era. Chandra-HETG exposures allow us to resolve spectrally the velocity profiles of Ne, Mg, Si, S, and Fe emission lines and monitor their evolution as tracers of the ejecta-circumstellar medium (CSM) interaction. To explain the diversity of X-ray line profiles, we...
The study of transient phenomena has entered a new phase with the advent of multi-messenger astronomy, as we now routinely search large areas of sky for an electromagnetic counterpart to a neutrino or gravitational wave trigger. This presents various new challenges. We need to understand the probability of serendipitously observing an X-ray transient during such follow up. We also need fast,...
The origin of extended emissions following prompt emissions of short gamma-ray bursts (SGRBs) is in mystery. The long-term activity of the extended emission is responsible for promising electromagnetic counterparts to gravitational waves and, so that it may be a key to uncovering the progenitor of SGRBs. We investigate the early X-ray light curves of 26 SGRBs with known redshifts observed with...
GRS 1915+105 is a black hole X-ray binary known for its characteristic variabilities of X-ray fluxes on timescales of minutes to hours, sometimes showing limit-cycle behavior in its X-ray light curves. More than ten patters of light curves has been recognized and classified. However, its long-term behavior, in particular, transitions among these variability classes have been difficult to...
We report the the discovery of a Tidal Disruption Event (TDE) occurred in the Active Galactic Nuclei. The X-ray spectral properties and the broad optical emission lines detected in the SDSS spectrum clearly revealed the AGN nature, with black hole mass of $\sim 10^6\,M_\odot$ and Eddington ratio of $\lambda_{Edd}=0.6$. A sudden increase in flux during the second half of 2009 is shown in the...
'eROSITA on-board the SRG satellite will perform the next large X-ray all-sky survey. With its 30-fold increased sensitivity relative to its predecessor ROSAT and its multi-visit, multi-cadence survey strategy, eROSITA will provide a new and deeper look into X-ray time domain astrophysics. To better handle the vast number of sources eROSITA is expected to detect, and assist with planning...
Low frequency quasi-periodic oscillations (QPO) with periods between ~10 s and ~0.05 s are often seen in the X-ray flux of accreting stellar-mass black holes. These are often attributed to the Lense-Thirring precession of the inner accretion flow, a General Relativistic effect caused by the spin of the black hole.
QPO phase-resolved spectroscopy, i.e. measuring how the X-ray spectrum changes...
Accreting LMXBs have long been known to emit relativistic jets from regions close to the compact object, but studying these regions is rendered difficult by the prohibitively short time scales associated with the inner jets, and the need to disentangle various compact emission components. In this talk, I will present some of the latest results in this field, where the new NICER instrument...
Transitional binaries are accreting pulsars observed in both Low Mass X-ray binary (LMXB) and Millisecond Radio Pulsar (MSP) phase.
They are considered the ”smoking gun" of the so-called recycling scenario, first proposed in the 70s to describe the acceleration of radio pulsars to millisecond periods.
They alternatively emit their pulsation in radio or X-rays depending on the accretion phase...
The Rossby-Wave Instability (RWI) has been proposed as the origin of the fast quasi-periodic variability (HFQPOs) observed in black-hole binaries. Here we are using NOVAs, our Numerical Observatory of Violent Accreting systems, to follow the evolution of the RWI arising in the accretion disk of a black-hole for a large range of spin. The first aim is to prove the ability of the RWI to...
We report for the first time the detection of X-ray burst in the IR K-band from the neutron star low mass X-ray binary 4U 1728-34. Using high time resolution IR observations we find a rapid increase of the IR emission 6 seconds after the appearance of an X-ray burst. We interpret such long delay as the light-travel time from the neutron star to the companion star surface, where the X-ray...
We present prospects for studying stellar-origin black hole (BH) and neutron star (NS) populations in nearby galaxies, focusing on science topics that require next generation X-ray telescopes. Time domain measurements of BHs and NSs will revolutionize our understanding of their formation and evolution by linking source characteristics to accretion and galaxy parameters. The central themes...
We present a multi-wavelength search for X-ray, optical and gamma-ray emission from the radio milli-second pulsar J1836-2354A (M22A, hereafter) hosted in the Galactic globular cluster M22 (NGC 6656), at 3.2 kpc far from Earth. In the last two decades, the cluster was observed with the X-ray satellites XMM-Newton, Chandra and Swift.
Thanks to the $\sim$85 ks of exposure time, the...
We present the analysis of all galaxies within a radius of 200 Mpc observed with XMM-Newton. These galaxies are the result of cross-correlation between the XMM-Newton archive and the HECATE catalogue, the most complete galaxy catalogue (~165,000 galaxies) of the local universe incorporating robust distances and stellar population parameters. In our analysis we will use data from all objects...
The spectral states of the Black Hole Binaries (BHBs) are characterised by different X/$\gamma$-ray luminosities, spectral shapes and timing properties over their outburst. The dominant hard X-ray component observed in the hard state spectrum is usually described by a cut-off power law and it is interpreted as thermal Comptonization.
We present the the spectral and timing analysis of...
Supersoft X-ray sources are characterized by black body temperatures below 100 eV and are found with luminosities that are explained by steady nuclear burning of hydrogen accreted onto white dwarf surfaces (in the range of $10^{36}-2\times10^{38}$ erg/s) or are ultraluminous (>$2\times10^{38}$ erg/s) requiring the
presence of a neutron star or black hole. We report the discovery of a new...
Orbital evolution in Low Mass X-ray Binaries is important in order to define the long-term evolution of these systems and their connection with millisecond pulsars through the recycling scenario. Timing analysis of periodic signals in binaries gives information on their orbital period changes on timespan of tens of years. Although this timespan is still short with respect to the secular...
Supernova remnants (SNRs) are complex, three-dimensional objects; properly accounting for this complexity when modeling the resulting X-ray emission presents quite a challenge and makes it difficult to accurately characterize the properties of the full SNR volume. We apply for the first time a novel analysis method, Smoothed Particle Inference (SPI), that can be used to study and characterize...
We probe models of disc truncation in the hard spectral state of an outburst of the X-ray transient GX 339-4. We test a large number of different models of disc reflection and its relativistic broadening, using two independent sets of codes. We apply it to a Rossi X-ray Timing Explorer spectrum in the rising part of the hard state. Our statistically best model has a physical thermal...
In some spiral galaxies the so-called "magnetic arms" have been reported, being interarm areas with significant polarized radio emission that suggests high ordering of the magnetic field. The most prominent example of such a galaxy is NGC 6946.
The nature of these magnetic features is still under debate. One of the possible explanations is the action of reconnection heating that could convert...
GRS 1758-258 is a bright and persistent hard X-ray source discovered in 1990.
It is a low mass X-ray binary whose companion star nature remains uncertain
due to the system's location close to the galactic centre and the large
interstellar absorption. The presence of a double-sided jet points towards
a microquasar character of the source. Frequent observations of GRS 1758-258
by the INTEGRAL...
