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 Erland 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 Erland Christensen, William W. Craig, Charles J. Hailey, William W. Zhang

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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∼10⁴⁶ cm⁻³ and ∼10⁴³cm⁻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
Article number	L14
Journal	The Astrophysical Journal Letters
Volume	820
Issue number	1
Number of pages	7
ISSN	2041-8205
DOIs	https://doi.org/10.3847/2041-8205/820/1/L14
Publication status	Published - 2016

Keywords

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

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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. The Astrophysical Journal Letters, 820(1), [L14]. https://doi.org/10.3847/2041-8205/820/1/L14

Hannah, Iain G. ; Grefenstette, Brian W. ; Smith, David M. ; Glesener, Lindsay ; Krucker, Säm ; Hudson, Hugh S. ; Madsen, Kristin K. ; Marsh, Andrew ; White, Stephen M. ; Caspi, Amir ; Shih, Albert Y. ; Harrison, Fiona A. ; Stern, Daniel ; Boggs, Steven E. ; Christensen, Finn Erland ; Craig, William W. ; Hailey, Charles J. ; Zhang, William W. / The first X-ray imaging spectroscopy of quiescent solar active regions with NuSTAR. In: The Astrophysical Journal Letters. 2016 ; Vol. 820, No. 1.

@article{85ab97f2c3d24836b50398603485adc2,

title = "The first X-ray imaging spectroscopy of quiescent solar active regions with NuSTAR",

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∼1046 cm−3 and ∼1043cm−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.",

keywords = "Sun: activity, Sun: corona, Sun: X-rays, gamma rays",

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

year = "2016",

doi = "10.3847/2041-8205/820/1/L14",

language = "English",

volume = "820",

journal = "The Astrophysical Journal Letters",

issn = "2041-8205",

publisher = "IOP Publishing",

number = "1",

}

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', The Astrophysical Journal Letters, vol. 820, no. 1, L14. https://doi.org/10.3847/2041-8205/820/1/L14

The first X-ray imaging spectroscopy of quiescent solar active regions with NuSTAR. / Hannah, Iain G.; Grefenstette, Brian W.; Smith, David M.; Glesener, Lindsay; Krucker, Säm; Hudson, Hugh S.; Madsen, Kristin K.; Marsh, Andrew; White, Stephen M.; Caspi, Amir; Shih, Albert Y.; Harrison, Fiona A.; Stern, Daniel; Boggs, Steven E.; Christensen, Finn Erland; Craig, William W.; Hailey, Charles J.; Zhang, William W.

In: The Astrophysical Journal Letters, Vol. 820, No. 1, L14, 2016.

Research output: Contribution to journal › Journal article › Research › peer-review

TY - JOUR

T1 - The first X-ray imaging spectroscopy of quiescent solar active regions with NuSTAR

AU - Hannah, Iain G.

AU - Grefenstette, Brian W.

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 Erland

AU - Craig, William W.

AU - Hailey, Charles J.

AU - Zhang, William W.

PY - 2016

Y1 - 2016

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∼1046 cm−3 and ∼1043cm−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∼1046 cm−3 and ∼1043cm−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.

KW - Sun: activity

KW - Sun: corona

KW - Sun: X-rays, gamma rays

U2 - 10.3847/2041-8205/820/1/L14

DO - 10.3847/2041-8205/820/1/L14

M3 - Journal article

VL - 820

JO - The Astrophysical Journal Letters

JF - The Astrophysical Journal Letters

SN - 2041-8205

IS - 1

M1 - L14

ER -