A search for cyclical sources of gamma-ray emission on the period range from days to years in the Fermi-LAT sky

TL;DR

This study systematically searches for periodic gamma-ray emissions in the Fermi-LAT sky across days to years, confirming known periodic sources and identifying new potential binary systems of supermassive black holes at high redshifts.

Contribution

It introduces a comprehensive method using pixel-based Lomb-Scargle periodograms to detect cyclical gamma-ray sources across a wide period range in the sky.

Findings

Confirmed periodicities in three binaries and three blazars.

Detected evidence of periodic behavior in four additional blazars.

Identified high-redshift blazars as potential supermassive black hole binaries.

Abstract

A systematic search for cyclical sources of gamma-ray emission on the period range from days to years in the Fermi-LAT sky is performed. Looking for cyclical emission, the sky is binned into equal-area pixels and the generalised Lomb-Scargle periodogram is computed for each of these pixels. The search on the period range between 2.5 and 30 days in the Galactic plane confirms periodicities of three binaries, LSI +61 303, LS 5039, and 1FGL J1018.6-5856. The all-sky search on the period range between 30 days and 2.5 years confirms periodicities of three blazars, PG 1553+113, PKS 2155-304, and BL Lacertae. Evidence for periodic behaviours of four blazars, 4C +01.28, S5 0716+71, PKS 0805-07, and PKS 2052-47, are presented. Three of these blazars, 4C +01.28, PKS 0805-07, and PKS 2052-47, are located at high redshifts. These three sources are potential candidates to binary systems of supermassive black holes provided that major galaxy mergers are more frequent and that galaxies are more gas-rich at high redshifts.