arXiv subjects

Luca Castaldini

Publications and source records attributed to Luca Castaldini.

3 recordsLinked to original sources

arXiv2025

SAG-SCI: the Real-time, High-level Analysis Software for Array Control and Data Acquisition of the Cherenkov Telescope Array Observatory

The Cherenkov Telescope Array Observatory (CTAO) is going to be the leading observatory for very-high-energy gamma-rays over the next decades. Its unique sensitivity, wide field of view, and rapid slewing capability make the CTAO especially suited to study transient astrophysical phenomena. The CTAO will analyse its data in real-time, responding to external science alerts on transient events and issuing its own. The Science Alert Generation (SAG) automated pipeline, a component of the Array Control and Data Acquisition (ACADA) software, is designed to detect and issue candidate science alerts. In this work, we present the current development status of SAG-SCI, the SAG component responsible for the real-time, high-level analysis of CTAO data. The SAG-SCI pipelines receive gamma-ray data from multiple reconstruction lines, merge them, store them in a database, and trigger several parallel scientific analyses on the latest data. These analyses include estimating target significance and flux, producing sky maps and light curves, and conducting blind searches for sources within the field of view. We execute SAG-SCI on a set of simulated gamma-ray data, detecting the simulated sources and accurately reconstructing their flux and position. We also estimate the systematic errors introduced by the analysis and discuss the results in relation to the generation of candidate science alerts.

astro-ph.HE↗

arXiv2025

The new architecture design of the Science Alert Generation pipeline of the Cherenkov Telescope Array Observatory

The Cherenkov Telescope Array Observatory (CTAO) represents the next-generation gamma-ray observatory and will operate for several decades. It will be particularly suited to analyse transients and variable phenomena, which will trigger real-time scientific alerts. To support this, the Science Alert Generation (SAG) pipeline within the Array Control and Data Acquisition (ACADA) system will process data from telescope arrays in real time, using dedicated pipelines for data reconstruction (SAG-RECO), data quality monitoring (SAG-DQ) and science monitoring (SAG-SCI). The Supervisor (SAG-SUP) oversees the dynamic operations of SAG and its integration with other ACADA components. SAG is designed to issue candidate science alerts within 20 s of data availability, processing events on multiple time scales (seconds to hours) and handling trigger rates of tens of kHz. Meeting these requirements necessitates optimised software and hardware architectures. This work presents recent developments in SAG's architecture, aimed at two main challenges: (1) selecting data only from telescopes that have entered a stable tracking state, even when they begin tracking at different times during multi-telescope observations, and (2) incorporating environmental and system monitoring information to ensure high data quality. SAG-SUP can retrieve real-time telescope status and environmental conditions from telescope managers and the weather station through the ACADA Monitoring system, collect them in a database and then use them to filter out data from slewing phases or degraded conditions. These enhancements are crucial to ensure the reliability of science alerts and improve the overall performance and responsiveness of the CTAO real-time analysis framework.

astro-ph.IM↗

arXiv2024

Towards a response function for the COSI anticoincidence system: preliminary results from Geant4 simulations

The Compton Spectrometer and Imager (COSI) is an upcoming NASA Small Explorer satellite mission scheduled for launch in 2027 and designed to conduct an all-sky survey in the energy range of 0.2-5 MeV. Its instrument consists of an array of germanium detectors surrounded on four sides and underneath by active shields that work as anticoincidence system (ACS) to reduce the contribution of background events in the detectors. These shields are composed of bismuth germanium oxide (BGO), a scintillator material, coupled with Silicon photomultipliers, aimed to collect optical photons produced from interaction of ionizing particles in the BGO and convert them into an electric signal. The reference simulation framework for COSI is MEGAlib, a set of software tools based on the Geant4 toolkit. The interaction point of the incoming radiation, the design of the ACS modules and the BGO surface treatment change the light collection and the overall shielding accuracy. The use of the Geant4 optical physics library, with the simulation of the scintillation process, is mandatory for a more realistic evaluation of the ACS performances. However, including the optical processes in MEGAlib would dramatically increase the computing time of the COSI simulations. We propose the use of a response function encoding the energy resolution and 3D light yield correction based on a separate Geant4 simulation of the ACS that includes the full optical interaction. We present the verification of the Geant4 optical physics library against analytical computations and available laboratory measurements obtained using PMTs as readout device, as a preparatory phase for the simulation of the COSI ACS response.

astro-ph.IM↗