Variability in the orbital profiles of the X-ray emission of the gamma-ray binary LS I +61 303

TL;DR

This study presents the largest continuous X-ray monitoring dataset of the gamma-ray binary LS I +61 303, revealing variability in its orbital X-ray profiles, short flares, and confirming its orbital periodicity.

Contribution

It provides the first extensive analysis of orbital profile variability and short-term flares in LS I +61 303 using RXTE PCA data.

Findings

Detected variability in orbital X-ray profiles.

Identified short flares possibly associated with the source.

Confirmed orbital periodicity in soft X-ray data.

Abstract

We report on the analysis of Rossi X-ray Timing Explorer (RXTE) Proportional Counter Array (PCA) monitoring observations of the $\gamma$-ray binary system LS I +61 303, covering 35 full cycles of its orbital motion. This constitutes the largest continuous X-ray monitoring dataset analyzed to date for this source. Such an extended analysis allows us to report: a) the discovery of variability in the orbital profiles of the X- ray emission, b) the existence of a few (recent) short flares on top of the overall behavior typical of the source, which, given the PCA field-of-view, may or may not be associated with LS I +61 303, and c) the determination of the orbital periodicity using soft X-ray data alone.