Polarimetry is a highly sensitive method to quantify changes of the polarization state of light when passing through matter and is therefore widely applied in material science. The progress of synchrotron and X-ray free electron laser (XFEL) sources has led to significant developments of X-ray polarizers, opening perspectives for new applications of polarimetry to study source and beamline parameters as well as sample characteristics. X-ray polarimetry has shown to date a polarization purity of less than $1.4\times {10}^{-11}$, enabling the detection of very small signals from ultrafast phenomena. A prominent application is the detection of vacuum birefringence. Vacuum birefringence is predicted in quantum electrodynamics and is expected to be probed by combining an XFEL with a petawatt-class optical laser. We review how source and optical elements affect X-ray polarimeters in general and which qualities are required for the detection of vacuum birefringence.

We performed photo-polarimetry observations for the blazar BL Lacertae (BL Lac) in 2020 to 2021, in which BL Lac showed historical outburst. As a result, we obtained microvariability with a timescale about five minutes and wavelength dependence of polarization degree and angle. These results indicate multiple emission regions and turbulent magnetic field structure.

Relativistic jets from supermassive black holes or stellar mass black holes are among the most powerful astrophysical phenomena. Magnetic field plays an important role in the jet launching and propagation, as well as particle acceleration and radiation. Polarimetry is the only way to observe the magnetic field evolution. The recent launch of the Imaging X-ray Polarimetry Explorer (IXPE) has opened up the X-ray polarization window, which has revealed very interesting phenomena for relativistic jets. However, the field of MeV gamma-ray polarimetry remains largely unexplored. This paper aims to summarize key scientific potentials for MeV polarimetry for blazars and gamma-ray bursts (GRBs) from recent theoretical modeling. These predictions, which are closely related to the cosmic ray acceleration, neutrino production, radiation mechanism, and the jet evolution, can be examined by future MeV polarimeters, such as the Compton Spectrometer and Imager (COSI), the LargE Area burst Polarimeter (LEAP), and the All-sky Medium-Energy Gamma-ray Observatory eXplorer (AMEGO-X).

IXPE is a NASA/ASI Small Explorer Mission. It will probe the X-ray polarization properties of celestial sources. In particular, for Accretion-powered Millisecond Pulsars (AMPs), IXPE can provide us with unique information on their geometry. These information together with pulse shape modelling will strongly boost the achievable sensitivity on measuring the AMPs mass and the radius. As a case-study, we simulated an observation of SAXJ1808.4-3658 and studied the accuracy that can be achieved in the measured time-dependent Stokes profiles. From these data we estimated how well IXPE will be able to constraint NS geometrical parameters, such as the inclination and hot-spot co-latitude angles.

The role of starburst winds versus active galactic nuclei (AGN) jets/winds in the formation of the kiloparsec scale radio emission seen in Seyferts is not yet well understood. In order to be able to disentangle the role of various components, we have observed a sample of Seyfert galaxies exhibiting kpc-scale radio emission suggesting outflows, along with a comparison sample of starburst galaxies, with the EVLA B-array in polarimetric mode at 1.4 GHz and 5 GHz. The Seyfert galaxy NGC 2639, shows highly polarized secondary radio lobes, not observed before, which are aligned perpendicular to the known pair of radio lobes. The additional pair of lobes represent an older epoch of emission. A multi-epoch multi-frequency study of the starburst-Seyfert composite galaxy NGC 3079, reveals that the jet together with the starburst superwind and the galactic magnetic fields might be responsible for the well-known 8-shaped radio lobes observed in this galaxy. We find that many of the Seyfert galaxies in our sample show bubble-shaped lobes, which are absent in the starburst galaxies that do not host an AGN.

We have built an imaging polarimeter for use at mid-infrared wavelengths (i.e. N band or 8–13 μm). The detecting element is a 128 × 128 element Si:Ga Focal Plane Array, supplied by Amber Engineering, USA. The polarimeter itself provides diffraction limited images on a 4-m class telescope and has a field of view of about 32 arcsec of sky with 0·25 arcsec pixels. We describe the optical design, control electronics, observing modes and detector sensitivities. Also presented are some observational results to demonstrate the power of this new imaging polarimetric system.

