The Multi-wavelength Characteristics of the TeV Binary LS I +61$^\circ$ 303

TL;DR

This study analyzes the multi-wavelength variability of the TeV binary LS I +61° 303 across radio to gamma-ray energies, revealing periodic long-term changes linked to a jet-dominated emission mechanism and suggesting it is a micro-quasar.

Contribution

It provides a comprehensive phase-dependent analysis of LS I +61° 303's emission across multiple wavelengths, proposing a jet-based emission model and classifying it as a micro-quasar.

Findings

Long-term variability follows a sine function of the super orbital period.

Variability phase and amplitude depend on the binary phase.

Emission is dominated by a jet structure with systematic variations.

Abstract

We study the characteristics of the TeV binary LS I +61$^\circ$ 303 in radio, soft X-ray, hard X-ray, and gamma-ray (GeV and TeV) energies. The long term variability characteristics are examined as a function of the phase of the binary period of 26.496 days as well as the phase of the super orbital period of 1626 days, dividing the observations into a matrix of 10$\times$10 phases of these two periods. It is found that the long term variability can be described by a sine function of the super orbital period, with the phase and amplitude systematically varying with the binary period phase. We also find a definite wavelength dependent change in this variability description. To understand the radiation mechanism, we define three states in the orbital/ super orbital phase matrix and examine the wide band spectral energy distribution. The derived source parameters indicate that the emission geometry is dominated by a jet structure showing a systematic variation with the orbital/ super orbital period. We suggest that LS I +61$^\circ$ 303 is likely to be a micro-quasar with a steady jet.