An official website of the United States government
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 from blazars. Here, we report the first X-ray polarization observation of the blazar S4 0954+65 in a high optical and X-ray state. During our multi-wavelength (MWL) campaign of the source, we detected an optical flare whose peak coincided with the peak of an X-ray flare. This optical-X-ray flare most likely took place in a feature moving along the parsec-scale jet, imaged at 43 GHz by the Very Long Baseline Array (VLBA). The 43 GHz polarization angle of the moving component underwent a rotation near the time of the flare. In the optical band, prior to the IXPE observation, we measured the polarization angle to be aligned with the jet axis. In contrast, during the optical flare, the optical polarization angle was perpendicular to the jet axis; after the flare, it reverted to being parallel to the jet axis. Due to the smooth behavior of the optical polarization angle during the flare, we favor shocks as the main acceleration mechanism. We also infer that the ambient magnetic field lines in the jet were parallel to the jet position angle. The average degree of optical polarization during the IXPE observation was (14.3 ± 4.1)%. Despite the flare, we only detected an upper limit of 14% (at 3σlevel) on the X-ray polarization degree; however, a reasonable assumption on the X-ray polarization angle results in an upper limit of 8.8% (3σ). We modeled the spectral energy distribution (SED) and spectral polarization distribution (SPD) of S4 0954+65 with leptonic (synchrotron self-Compton) and hadronic (proton and pair synchrotron) models. Our combined MWL polarization observations and SED modeling tentatively disfavor the use of hadronic models for the X-ray emission in S4 0954+65.
more »
« less
3D printing of gas-dynamic virtual nozzles and optical characterization of high-speed microjets
Gas dynamic virtual nozzles (GDVNs) produce microscopic flow-focused liquid jets and droplets and play an important role at X-ray free-electron laser (XFEL) facilities where they are used to steer a stream of hydrated biomolecules into an X-ray focus during diffraction measurements. Highly stable and reproducible microjet and microdroplets are desired, as are flexible fabrication methods that enable integrated mixing microfluidics, droplet triggering mechanisms, laser illumination, and other customized features. In this study, we develop the use of high-resolution 3D nano-printing for the production of monolithic, asymmetric GDVN designs that are difficult to fabricate by other means. We also develop a dual-pulsed nanosecond image acquisition and analysis platform for the characterization of GDVN performance, including jet speed, length, diameter, and directionality, among others. We show that printed GDVNs can form microjets with very high degree of reproducibility, down to sub-micron diameters, and with water jet speeds beyond 170 m/s.
more »
« less
- PAR ID:
- 10169952
- Publisher / Repository:
- Optical Society of America
- Date Published:
- Journal Name:
- Optics Express
- Volume:
- 28
- Issue:
- 15
- ISSN:
- 1094-4087; OPEXFF
- Format(s):
- Medium: X Size: Article No. 21749
- Size(s):
- Article No. 21749
- Sponsoring Org:
- National Science Foundation
More Like this
-
-
Abstract We report the Imaging X-ray Polarimetry Explorer (IXPE) polarimetric and simultaneous multiwavelength observations of the high-energy-peaked BL Lacertae object (HBL) 1ES 1959+650, performed in 2022 October and 2023 August. In 2022 October, IXPE measured an average polarization degree ΠX= 9.4% ± 1.6% and an electric-vector position angleψX= 53° ± 5°. The polarized X-ray emission can be decomposed into a constant component, plus a rotating component, with the rotation velocityωEVPA= (−117 ± 12) deg day−1. In 2023 August, during a period of pronounced activity of the source, IXPE measured an average ΠX= 12.4% ± 0.7% andψX= 20° ± 2°, with evidence (∼0.4% chance probability) for a rapidly rotating component withωEVPA= 1864 ± 34 deg day−1. These findings suggest the presence of a helical magnetic field in the jet of 1ES 1959+650 or stochastic processes governing the field in turbulent plasma. Our multiwavelength campaigns from radio to X-ray reveal variability in both polarization and flux from optical to X-rays. We interpret the results in terms of a relatively slowly varying component dominating the radio and optical emission, while rapidly variable polarized components dominate the X-ray and provide minor contribution at optical wavelengths. The radio and optical data indicate that on parsec scales the magnetic field is primarily orthogonal to the jet direction. On the contrary, X-ray measurements show a magnetic field almost aligned with the parsec jet direction. Confronting with other IXPE observations, we guess that the magnetic field of HBLs on subparsec scale should be rather unstable, often changing its direction with respect to the Very Long Baseline Array jet.more » « less
-
Nanowire arrays—vertically aligned metal wires with a few hundred nanometers in diameter—are promising nano-structured targets for high-energy-density physics and related applications. We have been developing ultrafast, time-resolved measurements on laser-irradiated targets using the x-ray free electron laser at the SACLA facility. Here, we present fabrication of various kinds of nanowire array in order to explore the absorption mechanism with ultrahigh intensity laser irradiation, and their application to the laser-irradiation experiment is performed at the SACLA facility. To fabricate nanowire arrays with control over their spatial and material parameters, we have developed an approach using an anodic aluminum oxide template and electroplating processes. The nanowire array samples were applied for ultrahigh intensity laser experiments, which coupled with x-ray free-electron-laser facility SACLA. We characterized fundamental “static” data on transmittance calibration for x-ray shadowgraph measurements. We also evaluated the effect of a pre-pulse on spatial changes of a nanowire, showing that the shape of the nanowires was maintained up to a few picoseconds after laser irradiation. On the preliminary laser-irradiation experiments, we observed time-resolved, two-dimensional x-ray images and observed the x-ray transmittance change due to the heating process.more » « less
-
Abstract 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 Πx= 8.0% ± 2.3% at an electric-vector position angleψx= 123° ± 8°. However, on 2022 June 9–12, only an upper limit of Πx≤ 5.1% could be derived (at the 99% confidence level). The degree of optical polarization at that time, ΠO∼ 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.more » « less
-
ABSTRACT X-ray emission from the gravitational wave transient GW170817 is well described as non-thermal afterglow radiation produced by a structured relativistic jet viewed off-axis. We show that the X-ray counterpart continues to be detected at 3.3 years after the merger. Such long-lasting signal is not a prediction of the earlier jet models characterized by a narrow jet core and a viewing angle ≈20 deg, and is spurring a renewed interest in the origin of the X-ray emission. We present a comprehensive analysis of the X-ray dataset aimed at clarifying existing discrepancies in the literature, and in particular the presence of an X-ray rebrightening at late times. Our analysis does not find evidence for an increase in the X-ray flux, but confirms a growing tension between the observations and the jet model. Further observations at radio and X-ray wavelengths would be critical to break the degeneracy between models.more » « less
