NuSTAR observation of X-ray pulsar 1E 1145.1−6141

Abstract

ABSTRACT In this work, we report on hard X-ray observations of the X-ray pulsar 1E 1145.1−6141 performed with the Nuclear Spectroscopic Telescope Array mission (NuSTAR). Coherent pulsation of the source with a period of $\sim \! 296.653\, \pm \, 0.021\, \mathrm{ s}$ is detected. The source may be in the equilibrium phase, according to the most recent measurements of its pulse period. The pulse profile reveals a mild energy dependence and generally hints at a pencil-beam pattern. The pulse profile has evolved with time. The pulse fraction is found to depend on energy, with a fall in value at $\sim \! 32\, \mathrm{ keV}$. The NuSTAR spectra can be approximated by a composite model with two continuum components, blackbody emission, a cut-off power law, and a discrete component in the form of a Gaussian to account for the emission line of iron. The estimated absorbed flux of the source is $\sim \! 6\times 10^{-10}\, \mathrm{ erg}\, \mathrm{ cm}^{-2}\, \mathrm{ s}^{-1}$, which corresponds to a luminosity of $\sim \! 5\times 10^{36}\, \mathrm{ erg}\, \mathrm{ s}^{-1}$. Pulse phase-resolved spectroscopy was performed to understand the evolution of the spectral parameters with pulse phase. The estimated blackbody radius is found to be consistent with the size of the theoretical prediction.