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arXiv · 2202.01093

A weighted analysis to improve the X-ray polarization sensitivity of IXPE

Alessandro Di Marco·Enrico Costa·Fabio Muleri·Paolo Soffitta·Sergio Fabiani·Fabio La Monaca·John Rankin·Fei Xie·Matteo Bachetti·Luca Baldini·Wayne Baumgartner·Ronaldo Bellazzini·Alessandro Brez·Simone Castellano·Ettore Del Monte·Niccolò Di Lalla·Riccardo Ferrazzoli·Luca Latronico·Simone Maldera·Alberto Manfreda·Stephen L. O'Dell·Matteo Perri·Melissa Pesce-Rollins·Simonetta Puccetti·Brian D. Ramsey·Ajay Ratheesh·Carmelo Sgrò·Gloria Spandre·Allyn F. Tennant·Antonino Tobia·Alessio Trois·Martin C. Weisskopf
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Abstract

IXPE is a Small Explorer mission that was launched at the end of 2021 to measure the polarization of X-ray emission from tens of astronomical sources. Its focal plane detectors are based on the Gas Pixel Detector, which measures the polarization by imaging photoelectron tracks in a gas mixture and reconstructing their initial directions. The quality of the single track, and then the capability of correctly determining the original direction of the photoelectron, depends on many factors, e.g., whether the photoelectron is emitted at low or high inclination with respect to the collection plane or the occurrence of a large Coulomb scattering close to the generation point. The reconstruction algorithm used by IXPE to obtain the photoelectron emission direction, also calculates several properties of the shape of the tracks which characterize the process. In this paper we compare several such properties and identify the best one to weight each track on the basis of the reconstruction accuracy. We demonstrate that significant improvement in sensitivity can be achieved with this approach and for this reason it will be the baseline for IXPE data analysis.

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Alessandro Di Marco, Enrico Costa, Fabio Muleri, Paolo Soffitta, Sergio Fabiani, Fabio La Monaca, John Rankin, Fei Xie, Matteo Bachetti, Luca Baldini, Wayne Baumgartner, Ronaldo Bellazzini, Alessandro Brez, Simone Castellano, Ettore Del Monte, Niccolò Di Lalla, Riccardo Ferrazzoli, Luca Latronico, Simone Maldera, Alberto Manfreda, Stephen L. O'Dell, Matteo Perri, Melissa Pesce-Rollins, Simonetta Puccetti, Brian D. Ramsey, Ajay Ratheesh, Carmelo Sgrò, Gloria Spandre, Allyn F. Tennant, Antonino Tobia, Alessio Trois, Martin C. Weisskopf. 2022-02-02. A weighted analysis to improve the X-ray polarization sensitivity of IXPE. https://doi.org/10.3847/1538-3881%2Fac51c9

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