We present results of the point spread function (PSF) calibration of the hard X-ray optics of the Nuclear Spectroscopic Telescope Array (NuSTAR). Immediately post-launch, NuSTAR has observed bright point sources such as Cyg X-1, Vela X-1, and Her X-1 for the PSF calibration. We use the point source observations taken at several off-axis angles together with a ray-trace model to characterize the in-orbit angular response, and find that the ray-trace model alone does not fit the observed event distributions and applying empirical corrections to the ray-trace model improves the fit significantly. We describe the corrections applied to the ray-trace model and show that the uncertainties in the enclosed energy fraction (EEF) of the new PSF model is < 3% for extraction apertures of R > 60" with no significant energy dependence. We also show that the PSF of the NuSTAR optics has been stable over a period of ~300 days during its in-orbit operation.
@article{arxiv.1406.7419,
title = {In-flight PSF calibration of the NuSTAR hard X-ray optics},
author = {Hongjun An and Kristin K. Madsen and Niels J. Westergaard and Steven E. Boggs and Finn E. Christensen and William W. Craig and Charles J. Hailey and Fiona A. Harrison and Daniel K. Stern and William W. Zhang},
journal= {arXiv preprint arXiv:1406.7419},
year = {2015}
}
Comments
10 pages, 6 figures. Presented at the SPIE conference Astronomical Telescopes + Instrumentation 2014