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<div>Dear Everyone,</div>
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<div>Mark Pearce will present recent XL-Calibur results in week's EO seminar, I highly</div>
<div>recommend the seminar to all crab, x-ray, and balloon enthusiasts.<br>
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<div>Where: A5:1003<br>
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When: Thursday 22nd of May at 13:15 <br>
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<div>Best, <br>
Haakon (on behalf of the organisers)<br>
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<div><b>Speaker: Mark Pearce<br>
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<b>Hard X-ray polarimetry of the Crab with XL-Calibur<br>
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<div>In summer 2024, the linear polarisation of hard X-ray emission from the Crab pulsar and wind nebula was measured by
<i>XL-Calibur</i>. Observations were made during a week-long stratospheric balloon flight between Sweden and Canada. The addition of polarimetry to the standard high-energy measurement techniques of spectroscopy, timing and imaging, allows systematically new
tests of source emission models. <i>XL-Calibur</i> is the most sensitive hard X-ray polarimetry mission to date, offering an order-of-magnitude improvement in signal-to-background performance compared to preceding missions. The energy range (15-80 keV) complements
the NASA/ASI IXPE mission (2-8 keV), allowing broadband studies. I will introduce the XL-Calibur mission, explain how the linear polarisation of hard X-rays is measured, and summarise results from Crab observations. Plans for further hard X-ray polarimetry
missions will be briefly described. <br>
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