README for the X-IFU responses after the reformulation of the Athena mission Date: 01/06/2023 Version: 1.0 ----------------- - RMF files ----------------- Four RMF files are provided. These provide the energy resolution of the instrument under the form of dE(energy) = np.sqrt((((m*energy)**n + K**n)**(1/n))**2 + constant with m=0.27235, n=5.859, K=1.9009 and a constant to reach the desired value at 7 keV (courtesy S. Smith GSFC) The energy resolution as a function of energy is provided in the attached PNG file for illustration (Dependency_of_energy_resolution_with_energy.png). Each of the files is made such that the energy resolution at 7 keV is of 3, 3.3, 3.5 and 4eV (FWHM). Responses are sampled to 1/5 of the local energy resolution for the 3 eV case (same sampling of all responses). The name of the files are the following: new_athena_xifu_4eV_gaussian.rmf --> 4 eV RMF file new_athena_xifu_3eV_gaussian.rmf --> 3 eV RMF file new_athena_xifu_3d3eV_gaussian.rmf --> 3.3 eV RMF file new_athena_xifu_3d5eV_gaussian.rmf --> 3.5 eV RMF file ----------------- - ARF files ----------------- The ARF files provided are generated for two mirror configurations of 13 and 15 rows For more information on the mirror, see the PDF document NewAthena mirror performance (E. Kuulkers et al. v1.0 11/05/23, NewAthena_mirrorPerformance_20230510.pdf). Please contact Erik Kuulkers/Matteo Guainazzi if more information is needed. Note that the ARF files are affected by high-frequency (in energy space) numerical noise at a level ~1-2% in some specific energy ranges. ESA investigations have unveiled that the noise is driven by the number of simulated rays – even if the simulations used for the delivered products already use several tens millions rays per keV! The ESA Study Team has created and validated a new algorithm, which enable ray-tracing curves with a <1% noise. [Evidently, the effective area envelope remains unchanged.] We expect the updated effective area curves to be delivered around the end of June 2023. The nominal X-IFU configuration is considered for instrument efficiency: - Transition Edge Sensor absorbers of 1.09µm Au / 5.51µm Bi - 317µm pitch and 6.34µm gap (average pixel filling factor of 0.9604) - 2% cryogenic anticoincidence + thermal background induced deadtime - Detector yield allocatiion of 91.6% - 3 internal thermal filters and 1 external thermal filter for a total of 285nm PI / 92nm Al / 28nm Al2O3 - No contamination (response files are generated without contimation) For each configuration, five ARFs are generated - The one with the filter wheel in open position (i.e. no filter) - One with a thin optical blocking filter (150nm polyimide / 23nm Aluminum / 7nm Al2O3) with a 3% blocking factor. - One with a thick optical blocking filter (150nm polyimide / 63nm Aluminum / 7nm Al2O3) with a 3% blocking factor. - Two with a Beryllium X-ray blocking filter of thicknesses of 20µm and 100µm respectively The optimization of the filter wheel optical blocking filters is to be performed. For more information about the instrument efficiency, please refer to Barret et al. (2023), The Athena X-ray Integral Field Unit: a consolidated design for the system requirement review of the preliminary definition phase, Experimental Astronomy, Volume 55, Issue 2, p.373-426. --> https://ui.adsabs.harvard.edu/abs/2023ExA....55..373B/abstract The istrument efficiency has changed a little compared to the baseline design presented at the System Requirement Review, in particular at high-energy (it is down by 1% at 1 keV and constant at 7 keV. The main change happens at 0.35 keV where the drop of instrument efficiency is about 5%). The changes in the instrument effective area is driven primarily by the mirror, e.g. by going from 15 to 13 rows, but also by the coating assumptions. In total 20 ARFs are provided. Each of the ARFs is generated for the nominal use (w/ geometrical filling factor of the pixel) and for SIXTE (w/o geometrical filling factor) Sampling in energy is the same as the 3eV RMF. For the 13 row case, the name of the ARF files are the following: new_athena_xifu_13_rows_no_filter.arf --> filter wheel in open position new_athena_xifu_13_rows_thin_optical_filter.arf --> filter wheel with a thin optical blocking filter on new_athena_xifu_13_rows_thick_optical_filter.arf --> filter wheel with a thick optical blocking filter on new_athena_xifu_13_rows_be_filter_20um.arf --> filter wheel with a 20 micron Beryllium like filter on (to be used for bright sources) new_athena_xifu_13_rows_be_filter_100um.arf --> filter wheel with a 100 micron Beryllium like filter on (to be used for bright sources SIXTE response follow the same name conventions, with _sixte_ included, e.g. new_athena_xifu_13_rows_sixte_no_filter.arf. They will be delivered as part of the SIXTE distribution, as they should uniquely be used with SIXTE. ----------------- - Background files ----------------- Three background files are provided to simulate the non X-ray background (NXB) of the instrument. Each corresponds to an area of: - 1 pixel - 1 arcmin² - a radius of 10 arcsec (roughly a two pixel radius) The NXB spectrum has been computed for the requirement value of 5x10-3 counts s-1 cm-2 keV-1 in the 2-10 keV energy range Sampling in energy is the same as the 3 eV RMF. The names of the files are: new_athena_nxb_1pix.pha --> corresponding to 1 pixel new_athena_nxb_1amin2.pha --> corresponding to 1 arcminute square new_athena_nxb_10asec_radius.pha --> corresponding to a 10 arcsec radius ----------------- For more information please contact: - Edoardo Cucchetti (edoardo.cucchetti@cnes.fr) - X-IFU performance manager - Didier Barret (didier.barret@irap.omp.eu) - X-IFU principal investigator - Vincent Albouys (vincent.albouys@cnes.fr) - X-IFU project manager