Jets provide an important channel of kinetic feedback from accreting black holes into their environments. In the absence of instantaneous jet power measurements the extent of this feedback has proven difficult to quantify. Here we report the detection of stellar wind-induced bending of the jets in black hole X-ray binary Cygnus X-1, using 18 years of high-resolution radio imaging. By...
The X-ray flux from black hole X-ray binaries in the hard state is highly variable on a broad range of timescales. On a timescale of seconds, such broadband noise is thought to arise in the turbulent accretion disk and propagated to the corona, which emits harder X-rays in the spectral shape of a powerlaw with a cut-off. The nature and geometry of the corona is subject to debate, but there is...
I will present results from a coordinated spectral study of the black hole X-ray binary GX 339–4 during its 2021 outburst, capturing its transition from the hard to soft accretion state. Using simultaneous observations from NuSTAR, NICER, and Insight–HXMT, we applied relativistic reflection models to track changes in the accretion disk, particularly the inner disk radius (𝑅𝑖𝑛). Interestingly,...
We compare observations at radio wavelengths made along three decades toward the prototypical galactic microquasar. In the year 2023 the source presented major changes with respect to the historical values since 1994. The position angle of the bipolar ejecta in the plane of the sky has increased counter-clockwise by 24◦. The inclination angle of the flow with respect to the line of sight...
Jets from stellar mass black holes in X-ray binaries (XRBs) and supermassive black holes in blazars provide distinct opportunities to study the jets of black holes across two different mass regimes. They also represent samples with very different selection effects. Historically, the apparent speeds of XRB jets have been observed to be lower than those of blazars, leading to the assumption that...
Ultraluminous X-ray sources (ULXs) are accreting stellar compact objects whose X-ray luminosities exceed the Eddington limit. In order to get more insights on the nature of their accreting compact object (black hole or neutron star) and the geometries of super-Eddington accretion flows, it is useful to look at the influence of ULXs on their environment. I will present how VLT/MUSE 3-D...
Understanding the dominant mechanisms behind radiation production and energisation, as well as the spatial distribution of emission sources near an accreting compact object, remains one of the fundamental problems in high-energy astrophysics. While it is generally agreed that multi-temperature plasma with emitting and Comptonizing components is involved, the exact mechanisms of photon...
Neutron star X-ray binaries often exhibit Type-I X-ray bursts, during which the X-ray luminosity can rise up to 100 times the persistent flux. These bursts are triggered by unstable thermonuclear burning of accreted hydrogen and/or helium on the neutron star’s surface. In certain instances, two bursts are observed in close succession, typically separated by an interval of 10–20 minutes. The...
Previous observational and simulation work has explored the role the kink instability (KI) could play in explaining the phenomenology of active galactic nuclei jets and gamma ray bursts. Internal modes of this instability have been shown to drive conversion of magnetic energy into thermal energy without disrupting the overall flow of the jet. We suggest that these modes may therefore be able...
Black Hole X-ray binaries (BHXBs) serve as powerful laboratories for studying relativistic jets and their impact on the surrounding medium. MAXI J1348-630 is a BHXB that was recently discovered in outburst. This source was shown to exhibit strong radio jets with a distinct deceleration pattern of motion, indicative of the presence of a jet-blown cavity in the interstellar medium (ISM)....
We investigate the 2018 main outburst and the subsequent mini-outbursts of the black hole low-mass X-ray binary MAXI J1820+070 using optical/ultraviolet data from the Las Cumbres Observatory (LCO), the American Association of Variable Star Observers (AAVSO), and SWIFT/UVOT, as well as X-ray data from Insight-HXMT and SWIFT/XRT. Given the high-cadence observations, we identify a broad dip-like...
One of the most amazing microquasars is the Cyg X-3 binary system with a black hole and a massive Wolf-Rayet star. In 2024, during multi-frequency monitoring with the RATAN-600 radio telescope, we detected five giant (>10Jy) flares from Cyg X-3. The onsets of flares was clearly associated with the detection of significant Gamma-ray radiation at 0.1-300 GeV (Fermi space observatory). The...