We present an innovative soft X-ray polarimeter and spectrometer SOLPEX. The instrument is to be mounted aboard the ISS within the Russian science complex KORTES. The measurements to be made by SOLPEX are expected to be of unprecedented quality in terms of sensitivity to detect the soft-X-ray polarization of solar emission emanating from active regions and flares in particular. Simultaneous measurements of the polarization degree and the other characteristics (eg. evolution of the spectra) constitute the last, rather unexplored area of solar X-ray spectroscopy providing substantial diagnostic potential. Second important science task to be addressed are the measurements of Doppler shifts in selected X-ray spectral emission lines formed in hot flaring sources. The novel-type Dopplerometer (flat Bragg crystal drum unit) is planned to be a part of SOLPEX and will allow to measure line Doppler shifts in absolute terms with unprecedented time resolution (fraction of a second) during the impulsive flare phases. We shall present some details of the SOLPEX instrument and discuss observing sequences in a view of science objectives to be reached.

The Daniel K. Inouye Solar Telescope (DKIST), formerly Advanced Technology Solar Telescope when it begins operation in 2019 will be by a significant margin Earth's largest solar research telescope. Science priorities dictate an initial suite of instruments that includes four spectro-polarimeters. Accurate polarization calibration of the individual instruments and of the telescope optics shared by those instruments is of critical importance. The telescope and instruments have been examined end-to-end for sources of polarization calibration error, allowable contributions from each of the sources quantified, and techniques identified for calibrating each of the contributors. Efficient use of telescope observing time leads to a requirement of sharing polarization calibrations of common path telescope components among the spectro-polarimeters and for those calibrations to be repeated only as often as dictated by degradation of optical coatings and instrument reconfigurations. As a consequence the polarization calibration of the DKIST is a facility function that requires facility wide techniques.

We present the innovative soft X-ray spectro-polarimeter, SolpeX. This instrument consists of three functionally independent blocks. They are to be included into the Russian instrument KORTES, to be mounted onboard the ISS. The three SolpeX units are: a simple pin-hole X-ray spectral imager, a polarimeter, and a fast-rotating drum multiple-flat-crystal Bragg spectrometer. Such a combination of measuring blocks will offer a new opportunity to reliably measure possible X-ray polarization and spectra of solar flares, in particular during the impulsive phase. Polarized Bremsstrahlung and line emission due to the presence of directed particle beams will be detected, and measurements of the velocities of evaporated hot plasma will be made. In this paper we discuss the details of the construction of the SolpeX units. The delivery of KORTES with SolpeX to the ISS is expected to happen in 2017/2018.

We performed an observational study of the relation between the interstellar magnetic field alignment and star formation in twenty (20) sky regions containing Bok Globules. The presence of young stellar objects in the globules is verified by a search of infrared sources with spectral energy distribution compatible with a pre main-sequence star. The interstellar magnetic field direction is mapped using optical polarimetry. These maps are used to estimate the dispersion of the interstellar magnetic field direction in each region from a Gaussian fit, σB. In addition to the Gaussian dispersion, we propose a new parameter, η, to measure the magnetic field alignment that does not rely on any function fitting. Statistical tests show that the dispersion of the magnetic field direction is different in star forming globules relative to quiescent globules. Specifically, the less organised magnetic fields occur in regions having young stellar objects.

We present recent experiments using a Levenberg-Marquardt algorithm and the polarised radiative transfer code COSSAM to produce a new ZDM code. Currently the code is able to recover the magnetic parameters of model stars with either a decentred dipole morphology or a morphology consisting of a centred dipole and a quadrupole, while simultaneously calculating multiple chemical abundances (including a basic stratification model). The ZDM code has been tested using both synthetic spectra and real, well studied stars. Additional features are currently being added such as a multipole morphology of arbitrary order and more sophisticated chemical stratification models.

We suggest the use of the area asymmetries of the Stokes V profile of a line sensitive to the Zeeman effect to diagnose variatios of the magnetic field along the line of sight in stellar atmospheres. This tool could allow to disentangle the magnetic topology of the observed stellar features in analogy to the solar case: a fibril topology as in plage and netwrok magnetic fields vs. a homogeneous and strong field as in sunspots. We also suggest the use of the Hanle effect as a means to observe weak global dipoles.

