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Discriminating blazar emission models with high-energy polarimetry: Multi-band predictions and detectability
Sara Capecchiacci, Ioannis Liodakis, Haocheng Zhang +2
Polarimetric properties of blazars provide key constraints on the acceleration mechanisms powering their relativistic jets, the high-energy emission processes involved, and the com…
Unique Science Opportunities for Space VLBI Systems with the SKA Telescopes
Y. Y. Kovalev, G. Bruni, T. An +17
To date, two dedicated Space Very Long Baseline Interferometry (SVLBI) missions, the VLBI Space Observatory Programme (VSOP) and RadioAstron, have provided groundbreaking insights…
Optical polarization variability and its relation to gamma-ray activity in blazars
Styliana Grigoriou, Anastasia Glykopoulou, Ioannis Liodakis
Optical polarization can be an important probe of particle acceleration and high-energy emission processes in relativistic jets from supermassive black holes. We combined publicly…
Exploring the nature of Galactic unassociated sources detected by the Fermi-LAT
F. Acero, A. Acharyya, A. Adelfio +120
We investigate the nature of the unassociated sources detected by the Fermi-LAT close (|b|<10°) to the Galactic plane, representing 16% of all sources in the 4FGL-DR4 catalog. The…
Hard X-ray Sources in Fermi UFOs
Alessandro Paggi, Ioannis Liodakis, John Antoniadis +7
Identification and/or association of unidentified -ray sources with lower-energy counterparts represents a key challenge in modern astronomy, due to the relatively large positio…
Gamma-ray signature of superluminous supernovae: Fermi-LAT GeV detection of SN 2017egm and evidence of a central engine
F. Acero, A. Acharyya, A. Adelfio +116
Superluminous supernovae (SLSNe) are a rare class of transients with peak luminosities 10-100 times greater than those of standard core-collapse supernovae (SNe). The mechanisms po…
Detectability of Polarized Gamma-ray Emission from Blazar Flares with COSI
Garrett A. Latiolais, Jorge Otero-Santos, Michela Negro +18
We investigate the detectability of polarized gamma-ray emission from blazar flares with the Compton Spectrometer and Imager (COSI). Using 17 years of Fermi Large Area Telescope ob…
X-Ray Polarization from the Gamma-Ray Binary LS I +61 303
Philip Kaaret, Sudip Chakraborty, Daniel Golonka +5
The gamma-ray emitting binary stellar system LS I +61 303 was observed with the Imaging X-ray Polarimetry Explorer (IXPE) on two successive orbits over orbital phases of 0.74 to 1.…
Tracking down the broadband polarimetric properties of PG 1553+113
Riccardo Middei, Svetlana G. Jorstad, Alan P. Marscher +78
We report on a nine-month monitoring campaign of the blazar PG 1553+113, relying on three observations carried out in 2025 with the Imaging X-ray Polarimetry Explorer (IXPE) and su…
Where within the 3C 84 jet are -rays produced?
