INTEGRAL observation of hard X-ray variability of the TeV binary LS5039 / RX J1826.2-1450

TL;DR

This study uses INTEGRAL satellite data to analyze the hard X-ray variability of the TeV binary LS5039, revealing orbital modulation in its emission and correlating it with TeV observations.

Contribution

First detailed analysis of hard X-ray spectral and timing properties of LS5039 across its orbit using INTEGRAL data, linking X-ray and TeV emission variability.

Findings

Hard X-ray emission detected from 25 to 200 keV.

Orbital variability in X-ray emission matches TeV modulation.

Power-law spectrum with index ~2 during inferior conjunction.

Abstract

LS 5039/RX J1826.2-1450 is one of the few High Mass X-ray binary systems from which radio and high energy TeV emission has been observed. Moreover, variability of the TeV emission with orbital period was detected. We investigate the hard X-ray (25 - 200keV) spectral and timing properties of the source with the monitoring IBIS/ISGRI instrument on-board the INTEGRAL satellite. We present the analysis of INTEGRAL observations for a total of about 3 Msec exposure time, including both public data and data from the Key Programme. We search for flux and spectral variability related to the orbital phase. The source is observed to emit from 25 up to 200 keV and the emission is concentrated around inferior conjunction. Orbital variability in the hard X-ray band is detected and established to be in phase with the orbitally modulated TeV emission observed with H.E.S.S. For this energy range we determine an average flux for the inferior conjunction phase interval of $(3.54 \pm 2.30) \times 10^{-11}$ erg cm$^{-2}$ s$^{-1}$, and a flux upper limit for the superior conjunction phase interval of $1.45 \times 10^{-11}$ erg cm$^{-2}$ s$^{-1}$ (90% conf. level respectively). The spectrum for the inferior conjunction phase interval follows a power law with an index $\Gamma = 2.0^{+0.2}_{-0.2} $ (90% conf. level).