NuSTAR Observation of LS 5039

LS 5039 is a high-mass gamma-ray binary hosting compact object of unknown type. NuSTAR observed during its entire 3.9 day period. We performed periodic signal search up to 1000 Hz which did not produce credible period candidates. do see the 9.05 s candidate, originally reported by Yoneda et al. 2020 using same data, in Fourier power spectrum, but we find that statistical significance this feature too low claim it as real detection. also significant bursts or quasi-periodic variability. The modulation with orbital clearly seen and remains unchanged over decade long timescale when compared earlier Suzaku light curve. joint analysis XIS data shows 0.7-70 keV spectrum can be satisfactory described single absorbed power-law model no evidence cutoff at higher energies. slope anti-correlates flux orbit. Therefore, if hosts young neutron star, X-ray pulsations appear outshined intrabinary shock emission. lack spectral lines and/or an exponential energies suggests putative star actively accreting. Although black hole scenario still possibility, variability Fe K$\alpha$ lines, typically accompany accretion, makes less likely.