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Measurement of the Absolute Crab Flux with NuSTAR

Madsen, Kristin K. and Forster, Karl and Grefenstette, Brian W. and Harrison, Fiona A. and Stern, Daniel (2017) Measurement of the Absolute Crab Flux with NuSTAR. Astrophysical Journal, 841 (1). Art. No. 56. ISSN 1538-4357.

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We present results from a Nuclear Spectroscopic Telescope Array (NuSTAR) observation of the Crab made at a large off-axis angle of 1 5. At these angles, X-rays do not pass through the optics and instead illuminate the detectors directly, due to incomplete baffling. Due to the simplicity of the instrument response in this configuration and the good absolute calibration of the detectors, we are able to measure the absolute intrinsic flux of the Crab to better than 4%. We find the spectral parameters of the power law to be Γ = 2.106 ± 0.006, N = 9.71 ± 0.16, in agreement with the values measured 42 years ago by Toor & Seward. This suggests that the observed variability of the Crab is not part of a long-term trend, but instead results from fluctuations around a steady mean. The NuSTAR observation also enabled improved measurement of the detector absorption parameters without the added complications of the mirror response.

Item Type:Article
Related URLs:
URLURL TypeDescription Paper
Madsen, Kristin K.0000-0003-1252-4891
Forster, Karl0000-0001-5800-5531
Grefenstette, Brian W.0000-0002-1984-2932
Harrison, Fiona A.0000-0003-2992-8024
Stern, Daniel0000-0003-2686-9241
Additional Information:© 2017 The American Astronomical Society. Received 2017 January 9; revised 2017 March 10; accepted 2017 March 23; published 2017 May 23. We thank the referee for the helpful comments and suggestions. This work was supported under NASA Contract No. NNG08FD60C, and made use of data from the NuSTAR mission, a project led by the California Institute of Technology, managed by the Jet Propulsion Laboratory, and funded by the National Aeronautics and Space Administration. We thank the NuSTAR Operations, Software and Calibration teams for support with the execution and analysis of these observations. This research has made use of the NuSTAR Data Analysis Software (NuSTARDAS) jointly developed by the ASI Science Data Center (ASDC, Italy) and the California Institute of Technology (USA). Facilities: CXO, NuSTAR, Swift, Suzaku, and XMM.
Group:NuSTAR, Space Radiation Laboratory, Astronomy Department
Funding AgencyGrant Number
Subject Keywords:space vehicles: instruments; X-rays: individual (Crab)
Issue or Number:1
Record Number:CaltechAUTHORS:20170523-091449570
Persistent URL:
Official Citation:Kristin K. Madsen et al 2017 ApJ 841 56
Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:77650
Deposited By: Tony Diaz
Deposited On:23 May 2017 16:32
Last Modified:04 Dec 2019 23:47

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