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Science 2 September 1994:
Vol. 265. no. 5177, pp. 1420 - 1422
DOI: 10.1126/science.265.5177.1420
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Articles

A Spectroscopic Measurement of the Coronal Density of Procyon

J. H. M. M. Schmitt 1, B. M. Haisch 2, and J. J. Drake 3

1 Max-Planck-Institut für Extraterrestrische Physik, 85740 Garching, Germany
2 Max-Planck-Institut für Extraterrestrische Physik, 85740 Garching, Germany, and Lockheed Solar and Astrophysics Laboratory, Division 91-30, Building 252, 3251 Hanover Street, Palo Alto, CA 94304, USA.
3 Center for Extreme Ultraviolet Astrophysics, University of California, Berkeley, CA 94720, USA.

One of the open key issues in the astrophysics of stellar coronae is the determination of their spatial structure and density. From almost all previous measurements, one can infer merely the presence of a corona, which for the most energetic stellar coronae may exceed the solar x-ray output by as much as five orders of magnitude, but no information can be obtained on the densities and hence volumes and sizes of the hot x-ray emitting material. A direct spectroscopic measurement of the coronal density was obtained for the star Procyon with the spectrometer on board the Extreme Ultraviolet Explorer satellite; the ratio of two Fe XIV lines at 211.32 and 264.79 angstroms was used to determine a density of sim4 x 109 to 7 x 109 electrons per cubic centimeter, which is a factor of 2 to 3 higher than typical solar active region densities. From this value, we estimate that sim6 percent of the stellar surface is covered with sim7 x 104 coronal loops.

Submitted on April 8, 1994
Accepted on July 5, 1994


THIS ARTICLE HAS BEEN CITED BY OTHER ARTICLES:
The Elemental Composition of the Corona of Procyon: Evidence for the Absence of the FIP Effect.
J. J. Drake, J. M. Laming, K. G. Widing, J. H. M. M. Schmitt, B. Haisch, and S. Bowyer (1995)
Science 267, 1470-1473
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Science. ISSN 0036-8075 (print), 1095-9203 (online)