Detection capability of Ultra-Long Gamma-Ray Bursts with the ECLAIRs telescope aboard the SVOM mission

Ultra-long gamma-ray bursts (ULGRBs) have very atypical durations of more than 2000 seconds. Even if their origins are discussed, the SVOM mission with its soft gamma-ray telescope ECLAIRs could detect ULGRBs and increase the sample of the few which have been detected so far by the Burst Alert Telescope aboard the Neil Gehrels Swift Observatory and some other instruments. In this paper, after a short description of the SVOM mission, we present methods developed to clean detector images from non-flat background and known source contributions in the onboard imaging process. We present an estimate of the ECLAIRs sensitivity to GRBs of various durations. Finally we study the capability of the image-trigger to detect ULGRBs.