Paterson, S., Hannah, I. G. , Grefenstette, B. W., Hudson, H. S. , Krucker, S., Glesener, L., White, S. M. and Smith, D. M. (2024) Time evolution of X-ray bright points observed with NuSTAR. Monthly Notices of the Royal Astronomical Society, 528(4), pp. 6398-6410. (doi: 10.1093/mnras/stae417)
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Abstract
We present analysis on two X-ray bright points observed over several hours during the recent solar minimum (2020 February 21 and 2020 September 12–13) with the Nuclear Spectroscopic Telescope Array (NuSTAR), a sensitive hard X-ray imaging spectrometer. This is so far the most detailed study of bright points in hard X-rays, emission which can be used to search for faint hot and/or non-thermal sources. We investigate the bright points’ time evolution with NuSTAR, and in extreme ultraviolet (EUV) and soft X-rays with Solar Dynamic Observatory/Atmospheric Imaging Assembly (SDO/AIA) and Hinode/X-Ray Telescope. The variability in the X-ray and EUV time profiles is generally not well matched, with NuSTAR detecting spikes that do not appear in EUV. We find that, for the 2020 February bright point, the increased X-ray emission during these spikes is due to material heated to ∼ 4.2–4.4 MK (found from fitting the X-ray spectrum). The 2020 September bright point also shows spikes in the NuSTAR data with no corresponding EUV signature seen by SDO/AIA, though in this case, it was due to an increase in emission measure of material at ∼ 2.6 MK and not a significant temperature change. So, in both cases, the discrepancy is likely due to the different temperature sensitivity of the instruments, with the X-ray variability difficult to detect in EUV due to cooler ambient bright point emission dominating. No non-thermal emission is detected, so we determine upper limits finding that only a steep non-thermal component between 3 and 4 keV could provide the required heating whilst being consistent with a null detection in NuSTAR.
| Item Type: | Articles |
|---|---|
| Additional Information: | SP acknowledges support from the UK’s Science and Technology Facilities Council (STFC) doctoral training grant (ST/T506102/1). IGH acknowledges support from a Royal Society University Fellowship (URF/R/180010) and STFC grant (ST/T000422/1). |
| Keywords: | Sun: X-rays, gamma rays, Sun: corona, Sun: atmosphere. |
| Status: | Published |
| Refereed: | Yes |
| Glasgow Author(s) Enlighten ID: | Paterson, Sarah and Hudson, Dr Hugh and Hannah, Dr Iain |
| Authors: | Paterson, S., Hannah, I. G., Grefenstette, B. W., Hudson, H. S., Krucker, S., Glesener, L., White, S. M., and Smith, D. M. |
| College/School: | College of Science and Engineering > School of Physics and Astronomy |
| Journal Name: | Monthly Notices of the Royal Astronomical Society |
| Publisher: | Oxford University Press |
| ISSN: | 0035-8711 |
| ISSN (Online): | 1365-2966 |
| Published Online: | 09 February 2024 |
| Copyright Holders: | Copyright © 2024 The Author(s) |
| First Published: | First published in Monthly Notices of the Royal Astronomical Society 528(4):6398–6410 |
| Publisher Policy: | Reproduced under a Creative Commons licence |
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