The bipolar or more complex morphology observed in planetary nebulae have been explained by two principal hypothesis: by the existence of a companion and an accreting disk or by the effects of magnetic field, (or a combination of both). Symbiotics are binary systems and some of them show morphologies similar to those observed on planetary nebulae. This fact could support the binary hypothesis for PNe. We have therefore performed polarimetric observations of symbiotic systems and some planetary nebulae in order, first to detect linear polarisation with POLIMA at the San Pedro Mártir observatory, and ultimately to prove the existence and physical properties of those disks. We present here the first results of a project dedicated to the analysis of the polarisation observed in evolved objects starting with the PN M2-9 and R Aqr.

We have been operating an infrared Stokes spectro-polarimeter, whose observing wavelength bands include the He i 10830 Å and Fe i 15648 Å lines. A couple of full-Sun, full-Stokes maps in both wavelength bands are taken on a daily basis, with the polarization sensitivity better than 10−3. With this sensitivity, the helium polarization maps clearly show the atomic and Hanlé polarizations besides the Zeeman polarization, particularly in prominences/filaments. On these polarization maps, we can track the magnetic field signals of the prominences/filaments during their passages on the solar disk. Therefore, this instrument works as a ‘synoptic prominence magnetograph’. Our preliminary study of the linear polarizations seen in quiescent filaments suggests that the magnetic field producing the polarization signals is located at the bottom part of a flux-rope, which supports a filament.

The observation of prominences with ground-based telescopes suffers from poor image quality due to atmospheric turbulence when compared with space-borne instruments which, for solar observations, are of similar apertures. To make ground-based instruments competitive, they should rely on spectropolarimetry and the measurement of prominence magnetic fields, a task which no foreseable space instrument will perform. But spectropolarimetry alone does not suffice, and we argue that future instrumentation should combine it with imaging in a large field of view and good temporal resolution. We place numbers on those requirements and give examples of instrumental accomplishments already at work today that forecast a new generation of instruments for the observation of prominences from ground-based telescopes.

Observations of the Cosmic Microwave Background (CMB) have played a leading role in establishing an understanding of the structure and evolution of the Universe on the largest scales. This achievement has been enabled by a series of extremely successful experiments, coupled with the simplicity of the relationship between the cosmological theory and data. Antarctic experiments, including both balloon-borne telescopes and instruments at the South Pole, have played a key role in realizing the scientific potential of the CMB, from the characterization of the temperature anisotropies to the detection and study of the polarized component. Current and planned Antarctic long duration balloon experiments will extend this heritage of discovery to test theories of cosmic genesis through sensitive polarized surveys of the millimeter-wavelength sky. In this paper we will review the pivotal role that Antarctic balloon borne experiments have played in transforming our understanding of the Universe, and describe the scientific goals and technical approach of current and future missions.

The SCUPOL catalog is a compilation of 83 regions that were observed at the JCMT between 1997 and 2005. For sufficiently sampled maps, we conduct an analysis for characterizing the polarization and magneto-turbulent properties of the observed regions. The same analysis is done on 2D polarization maps produced by 3D MHD 1024 pixel grid simulations that have been scaled on a sample of observed maps. Each scaled MHD cube of simulated data is used to calculate the mean turbulent regime of each observed regions.

Retrieval of cloud parameters in weather radar benefits from polarimetric measurements. Most polarimetric radars measure the full backscatter matrix (BSM) using a few alternating polarized sounding signals. Using specially encoded orthogonal frequency division multiplexing (OFDM) signals however, the BSM can be measured in a single simultaneous transmission of two orthogonally polarized signals. Based on a set of parameters for weather radar, the properties of such a signal are explored and its merit as a useful capability is shown.

Time-resolved polarisation measurements of pulsars provide an unique insight into the geometry of the emission regions. Hubble Space Telescope (HST) polarisation data of the Crab Nebula were obtained from the Multimission Archive at STScI (MAST). The data are composed of a series of observations of the Crab Nebula with the HST and ACS camera system taken in three different polarisation filters (0°, 60° and 120°) between 2003 August and 2005 December. Polarisation vector maps of the Nebula were produced with the polarimetry software IMPOL. The degree of polarisation (P.D.) and the position angle (P.A.) of the pulsar's integrated pulse beam were measured, and also that of the nearby Synchrotron Knot, yielding P.D. = 4.90 ± 0.33 %, P.A. = 106°.46 ± 1°.9 for the pulsar, and P.D. = 61.70 ± 0.72 %, P.A. = 126°.86 ± 0°.23 for the Synchrotron Knot. These results are consistent with those of obtained by others using INTEGRAL.