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Time-dependent modelling of short-term variability in the TeV-blazar VER J0521+211 during the major flare in 2020
MAGIC Collaboration, S. Abe, J. Abhir +228
The BL Lacertae object VER J0521+211 underwent a notable flaring episode in February 2020. A short-term monitoring campaign, led by the MAGIC (Major Atmospheric Gamma Imaging Chere…
Search for Extended GeV Sources in the Inner Galactic Plane
S. Abdollahi, F. Acero, A. Acharyya +108
The recent detection of extended -ray emission around middle-aged pulsars is interpreted as inverse-Compton scattering of ambient photons by electron-positron pairs escaping the…
IXPE Observation of the Low-Synchrotron Peaked Blazar S4 0954+65 During An Optical-X-ray Flare
Pouya M. Kouch, Ioannis Liodakis, Francesco Fenu +134
The X-ray polarization observations made possible with the Imaging X-ray Polarimetry Explorer (IXPE) offer new ways of probing high-energy emission processes in astrophysical jets…
Evidence for a shock-compressed magnetic field in the northwestern rim of Vela Jr. from X-ray polarimetry
Dmitry A. Prokhorov, Yi-Jung Yang, Riccardo Ferrazzoli +97
Synchrotron X-ray emission has been detected from nearly a dozen young supernova remnants (SNRs). X-rays of synchrotron origin exhibit linear polarization in a regular, non-randoml…
A Two-Week Monitoring Campaign on Mrk 421
W. Peter Maksym, Ioannis Liodakis, M. Lynne Saade +153
X-ray polarization is a unique new probe of the particle acceleration in astrophysical jets made possible through the Imaging X-ray Polarimetry Explorer. Here we report on the firs…
Insights from the first flaring activity of a high-synchrotron-peaked blazar with X-ray polarization and VHE gamma rays
MAGIC Collaboration, K. Abe, S. Abe +250
We study a flaring activity of the HSP Mrk421 that was characterized from radio to very-high-energy (VHE; E TeV) gamma rays with MAGIC, Fermi-LAT, Swift, XMM-Newton and sever…
Magnetic field geometry of the gamma-ray binary PSR B1259-63 revealed via X-ray polarization
Philip Kaaret, Oliver J. Roberts, Steven R. Ehlert +6
Some X-ray binaries containing an energetic pulsar in orbit around a normal star accelerate particles to high energies in the shock cone formed where the pulsar and stellar winds c…
GRB 221009A: the B.O.A.T Burst that Shines in Gamma Rays
M. Axelsson, M. Ajello, M. Arimoto +151
We present a complete analysis of Fermi Large Area Telescope (LAT) data of GRB 221009A, the brightest Gamma-Ray Burst (GRB) ever detected. The burst emission above 30 MeV detected…
A Comparison of the X-ray Polarimetric Properties of Stellar and Supermassive Black Holes
M. Lynne Saade, Philip Kaaret, Ioannis Liodakis +1
X-ray polarization provides a new way to probe accretion geometry in black hole systems. If the accretion geometry of black holes is similar regardless of mass, we should expect th…
PKS~J08050111: A Second Owens Valley Radio Observatory Blazar Showing Highly Significant Sinusoidal Radio Variability -- The Tip of the Iceberg
P. V. de la Parra, S. Kiehlmann, P. Mroz +23
Owens Valley Radio Observatory (OVRO) observations of supermassive black hole binary (SMBHB) candidate PKS~2131021 revealed, for the first time, six likely characteristics of th…
Analysis of Crab X-ray Polarization using Deeper IXPE Observations
Josephine Wong, Tsunefumi Mizuno, Niccoló Bucciantini +98
We present Crab X-ray polarization measurements using IXPE data with a total exposure of 300ks, three times more than the initial 2022 discovery paper. Polarization is detected in…
X-ray and multiwavelength polarization of Mrk 501 from 2022 to 2023
Chien-Ting J. Chen, Ioannis Liodakis, Riccardo Middei +143
We present multiwavelength polarization measurements of the luminous blazar Mrk~501 over a 14-month period. The 2--8 keV X-ray polarization was measured with the Imaging X-ray Pola…
Association of the IceCube neutrinos with blazars in the CGRaBS sample
