%0 Journal Article
%T Broadband X-ray Properties of the Gamma-ray Binary 1FGL J1018.6-5856
%A Hongjun An
%A Eric Bellm
%A Varun Bhalerao
%A Steven E. Boggs
%A Finn E. Christensen
%A William W. Craig
%A Felix Fuerst
%A Charles J. Hailey
%A Fiona A. Harrison
%A Victoria M. Kaspi
%A Lorenzo Natalucci
%A Daniel Stern
%A John A. Tomsick
%A William W. Zhang
%J Physics
%D 2015
%I arXiv
%X We report on NuSTAR, XMM-Newton and Swift observations of the gamma-ray binary 1FGL J1018.6-5856. We measure the orbital period to be 16.544+/-0.008 days using Swift data spanning 1900 days. The orbital period is different from the 2011 gamma-ray measurement which was used in the previous X-ray study of An et al. (2013) using ~400 days of Swift data, but is consistent with a new gamma-ray solution reported in 2014. The light curve folded on the new period is qualitatively similar to that reported previously, having a spike at phase 0 and broad sinusoidal modulation. The X-ray flux enhancement at phase 0 occurs more regularly in time than was previously suggested. A spiky structure at this phase seems to be a persistent feature, although there is some variability. Furthermore, we find that the source flux clearly correlates with the spectral hardness throughout all orbital phases, and that the broadband X-ray spectra measured with NuSTAR, XMM-Newton, and Swift are well fit with an unbroken power-law model. This spectrum suggests that the system may not be accretion-powered.
%U http://arxiv.org/abs/1505.02096v2