Periodic Emission from the Gamma-ray Binary 1FGL J1018.6-5856

TL;DR

This paper confirms 1FGL J1018.6-5856 as a gamma-ray binary through multi-wavelength observations, revealing its orbital modulation and suggesting many such faint systems may exist in our Galaxy.

Contribution

The study provides the first detailed multi-wavelength characterization of 1FGL J1018.6-5856, establishing it as a gamma-ray binary and highlighting the potential for discovering more such systems.

Findings

Detected 16.6-day gamma-ray modulation.

Identified variable X-ray and radio counterparts.

Confirmed optical counterpart as O6V((f)) star.

Abstract

Gamma-ray binaries are stellar systems containing a neutron star or black hole with gamma-ray emission produced by an interaction between the components. These systems are rare, even though binary evolution models predict dozens in our Galaxy. A search for gamma-ray binaries with the Fermi Large Area Telescope (LAT) shows that 1FGL J1018.6-5856 exhibits intensity and spectral modulation with a 16.6 day period. We identified a variable X-ray counterpart, which shows a sharp maximum coinciding with maximum gamma-ray emission, as well as an O6V((f)) star optical counterpart and a radio counterpart that is also apparently modulated on the orbital period. 1FGL J1018.6-5856 is thus a gamma-ray binary, and its detection suggests the presence of other fainter binaries in the Galaxy.