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arXiv · 2010.10608

XL-Calibur -- a second-generation balloon-borne hard X-ray polarimetry mission

Q. Abarr·H. Awaki·M. G. Baring·R. Bose·G. De Geronimo·P. Dowkontt·M. Errando·V. Guarino·K. Hattori·K. Hayashida·F. Imazato·M. Ishida·N. K. Iyer·F. Kislat·M. Kiss·T. Kitaguchi·H. Krawczynski·L. Lisalda·H. Matake·Y. Maeda·H. Matsumoto·T. Mineta·T. Miyazawa·T. Mizuno·T. Okajima·M. Pearce·B. F. Rauch·F. Ryde·C. Shreves·S. Spooner·T. -A. Stana·H. Takahashi·M. Takeo·T. Tamagawa·K. Tamura·H. Tsunemi·N. Uchida·Y. Uchida·A. T. West·E. A. Wulf·R. Yamamoto
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Abstract

XL-Calibur is a hard X-ray (15-80 keV) polarimetry mission operating from a stabilised balloon-borne platform in the stratosphere. It builds on heritage from the X-Calibur mission, which observed the accreting neutron star GX 301-2 from Antarctica, between December 29th 2018 and January 1st 2019. The XL-Calibur design incorporates an X-ray mirror, which focusses X-rays onto a polarimeter comprising a beryllium rod surrounded by Cadmium Zinc Telluride (CZT) detectors. The polarimeter is housed in an anticoincidence shield to mitigate background from particles present in the stratosphere. The mirror and polarimeter-shield assembly are mounted at opposite ends of a 12 m long lightweight truss, which is pointed with arcsecond precision by WASP - the Wallops Arc Second Pointer. The XL-Calibur mission will achieve a substantially improved sensitivity over X-Calibur by using a larger effective area X-ray mirror, reducing background through thinner CZT detectors, and improved anticoincidence shielding. When observing a 1 Crab source for $t_{\rm day}$ days, the Minimum Detectable Polarisation (at 99% confidence level) is $\sim$2$\%\cdot t_{\rm day}^{-1/2}$. The energy resolution at 40 keV is $\sim$5.9 keV. The aim of this paper is to describe the design and performance of the XL-Calibur mission, as well as the foreseen science programme.

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Q. Abarr, H. Awaki, M. G. Baring, R. Bose, G. De Geronimo, P. Dowkontt, M. Errando, V. Guarino, K. Hattori, K. Hayashida, F. Imazato, M. Ishida, N. K. Iyer, F. Kislat, M. Kiss, T. Kitaguchi, H. Krawczynski, L. Lisalda, H. Matake, Y. Maeda, H. Matsumoto, T. Mineta, T. Miyazawa, T. Mizuno, T. Okajima, M. Pearce, B. F. Rauch, F. Ryde, C. Shreves, S. Spooner, T. -A. Stana, H. Takahashi, M. Takeo, T. Tamagawa, K. Tamura, H. Tsunemi, N. Uchida, Y. Uchida, A. T. West, E. A. Wulf, R. Yamamoto. 2020-10-20. XL-Calibur -- a second-generation balloon-borne hard X-ray polarimetry mission. https://doi.org/10.1016/j.astropartphys.2020.102529

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