Conveners
Polarimetry (X-ray, Optical, Radio…)
- Michal Dovciak (Astronomical Institute of the Czech Academy of Sciences)
Polarimetry (X-ray, Optical, Radio…)
- Alexandra Veledina (University of Turku)
Polarimetry (X-ray, Optical, Radio…): Flash Talk
- There are no conveners in this block
X-ray polarimetry provides a powerful new window into the geometry and physical conditions of the innermost regions of microquasars. In this review, I will present recent results from the IXPE mission that have revealed the X-ray polarimetric properties of accreting compact objects across different accretion states. These polarimetric signatures offer direct insight into scattering...
In this talk, I’ll present the results of a comprehensive, 3-year-long multiwavelength polarimetric campaign on the prototypical black hole X-ray binary Cygnus X-1, conducted between 2022 and 2024. Using data from the Imaging X-ray Polarimetry Explorer (IXPE), we measured X-ray polarization 13 times across both hard and soft spectral states. We found that the polarization degree in the hard...
Accreting, weakly magnetized Neutron Stars in Low-mass X-ray binaries (NS-LMXBs) are a fundamental laboratory to study radiation processes in the strong gravity regime. Z-sources are NS-LMXBs characterized by a wide Z-like three branches track in the Color-Color Diagram, typically accreting close to the Eddington limit.
In this talk, we discuss the spectro-polarimetric results obtained by...
MAXI J1744–294 is a bright X-ray transient discovered in early January 2025 within 20″ of Sgr A* by MAXI/GSC. Multi-instrument follow-up observations established it as a black hole low-mass X-ray binary in outburst, with a soft-state spectrum characterized by strong absorption, a disk component, a steep power-law tail, and a prominent Fe K$\alpha$ line, albeit with possible contamination from...
The geometry of the corona in accreting black hole binaries remains a central puzzle in high-energy astrophysics, particularly during their outburst phases when dramatic structural changes occur. Two powerful observational tools available—X-ray reverberation mapping and X-ray polarization—now offer complementary but seemingly conflicting insights into the innermost regions around black holes....
Transitional millisecond pulsars (tMSPs) bridge the gap between accreting neutron stars in low-mass X-ray binaries and millisecond radio pulsars, offering a unique laboratory to study the interplay between accretion and pulsar activity. These systems exhibit a subluminous X-ray state characterized by alternating high, low and flaring emission modes.
Multi-wavelength campaigns on the prototype...
Swift J1727.8–1613 is a recently discovered X-ray binary system entered in outburst in August 2023 and observed by SWIFT, IXPE, NiCER, NuSTAR and INTEGRAL. In this work, we analyze the source within the framework of the Jet Emitting Disk–Standard Accretion Disc (JED-SAD) model, which provides a self-consistent description of accretion and ejection processes in X-ray binaries. We focus on 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...
X-ray binaries are key laboratories for studying accretion and jet ejection mechanisms in strong gravitational fields. Among them, Cygnus X-3 stands out due to its distinctive properties and long-standing observational interest. In this talk, I will present results from the second and third observations of Cygnus X-3 by the Imaging X-ray Polarimetry Explorer (IXPE), focusing on the evolution...
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...
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...
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...
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 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...
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...
