Search for gamma rays from SNe with a variable-size sliding-time-window analysis of the Fermi-LAT data

TL;DR

This study systematically searched for gamma-ray emissions from supernovae using Fermi-LAT data, discovering new transient signals and confirming variable gamma-ray activity near known sources, advancing understanding of high-energy phenomena associated with SNe.

Contribution

Introduces a variable-size sliding-time-window analysis method to detect gamma-ray transients from a large supernova candidate sample, identifying new gamma-ray transient signals and confirming variable activity.

Findings

Detected two new gamma-ray transients near SN candidates in 2019.

Confirmed variable gamma-ray signals from known sources like SN iPTF14hls.

Identified additional gamma-ray transient candidates through all-sky search.

Abstract

We present a systematic search for gamma-ray emission from supernovae (SNe) in the Fermi Large Area Telescope (LAT) Pass 8 data. The sample of targets consists of 55,880 candidates from the Open Supernova Catalog. We searched for gamma rays from SNe by means of a variable-size sliding-time-window analysis. Our results confirm the presence of transient gamma-ray emission from the sources of non-AGN classes, including transitional pulsars, solar flares, gamma-ray bursts, novae, and the Crab Nebula, which are projected near some of these SN's positions, and also strengthen support to the variable signal in the direction of SN iPTF14hls. The analysis is successful in finding both short (e.g. solar flares) and long (e.g. transitional pulsars) high flux states. Our search reveals two new gamma-ray transient signals occurred in 2019 in the directions of optical transients that are SN candidates, AT2019bvr and AT2018iwp, with their flux increases within 6 months after the dates of SN's discoveries. These signals are bright and their variability is at a higher statistical level than that of iPTF14hls. An exploration of archival multi-wavelength observations towards their positions is necessary to establish their association with SNe or other classes of sources. Our analysis, in addition, shows a bright transient gamma-ray signal at low Galactic latitudes in the direction of PSR J0205+6449. In addition, we report the results of an all-sky search for gamma-ray transient sources. This provided two additional candidates to gamma-ray transient sources.