THE FIRST X-RAY IMAGING SPECTROSCOPY of QUIESCENT SOLAR ACTIVE REGIONS with NuSTAR

Iain G. Hannah; Brian W. Grefenstette; David M. Smith; Lindsay Glesener; Säm Krucker; Hugh S. Hudson; Kristin K. Madsen; Andrew Marsh; Stephen M. White; Amir Caspi; Albert Y. Shih; Fiona A. Harrison; Daniel Stern; Steven E. Boggs; Finn E. Christensen; William W. Craig; Charles J. Hailey; William W. Zhang

doi:10.3847/2041-8205/820/1/L14

THE FIRST X-RAY IMAGING SPECTROSCOPY of QUIESCENT SOLAR ACTIVE REGIONS with NuSTAR

Iain G. Hannah, Brian W. Grefenstette, David M. Smith, Lindsay Glesener, Säm Krucker, Hugh S. Hudson, Kristin K. Madsen, Andrew Marsh, Stephen M. White, Amir Caspi, Albert Y. Shih, Fiona A. Harrison, Daniel Stern, Steven E. Boggs, Finn E. Christensen, William W. Craig, Charles J. Hailey, William W. Zhang

Physics and Astronomy (Twin Cities)

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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.

Original language	English (US)
Article number	L14
Journal	Astrophysical Journal Letters
Volume	820
Issue number	1
DOIs	https://doi.org/10.3847/2041-8205/820/1/L14
State	Published - Mar 20 2016

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© 2016. The American Astronomical Society. All rights reserved..

Keywords

Sun: X-rays, gamma rays
Sun: activity
Sun: corona

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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., & Zhang, W. W. (2016). THE FIRST X-RAY IMAGING SPECTROSCOPY of QUIESCENT SOLAR ACTIVE REGIONS with NuSTAR. Astrophysical Journal Letters, 820(1), Article L14. https://doi.org/10.3847/2041-8205/820/1/L14

Hannah, IG, Grefenstette, BW, Smith, DM, Glesener, L, Krucker, S, Hudson, HS, Madsen, KK, Marsh, A, White, SM, Caspi, A, Shih, AY, Harrison, FA, Stern, D, Boggs, SE, Christensen, FE, Craig, WW, Hailey, CJ & Zhang, WW 2016, 'THE FIRST X-RAY IMAGING SPECTROSCOPY of QUIESCENT SOLAR ACTIVE REGIONS with NuSTAR', Astrophysical Journal Letters, vol. 820, no. 1, L14. https://doi.org/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.",

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AU - Hannah, Iain G.

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AU - Smith, David M.

AU - Glesener, Lindsay

AU - Krucker, Säm

AU - Hudson, Hugh S.

AU - Madsen, Kristin K.

AU - Marsh, Andrew

AU - White, Stephen M.

AU - Caspi, Amir

AU - Shih, Albert Y.

AU - Harrison, Fiona A.

AU - Stern, Daniel

AU - Boggs, Steven E.

AU - Christensen, Finn E.

AU - Craig, William W.

AU - Hailey, Charles J.

AU - Zhang, William W.

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N2 - 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.

AB - 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.

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KW - Sun: activity

KW - Sun: corona

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THE FIRST X-RAY IMAGING SPECTROSCOPY of QUIESCENT SOLAR ACTIVE REGIONS with NuSTAR

Abstract

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Keywords

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