Hostname: page-component-7bb8b95d7b-fmk2r Total loading time: 0 Render date: 2024-09-12T02:26:11.383Z Has data issue: false hasContentIssue false
  • English
  • Français

ϵ Canis Majoris and the Ionization of the Local Cloud

Published online by Cambridge University Press:  12 April 2016

J.V. Vallerga  and
B.Y. Welsh
J.V. Vallerga
Affiliation:
Eureka Scientific, 2452 Delmer St., Oakland, CA 94602, USA
B.Y. Welsh
Affiliation:
Eureka Scientific, 2452 Delmer St., Oakland, CA 94602, USA

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.

Using the EUV (70 – 730 Å) spectrum of the brightest EUV source, ϵ CMa taken with the Extreme Ultraviolet Explorer Satellite (EUVE) and simple models that extrapolate this spectrum to the Lyman edge at 912 Å, we have determined the local interstellar hydrogen photoionization parameter, Г, solely from this B2 II star to be 1.1 × 10−15 s−1. This figure is a factor of 7 greater than previous estimates of Г calculated for all nearby stars combined (Bruhweiler & Cheng 1988). Using measured values of the density and temperature of neutral interstellar hydrogen gas in the Local Cloud, we derive a particle density of ionized hydrogen, n(H+), and electrons, ne, of 0.015 – 0.019 cm−3 assuming ionization equilibrium and a helium ionization fraction of less than 20%. These values correspond to a hydrogen ionization fraction, XH from 19% to 15%, respectively.

Type
V. The Interstellar Medium and Diffuse Background
Information
International Astronomical Union Colloquium , Volume 152: Astrophysics in the Extreme Ultraviolet , 1996 , pp. 277 - 282
Copyright
Copyright © Kluwer 1996

References

Aldrovandi, S.M.V. & Pequignot, D. 1973, A&A, 25, 137 Google Scholar
Bertaux, J.L., Lallement, R., Kurt, V.G., & Mironova, E.N. 1985, A&A, 150, 1 Google Scholar
Bruhweiler, F.C. & Cheng, K.P. 1988, ApJ, 355, 188 CrossRefGoogle Scholar
Bruhweiler, F.C., Oegerle, W., Weiler, E., Stencel, R., & Kondo, Y. 1984, In IAU Colloq. 81, The Local Interstellar Medium, ed. Kondo, Y., Bruhweiler, F.C., & Savage, B.D., NASA CP-2345, 64 CrossRefGoogle Scholar
Cassinelli, J.P., Cohen, D.H., MacFarlane, J.J., Drew, J.E., Hoare, M.G., Val-Lerga, J.V., Vedder, P.W., Welsh, B.Y. & Hubeny, I. 1994, ApJ, in pressGoogle Scholar
Chassefiere, E., Bertaux, J.L., Lallement, R., & Kurt, V.G. 1986, A&A, 160, 229 Google Scholar
Cheng, K.P. & Bruhweiler, F.C. 1990, ApJ, 364, 573 CrossRefGoogle Scholar
Cox, D.P. & Reynolds, R.J. 1987, ARA&A, 25, 303 Google Scholar
Halpern, J.P. & Grindlay, J.E. 1980, ApJ, 242, 1041 CrossRefGoogle Scholar
Jelinsky, P., Edelstein, J., & Vallerga, J. 1994, ApJ, submittedGoogle Scholar
Linsky, J.L., Brown, A., Gayley, K., Diplas, A., Savage, B.D., Ayres, T.R., Landsman, W., Shore, S.N., & Heap, S.R. 1993, ApJ, 402, 694 CrossRefGoogle Scholar
Linsky, J.L., Diplas, A., Andrulis, C., Brown, A., Savage, B.D., & Ebbets, D. 1994, In “Frontiers of Space and Ground-Based Astronomy,” ed. Wamsteker, W., Longair, M.S., & Kondo, Y., Dordrecht: Kluwer, 102 Google Scholar
Lotz, W. 1967, ApJS, 14, 207 CrossRefGoogle Scholar
Slavin, J.D. 1989, ApJ, 346, 718 CrossRefGoogle Scholar
Vallerga, J. & Welsh, B.Y. 1995, ApJ, 444, 702 CrossRefGoogle Scholar
Vallerga, J., Vedder, P., & Welsh, B. 1993, ApJ, 414, L65 CrossRefGoogle Scholar
Vennes, S., Dupuis, J., Rumph, T., Drake, J.J., Bowyer, S., Chayer, P., & Fontaine, G. 1993, ApJ, 410, L119 CrossRefGoogle Scholar
Welsh, B.Y. 1991, ApJ, 373, 556 CrossRefGoogle Scholar