X-ray reflection spectroscopy is a powerful tool to study the accretion geometry near black holes and spacetime properties. The spirit of this method is to study the reprocessed corona emission by the cold accretion disk that extends close to the black hole. Previous X-ray reflection models consider a disk density of 10^-15 cm^-3, which is only appropriate for very massive black holes (> 10^7...
Recent endeavors to directly classify the donor star mass of extragalactic X-ray binaries (XRBs) through optical photometric modeling has uncovered an apparent overabundance of XRBs with donor stars with a mass between 3 and 8 solar masses. These so-called 'intermediate-mass XRBs' (IMXBs) make up as many as 30% of the XRBs in nearby spiral galaxies. A population of this size is in...
Black hole X-ray binaries in outburst launch discrete, large-scale jet ejections which can propagate to parsec scales. The kinematics of these ejecta appear to be well described by relativistic blast wave models originally devised for gamma-ray burst afterglows. In kinematic-only modelling a crucial degeneracy prevents the ejecta energy and interstellar medium density from being accurately...
We have used The Chandra Source Catalog to extract light curves of point sources from nearby galaxies, ULXs, and 25 nearby (z lt 0.2) QSOs. We have Chandra grating observations of 25 Galactic XRBs adjusted to ACIS count rates at a distance of 1 Mpc. A three-dimensional color-color-RelInt diagram shows that the distribution of ULXs is well matched in both color and luminosity with point...
The wealth and complexity of X-ray data provided by modern observatories has seen a dramatic improvement in recent years, in part due to new facilities like NICER and IXPE. This trend will accelerate further with new techniques like polarimetry timing, as well as future missions like eXTP and Athena. On the other hand, the software modelling tools utilized by the community to model spectral...
Studying the chemical composition of accretion discs around compact objects, such as neutron stars in low-mass X-ray binaries (LMXBs), provides vital information about their formation and evolutionary history. This touches on a range of important topics, including key uncertainties in binary evolution such as mass transfer efficiency and common-envelope phases, that in turn impact the...
The spectral modelling of accreting X-ray pulsars is difficult owing to the anisotropy linked to the strong magnetic field and the geometrical properties such as the inclination of the line of sight and the location of the magnetic poles. This strongly influences the observed phase variability at the spin frequency. In Ferrigno et al. (2023), we introduced a method to compute pulsed profiles...
We analyze all NuSTAR observations of the accreting X-ray pulsar 4U 1538–52 to investigate the energy-dependent pulse profiles and the phase-dependent spectral variability of its fundamental cyclotron resonant scattering feature (CRSF). Fourier decomposition of energy-resolved pulse profiles reveals a broad bump in the pulsed fraction spectrum (PFS) near the CRSF energy, contrasting with the...
The Imaging X-ray Polarimetry Explorer (IXPE) is opening a new observational window into the physics of weakly magnetized neutron stars in low-mass X-ray binaries (LMXBs). In particular, coordinated multi-instrument campaigns have enabled the first systematic studies of the polarization signatures from bright Atoll-type sources. In this contribution, we focus on the source GX 9+1 and present...
Accreting X-ray binary systems with compact objects exhibit Quasi-Periodic Oscillations (QPOs) characterized by peaked features in their power density spectra. It is known that stochastic variations in the truncated accretion disc may propagate to the hot corona with a time delay, and the resulting hard X-rays from the corona impact the disc, leading to reflection features in the energy...
I will discuss recent results of the radiation effect on magnetically-arrested disks (MAD) around rotating black holes and the resulting jets, obtained using the general-relativistic radiative magneto-hydrodynamic (GR-R-MHD) code cuHARM. I will show that (i) The jet width, MAD parameter and jet efficiency increase with the accretion rate, before saturation caused by gas-pressure to...
We present a reanalysis of archive radio interferometric data for the gamma-ray binary LS I +61303. Our aim is to expand our previous searches for associated extended emission at the few arc-second/arc-minute level. The existence of such large scale features is expected no matter the physical scenario that is really at work in this system: pulsar wind interaction or microquasar. The main...
