X-ray Polarization Observations of BL Lacertae

Blazars are a class of jet-dominated active galactic nuclei with a typical double-humped spectral energy distribution. It is of common consensus the Synchrotron emission to be responsible for the low frequency peak, while the origin of the high frequency hump is still debated. The analysis of X-rays and their polarization can provide a valuable tool to understand the physical mechanisms responsible for the origin of high-energy emission of blazars. We report the first observations of BL Lacertae performed with the Imaging X-ray Polarimetry Explorer ({IXPE}), from which an upper limit to the polarization degree $\Pi_X<$12.6\% was found in the 2-8 keV band. We contemporaneously measured the polarization in radio, infrared, and optical wavelengths. Our multiwavelength polarization analysis disfavors a significant contribution of proton synchrotron radiation to the X-ray emission at these epochs. Instead, it supports a leptonic origin for the X-ray emission in BL Lac.Comment: 17 pages, 5 figures, accepted for publication in ApJ

Polarized blazar X-rays imply particle acceleration in shocks

Most of the light from blazars, active galactic nuclei with jets of magnetized plasma that point nearly along the line of sight, is produced by high-energy particles, up to around 1 TeV. Although the jets are known to be ultimately powered by a supermassive black hole, how the particles are accelerated to such high energies has been an unanswered question. The process must be related to the magnetic field, which can be probed by observations of the polarization of light from the jets. Measurements of the radio to optical polarization—the only range available until now—probe extended regions of the jet containing particles that left the acceleration site days to years earlier1,2,3, and hence do not directly explore the acceleration mechanism, as could X-ray measurements. Here we report the detection of X-ray polarization from the blazar Markarian 501 (Mrk 501). We measure an X-ray linear polarization degree ΠX of around 10%, which is a factor of around 2 higher than the value at optical wavelengths, with a polarization angle parallel to the radio jet. This points to a shock front as the source of particle acceleration and also implies that the plasma becomes increasingly turbulent with distance from the shock

Malformaciones vasculares: Manejo mediante técnicas de radiología intervencional y satisfacción de los pacientes Vascular malformations

Introducción: Las anomalías vasculares son una patología frecuente en la población general, y son causa de deterioro de la calidad de vida de los pacientes que las padecen. En los últimos años, las técnicas mínimamente invasivas de radiología intervencional se han convertido en una alternativa eficaz para el tratamiento de estos pacientes. El objetivo del presente estudio es mostrar nuestra experiencia en el manejo de malformaciones vasculares con estas técnicas en la Clínica Alemana de Santiago y evaluar la satisfacción de los pacientes con este manejo. Material y Métodos: Evaluación del seguimiento de todos los pacientes con malformaciones vasculares tratados en la Unidad de Radiología Intervencional desde el año 2006 hasta junio del año 2009. Los pacientes fueron clasificados en base a la hemodinamia de la malformación vascular (alto flujo vs. bajo flujo). Se evaluaron las complicaciones, y se realizó una encuesta sobre la satisfacción de los pacientes con el tratamiento. Resultados: Ochenta y siete pacientes (253 procedimientos) fueron incluidos en el estudio, 36 hombres y 51 mujeres, todos con seguimiento completo en este periodo. La edad promedio de ellos fue de 20,6 años. En más del 50% de los pacientes la anomalía vascular se ubicó en la cara o extremidades inferiores. Un 28% (25 pacientes) presentó malformación de alto flujo (pura o mixta) y 72% (62 pacientes) de bajo flujo (malformaciones vasculares, linfangiomas o mixtas). En promedio, cada paciente se realizó 2,9 procedimientos (1-10). Del total de procedimientos realizados, hubo 4 complicaciones mayores (1,65%), una de ellas con secuelas estéticas producto de necrosis de la zona. El promedio de satisfacción fue de un 7,95 en una escala de 1 a 10, siendo significativamente mayor en pacientes con malformaciones de bajo flujo (8,27) que en los de alto flujo (7,16) (p Background: Vascular anomalies are prevalent in the general population and may produce significant impairment in quality of life. In recent years, minimally invasive interventional radiology techniques have become an efficient alternative for the treatment of these patients. The aim of this study was to present our experience in the management of vascular malformations with such techniques at Clínica Alemana in Santiago, Chile, and assess the satisfaction of patients with this management. Material and Methods: Evaluation of the follow-up of patients with vascular malformations treated in the Interventional Radiology Unit at our center since June - 2006 to June - 2009. Patients were classified according to the hemodynamics of the lesions (high vs low-flow). Complications and patient satisfaction with the treatment were assessed. Results: Eighty-seven patients (253 procedures) were included in the study, 36 men and 51 women, all with complete follow-up during the period of the study. Their average age was 20.6 years. In over 50% of the patients the vascular anomaly was located on the face or the lower extremities. Twenty-eight percent (25 patients) had a high-flow malformation (pure or mixed) and 62 (72%) had a low-flow lesion (vascular malformation, lymphangioma or mixed). On average, each patient underwent 2.9 procedures (1-10). There were 4 major complications (1.65%), one of which was predominantly cosmetic with necrosis in the area of the lesion. The average satisfaction rate was 7.95 (on a rating scale of 1 to 10). Satisfaction was significantly higher in patients with low-flow malformations (8.27) than in those with high-flow lesions (7.16). (p < 0.05) Discussion: Treatment of vascular malformations using interventional radiology techniques is an effective alternative, with good prospects of clinical improvement, patient satisfaction and low complication rates

