Abstract
Abstract The Gas Pixel Detector (GPD) is an X-ray polarimeter to fly onboard IXPE and other missions. To correctly measure the source polarization, the response of IXPE’s GPDs to unpolarized radiation has to be calibrated and corrected. In this paper, we describe the way such response is measured with laboratory sources and the algorithm to apply such correction to the observations of celestial sources. The latter allows to correct the response to polarization of single photons, therefore allowing great flexibility in all the subsequent analysis. Our correction approach is tested against both monochromatic and nonmonochromatic laboratory sources and with simulations, finding that it correctly retrieves the polarization up to the statistical limits of the planned IXPE observations.
Highlights
Astronomical X-ray polarimetry has up until now seen significative detections only of the Crab Nebula (Weisskopf et al 1978; Feng et al 2020), but this unexplored window will soon be reopened thanks to the Imaging X-ray Polarimetry Explorer (IXPE) mission (Weisskopf et al 2016; Soffitta et al 2021), with the onboard polarizationsensitive Gas Pixel Detector (GPD; Costa et al 2001; Bellazzini et al 2006, 2007)
IXPE’s GPDs—and often other real X-ray polarimeters—show systematic effects that mimic the signal generated by a genuine source polarization even for truly unpolarized radiation (Baldini et al 2021)
We describe the algorithm to calibrate and correct the response of IXPE’s GPDs to unpolarized radiation in order to remove the spurious instrumental signal, referred to as spurious modulation
Summary
Astronomical X-ray polarimetry has up until now seen significative detections only of the Crab Nebula (Weisskopf et al 1978; Feng et al 2020), but this unexplored window will soon be reopened thanks to the IXPE mission (Weisskopf et al 2016; Soffitta et al 2021), with the onboard polarizationsensitive Gas Pixel Detector (GPD; Costa et al 2001; Bellazzini et al 2006, 2007). Due to the characteristics of this effect, and to facilitate its correction, part of it will be compensated by the fact that IXPE’s observations will be dithered (i.e., the pointing direction of the telescope will oscillate during the observations, distributing source photons over a relatively large region, nearly uniformly illuminated and centered on the field of view) The remainder of these systematic effects need to be calibrated The testing of this algorithm applied to.
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Free) 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a call