Spectral-timing analyses are a key tool to investigate the innermost region in accreting X-ray sources.
However, when encounter them, such techniques can appear strenuous to implement and use in an easy way. An advantageous way is to rely on well-maintained and reliable software such as Stingray.
Stingray is an open-source Python library that is able to compute the main Fourier analyses...
The BHB GRS~1915+105 was bright for 26 years since its discovery and is well known for its disk instabilities, quasi-periodic oscillations, and disk wind signatures. We report a long-term spectral-timing tracing of this source from mid-2017 until the onset of the so-called obscured state based on the complete data from NICER and other potential X-ray missions. In the soft state predating 2018,...
Strong radio flare events were detected in black hole X-ray binary system 4U 1543-47 by MeerKAT. In this work, we investigated X-ray observation data during these periods. Our results suggest a four-step jet cycle: (1) the accretion disk is full, (2) the inner disk becomes unstable, (3) the jet is formed, (4) the disk refills.
The energy-dependent variability of black hole X-ray binaries (BHXRBs) provide crucial insights into the physical processes at play in the accretion flow of these systems. We analyze the rapid X-ray variability of the BHXRB Swift J1727.8-1613 during its 2023 outburst, using observations from the Hard X-ray Modulation Telescope. We detect, for the first time, a dip-like feature in the Real part...
Accretion states, which are universally observed in stellar-mass black holes in X-ray binaries, are also anticipated in active galactic nuclei (AGN). The luminosity-excitation diagram (LED), based on IR nebular emission-line ratios, successfully identifies distinct accretion regimes in AGN —from jet/corona-dominated emission in low-luminosity AGN (LLAGN) to disc-dominated emission in Seyfert...
Currently a sample of 5 microquasars are reported by LHASSO to have ultrahigh-energies (UHE, above 100TeV) emissions which remains a puzzle for the mechanism underneath. Among this sample, evidences of jet-dominated X-ray emissions were revealed from MAXI J1820+070 during an outburst well observed by Insight-HXMT. Here we report similar properties found in Swift J1727.8–1613 from the joint...
The study of fast variability properties in X-ray binaries advances our understanding of the properties of the accretion flow around the compact object. As most timing studies focus on the power spectrum (PS), the phenomenology of the cross spectrum (CS), especially the coherence, is less understood. In this talk, I will present the results of a systematic study of the evolution of both PS...
Black hole X-ray binaries (BHXBs) show strong variability in their X-ray light curves over a broad range of time scales. Fast X-ray variability in BHXBs is key to understanding the properties of the innermost regions of the accretion flow in these sources. Among the most notable features of this variability are quasi-periodic oscillations (QPOs), which provide a unique insight due to their...
GX 339–4 is a low-mass X-ray binary often used as an archetype, showing typical source behaviors. The source undergoes a full outburst every 2-3 years, passing through all known accretion
states. The 2023-2024 outburst was monitored as part of a multiwavelength campaign, which
included X-ray observations by IXPE and NICER. We
used NICER data to analyze the spectral-timing properties of GX...
Recent discoveries by the IXPE mission since 2022 have highlighted the need for more sophisticated spectro-polarimetric models to interpret photon reprocessing in various components of X-ray binaries (XRBs) and active galactic nuclei (AGN). To address this, our group has developed several models compatible with XSPEC, a widely used tool for X-ray data analysis. These models include STOKES...
The timing analysis of X-ray binaries (XBs) is crucial for understanding the structure and dynamics governing these systems. Since the memorable 2023 outburst of the Low-Mass X-ray binary Swift J1727.8–1613, observations have been conducted across the entire electromagnetic spectrum, progressively constraining the source parameters. Here, we present the first XMM-Newton timing analysis of...
We report the results obtained from the analysis of XMM–Newton observations together with simultaneous NICER and NuSTAR observations of the ultraluminous X-ray source NGC 4190 ULX-1. Our goal is to constrain the structure of the accretion disk and the geometrical properties of the source, performing temporal and spectral analyses in the 0.4−30 keV energy range. The temporal analysis shows no...
