Hannah, I. G. et al. (2016) The first X-ray imaging spectroscopy of quiescent solar active regions with NuSTAR. Astrophysical Journal Letters, 280, 1. (doi: 10.3847/2041-8205/820/1/L14)
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Abstract
We present the first observations of quiescent active regions (ARs) using the Nuclear Spectroscopic Telescope Array (NuSTAR), a focusing hard X-ray telescope capable of studying faint solar emission from high-temperature and non-thermal sources. We analyze the first directly imaged and spectrally resolved X-rays above 2 keV from non-flaring ARs, observed near the west limb on 2014 November 1. The NuSTAR X-ray images match bright features seen in extreme ultraviolet and soft X-rays. The NuSTAR imaging spectroscopy is consistent with isothermal emission of temperatures 3.1–4.4 MK and emission measures 1–8 × 1046 cm−3. We do not observe emission above 5 MK, but our short effective exposure times restrict the spectral dynamic range. With few counts above 6 keV, we can place constraints on the presence of an additional hotter component between 5 and 12 MK of cm−3 and cm−3, respectively, at least an order of magnitude stricter than previous limits. With longer duration observations and a weakening solar cycle (resulting in an increased livetime), future NuSTAR observations will have sensitivity to a wider range of temperatures as well as possible non-thermal emission.
| Item Type: | Articles |
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| Status: | Published |
| Refereed: | Yes |
| Glasgow Author(s) Enlighten ID: | Hannah, Dr Iain |
| Authors: | Hannah, I. G., Grefenstette, B. W., Smith, D. M., Glesener, L., Krucker, S., Hudson, H. S., Madsen, K. K., Marsh, A., White, S. M., Caspi, A., Shih, A. Y., Harrison, F. A., Stern, D., Boggs, S. E., Christensen, F. E., Craig, W. W., Hailey, C. J.,, and Zhang, W. W. |
| College/School: | College of Science and Engineering > School of Physics and Astronomy |
| Journal Name: | Astrophysical Journal Letters |
| Publisher: | IOP Publishing |
| ISSN: | 2041-8205 |
| ISSN (Online): | 2041-8213 |
| Copyright Holders: | Copyright © 2016 The American Astronomical Society |
| First Published: | First published in Astrophysical Journal Letters 288:1 |
| Publisher Policy: | Reproduced with permission of publisher |
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