I present results form our analysis of recent outbursts of the Be X-ray binaries 2S 1417-624 and 4U 1901+03. Both sources enter outbursts only very rarely, but their giant outbursts in 2018 afforded us with the chance to study their accretion behaviour in detail using modern X-ray telescopes such as NuSTAR, NICER, Swift, and Chandra.
For 2S 1417-624 we updated the orbital ephemeris and find a...
We report the discovery of a previously unnoticed X-ray source with a periodic variability at 614.28s. Its spectrum is an absorbed 1.8keV-blackbody with an iron-line feature. It has a Lx about $1.2\times10^{34}\times$(D/10 kpc)$^{2}$ erg s$^{-1}$ and has no obvious optical counterpart(fx/fo larger than 1600). We argue it is most likely a neutron-star ultra-compact X-ray binary with the...
Using machine learning techniques, we have picked pulsar-like gamma-ray sources from the unidentified objects in the third Catalog of Hard Fermi LAT sources (3FHL). In order to further pinpoint their nature, we have performed a systematic search for the X-ray and optical/IR counterparts of these short-listed 3FHL sources.
Structures of X-ray emitting magnetic polar regions on neutron stars in X-ray pulsars are studied. It is shown that a thin, optically thick, radiation energy dominated, X-ray emitting polar cone appears in each of the polar regions. The height of the polar cone from the neutron star surface to a standing shock at the top has a large dependence on the accretion rate. When $\dot{M} \simeq...
The Galactic Centre (GC) region contains many bright X-ray sources and has a high column density of foreground gas and dust. This suggests that X-ray dust scattering should be ubiquitous and intensive in the GC direction. In this poster, I will show our latest results of discovering significant dust scattering effects for a few bright X-ray sources in the GC. The effects include the existence...
We discuss the emission properties of the population of neutron stars that is expected to be present in the innermost parts of the Galactic center. Part of the population of isolated neutron stars should propagate supersonically through denser ionized streams of the Minispiral (Sgr A West), forming bow shocks where particles are accelerated and expected to produce polarized X-ray synchrotron...
We have studied the X-ray bow-shock nebula powered by the old non-recycled pulsar PSR B1929+10 with XMM-Newton data of an effective exposure ~310 ks, which provides the deepest investigation of this system so far. We found the X-ray tail has a length of ~8 arcmin, which is a factor of two longer than that reported in previous study. Evidence for spectral hardening along the tail has been found...
X-ray emission from star-forming galaxies is a new frontier for probing recent star-formation. X-ray emission, SFR, and stellar mass scaling relations are a unique probe of the connection between X-ray binaries and stellar populations. While most scaling relations are based on studies of the integrated emission of galaxies, very little is known about their validity and scatter in sub-galactic...
Ultraluminous X-ray Sources (ULXs) are off-nuclear point sources exceeding the Eddington limit for an accreting stellar mass black hole. Their high accretion rates challenge our understanding of accretion physics (e.g. beaming, super-Eddington accretion). The nature of their compact objects and their formation channels are of great interest for the single/binary stellar evolution and the...
The spectrum of X-ray accreting pulsars is usually well described by a hard power-law model, although several sources show also a significant soft excess at low energies. This feature is essential to investigate the physical processes on-going in accreting sources and can be ontained only through high-quality spectral data for such pulsars. To this aim, the best targets to observe are the...
In the last decade the high throughput and spectral resolution of the XMM-Newton and Chandra X-ray telescopes has allowed us to investigate the X-ray emission from hot subdwarf stars. Up to now, we have detected in X-rays five sdO stars. All of them show intrinsic X-ray emission and their spectrum can be described with the sum of two or three thermal-plasma components, as in the case of...
Along with available optical data of the Magellanic Bridge (the interconnecting region between the Small & Large Magellanic Cloud), we aim to characterise the X-ray binary population as a function of the local stellar population (in terms of age, metallicity, and stellar density) in the Bridge. Gardiner & Noguchi (1996) suggests that closest approach between Small & Large Magellanic Cloud, as...
An electron/positron pair halo is the electromagnetic cascade generated under extragalactic magnetic field when very high energy $\gamma$-rays, particularly from blazar, interact with the extragalactic background light and/or the cosmic microwave background forming the pairs of electron/positron and further lower energy $\gamma$-rays. These result in an extended emission of the $\gamma$-rays...
We have conducted a systematic survey for the X-ray properties of millisecond pulsars (MSPs). Currently, there are 47 MSPs with confirmed X-ray detections. We have also placed the upper limits for the X-ray emission from the other 36 MSPs by using the archival data. We have normalized their X-ray luminosities L x and their effective photon indices Γ into a homogeneous data set, which enables...
We review 10 years of continuous monitoring of accretion-powered X-ray pulsars with the Gamma-ray Burst Monitor (GBM), the softer-energy all-sky monitoring instrument aboard the Fermi Gamma-ray Space Telescope. The excellent combination of timing, spectral and full-sky coverage capabilities of GBM make it a unique instrument for the study of those objects. After discussing our analysis...
Ultracompact X-ray binaries (UCXBs) are binaries with a neutron star accretor and an orbital period less than 80 minutes. Here, I focus on our comprehensive review of Chandra observations of the unique UCXB 4U 1626-67, the only known UCXB to host a strongly-magnetized accreting pulsar. Our sophisticated modeling of the X-ray gratings spectra finds intriguing results: we observe strong,...
Thermally emitting X-ray isolated neutron stars represent excellent targets for testing cooling surface emission and atmosphere models, which are used to infer physical parameters of the neutron star. Among the seven known members of this class, RX J1605.3+3249 is the only one that still lacks confirmation of its spin period. Here we analyze NICER and XMM-Newton observations of RX...
We discuss the hot gas detected in X-rays around Galactic Wolf-Rayet stars. In particular, we discuss the XMM-Newton detection of extended X-ray emission from the Wolf-Rayet ring nebula NGC 3199, unveiling the powerful effect of the fast wind from WR 18. The X-ray emission is brighter in the region southeast of the star and an analysis of the spectral properties of the X-ray emission reveals...
The version 2.0 of the Chandra Source Catalog (CSC2) offers an unprecedented opportunity for serendipitous discovery. Out of $\sim 315,000$ CSC2 sources, two thirds are detected for the first time in X-rays, while a significant fraction of the remaining objects has never been studied in detail. CSC2 sources are characterized in terms of their X-ray fluxes, hardness ratios, variability, and...
The eclipsing high mass X-ray binary Vela X-1 consists of an accreting X-ray pulsar orbiting an early type supergiant with an orbital period of ~ 9 days. It was discovered as an X-ray source by the Uhuru satellite and it has been observed since then by every X-ray observatory. Due to its brightness and variability as well as the large observational archives, Vela X-1 is the Rosetta stone for...
Both galactic and supermassive black holes display characteristic features in their energy spectra, including an Fe K$\alpha$ line and a Compton hump, that result from reprocessing of hard X-ray photons by the accretion disk. This reflected emission provides a probe of the innermost region of the accretion disk through general relativistic distortions to the line profile. However, these...
