A blind search for intraday gamma-ray transients with Fermi -LAT: Detections of GRB and solar emissions

Abstract

***General notes. a) I have edited to UK English convention as this most closely matches your spelling and punctuation use. b) A A uses the past tense to describe the specific steps used in a paper and the present tense to describe general methods and recent findings. Please make sure this is followed throughout the paper. For details, see Sect. 6 of the Language Guide: https://www.aanda.org/for-authors/language-editing/6-verb-tenses c) All abbreviations and acronyms are introduced at first use, once in the Abstract and again in the main text. Instrument and program names are introduced at first use (when appropriate) in the main text. All abbreviations should be used consistently. Please check throughout We present a search for intraday transient gamma -ray signals using years of the Fermi Large Area Telescope data. The search is based on a recently developed variable-size sliding-time-window (VSSTW) analysis and is aimed at studying variable gamma -ray emission from gamma-ray bursts (GRBs) and the Sun. We refined the algorithm for searches for transient sources in order to solve the search problem within a reasonable amount of CPU time. These refinements allowed us to increase the number of gamma-ray bursts, solar flares, and quiescent solar events detected with the VSSTW technique by several times compared to the previous VSSTW search. The current search revealed a new gamma -ray signal recorded with Fermi -LAT on 2018 January 12. This signal is probably from a GRB and deserves an exploration of the existing archival multiwavelength observations in order to identify it in an unambiguous way. We also report a gamma -ray signal from the solar flare on 2023 December 31 that occurred during the 25th solar cycle.