Hostname: page-component-cd9895bd7-7cvxr Total loading time: 0 Render date: 2024-12-23T15:33:35.341Z Has data issue: false hasContentIssue false
  • English
  • Français

Quiescent Coronae of Active Chromosphere Stars

Published online by Cambridge University Press:  12 April 2016

Leon Golub
Leon Golub*
Affiliation:
Harvard-Smithsonian Center for Astrophysics

Abstract

Core share and HTML view are not available for this content. However, as you have access to this content, a full PDF is available via the ‘Save PDF’ action button.

The EINSTEIN Observatory has for the first time provided high sensitivity X-ray measurements of quiescent coronal emission from a large sample of dwarf stars. We now have observed a sufficient number of the nearby M-dwarfs to determine an X-ray luminosity function and we have explored the activity and variability of these stars to the extent of observing, for the first time, X-ray flares with simultaneous groundbased optical and IUE ultraviolet coverage.

The M dwarfs are found to have a much higher degree of variability in X-rays than does the Sun; however, in most cases a quiescent level is definable. We will discuss the quiescent emission from these stars and the changes in quiescent level on time scales from hours to ~ 1 year. We have determined coronal temperatures for many of these stars; they are generally hotter than the Solar corona and some of the more active dM stars have Tcor ~ 107 K.

Arguments are presented in support of the hypothesis that M-dwarf coronae are magnetically dominated, as is the Solar corona. We then examine the usefulness of loop model atmosphere calculations in elucidating the coronal heating mechanism and the ways in which observations may be used to test competing theories. The X-ray measurements can be used to predict magnetic field strengths on these stars, with testable implications.

Type
Session I: General Characteristics of Active Dwarfs
Information
International Astronomical Union Colloquium , Volume 71: Activity in Red-Dwarf Stars , 1983 , pp. 83 - 108
Copyright
Copyright © Reidel 1983

References

Ayres, T.R., Linsky, J.L., Garmire, G. and Cordova, F.: 1979, Ap.J.(Letters), 232, L117.Google Scholar
Caillault, J.-P.: 1982, Astron. J., 87, 558.Google Scholar
Cash, W., Charles, P., Bowyer, S., Walter, F., Ayres, T.R. and Linsky, J.L.: 1979, Ap.J.(Letters), 231, L137.Google Scholar
Copeland, H., Jensen, J.O. and Jorgensen, H.E.: 1970, A. & A., 5, 12.Google Scholar
Giampapa, M.S.: 1983, in Proc. IAU Symp. 102, ed. Stenflo, , (Reidel: Dordrecht).Google Scholar
Golub, L., Harnden, F.R. Jr., Pallavicini, R.P., Rosner, R. and Vaiana, G.S.: 1982, Ap.J., 253, 242.Google Scholar
Golub, L., Maxson, C.W., Rosner, R., Serio, S. and Vaiana, G.S.: 1980, Ap.J., 238, 343.Google Scholar
Golub, L., Noci, G., Poletto, G. and Vaiana, G.S.: 1982a, Ap.J. 259, 359.Google Scholar
Haisch, B.M., Linsky, J.L., Lampton, M., Paresce, F., Margon, B. and Stern, R.: 1977, Ap.J.(Letters), 213, L119.Google Scholar
Haisch, B.M., Linsky, J.L., Harnden, F.R. Jr., Rosner, R., Seward, F.D. and Vaiana, G.S.: 1980, Ap.J. (Letters), 242, L99.Google Scholar
Haisch, B.M., Linsky, J.L., Bornmann, P.L., Stencel, R.E., Antiochos, S.K., Golub, L. and Vaiana, G.S.: 1982, Ap.J. (in press).Google Scholar
Haisch, B.M. and Tsikoudi, V.: 1982 (preprint).Google Scholar
Heise, J., Brinkman, A.C., Shrijver, J., Mewe, R., Gronenschild, E., den Boggende, A. and Grindlay, J.: 1975, Ap.J.(Letters), 202, L73.Google Scholar
Kahler, S.W.: 1977, Ap.J., 214, 891.CrossRefGoogle Scholar
Kahler, S.W. et al.: 1982, Ap.J., 252, 239.Google Scholar
Kahn, S.M., Linsky, J.L., Mason, K.O., Haisch, B.M., Bowyer, C.S., White, N.M. and Pravdo, S.H.: 1979, Ap.J.(Letters), 234, L107.Google Scholar
Maccacaro, et al.: 1982 (in preparation).Google Scholar
Pallavicini, R.P., Golub, L., Rosner, R., Vaiana, G.S. Ayres, T.R. and Linsky, J.L.: 1981, Ap.J., 248, 279.Google Scholar
Parker, E.N.: 1974, Ap.J., 191, 245.Google Scholar
Rosner, R.: 1983, in Proc. IAU Symp. 102, ed. Stenflo, (Reidel: Dordrecht).Google Scholar
Rosner, R., Golub, L. and Vaiana, G.S.: 1982, Ap.J. (submitted).Google Scholar
Rosner, R., Tucker, W.H. and Vaiana, G.S.: 1978, Ap.J., 220, 643.Google Scholar
Schüssler, M.: 1983, in Proc. IAU Symp. 102, ed. Stenflo, (Reidel: Dordrecht).Google Scholar
Swank, J.H. and Johnson, H.M.: 1982 (preprint).Google Scholar
Topka, K.: 1981, Ph.D. Thesis, Harvard University.Google Scholar
Vaiana, G.S. et al.: 1981, Ap.J., 245, 163.Google Scholar
Vaiana, G.S. and Rosner, R.: 1978, Ann. Rev. Astron. & Astrophys., 16, 393.Google Scholar
Vaiana, G.S., Serio, S., Blanco, C, Catalano, S., Marilli, E., Rodono1, M. and Golub, L.: 1982, in preparation.Google Scholar
Walter, F.: 1982, Ap.J., 253, 745.Google Scholar