Battaglia, M., Hudson, H. S. , Hurford, G. J., Krucker, S. and Schwartz, R. A. (2017) The solar x-ray limb. Astrophysical Journal, 843(2), 123. (doi: 10.3847/1538-4357/aa76da)
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Abstract
We describe a new technique to measure the height of the X-ray limb with observations from occulted X-ray flare sources as observed by the RHESSI (the Reuven Ramaty High-Energy Spectroscopic Imager) satellite. This method has model dependencies different from those present in traditional observations at optical wavelengths, which depend upon detailed modeling involving radiative transfer in a medium with complicated geometry and flows. It thus provides an independent and more rigorous measurement of the “true” solar radius, which means that of the mass distribution. RHESSI’s measurement makes use of the flare X-ray source’s spatial Fourier components (the visibilities), which are sensitive to the presence of the sharp edge at the lower boundary of the occulted source. We have found a suitable flare event for analysis, SOL2011-10-20T03:25 (M1.7), and report a first result from this novel technique here. Using a four-minute integration over the 3–25 keV photon energy range, we find RX ray ‐ = 960.11 0.15 0.29 arcsec, at 1 au, where the uncertainties include statistical uncertainties from the method and a systematic error. The standard VAL-C model predicts a value of 959.94 arcsec, which is about 1σ below our value.
| Item Type: | Articles |
|---|---|
| Additional Information: | This work was supported by Swiss National Science Foundation (200021-140308), by the European Commission through HESPE (FP7-SPACE-2010-263086), and through NASA Contract NAS5-98033 for RHESSI. |
| Status: | Published |
| Refereed: | Yes |
| Glasgow Author(s) Enlighten ID: | Hudson, Dr Hugh and Battaglia, Dr Marina |
| Authors: | Battaglia, M., Hudson, H. S., Hurford, G. J., Krucker, S., and Schwartz, R. A. |
| College/School: | College of Science and Engineering > School of Physics and Astronomy |
| Journal Name: | Astrophysical Journal |
| Publisher: | American Astronomical Society |
| ISSN: | 0004-637X |
| ISSN (Online): | 1538-4357 |
| Published Online: | 12 July 2017 |
| Copyright Holders: | Copyright © 2017 American Astronomical Society |
| First Published: | First published in Astrophysical Journal 843(2):123 |
| Publisher Policy: | Reproduced in accordance with the copyright policy of the publisher |
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