The low mass X-ray binary systems (LMXBs) are composed of an accreting neutron star (NS) and a late-type companion (CS). They show very interesting spectral and timing characteristics. We distinguish some typical features in their light curve, like eclipses and dips, depending on the value of the inclination angle between the line of sight with respect to the perpendicular to the orbital plan...
HD49798/RX J0648.0–4418 is the only known binary composed of a hot subdwarf star and an accreting neutron star or white dwarf. We discovered that the compact objects has a spin period of 13.2 s and is spinning up at a rate of 2$\times10^{-15}$ s/s.
The precise distance of 508 pc recently measured with Gaia strongly disfavours
the possibility that the pulsar be a neutron star. On the other...
We are looking for changes of spectral states of X-ray binary system X-6 in Galaxy M33 and similarities with other known Z-sources. In our previous work (Nikolaeva et al., 2018) we showed that there is a neutron star as a compact object. And spectrum shape looks like the spectrum in one of the spectral states of Z-source (neutron star with low magnetic field) RX J0042.6+4115 in M31 - the...
We present NICER observations in which the modulations of the X-ray flux in two supersoft X-ray sources were measured with unprecedented data quality. We observed two luminous targets, CAL 83 in the LMC with its intriguing 67 seconds periodicity, and MR Vel in the Galaxy. We discuss the results in the context of the structure and evolution of the two binaries, especially focusing on what they...
This Bachelor's Thesis is mainly focused on Neutron Star Inner Composition ExploreR(NICER) Observations of MAXI(The Monitor of All-Sky X-Ray Image) J1535-571, a Galactic Black Hole Candidate with an accompanying Star. Research conducted by J.M. Miller et al. 2018 and A. L. Stevens et al. 2018 were followed in order to acquire similar results, that is; confirming the existence of relativistic...
Quasi-simultaneous optical (ULTRACAM/NTT, SALT), X-ray (NuSTAR, XRT/Swift) and radio(ATCA) observations of the short P , high latitude LMXB transient, Swift J1357.2-0933 during its 2017 out- burst have revealed remarkable additional properties. In addition to confirming the variable frequency optical dipping seen during its 2011 discovery outburst, we also find: (1) the dip shape is consistent...
Variability in the emission of neutron stars and black holes X-ray binaries is a very puzzling field of study: the nature of the mechanism that produces the oscillations is still a subject of debate and unravelling this mystery could bring us closer to understand the physics in extreme environments like the ones around compact objects. Using Fourier techniques in X-ray timing analysis, we...
Among the most important and debatable problems in astrophysics and cosmology is the formation of supermassive black holes. The detection of fully-grown supermassive black holes in active galactic nuclei at high redshift, when the Universe was young, challenges the theories of black holes growth, requiring long periods of high accretion, most likely above the Eddington limit. This is a focus...
N132D is the most X-ray luminous supernova remnant (SNR) in the Local Group
with a luminosity of $\mathrm{L_x} $ (0.3-10.0 keV) $= 1.0\times10^{38}$ ergs/s. Given its location
in the Large Magellanic Cloud, it is a prime target for detailed X-ray studies
with the Chandra X-ray Observatory. The existing 87 ks Chandra observation of
N132D has revealed the complicated spatial and spectral...
The interstellar dust permeates our Galaxy and plays a crucial role in star formation processes. It can control the temperature of the ISM and it is the catalyst for the formation of complex molecules. However, the exact chemical composition of dust grains is not yet fully understood. Insights can be gained by combining X-ray observations and laboratory measurements. High resolution X-ray...
X-ray binaries exhibit ionized emission from an extended disk atmosphere that surrounds the accretion disk. However, the nature and exact geometry of the atmosphere are not fully understood. Here, I will present results from our recently published paper (Psaradaki et al. 2018) about the case study of the bright low-mass X-ray binary EXO 0748-676. In this work we carry out high-resolution X-ray...
Compact Wolf-Rayet X-ray binaries with orbital periods of less than a day are a rare class of sources, probing a short-lived (few 10^5 yr) but key evolutionary stage of binary systems. They emerge from a common envelope phase and (if they survive the second SN explosion) they form double compact objects that can merge via gravitational decay in less than a Gyr. We studied the candidate...
The Hard X-ray Modulation Telescope (Insight-HXMT) is China’s first astronomical satellite and launched on 15th June 2017. Thanks to its large effective area at high energy detector (up to 250 keV), some important achievements in X-ray binaries have been obtained. Here we only show a few interesting timing results: the high energy QPO up to 250 keV is discovered in black hole transient MAXI...
GRS 1758-258 is a persistent X-ray source, located in the Galactic center, and considered to be an accreting stellar mass black hole on the basis of its hard X-ray emission and similarities to Cygnus X-1. The additional detection of relativistic jets from GRS 1758-258 is of great interest given the potential to test theoretical accretion in/outflow models. However, prior observations of GRS...
The use of Big Data techniques and High Performance Computing (HPC) allows us to explore High-energy data archives in new ways, exploring and extracting new information buried in the fast growing volume of astrophysical data. I will talk about our mixed Data Mining and HPC approach and how it has allowed us to uncover a new population of Extragalactic Neutron Stars (NS), most of them - Ultra...
OAO 1657-415 is an X-ray binary pulsar that exhibited a long-term spin-up trend with short-term torque reversals in the past. In this work we present over 10 years of data from Fermi/GBM and Swift/BAT to study the long-term spin behavior and the torque-flux relation of this source, using current accretion torque models. The frequency history shows that the source is no longer on a spin-up...
ULXs are extra-galactic X-ray binaries with X-ray luminosities in excess of 10$^{39}$ erg s$^{-1}$, the Eddington limit for accretion onto a ~10M$_{sun}$ object. They are composed of a compact object and a companion star. The nature of the compact object is still not clear: it could be a neutron star, a stellar mass black hole or an intermediate mass black hole. Since measuring the mass is...
The chemical evolution of the Universe embraces aspects that reach
deep into modern astrophysics and cosmology. We want to know how present
and past matter is affected by various levels and types of nucleo-synthesis
and stellar evolution. Three major categories include the study
of pre-mordial star and black hole formation, the embedded evolution
of the intergalactic medium (IGM), and the...
Among High Mass X-ray Binaries, accreting from the stellar wind of its massive OB star companions, there is a growing number of systems in which a magnetized neutron star harboring magnetic fields beyond the quantum critical limit (B>10^13 G) is required to explain the observational properties. Such Accreting Magnetars have been invoked to explain Supergiant Fast X-ray Transients and, more...
We investigated the effects of dust scattering halo (DSH) of the high NH source ( ~10^23 cm^-2) 1E 1740.7-2942 on it’s timing properties during the hard state. We observed the source simultaneously using XMM-Newton and RXTE for ~20 ks. Our results show that the observed fractional rms amplitude of variability is low compared to the typical values for the GBH sources in the hard state. Imaging...
Intermediate-mass black holes (IMBH) are thought to be the building blocks of supermassive black holes that are found at the center of massive galaxies, but evidence for their existence is elusive. We performed a search for IMBH in Swift-XRT data by studying hyperluminous X-ray source candidates (HLX), which were identified through a cross-correlation of the Swift-XRT catalog with the Galaxy...
