{"id":101331,"date":"2025-08-27T17:45:10","date_gmt":"2025-08-27T17:45:10","guid":{"rendered":"https:\/\/www.newsbeep.com\/ca\/101331\/"},"modified":"2025-08-27T17:45:10","modified_gmt":"2025-08-27T17:45:10","slug":"first-measurement-of-x-ray-polarization-from-a-magnetar-outburst","status":"publish","type":"post","link":"https:\/\/www.newsbeep.com\/ca\/101331\/","title":{"rendered":"First measurement of X-ray polarization from a magnetar outburst"},"content":{"rendered":"

NASA\u2019s Imaging X-ray Polarimetry Explorer (IXPE) measured X-ray polarization during an outburst from the magnetar 1E 1841-045<\/a>, marking the first such measurement in the midst of an active flare.<\/p>\n

The source sits near the supernova remnant<\/a> Kes 73, and the data arrived during a rare window when the star was dramatically brighter than usual.<\/p>\n

Who and what are we looking at
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Rachael Stewart of George Washington University (GWU<\/a>) and Michela Rigoselli of the Italian National Institute for Astrophysics (INIF<\/a>) led companion studies that report the result<\/a>. <\/p>\n

Their teams analyzed IXPE<\/a> data on x-ray polarization taken roughly six weeks after the activity surged.<\/p>\n

A neutron star<\/a> is the compact core left after a massive star collapses. A magnetar is a neutron star with a magnetic field hundreds to thousands of times stronger than typical neutron star fields, often above 1014 gauss. This type of star is prone to long-lived outbursts.<\/p>\n

The object sits inside the shell of Kes 73, and early kinematic work placed it about 8.5 to 9.8 kiloparsecs from Earth, which is roughly equivalent to 28,000 light-years in distance. <\/p>\n

Later hydrogen-line studies revised the distance to about 5.8 \u00b1 0.3 kiloparsecs, showing why numbers differ across sources.<\/p>\n

For context, the measurements span standard X-ray bands described in keV, which is a unit of photon energy. Values near 2 to 8 keV cover the IXPE range, while higher energies fall to other instruments.<\/p>\n

Why polarization matters<\/p>\n

Polarization encodes the orientation of light\u2019s electric field and its coherence. <\/p>\n

In ultra-strong fields, quantum electrodynamics<\/a> predicts vacuum birefringence, which can imprint distinct energy and phase trends on polarization from magnetized stars.<\/p>\n

Tracking both the degree and angle across energy bands helps separate thermal surface emission from high-altitude processes. The angle can diagnose field geometry, and the degree can tag the radiation mechanism.<\/p>\n

When combined with timing and spectra, polarimetry breaks model degeneracies that spectroscopy alone cannot. It can show whether the emission region is close to the surface or higher in the magnetosphere.<\/p>\n

Telescopes recorded X-ray polarization<\/p>\n

Swift, Fermi, and NICER<\/a> flagged burst activity on August 21, 2024, and IXPE and NuSTAR<\/a> followed with coordinated observations beginning about 40 days later, the first-ever IXPE observation of a magnetar in an enhanced state.<\/p>\n

At energies above about 5 keV, a hard X-ray tail<\/a> dominated the flux, consistent with earlier studies of this source outside of outburst phases.<\/p>\n

Energy-resolved polarimetry showed roughly 20 percent polarization at 2 to 3 keV and up to about 55 to 70 percent in the 6 to 8 keV band, while the polarization angle stayed close to celestial north.<\/p>\n

What the X-ray polarization means <\/p>\n

The spectra and polarization fit either a blackbody plus two power laws or two blackbodies plus one power law, with the highest-energy component carrying the strongest polarization signal.<\/p>\n

Two leading ideas<\/a> explain the high-energy photons: resonant inverse Compton scattering, where ultra-fast charges boost soft X-rays to higher energies, and synchrotron radiation from electron-positron pairs created higher up.<\/p>\n

Both mechanisms can reproduce the data under realistic geometries and particle energies, though models often favor a synchrotron origin when polarization grows with energy and the angle remains steady.<\/p>\n

Why this first measurement matters<\/p>\n

Catching polarization during an outburst ties the emission to specific zones and tests how the magnetic geometry behaves during a bright, stressed state. It also provides a benchmark for comparing quiescent and active phases in the same star.<\/p>\n

\u201cThis unique observation will help advance the existing models aiming to explain<\/a> magnetar hard X-ray emission by requiring them to account for this very high level of synchronization we see among these hard X-ray photons,\u201d said Stewart.<\/p>\n

Phase-resolved polarimetry becomes possible when the signal is strong, which opens a path to mapping changes through a rotation. That test is central to separating surface effects from magnetospheric processes.<\/p>\n

What comes next<\/p>\n

\u201cIt will be interesting to observe 1E 1841-045 once it has returned to its quiescent, baseline state to follow the evolution of its polarimetric properties,\u201d said Rigoselli.<\/p>\n

A follow-up in quiet times can show whether the hard tail aligns with the softer component or originates at different heights, and whether the polarization angle tracks a stable field configuration. <\/p>\n

A consistent angle across energies would point to a simple topology, while shifts would argue for multiple zones.<\/p>\n

X-ray polarization added to mission <\/p>\n

IXPE launched on a Falcon 9<\/a> in December 2021 and is a joint mission of NASA and the Italian Space Agency, with operations led from NASA\u2019s Marshall Space Flight Center.<\/p>\n

By adding polarization to the usual timing and spectral tools, the mission turns long-standing debates about neutron star emission into testable questions. <\/p>\n

This event shows the pay-off, with a clear, energy-linked polarization pattern that models must now match.<\/p>\n

The study is published in The Astrophysical Journal Letters<\/a>.<\/p>\n

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Check us out on EarthSnap<\/a>, a free app brought to you by Eric Ralls<\/a> and Earth.com.<\/p>\n

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