Issue |
A&A
Volume 664, August 2022
|
|
---|---|---|
Article Number | A29 | |
Number of page(s) | 10 | |
Section | Astronomical instrumentation | |
DOI | https://doi.org/10.1051/0004-6361/202243606 | |
Published online | 03 August 2022 |
The defocused observations of bright sources with Athena/X-IFU
1
IRAP, Université de Toulouse, CNRS, UPS, CNES,
9 Avenue du Colonel Roche, BP 44346,
31028
Toulouse Cedex 4, France
e-mail: ekammoun@irap.omp.eu
2
INAF – Osservatorio Astrofisico di Arcetri,
Largo Enrico Fermi 5,
50125
Firenze, Italy
3
Centre National d’Études Spatiales (CNES),
18 Avenue Edouard Belin,
31400
Toulouse Cedex 4, France
4
Department of Physics and Astronomy, University of Leicester,
Leicester, UK
5
Dr. Karl Remeis-Observatory and Erlangen Centre for Astroparticle Physics,
Sternwartstr. 7,
96049
Bamberg, Germany
6
ESA European Space Research and Technology Centre (ESTEC),
Keplerlaan 1,
2201 AZ
Noordwijk, The Netherlands
7
Department of Astronomy, University of Michigan,
1085 South University Avenue,
Ann Arbor,
MI 48109
USA
Received:
22
March
2022
Accepted:
29
April
2022
Context. The X-ray Integral Field Unit (X-IFU) is the high resolution X-ray spectrometer of ESA’s Athena X-ray observatory. It will deliver X-ray data in the 0.2–12 keV band with an unprecedented spectral resolution of 2.5 eV up to 7 keV. During the observation of very bright X-ray sources the X-IFU detectors will receive high photon rates. The count rate capability of the X-IFU will be improved by using the defocusing option, which will enable the observations of extremely bright sources with fluxes up to ≃1 Crab. In the defocused mode, the point spread function (PSF) of the telescope will be spread over a large number of pixels. In this case each pixel receives a small fraction of the overall flux. Due to the energy dependence of the PSF, this mode will generate energy-dependent artefacts increasing with count rate if not analysed properly. To account for the degradation of the energy resolution with pulse separation in a pixel, a grading scheme (of four grades) will be defined to realize the proper energy response to each event. This will create selection effects preventing the use of the nominal auxiliary response file (ARF) for all events.
Aims. We present a new method for the reconstruction of the spectra obtained from observations performed with a PSF that varies as a function of energy. We apply our method to the case of the X-IFU spectra obtained during the defocused observations.
Methods. We used the end-to-end SIXTE simulator to model defocused X-IFU observations. Then we estimated a new ARF for each of the grades by calculating the effective area at the level of each pixel.
Results. Our method allows us to successfully reconstruct the spectra of bright sources when employed in the defocused mode, without any bias. Finally, we address how various sources of uncertainty related to our knowledge of the PSF as a function of energy affect our results.
Key words: techniques: spectroscopic / instrumentation: detectors / X-rays: general
© E. S. Kammoun et al. 2022
Open Access article, published by EDP Sciences, under the terms of the Creative Commons Attribution License (https://creativecommons.org/licenses/by/4.0), which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.
This article is published in open access under the Subscribe-to-Open model. Subscribe to A&A to support open access publication.
Current usage metrics show cumulative count of Article Views (full-text article views including HTML views, PDF and ePub downloads, according to the available data) and Abstracts Views on Vision4Press platform.
Data correspond to usage on the plateform after 2015. The current usage metrics is available 48-96 hours after online publication and is updated daily on week days.
Initial download of the metrics may take a while.