X-ray binaries (XRBs) trace old and new stellar populations in galaxies, and thus star formation history and star formation rate. X-ray emission from XRBs may be responsible for significant amounts of heating of the early Intergalactic Medium (IGM) at Cosmic Dawn and may also play a significant role in reionization. Until recently, the hard emission from these populations could only be...
X-ray Isolated Neutron Stars (XINSs) are nearby, strongly magnetized, thermally emitting neutron stars without non-thermal emission in any energy band, from radio to Gamma-ray. So far, only seven XINSs discovered by ROSAT are known. Since the discovery in 1990s, their X-ray spectra have been interpreted simply with a single-temperature blackbody (1BB) model.
Stacking all the data observed with...
Comptonization by thermal electrons at mildly relativistic temperatures appears to be one of the major radiative processes giving rise to the observed X-ray emission from accretion onto compact objects. This is evidenced by ubiquitous high-energy cutoffs in hard spectral states occuring at E>kT, which are usually well fitted by models of that process. Accurate determination of the electron...
Although corona has been being well used in modelling accretion of XRBs, especially on aspects of the spectral state transitions and correlation with launching of a jet, so far its nature is still less known, especially on aspect of the formation mechanism. To probe this puzzle observationally, one has firstly to have a proper probe like the intense short soft X-ray shower, since the corona is...
Swift J1753.5-0127 (J1753 hereafer) is a Low Mass X-ray Binariy (LMXB) hosting a Black Hole of ~3 solar masses (BHC), with a very short orbital period of around 3 hrs. The source exhibited an unusually long outburst cycle which lasted for approximately 12 years between 2005 and 2017 before returning to quiescence. We have obtained and analyzed multi-epoch series of archival data from...
The globular clusters (GCs) are dense stellar systems which can produce the compact binaries (e.g. cataclysmic variables (CVs), millisecond pulsars (MSPs), quiescent low-mass X-ray binary (qLMXBs)) through frequent dynamical interactions. M62 is among the GCs with the highest stellar encounter rate. In our analysis, we identify 43 X-ray sources within M62’s half-light radius from two different...
The distribution of hot ISM in early type galaxies (ETGs) bear the imprint of its formation and evolutionary history. The high sensitivity and large field of view of XMM-Newton has made it possible to investigate this diffuse emission in the galaxy outskirts, which is critical in understanding the interaction of this hot gas with the surrounding medium (e.g., by ram pressure stripping) and...
We describe the merger of the NGC 4839 group with the Coma cluster using X-ray observations from the XMM-Newton and Chandra Obsservatories (Lyskova et al. 2019). X-ray data show two prominent features: (i) a long (600 kpc in projection), bent tail of cool gas trailing (towards the south-west) the optical center of NGC 4839, and ii) a `sheath' region of enhanced X-ray surface brightness...
JW100 is a massive spiral galaxy infalling in the galaxy cluster Abell 2626. The extreme intra-cluster medium pressure is currently stripping the galaxy of its cold gas, producing the peculiar filaments typical of a jellyfish galaxy, where star formation is taking place. Interestingly, MUSE and Chandra observations revealed two odd characteristics of this galaxy. On the one hand, MUSE revealed...
Recent stacking analysis of Sunyaev-Zel'dovich (SZ) oberservations of hundreds of superclusters have revealed the presence of the warm-hot intergalactic medium (WHIM) as a component of the intercluster gas. This indicates that superclusters are good targets to directly study the WHIM.
We are conducting a detailed study of two triple-cluster systems detected by Planck. We will jointly analyse...
We investigate the spatial distribution of iron in the intracluster medium (ICM) of massive clusters at different cosmic epoch, focusing on two distinct components: a central peaked distribution, and a wider, flatter component. Thanks to the angular resolution of Chandra data, we are able to follow the increase in the size of the central component, which, however, does not grow significantly...
The ICM often shows significant two-dimensional structure generated by mergers and/or AGN feedback. Thermodynamical 2D maps have been extensively used in the study of galaxy clusters thanks to their great potential to characterize the dynamical state of a system. However, to date they are only used for a qualitative analysis (e.g. the determination of a shock or a cold front) leaving their...
Whereas the extreme conditions of the first minutes after the Big Bang produced nearly all the hydrogen and helium in the Universe, the most common heavier elements - or metals - are synthesized in the core of stars and in supernova explosions. On the other hand, the very hot and diffuse intracluster medium (ICM), glowing in X-ray and detected in the large gravitational potential well of...
We present a combined radio/X-ray analysis of the poorly studied galaxy cluster Abell 2495 (z=0.07923) based on new EVLA and Chandra data. We also analyze and discuss Hα emission and optical continuum data retrieved from the literature. We find an offset of ∼ 6 kpc between the cluster BCG (MCG+02-58-021) and the peak of the X-ray emission, suggesting that the cooling process is not taking...
Cluster outskirts are an area of great interest as they contain a wealth of information as to how the hot intracluster medium (ICM) forms and contributes to the growth of large scale structures. With the advent of Athena, measurements of the ICM should be possible beyond the virial radius. To this end, we present the metallicity profiles and distribution of different metals for the C-EAGLE...
The observable thermodynamical properties of the intracluster medium reflect the complex interplay between astrophysical processes such as AGN feedback and the gravitational collapse of the host halo. Using the IllustrisTNG simulations, we measure the X-ray emission and the impact of the gas on CMB through the Sunyaev-Zel'dovich effect over a wide range of mass scales: from galaxies and...
A {\it XMM-Newton} catalogue of BL Lac X-ray properties is presented based on the cross-correlation with the 1374 BL Lacs listed in the 13th edition of the V\'{e}ron-Cetty and V\'{e}ron (2010) catalogue. {X-ray counterparts to these objects are searched in the field of view of around 10000 {\it XMM-Newton} pointed observations. The cross-correlation yielded a total of 352 {\it XMM-Newton}...
The NuSTAR and Swift survey of more than 150 obscured AGN in the local universe recently enabled basic parameters of the obscuring torus, such as the covering factor and the globally averaged column density, to be observationally constrained from the X-ray band. However, detailed analyses of particular AGN reveal that structural parameters of the torus may depend on the choice of the fitting...
The Chandra Source Catalog 2.0 is a powerful tool providing properties for 315,000 X-ray sources detected in the observations taken prior of 2015. We cross-matched the Sloan Digital Sky Survey DR14 and the CSC2.0 to build a sample of >6500 optically selected quasars that have both optical and X-ray spectroscopic information. This sample can be considered as a gold mine for studies on the...
We have been awarded a Large Program of ~1.6 Ms with XMM-Newton in AO18, SUBWAYS (“Supermassive Black Hole Winds in X-rays”), designed to provide a unique observational framework to test the validity of physical models for Active Galactic Nuclei (AGN) outflows, and to ultimately understand their impact into their host galaxies. SUBWAYS will observe a representative sample of 19 objects at...