Evidence for current-controlled morphology along the western slope of Hatton Bank (Rockall Plateau, NE Atlantic Ocean)

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Detection of X-Ray Polarization from the Blazar 1ES 1959+650 with the Imaging X-Ray Polarimetry Explorer

Observations of linear polarization in the 2–8 keV energy range with the Imaging X-ray Polarimetry Explorer (IXPE) explore the magnetic field geometry and dynamics of the regions generating nonthermal radiation in relativistic jets of blazars. These jets, particularly in blazars whose spectral energy distribution peaks at X-ray energies, emit X-rays via synchrotron radiation from high-energy particles within the jet. IXPE observations of the X-ray-selected BL Lac–type blazar 1ES 1959+650 on 2022 May 3–4 showed a significant linear polarization degree of Π _x = 8.0% ± 2.3% at an electric-vector position angle ψ _x = 123° ± 8°. However, on 2022 June 9–12, only an upper limit of Π _x ≤ 5.1% could be derived (at the 99% confidence level). The degree of optical polarization at that time, Π _O ∼ 5%, is comparable to the X-ray measurement. We investigate possible scenarios for these findings, including temporal and geometrical depolarization effects. Unlike some other X-ray-selected BL Lac objects, there is no significant chromatic dependence of the measured polarization in 1ES 1959+650, and its low X-ray polarization may be attributed to turbulence in the jet flow with dynamical timescales shorter than 1 day

Discovery of X-ray polarization angle rotation in the jet from blazar Mrk 421

International audienceThe magnetic-field conditions in astrophysical relativistic jets can be probed by multiwavelength polarimetry, which has been recently extended to X-rays. For example, one can track how the magnetic field changes in the flow of the radiating particles by observing rotations of the electric vector position angle Ψ. Here we report the discovery of a ΨX rotation in the X-ray band in the blazar Markarian 421 at an average flux state. Across the 5 days of Imaging X-ray Polarimetry Explorer observations on 4-6 and 7-9 June 2022, ΨX rotated in total by ≥360°. Over the two respective date ranges, we find constant, within uncertainties, rotation rates (80 ± 9° per day and 91 ± 8° per day) and polarization degrees (ΠX = 10% ± 1%). Simulations of a random walk of the polarization vector indicate that it is unlikely that such rotation(s) are produced by a stochastic process. The X-ray-emitting site does not completely overlap the radio, infrared and optical emission sites, as no similar rotation of Ψ was observed in quasi-simultaneous data at longer wavelengths. We propose that the observed rotation was caused by a helical magnetic structure in the jet, illuminated in the X-rays by a localized shock propagating along this helix. The optically emitting region probably lies in a sheath surrounding an inner spine where the X-ray radiation is released

X-Ray Polarization of the BL Lacertae Type Blazar 1ES 0229+200

International audienceWe present polarization measurements in the 2-8 keV band from blazar 1ES 0229+200, the first extreme high synchrotron peaked source to be observed by the Imaging X-ray Polarimetry Explorer (IXPE). Combining two exposures separated by about two weeks, we find the degree of polarization to be ΠX = 17.9% ± 2.8% at an electric-vector position angle ψ X = 25.°0 ± 4.°6 using a spectro-polarimetric fit from joint IXPE and XMM-Newton observations. There is no evidence for the polarization degree or angle varying significantly with energy or time on both short timescales (hours) or longer timescales (days). The contemporaneous polarization degree at optical wavelengths was >7× lower, making 1ES 0229+200 the most strongly chromatic blazar yet observed. This high X-ray polarization compared to the optical provides further support that X-ray emission in high-peaked blazars originates in shock-accelerated, energy-stratified electron populations, but is in tension with many recent modeling efforts attempting to reproduce the spectral energy distribution of 1ES 0229+200, which attribute the extremely high energy synchrotron and Compton peaks to Fermi acceleration in the vicinity of strongly turbulent magnetic fields