Estimate of the Background and Sensitivity of theFollow-up X-ray Telescope onboard Einstein Probe

Abstract

As a space X-ray imaging mission dedicated to time-domain astrophysics, the Einstein Probe (EP) carries two kinds of scientific payloads, the wide-field X-ray telescope (WXT) and the follow-up X-ray telescope (FXT). FXT utilizes Wolter-I type mirrors and the pn-CCD detectors. In this work, we investigate the in-orbit background of FXT based on Geant4 simulation. The impact of various space components present in the EP orbital environment are considered, such as the cosmic photon background, cosmic ray primary and secondary particles (e.g. protons, electrons and positrons), albedo gamma rays, and the low-energy protons near the geomagnetic equator. The obtained instrumental background at 0.5-10 keV, which is mainly induced by cosmic ray protons and cosmic photon background, corresponds to a level of $\sim$3.1$\times$10${}^{-2}$ counts s${}^{-1}$ keV${}^{-1}$ in the imaging area of the focal plane detector (FPD), i.e. 3.7$\times$10${}^{-3}$ counts s${}^{-1}$ keV${}^{-1}$ cm${}^{-2}$ after normalization. Compared with the instrumental background, the field of view (FOV) background, which is induced by cosmic photons reflected by the optical mirror, dominates below 2 keV. Based on the simulated background level within the focal spot (a 30${}^{\prime \prime }$-radius circle), the sensitivity of FXT is calculated, which could theoretically achieve several $\mu$crab (in the order of 10${}^{-14}$ erg cm${}^{-2}$ s${}^{-1}$) in 0.5-2 keV and several tens of $\mu$crab (in the order of 10${}^{-13}$ erg cm${}^{-2}$ s${}^{-1}$) in 2-10 keV for a pointed observation with an exposure of 25 minutes. This sensitivity becomes worse by a factor of $\sim 2$ if additional 10% systematic uncertainty of the background subtraction is included.

38 pages, 19 figures, accepted for publication in Astroparticle Physics

References in corpus (7)

• The eROSITA X-ray telescope on SRG
• Perspectives on Gamma-Ray Burst Physics and Cosmology with Next Generation Facilities
• Geant4 Simulations Of A Wide-Angle X-Ray Focusing Telescope
• X-ray tracing using Geant4
• Monte Carlo simulations of soft proton flares: testing the physics with XMM-Newton
• Comparison of simulated backgrounds with in-orbit observations for HE, ME and LE onboard Insight-HXMT
• Soft proton scattering at grazing incidence from X-ray mirrors: analysis of experimental data in the framework of the non-elastic approximation

Cited by in corpus (14)

• The Einstein Probe Mission
• Science objectives of the Einstein Probe mission
• Tidal Stripping of a White Dwarf by an Intermediate-Mass Black Hole
• Observing white dwarf tidal stripping with TianQin gravitational wave observatory
• Simulation Studies for the First Pathfinder of the CATCH Space Mission
• Target Detection Framework for Lobster Eye X-Ray Telescopes with Machine Learning Algorithms
• In-orbit background simulation of a type-B CATCH satellite
• X-ray Sources Classification Using Machine Learning: A Study with EP-WXT Pathfinder LEIA
• Measuring the Cosmic X-ray Background accurately
• Imaging-spectroscopy diagnosis of the giant sloshing spiral in the Virgo cluster with the Einstein Probe Follow-up X-ray Telescope
• A Complete X-ray View of Supernova Remnant W28 with Einstein Probe: Spatial Distribution of Parameters and Origin of the Thermal-Composite Morphology
• Probing millisecond magnetar formation in binary neutron star mergers through X-ray follow-up of gravitational wave alerts
• Planetary Nebulae in the eROSITA eRASS1 catalog
• Predicting Multiwavelength Emission Associated with X-Ray Flares and Extended Emission of Gamma-Ray Bursts