scholarly journals Multicolor polarimetric observation of 15 min variability in S5 0716 714

2009 ◽  
Author(s):  
Mahito Sasada
Keyword(s):  
Polarimetric Observation

scholarly journals High-sensitivity radio study of the non-thermal stellar bow shock EB27

2021 ◽  
Author(s):  
Paula Benaglia ◽  
Santiago del Palacio ◽  
Christopher Hales ◽  
Marcelo E Colazo
Keyword(s):  
Radio Emission ◽  
Massive Star ◽  
High Sensitivity ◽  
Bow Shock ◽  
Relativistic Electrons ◽  
Polarimetric Observation ◽  
Very Large Array ◽  
Thermal Radio Emission ◽  
The Magnetic Field ◽  
Linear Polarisation

Abstract We present a deep radio-polarimetric observation of the stellar bow shock EB27 associated to the massive star BD+43○3654. This is the only stellar bow shock confirmed to have non-thermal radio emission. We used the Jansky Very Large Array in S band (2–4 GHz) to test whether this synchrotron emission is polarised. The unprecedented sensitivity achieved allowed us to map even the fainter regions of the bow shock, revealing that the more diffuse emission is steeper and the bow shock brighter than previously reported. No linear polarisation is detected in the bow shock above 0.5%, although we detected polarised emission from two southern sources, probably extragalactic in nature. We modeled the intensity and morphology of the radio emission to better constrain the magnetic field and injected power in relativistic electrons. Finally, we derived a set of more precise parameters for the system EB27–BD+43○3654 using Gaia Early Data Release 3, including the spatial velocity. The new trajectory, back in time, intersects the core of the Cyg OB2 association.

scholarly journals Significantly high polarization degree of the very low-albedo asteroid (152679) 1998 KU2

2018 ◽  
Vol 611 ◽  
pp. A31 ◽  
Author(s):  
Daisuke Kuroda ◽  
Masateru Ishiguro ◽  
Makoto Watanabe ◽  
Sunao Hasegawa ◽  
Tomohiko Sekiguchi ◽  
...  
Keyword(s):  
Solar System ◽  
Polarization Degree ◽  
Polarimetric Observation ◽  
High Polarization ◽  
Planetary Satellites ◽  
Large Phase ◽  
Solar Phase ◽  
Phase Angles ◽  
Similar Phase ◽  
Geometric Albedo

We present a unique and significant polarimetric result regarding the near-Earth asteroid (152679) 1998 KU2, which has a very low geometric albedo. From our observations, we find that the linear polarization degrees of 1998 KU2are 44.6 ± 0.5% in theRCband and 44.0 ± 0.6% in theVband at a solar phase angle of 81.0°. These values are the highest of any known airless body in the solar system (i.e., high-polarization comets, asteroids, and planetary satellites) at similar phase angles. This polarimetric observation is not only the first for primitive asteroids at large phase angles, but also for low-albedo (<0.1) airless bodies. Based on spectroscopic similarities and polarimetric measurements of materials that have been sorted by size in previous studies, we conjecture that 1998 KU2has a highly microporous regolith structure comprising nano-sized carbon grains on the surface.

scholarly journals VLBI OH maser polarimetry with the Australian Long Baseline Array: the star-forming region G340.054–0.244

2007 ◽  
Vol 3 (S242) ◽  
pp. 64-65
Author(s):  
I. Bains ◽  
J. Caswell ◽  
A. M. S. Richards ◽  
C. Phillips ◽  
S. Tingay ◽  
...  
Keyword(s):  
Spectral Line ◽  
Spatial Resolution ◽  
Radio Astronomy ◽  
High Velocity ◽  
High Spatial Resolution ◽  
Polarimetric Observation ◽  
Polarization Structure ◽  
Star Forming ◽  
Long Baseline ◽  
The Subject

AbstractUntil recently, high spatial resolution full Stokes maser polarimetry was the sole domain of northern interferometers and a wealth of sources in the far south remained unexplored due to a lack of suitable instrumentation having both high spatial and high velocity resolution. The Australia Telescope Long Baseline Array (LBA) has now switched to disk-based software correlation, permitting full Stokes observing in spectral line mode with velocity channels which are sufficiently narrow to sample usefully the polarization structure. To illustrate the utility of this valuable addition to radio astronomy, we present preliminary results of the first such polarimetric observation, the subject of which are the OH masers in the star-forming region G340.054–0.244.

scholarly journals Simulating Radar Observations of Precipitation at Higher Frequencies from Lower-Frequency Polarimetric Measurements

2012 ◽  
Vol 29 (10) ◽  
pp. 1435-1454 ◽  
Author(s):  
Jason Fritz ◽  
V. Chandrasekar
Keyword(s):  
Radar Data ◽  
Complete Characterization ◽  
Convective Storm ◽  
Polarimetric Observation ◽  
Robust Solution ◽  
High Frequencies ◽  
Improve Model ◽  
X Band ◽  
Radar Measurements

Abstract The translation of radar data from one frequency to another based on electromagnetic absorption and scattering models has been used to convert S-band measurements to higher frequencies, such as those within the X or Ku bands, in order to create realistic simulations. As the target frequency of simulations for weather radar increase to X band and above, the size of large raindrops and hail either approach or exceed the radar wavelength, resulting in a radar cross section that is no longer in the linear Rayleigh region. The Mie solution to scattering models is then required. With the advent of dual-polarization systems, a more complete characterization of the effect of precipitation on radar is possible in order to improve model effectiveness. However, typical curve- or surface-fitting methods still have limitations as particle size increases. A more robust solution is presented here in the form of a neural network that incorporates the nonlinear relationship among various polarimetric observation variables and the radar wavelength and look angle. Thus, high-frequency observations of a convective storm containing hail can be simulated using polarimetric ground radar measurements. Adequate polarimetric data from hail storms at high frequencies do not exist, however, so network outputs for this case can only be compared to theoretical observations. An application of the simulation procedure to characterize the effect of precipitation on spaceborne synthetic aperture radar (SAR) using ground observations is presented.

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