X-ray reverberation in Active Galactic Nuclei, believed to be the result of the reprocessing of coronal photons by the underlying accretion disc, has allowed us to probe the properties of the inner-most regions of the accretion flow and the central black hole. Our current model (KYNREFREV) computes the time-dependent reflection spectra of the disc as a response to a flash of primary power-law...
Extensive efforts have been devoted during the past decade to uncover the AGN hidden under the most extreme X-ray column densities, the so called Compton-thick AGN. Still, although Compton-thick AGN could represent a significant fraction of the entire AGN population, they have escaped detection. Mid-IR surveys with the all-sky Wide-field Infrared Survey Explorer could uncover, at least in...
The Chandra Source Catalog release 2.0 (CSC 2.0) includes all the observations prior to end of 2014, performing detection and extracting source properties, and making them available in an easily accessible format ready for scientific discoveries. The CSC 2.0 covers ~600 deg2 of the sky, sampling widely different astrophysical environments, allowing both galactic and extragalactic studies with...
The dynamics and geometry of the innermost regions of accretion flows in Active Galactic Nuclei (AGN) are still largely uncertain. A fundamental way to understand these phenomena is the study of X-ray variability properties of the Fe K line complex since it is assumed to be a probe of the geometry of the matter flows close to SMBH and also of their physical state (i.e. ionization, density,...
We will present results from the MAGNA (Multiple AGN Activity) project focused on the detection and study of multiple supermassive black hole systems.
With the main goal of understanding the mechanisms that trigger the AGN in different stages of galaxy mergers, we compare the physical properties of merging galaxies hosting at least one AGN with isolated systems. Optical (SDSS) and X-ray (XMM...
Fe-K reverberation lags are commonly observed in Seyfert galaxies.
If the observed short lag timescale (~100 sec) is literally interpreted as the
light-travel time, an extremely compact X-ray emitting corona is hinted
to locate at very close to the black hole.
Alternatively, the apparently short Fe-K lag may be a natural consequence
of the much further reprocessing site where the...
This work presents preliminary results of the survey carried out on one of the deepest X-ray field observed by the XMM Newton satellite. The survey is made by 13 observations taken over 2 years with a total exposure time of 1.6 Ms over a field of 30 × 30 𝑎𝑟𝑐𝑚𝑖𝑛2 around the blazar 1ES 1553+113, which were originally addressed to the study of the Warm Hot Intergalactic Medium (Nicastro et al....
To understand the diversity of classes observed in active galactic nuclei (AGN) it is required to obscure the inner parts of a geometrically and optically thick torus of gas and dust from some lines of sight. However, this torus is not spatially resolved even for the closest AGN. Spectroscopic studies have been broadly used to characterize the main properties of the torus. However, the torus...
We will present recent high resolution Chandra work on the inner few arc seconds regions of AGNs, including our recent work on ESO 428-G014 and NGC2110. Together with ALMA and optical data these results give us a new view of the multi-phase ISM, excited by the AGN
A large fraction of accreting black hole systems present clear evidence of the reprocessing of X-rays in the atmosphere of the accretion disk. The copious X-rays produced in the vicinity of a black hole illuminate the disk and produce a reflection spectrum which main hallmarks include fluorescent emission K-shell lines from iron (~6.4-6.9 keV), and a broad featureless component known as the...
Feeding and feedback tied to SMBHs play central role in the cosmic evolution of galaxies. The self-regulated AGN cycle is matter of intense debate. I review key numerical and observational results of how SMBHs are coupled to the multiphase gaseous halos, linking the inner gravitational radius to the galactic scale, and vice versa. The turbulent galactic halo radiatively cools through a...
We present our results of fitting 663 X-ray spectra of AGN sources in the XMM-COSMOS field detected in 2-7 keV band, all of which have a spectroscopic redshift. We developed a new approach based on a Bayesian hierarchical model in order to correctly propagate on the main spectral parameters like Gamma and Nh the uncertainties due to the presence of additional, ill-constrained components like...
We study the X-ray properties (using XMM-Newton) of mid-infrared (mid-IR) selected AGN. For that purpose, we use WISE sources
in the Stripe82-XMM area to identify mid-IR AGN candidates, applying the Assef et al. criteria. . XMM-Newton observations cover 26 deg2. Our sample consists of 1946 IR AGN candidate and about 1/3 is detected in X-rays. 1507 have SDSS detection and 824 sources have...
Quasi-Periodic Eruptions have been recently discovered in the nucleus of the low-mass black hole galaxy GSN 069. QPEs are abrupt increases in the X-ray count rate over a quiescent flux level, and recur quasi-periodically every few hours (Miniutti et al. 2019, Nature in press). Thanks to a new XMM-Newton observation performed at the end of May 2019, we have discovered X-ray QPEs in a second...
In the global scenario proposed by Giustini & Proga (2019), most of the diversity observed in AGN can be explained by different accretion/ejection flows, which depend on the Eddington ratio and on the black hole mass, and therefore on the presence or absence of accretion disc winds driven by radiation pressure.
X-ray observations are crucial to test this scenario: in fact, they allow to...
Accreting supermassive black holes, also known as active galactic nuclei (AGN), are surrounded by large quantities of gas and dust. Based on the column density of the material in the line of sight, AGNs can be classified as obscured and unobscured. In the case of obscured AGNs, the torus depletes most of the light produced by the accreting black hole and a useful way to study them is in the...
ANEPD-CXO245: A COMPTON THICK AGN WITH DOUBLE-PEAKED NARROW LINES.
In our multi-wavelength survey of the AKARI North Ecliptic Pole Deep Field, including X-ray observations obtained with Chandra (Krumpe et al. 2015), we have found a highly absorbed AGN (ANEPD-CXO245, hereafter CXO245; $\it{z}$ = 0.449) that shows double-peaked narrow emission lines. The X-ray spectrum of CXO245 from our...
We present the X-ray properties of a complete and well-defined sample of 24 high-z (z=4-5.5) blazar candidates selected from the CLASS radio survey. After completing the existing archival data (Swift-XRT, Chandra and XMM-Newton) with dedicated Swift-XRT observations, we identified the bona-fide blazars based on the X-ray intensity (compared to the optical one) and flatness of the spectrum. We...
I will present the publicly available XSPEC model RELTRANS. The model calculates the light-crossing delays and energy shifts experienced by X-ray photons originally emitted close to the black hole when they reflect from the accretion disk and are scattered into our line-of-sight, accounting for all general relativistic effects. The model is fast and flexible enough to be simultaneously fit to...
XMM-Newton observed the Chandra Deep Field South (CDFS) with a ~3 Ms exposure time. EPIC spectra of bright 185 sources, practically all AGN with redshift up to z=3.8 , are compiled and their basic properties are studied by conventional spectral fitting, as well as an exploratory analysis with two, rest-frame X-ray colours and the Fe K line strength indicator and rest-frame spectral stacking. A...
X-ray observations suggest high compactness of coronæ in active galactic nuclei as well as in X-ray binaries. The compactness of the source implies a strong radial dependence in the illumination of the accretion disk. This will, for any reasonable radial profile of the density, lead to a radial profile of the disk ionization. Thus, an artificial increase of the radial emissivity parameter can...