Georgios F. Paraschos, Ioannis Liodakis, Svetlana Jorstad +49
The location of -ray creation and emission within extra-galactic jets is a matter of active debate. One particularly well-suited source to pinpoint the location is the nearby, b…
Polarisation angle variability in tidal disruption events
A. Floris, I. Liodakis, K. I. I. Koljonen +9
Tidal disruption events (TDEs) occur when a star is disrupted by the tidal forces of a supermassive black hole, and these events produce bright multi-wavelength flares. Polarimetri…
Magnetic-field Order in the Southwestern Rim of RCW 86 Constrained Using X-Ray Polarimetry
Stefano Silvestri, Dmitry Prokhorov, Jacco Vink +97
RCW 86 is a supernova remnant whose origin has recently been linked to an off-center explosion within a cavity created by its progenitor star. In the southwestern region, the forwa…
Super-Eddington Accretion Geometry: a Remarkable Stability of the Hidden Ultraluminous X-Ray Source Cygnus X-3
Romana Mikušincová, Alexandra Veledina, Fabio Muleri +112
We report on the average and orbital phase-resolved polarization of Cyg X-3 in the hard state during the 2023 Imaging X-ray Polarimetry Explorer (IXPE) observational campaign. We f…
The IXPE and multifrequency polarimetric view of the extreme blazars 1ES 1101-232 and RGB J0710+591
Fabrizio Tavecchio, Dawoon E. Kim, Gabriel Emery +53
Multiwavelength polarimetry is a powerful tool to probe magnetic field and flow geometries in the relativistic jets of blazars. In this respect, particularly interesting are the so…
Compelling Evidence for a Harmonic in the Light Curve of the Supermassive Black Hole Binary Candidate PKS J1309+1154
A. C. S. Readhead, M. F. Aller, A. G. Sullivan +23
We recently discovered a supermassive black hole binary (SMBHB) candidate, PKS J1309+1154, in the combined 46-yr University of Michigan Radio Astronomy Observatory (UMRAO) plus Owe…
Detection of Compton scattering in the jet of 3C 84
Ioannis Liodakis, Sudip Chakraborty, Frédéric Marin +77
3C 84 is the brightest cluster galaxy in the Perseus Cluster. It is among the closest radio-loud active galaxies and among the very few that can be detected from low frequency radi…
A Search for Supermassive Black Hole Binary Candidates in 46-Year Radio Light Curves of 83 Blazars
B. Molina, P. Mróz, P. V. De la Parra +23
The combined University of Michigan Radio Astronomy Observatory (UMRAO) and Owens Valley Radio Observatory (OVRO) blazar monitoring programs at 14.5/15 GHz provide uninterrupted li…
Association of the IceCube neutrinos with CAZ blazar light curves
Pouya M. Kouch, Talvikki Hovatta, Elina Lindfors +3
The IceCube Neutrino Observatory has detected several hundred high-energy neutrinos from cosmic sources. Despite numerous studies searching for their origin, it is still not known…
CAZ catalog and optical light curves of 7918 blazar-selected active galactic nuclei
Pouya M. Kouch, Elina Lindfors, Talvikki Hovatta +10
Active galactic nuclei (AGN) are some of the brightest and most variable objects in the Universe. Those with relativistic jets observed at small viewing angles are blazars. Due to…
Polarimetric Diversity in Tidal Disruption Events: Comparative Study of Low-Polarised sources with AT2020mot
A. Floris, I. Liodakis, K. I. I. Koljonen +13
Tidal disruption events (TDEs) occur when a star is disrupted by the tidal forces of a supermassive black hole (SMBH), producing bright multi-wavelength flares. Among these events,…
Unveiling blazar synchrotron emission: a multiwavelength polarimetric study of HSP and LSP populations
Sara Capecchiacci, Ioannis Liodakis, Riccardo Middei +96
Polarimetric properties of blazars allow us to put constraints on the acceleration mechanisms that fuel their powerful jets. By studying the multiwavelength polarimetric behaviour…
Optical polarization properties of the closest tidal disruption event AT 2023clx indicate origin from tidal stream shocks
Karri I. I. Koljonen, Kari Nilsson, Ioannis Liodakis +1
Polarization observations of tidal disruption events offer unique insights into the accretion processes around supermassive black holes. Here, we present optical polarization obser…
Polarisation as a probe of neutrino emission from blazars
G. F. Paraschos, E. Traianou, L. C. Debbrecht +2
The source of extragalactic neutrinos in the TeV-PeV range is a matter of very active research, with blazar jets having been postulated to be the origin of at least some of the det…
Polarization of reflected X-ray emission from the Sgr A molecular complex: multiple flares, multiple sources?
Ildar Khabibullin, Eugene Churazov, Riccardo Ferrazzoli +100
The extended X-ray emission observed in the direction of several molecular clouds in the central molecular zone of our Galaxy exhibits spectral and temporal properties consistent w…