Timing Calibration of the NuSTAR X-ray Telescope. (arXiv:2009.10347v3 [astro-ph.IM] UPDATED)
<a href="http://arxiv.org/find/astro-ph/1/au:+Bachetti_M/0/1/0/all/0/1">Matteo Bachetti</a> (1 and 2), <a href="http://arxiv.org/find/astro-ph/1/au:+Markwardt_C/0/1/0/all/0/1">Craig B. Markwardt</a> (3), <a href="http://arxiv.org/find/astro-ph/1/au:+Grefenstette_B/0/1/0/all/0/1">Brian W. Grefenstette</a> (2), <a href="http://arxiv.org/find/astro-ph/1/au:+Gotthelf_E/0/1/0/all/0/1">Eric V. Gotthelf</a> (4), <a href="http://arxiv.org/find/astro-ph/1/au:+Kuiper_L/0/1/0/all/0/1">Lucien Kuiper</a> (5), <a href="http://arxiv.org/find/astro-ph/1/au:+Barret_D/0/1/0/all/0/1">Didier Barret</a> (6), <a href="http://arxiv.org/find/astro-ph/1/au:+Cook_W/0/1/0/all/0/1">W. Rick Cook</a> (2), <a href="http://arxiv.org/find/astro-ph/1/au:+Davis_A/0/1/0/all/0/1">Andrew Davis</a> (2), <a href="http://arxiv.org/find/astro-ph/1/au:+Furst_F/0/1/0/all/0/1">Felix Fürst</a> (7), <a href="http://arxiv.org/find/astro-ph/1/au:+Forster_K/0/1/0/all/0/1">Karl Forster</a> (2), <a href="http://arxiv.org/find/astro-ph/1/au:+Harrison_F/0/1/0/all/0/1">Fiona A. Harrison</a> (2), <a href="http://arxiv.org/find/astro-ph/1/au:+Madsen_K/0/1/0/all/0/1">Kristin K. Madsen</a> (2 and 3), <a href="http://arxiv.org/find/astro-ph/1/au:+Miyasaka_H/0/1/0/all/0/1">Hiromasa Miyasaka</a> (2), <a href="http://arxiv.org/find/astro-ph/1/au:+Roberts_B/0/1/0/all/0/1">Bryce Roberts</a> (8), <a href="http://arxiv.org/find/astro-ph/1/au:+Tomsick_J/0/1/0/all/0/1">John A. Tomsick</a> (8), <a href="http://arxiv.org/find/astro-ph/1/au:+Walton_D/0/1/0/all/0/1">Dominic J. Walton</a> (9) ((1) INAF-Osservatorio Astronomico di Cagliari, Italy, (2) Caltech, USA, (3) NASA-Goddard, USA, (4) Columbia University, USA, (5) SRON, The Netherlands, (6) IRAP, France, (7) ESAC, Spain, (8) UC Berkeley, USA, (9) U. Cambridge, UK)
The Nuclear Spectroscopic Telescope Array (NuSTAR) mission is the first
focusing X-ray telescope in the hard X-ray (3-79 keV) band. Among the phenomena
that can be studied in this energy band, some require high time resolution and
stability: rotation-powered and accreting millisecond pulsars, fast variability
from black holes and neutron stars, X-ray bursts, and more. Moreover, a good
alignment of the timestamps of X-ray photons to UTC is key for multi-instrument
studies of fast astrophysical processes. In this Paper, we describe the timing
calibration of the NuSTAR mission. In particular, we present a method to
correct the temperature-dependent frequency response of the on-board
temperature-compensated crystal oscillator. Together with measurements of the
spacecraft clock offsets obtained during downlinks passes, this allows a
precise characterization of the behavior of the oscillator. The calibrated
NuSTAR event timestamps for a typical observation are shown to be accurate to a
precision of ~65 microsec.
The Nuclear Spectroscopic Telescope Array (NuSTAR) mission is the first
focusing X-ray telescope in the hard X-ray (3-79 keV) band. Among the phenomena
that can be studied in this energy band, some require high time resolution and
stability: rotation-powered and accreting millisecond pulsars, fast variability
from black holes and neutron stars, X-ray bursts, and more. Moreover, a good
alignment of the timestamps of X-ray photons to UTC is key for multi-instrument
studies of fast astrophysical processes. In this Paper, we describe the timing
calibration of the NuSTAR mission. In particular, we present a method to
correct the temperature-dependent frequency response of the on-board
temperature-compensated crystal oscillator. Together with measurements of the
spacecraft clock offsets obtained during downlinks passes, this allows a
precise characterization of the behavior of the oscillator. The calibrated
NuSTAR event timestamps for a typical observation are shown to be accurate to a
precision of ~65 microsec.
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