Current measurements show that the observed fraction of Compton-thick (CT) active galactic nuclei (AGN) is smaller than the expected values needed to explain the cosmic X-ray background. Thanks to its unprecedented sensitivity covering the 3 - 79 keV band, NuSTAR is playing a key role in identifying the missing fraction of these sources and determining their properties. In this talk, I will...
Nuclear activities of 67 nearby quasars show the bolometric correction factor is correlated with their accretion rate, both in infrared (IR), optical, and X-ray. We present a comprehensive study of the full AGN intrinsic spectral energy distributions (SEDs) of 67 redshift < 0.5 quasars selected from the Palomar-Green sample, using spectroscopies from XMM-Newton, HST , SDSS and photometric...
Multi-messenger astronomy entered a new phase after the detection of gravitational waves, fast radio bursts and a recent progress in the neutrino astrophysics. It is evident that the observations over the whole electromagnetic domain become more and more important. Deailed spectral information in the soft gamma-ray band (100 keV - 100 MeV) is essential to study the physical processes...
Ultra-fast outflows (UFO) in the X-ray band are now observed in about half of of active galactic nuclei (AGN). They are likely launched at accretion disk scales with relativistic speeds (around 0.1-0.3 $c$), and can reach a very high mechanical power. However, up to now very little is known about the physics behind these extreme phenomena, including the launching mechanisms and their geometry....
Radio Galaxies (RG) are Radio-Loud Active Galactic Nuclei (AGN) characterized by powerful relativistic jets, oriented at relatively large inclination angles with respect to the observer’s line of sight. They are extraordinarily relevant to address important issues such as the interaction between Super Massive Black Holes, the radio jets and their environment.
RGs are commonly classified on the...
According to the different models of Cosmic X-ray Background (CXB), the diffuse X-ray emission observed in the 1 to ~200-300 keV band, is mainly caused by accreting supermassive black holes, the so-called active Galactic Nuclei (AGN). Particularly, at the peak of the CXB (~30 keV) a significant fraction of emission (10-25%) is expected to be produced by a numerous population of heavily...
Variability is one of the best tools to investigate the emission mechanisms in Active Galactic Nuclei (AGN). We report on the 2010 XMM-Newton monitoring of the highly variable Seyfert 2 Galaxy NGC 2992, which was subsequently targeted by Swift and NuSTAR in 2015. XMM-Newton always caught the source in a faint state but NuSTAR observed a brightening of the source, with evidence of an Ultra Fast...
X-ray surveys are one of the most efficient ways to detect active galactic nuclei (AGN) and perform statistically meaningful population studies. In the past decade, important results in this field came from both wide and deep X-ray surveys of the sky, performed following the well-known "wedding cake" approach.
Thanks to these surveys, there is now compelling evidence that there is a strong...
We present a detailed analysis of a joint XMM-Newton & NuSTAR observation of the nearby ($z=0.062$) luminous NLSy 1 galaxy TON S180 taken in 2016. We find that the observed steep soft excess is likely produced by Comptonization rather than relativistic reflection. By analyzing the broadband SED from 1 eV to 35 keV, we find that the overall intrinsic properties of the continuum can be...
We report Chandra observations of the environment of the unusual
redshift 1 quasar PG1407+265 and discuss a new X-ray cluster found 1
arcminute from it. We discuss the X-ray variability of the quasar and
estimate the cluster contribution to the X-ray flux in previous lower
resolution observations. Optical observations complement the Chandra
data and allow us to estimate the physical...
We conducted a broadband multi-epoch campaign to observe the nearby Narrow Line Seyfert 1 galaxy Mrk 359. The monitoring consisted in 5 simultaneous XMM-Newton/NuSTAR observations (50 ks each) over a timescale of 10 days. During the campaign, Mrk 359 showed significant intra-observation variability, as well as among the pointings. Changes in the spectral slope occurred down to days timescales....
NGC5548 is known to exhibit complicated X-ray spectral variations such that double partial covering layers may have different covering fractions and that one of the fractions correlates with the photon-index of the power-law component (Cappi et al. 2016). It is hard to understand such a correlation between the two parameters that should be physically independent.
Here, we propose a simple...
Clustering of AGNs give additional clues to understanding the physical processes of supermassive black hole accretion. The strength of large scale clustering (bias parameter) gives a typical mass of Dark Matter Halos (DMHs) in which the AGN live in. Small scale clustering give additional clues on how the AGNs distribute among DMHs through Halo Occupation Distribution (HOD) modelings. We...
UltraFast Outflows (UFO) are seen in some active galactic nuclei (AGNs), with blueshifted absorption lines of highly ionised iron ion. AGN typically has a UV-bright accretion flow, so UV line driving is an obvious candidate for launching these winds. However, it requires that material in the acceleration zone has substantial UV opacity, in conflict with the observed very high ionisation state...
We have recently obtained deep XMM-Newton observations of 30 bright quasars, selected in the optical from the SDSS-DR7 to be representative of the most luminous, intrinsically blue quasars at high redshift (3.0 < z < 3.3). Despite the uniform selection in terms of optical/UV spectral properties and the narrow range of luminosity, black-hole mass and accretion rate probed by our sample, two...
Ultra-fast Outflows in AGN were first suggested based upon low spectral resolution CCD data in the 6-8 keV range, and were ascribed to absorption by highly ionized Fe. In this region, CCD resolution isn't dramatically below that of gratings. Further evidence for UFOs has been claimed from high spectral resolution observations with the XMM-Reflection Gratings Spectrometer, and has been...
Compton thick (CT) AGN are predicted by unified models, which attribute most of the AGN diversity to their inclination, and play an important role for the understanding of the growth of black holes in the early Universe. The fraction of CT AGN at low redshift can be derived from the observed CXB spectrum assuming AGN spectral templates and luminosity functions. We show that high...
NGC 1566 is one of only a handful of AGN that have undergone more than one changing-look event, having changed from Sy 1.9 to Seyfert 1.2 and at least five times. The most recent event was in 2018, where the source increased in X-ray flux by a factor of ~70 and nearly three magnitudes in the UV in under 9 months, coinciding with the reappearance of strong broad lines in the optical...
I will present the X-ray spectral analysis of a sample of obscured AGN candidates in the 17'x17' field surrounding the bright $z=6.31$ QSO SDSS J1030+0524, observed for 500ks with Chandra ACIS-I.
The sample objects are selected to have an hardness ratio $HR>-0.1$, suggestive of the presence of moderate to heavy obscuration ($10^{22} \le N_H\le10^{24}$ $cm^{-2}$), and a range of net counts...
The X-ray spectrum from the corona of an AGN is generally approximated as a power law up to certain energies after which the spectrum turns over called as cut-off energy. Thus, the two main observables in the X-ray spectrum of an AGN are the power law photon index and the energy at which the cut-off occurs. This high energy cut-off is a manifestation of the temperature of the electrons in the...