Pouya M. Kouch, Elina Lindfors, Talvikki Hovatta +11
The origin of high-energy (HE) astrophysical neutrinos has remained an elusive hot topic in the field of HE astrophysics for the past decade. Apart from a handful of individual ass…
PKS 2131-021 -- Discovery of Strong Coherent Sinusoidal Variations from Radio to Optical Frequencies: Compelling Evidence for a Blazar Supermassive Black Hole Binary
S. Kiehlmann, P. V. de la Parra, A. G. Sullivan +31
Haystack and Owens Valley Radio Observatory (OVRO) observations recently revealed strong, intermittent, sinusoidal total flux-density variations that maintained coherence between 1…
Systems design, assembly, integration and lab testing of WALOP-South Polarimeter
Siddharth Maharana, A. N. Ramaprakash, Chaitanya Rajarshi +28
Wide-Area Linear Optical Polarimeter (WALOP)-South is the first wide-field and survey-capacity polarimeter in the optical wavelengths. On schedule for commissioning in 2024, it wil…
Testing particle acceleration in blazar jets with continuous high-cadence optical polarization observations
Ioannis Liodakis, Sebastian Kiehlmann, Alan P. Marscher +44
Variability can be the pathway to understanding the physical processes in astrophysical jets, however, the high-cadence observations required to test particle acceleration models a…
An IXPE-Led X-ray Spectro-Polarimetric Campaign on the Soft State of Cygnus X-1: X-ray Polarimetric Evidence for Strong Gravitational Lensing
James F. Steiner, Edward Nathan, Kun Hu +134
We present the first X-ray spectropolarimetric results for Cygnus X-1 in its soft state from a campaign of five IXPE observations conducted during 2023 May-June. Companion multiwav…
Probing the polarized emission from SMC X-1: the brightest X-ray pulsar observed by IXPE
Sofia V. Forsblom, Sergey S. Tsygankov, Juri Poutanen +101
Recent observations of X-ray pulsars (XRPs) performed by the Imaging X-ray Polarimetry Explorer (IXPE) have made it possible to investigate the intricate details of these objects i…
Discovery of a shock-compressed magnetic field in the north-western rim of the young supernova remnant RX J1713.7-3946 with X-ray polarimetry
Riccardo Ferrazzoli, Dmitry Prokhorov, Niccolò Bucciantini +99
Supernova remnants (SNRs) provide insights into cosmic-ray acceleration and magnetic field dynamics at shock fronts. Recent X-ray polarimetric measurements by the Imaging X-ray Pol…
IXPE observation of PKS 2155-304 reveals the most highly polarized blazar
Pouya M. Kouch, Ioannis Liodakis, Riccardo Middei +133
We report the X-ray polarization properties of the high-synchrotron-peaked (HSP) blazar PKS 2155304 based on observations with the Imaging X-ray Polarimetry Explorer (IXPE). We…
Evidence for a toroidal magnetic field in the core of 3C 84
G. F. Paraschos, L. C. Debbrecht, J. A. Kramer +13
The spatial scales of relativistic radio jets, probed by relativistic magneto-hydrodynamic jet launching simulations (RMHDs) and by most very-long-baseline interferometry (VLBI) ob…
Revisiting High-Energy Polarization from Leptonic and Hadronic Blazar Scenarios
Haocheng Zhang, Markus Böttcher, Ioannis Liodakis
X-ray and MeV polarization can be powerful diagnostics for leptonic and hadronic blazar models. Previous predictions are mostly based on a one-zone framework. However, recent IXPE…
Studying geometry of the ultraluminous X-ray pulsar Swift J0243.6+6124 using X-ray and optical polarimetry
Juri Poutanen, Sergey S. Tsygankov, Victor Doroshenko +108
Discovery of pulsations from a number of ULXs proved that accretion onto neutron stars can produce luminosities exceeding the Eddington limit by several orders of magnitude. The co…
Galactic transient sources with the Cherenkov Telescope Array Observatory
Cherenkov Telescope Array Observatory Consortium
A wide variety of Galactic sources show transient emission at soft and hard X-ray energies: low- and high-mass X-ray binaries containing compact objects, isolated neutron stars exh…