Onboard catalogue of known X-ray sources for SVOM/ECLAIRs

Abstract

The SVOM mission under development will carry various instruments, and in particular the coded-mask telescope ECLAIRs, with a large field of view of about 2 sr, operating in the 4--150 keV energy band, whose goal is to detect high energy transients such as gamma-ray bursts. The trigger software onboard ECLAIRs will search for new hard X-ray sources appearing in the sky, as well as peculiar behaviour (e.g. strong outbursts) from known sources, in order to repoint the satellite to perform follow-up observations with its onboard narrow field of view instruments. The presence of known X-ray sources must be disentangled from the appearance of new sources. This is done with the help of an onboard source catalogue, which we present in this paper. As an input we use catalogues of X-ray sources detected by Swift/BAT and MAXI/GSC and we study the influence of the sources on ECLAIRs' background level and on the quality of the sky image reconstruction process. We show that the influence of the sources depends on the pointing direction on the sky, on the energy band and on the exposure time. In the Galactic centre, the known sources contribution largely dominates the cosmic X-ray background, which is, on the contrary, the main background in sky regions empty of strong sources. We also demonstrate the need to clean the sources contributions in order to maintain a low noise level in the sky images and to keep the threshold applied for the detection of new sources as low as possible, without introducing false triggers. We briefly describe one of our cleaning methods and its challenges. Finally, we present the overall structure of the onboard catalogue and the way it will be used to perform the source cleaning and disentangle the detections of new sources from outbursts of known sources.

arXiv commentAccepted in Astronomy & Astrophysics, section 13. Astronomical instrumentation. Additional data to be archived at CDS

References in corpus (15)

• The SIMBAD astronomical database
• HI4PI: A full-sky HI survey based on EBHIS and GASS
• The MAXI Mission on the ISS: Science and Instruments for Monitoring All Sky X-Ray Images
• The McGill Magnetar Catalog
• The 70 Month Swift-BAT All-Sky Hard X-Ray Survey
• The Swift/BAT Hard X-ray Transient Monitor
• The 105 month Swift-BAT all-sky hard X-ray survey
• The INTEGRAL/IBIS Scientific Data Analysis
• The Multi-INstrument Burst ARchive (MINBAR)
• Localization of Gamma-Ray Bursts using the Fermi Gamma-Ray Burst Monitor
• On Calibrations using the Crab Nebula and Models of the Nebular X-ray Emission
• Three years of Fermi GBM Earth Occultation Monitoring: Observations of Hard X-ray/Soft Gamma-Ray Sources
• Broad-band spectral study of X-ray transient MAXI J1820+070 using Swift/XRT and NuSTAR
• Ultra-Long Gamma-Ray Bursts detection with SVOM/ECLAIRs
• Simulations of the SVOM/ECLAIRs Dynamic Background: A fast, accurate and general approach for wide-field hard X-ray instruments

Cited by in corpus (5)

• The SVOM Mission
• Prospects for multi-messenger detection of binary neutron star mergers in the fourth LIGO-Virgo-KAGRA observing run
• Detection of short high-energy transients in the localuniverse with SVOM/ECLAIRs
• The SVOM/ECLAIRs image trigger with wavelet-based background correction optimised with a one-year simulation of observations
• Full-frame data reduction method: a data mining tool to detect the potential variations in optical photometry