The non-linear X-ray to UV relation in quasars can be used to estimate their luminosity. Our analysis of a sample of several thousand quasars with SDSS spectra and X-ray serendipitous observations shows that, quite unexpectedly, the observed dispersion of the relation is almost entirely due to observational effects, while intrinsically the relation holds with a very small dispersion -lower...
Comparison of properties of quasars with those of low redshift AGNs with similar BH masses but accreting at much lower accretion rates provides exceptional opportunity to study the dependence of the properties of these massive accretion systems on the specific accretion rate. This particularly concerns abilities of such systems to produce powerful jets. We present here results of comparison of...
A tight non-linear relation between the X-ray and optical-ultraviolet emission has been observed in unobscured Active Galactic Nuclei (AGN) over several orders of magnitude in luminosity and irrespective of the sample selection, suggesting a universal coupling between the disk, emitting the primary radiation in the UV band, and the hot corona emitting in the X-ray.
Recently, our group...
Supermassive black hole (SMBH) winds are believed to be a key player in the evolution of galaxies. In fact, outflows from active galactic nuclei (AGN) may be one of the fundamental mechanisms by which a SMBH transfers a significant fraction of its accretion energy to the surrounding environment. Disk-scale ionized ultra-fast outflows (UFOs) and large-scale warm absorbers (WAs) are commonly...
Ordinary Type 1 AGNs show X-ray spectra dominated by a hard power law sometimes accompanied by soft X-ray excess emission and only a limited number of AGNs are known to show soft X-ray dominated spectra, which are reminiscent of high/soft or very high state of Galactic black holes. We present our selection of soft X-ray dominated AGNs using the XMM-Newton serendipitous source catalogue. We...
Observations performed in the last decades have shown that supermassive black holes (SMBHs) and cosmic structures are not separate elements of the Universe. While galaxies have sizes roughly ten orders of magnitude larger than SMBHs, black holes would not exist without matter feeding them, and cosmic structures would not be the same without feedback from SMBHs. Powerful winds/jets in active...
An important problem in extragalactic astronomy concerns the influence of the presence of active nucleus (AGN) on the large-scale processes in the host galaxy and the correlation between the evolution of the host galaxy and the supermassive black hole (SMBH) in its centre. This connection between galaxies and SMBHs is suggested by the observed tight correlation between the evolution of...
We present a systematic study of the nuclear X-ray
luminosity function (XLF) of Brightest Cluster Galaxies (BCGs) for a
wide range of halo masses, exploiting the entire Chandra archive (~600
BCGs). Thanks to the ~1 arcsec angular resolution, we are able to
trace their radiatively-efficient nuclear activity through cosmic
epochs from z=0.1 to z~>1, and to investigate the properties of...
20 years after its launch, XMM-Newton has performed more than 13,000 pointed observations which cover a total of more than 1,100 square degrees. The XMM-Newton Survey Science Centre consortium (SSC) generates serendipitous source catalogues from all public observations, which list positions and source parameters such as position, fluxes, hardness ratios, and extent. In 2018, we have published...
Here we present some preliminary results of our analysis of the Chandra observations of the Western and Eastern hotspots in the Pictor A radio galaxy. All the available Chandra data for the target, consisting of multiple pointings spanning over 15 years and amounting to the total exposure time of 464ks, have been included in the analysis. In particular, with the image deconvolution method we...
Giant radio galaxies (GRGs) are the largest (size >0.7 Mpc) and most energetic single objects in the Universe and represent an extreme class among radio-loud/jetted active galactic nuclei. Such large and old sources are ideal targets to study the duty cycle of the jet and nuclear activity. Here we discuss the X-ray and radio properties of a complete subsample of 15 GRGs; the sources were...
In this talk I present the first results regarding the X-ray variability of the nearby Low luminsity AGN NGC 5273. The source was observed with a 90 ks pointing by XMM in 2017 and was found to be significantly variable down to timescales of 1000 seconds. From the Fourier analysis it was possible to detect for the fist time the presence of reverberation lag at the iron K line of ~700 seconds....
The Seyfert 1 galaxy NGC 7469 was the target of an extensive observing campaign with XMM-Newton in 2015. Analysis of the 640 ks RGS spectrum with the spectral fitting code SPEX, and the physically self-consistent photoionisation model PION, shows that the emission line region (ELR) is multi-phased, while also accounting for three warm absorber (WA) components. For the first time we...
We present a statistical analysis of the optical properties of an X-ray selected Type 1 AGN sample using high signal-to-noise ratio (S/N>20) spectra of the counterparts of the ROSAT/2RX sources in the footprint of the SDSS-IV/SPIDERS (Spectroscopic IDentification of eROSITA Sources) programme. The sample of 2100 source is a factor of 4-18 larger than samples used in previous studies of this...
Recent X-ray studies suggest that mergers play an important role for obscuration of active galactic nuclei (AGNs) in ultra/luminous infrared galaxies (U/LIRGs). Here we analyze the broadband X-ray spectra (0.5-50 keV) of two “non-merging” LIRGs (NGC 5135 and UGC 2608) utilizing the data of NuSTAR, Suzaku, XMM-Newton, and Chandra, in order to search for differences in the torus structure from...
The archetypal and one of the brightest Compton-thick AGN is NGC 1068, which was observed by all the main X-ray observatories during the last 20 years. Keeping in mind the previous studies, I will discuss the results obtained through the spectroscopic analysis of the latest NuSTAR monitoring campaign, during which we detected one unveiling and one eclipsing event due to Compton-thick matter...
The size and geometry of the X-ray emitting corona in AGNs are still not well constrained. Dovčiak & Done (2016) proposed a method based on calculations assuming a point-like lamp-post corona. To perform more self-consistent calculations of energy spectra of extended coronae, we develop monk, a Monte Carlo radiative transfer code dedicated to calculations of Comptonised spectra in the Kerr...
The cosmic X-ray background (CXB), the diffuse X-ray emission observed between 0.5 keV and 300 keV, is thought to be mainly produced by obscured and unobscured active galactic nuclei (AGNs). According to the historical AGN unified model, different types of AGNs are obscured by a structure of gas and dust named torus but with different inclination angle. With the successful launch of the...
Formation and launching of relativistic jets is one manifestation of black hole activity. Jets impact the black hole surrounding and thus affect further black hole feeding and growth. This coupling is believed to be essential to the idea of AGN-galaxy feedback. Theory predicted that young radio jets should be strong high-energy emitters. However, they proved to be relatively faint and...
We summarize the contributions of Riccardo Giacconi starting from UHURU, through deep survey studies with the Einstein and ROSAT Observatories, to his exploration of the Chandra Deep Field South. In his earliest research with UHURU, Giacconi focussed on Galactic X-ray astronomy with studies of binary X-ray sources, especially Centaurus X-3 and Hercules X-1. With the dramatic increase in...
We demonstrate that a CMOS pixel sensor with a pixel size of 2.5 μm can work as a photo-electron tracking X-ray polarimeter. Although it is designed for visible light by GPixel Inc., we succeed in detecting X-ray photons with an energy res- olution of 176 eV @5.9 keV (FWHM) at room temperature. This performance is remarkable considering that conventional X-ray CCD detectors need to be cooled...
ESA's Athena mission is due for launch in the early 2030's. The calibration of its optics and instruments is, nevertheless, already subject of several studies and plans. This poster summarises the current calibration baseline of the telescope, the X-IFU micro-calorimeter, and the Wide-Field Imager.
With the advent of the IXPE (Imaging X-ray Polarimetry Explorer) satellite expected for launch in 2021, the study of the X-ray polarization properties of several bright nearby sources will become possible. Blazars are obvious candidates for X-ray polarization observations. For instance, a high degree of X-ray polarization is expected from high-peaked blazars (HBL) because synchrotron...
The launch of the NASA/ASI Imaging X-ray Polarimetry Explorer (IXPE) mission in Spring 2021 will open a new era of X-ray polarimetry, thanks to the imaging and polarimetric capabilities of the Gas Pixel Detectors.
The unique combination of imaging and polarimetric capabilities over the wide Field of View (8 arcmin) will allow IXPE to investigate the polarimetric properties of complex fields...
ESA’s X-ray flagship the XMM-Newton space observatory is soon entering it’s third decade of operations.
Both the spacecraft and the payload are operating without major degradation and scientific
demand is continuously very high. Changing the on board Attitude and Orbit Control System Software in 2013 we managed to reduce the fuel consumption by a factor of two, additionally reducing stress on...
I will summarize our recent results on X-ray polarization simulations
for the X-ray binary GRS 1915+105 in thermal state with the aim
to assess the capability of the future X-ray polarimetry measurements
to put independent constraints on black hole spin and orientation of the system.
For this purpose, we simulate X-ray polarimetric properties of GRS 1915+105
for the planned Imaging X-ray...
Calibration of the ATHENA telescope is a critical aspect of the project and raises significant difficulties due to the unprecedented size, mass and focal length of the mirror assembly. The VERT-X project, financed by ESA and started in January 2019 by a Consortium led by INAF and which includes EIE, Media Lario Technologies, GPAP, and BCV Progetti, aims to design an innovative calibration...
Low density overcoatings (mainly based on materials containing Carbon) onto usual hi Z materials (like Ir, Au or Pt) have been proposed more than 10 years ago for enhancing the X-ray reflectivity at low energy (between 0.5 and 4 keV) in X-ray astronomical optics. The hack is to use the total reflection from the low density material (which do not suffer much the photoelectric absorption) at low...
X-ray Polarimetry will open a new window in X-ray Astronomy that can revolutionize the current understanding of the accretion and ejection mechanisms of black holes X-ray binaries (BHXBs).. With the upcoming launch of the Imaging X-ray Polarimetry Explorer (IXPE) in 2021, X-ray astronomy will be benefited with the additional Polarimetry signal along the currently existing timing and...
The Wide Field Imager (WFI) is powerful new spectral-imaging camera for Athena, ESA's next large X-ray observatory to be launched in the early 2030ies. The WFI will provide two defining capabilities to mission, sensitive wide-field imaging spectroscopy over a 40x40 arcmin field of view with an angular resolution of 5" HEW, and the power to observe even the brightest X-ray point sources with...
Arcus will provide high-resolution soft X-ray spectroscopy in the 12-50Å bandpass with sensitivity orders of magnitude higher than any previous astronomical observatory. Its capabilities include spectral resolution >2500 and effective area of ~250 cm^2. The three top science goals for Arcus are to (1) measure the effects of structure formation imprinted upon the hot baryons that are predicted...
The optics of ATHENA (Advanced Telescope for High-ENergy Astrophysics) – the next high-energy astrophysical mission of the European Space Agency – consists of 678 Silicon Pore Optics mirror modules integrated and co-aligned onto a common supporting structure. The integration process, already proved, exploits an optical bench to capture the focal plane image of each mirror module when...
The Athena Community Office (ACO) was established by ESA’s Athena Science Study Team (ASST) in order to obtain support in performing its tasks assigned by ESA, and most especially in the ASST 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 the University of Geneva, MPE...
Athena is the second large-class X-ray mission of the European Space Agency Cosmic Vision, with a launch foreseen in 2031 towards an L2 halo orbit and dedicated to the study of the hot and energetic universe. X-ray observations are usually severely limited by the background, due to the intrinsic faintness of the astrophysical sources involved or to their diffuse nature. Here we are going to...
E' piu` di un secolo che abbiamo scoperto questi misteriosi raggi capaci di penetrare il nostro corpo e di rivelare le nostra ossa. I raggi X sono diventati indispensabili in campo medico, ma sono diventati altrettanto importanti per scoprire i fenomeni piu' energetici dell'Universo. E' con i raggi X che possiamo vedere la materia che cade in un buco nero, assistere in diretta allo scontro di...
A rich phenomenology of jets, winds, and accretion states has been observed in both active galactic nuclei (AGN) and X+ray binaries (XRBs), suggesting a connection between the accretion and ejection flows at different black hole masses, from supermassive down to stellar mass. In AGN, the radiation field from the disk and the outflows, both of winds and jets, are thought to play a fundamental...
We report on the first analysis of AstroSat observation of the Z-source GX 5-
1 on February 26-27, 2017. The hardness-intensity plot reveals that the source traced out
the Horizontal and Normal branches. The 0.8-20 keV spectra from simultaneous SXT and
LAXPC data at different locations of the hardness-intensity plot can be well described by a
disk emission and a thermal Comptonized component....
We explore the dependence of Active Galactic Nuclei from the BH mass and luminosity for the ~30 supermassive BHs with mass estimates in the Chandra Deep Field south. With this dataset we can test wether the results are consistent with the models based on low-redshift AGNs, and validate the use of AGN variability to estimate the accretion history of SMBH as well as for future cosmological applications.
During Galactic Center survey program by IBIS telescope on-board INTEGRAL the supernova remnant RX J1713.7-3046 was observed in hard X-ray band (17-60 keV) for the first time. The surface brightness maps of the supernova remnant in 17-27-36-50-120 and 17-60 keV energy bands will presented in this talk. The spectra of two brightest clumps of RX J1713.7-3946 are characterized by a power law...
X-ray observations performed during the last few decades have provided a rich data base on black-hole X-ray binaries. A strong coupling between the properties of the accretion flow and the presence of outflows, such as radio-jets and hot X-ray winds, has been found to be a fundamental characteristic of their powerful outbursts.
Since 2015 we have discovered optical accretion disc winds in...
Before the launch of the Fermi satellite only two classes of AGN were known to generate relativistic jets and thus to emit up to the gamma-ray energy range: blazars and radio galaxies, both hosted in giant elliptical galaxies. The discovery by the Large Area Telescope on-board the Fermi satellite of variable gamma-ray emission from a few radio-loud narrow-line Seyfert 1 galaxies (NLSy1)...
We make use of the XCOP sample to address two fundamental and unanswered questions: 1)What is the metal content of the Intra-Cluster Medium? 2) Is the metal content of the ICM consistent with that expected from the stellar population? We do this with XCOP, a very large program (VLP) on XMM-Newton designed to characterize a sample of 12 Massive Clusters out to large radii.
