Hostname: page-component-7479d7b7d-c9gpj Total loading time: 0 Render date: 2024-07-12T14:02:22.488Z Has data issue: false hasContentIssue false
  • English
  • Français

Ultraviolet Spectroscopy of Chemically Peculiar Stars

Published online by Cambridge University Press:  30 March 2016

David S. Leckrone
David S. Leckrone*
Affiliation:
NASA, Goddard Space Flight Center, Laboratory for Astronomy and Solar Physics

Extract

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.

This discussion focuses on high dispersion spectroscopic observations of chemically peculiar (CP) stars of the upper main sequence, classical HgMn, Si and SrCrEu stars, obtained with the IUE. Two subjects will be emphasized - the confirmation of composition anomalies previously identified in ground-based spectra and evidence relating to the validity of the diffusion theory for the production of chemical pecularities.

The gallium anomaly occurs primarily in the hotter Mn stars (Cowley 1975). Model atmospheres analyses of Mn stars yield overabundances of Ga as large as 2×105 relative to the solar value (Heacox 1979). The identification of the Ga peculiarity and estimates of Ga abundances are based upon a few high excitation lines observed in the blue. Figure 1 illustrates the resonance line of GaII, λ1414.44, observed in six Mn stars. The feature is strong and broad in the hotter stars, к Cnc and μ Lep. It is present but weaker in 46 Dra (A+B). It is absent in the cooler stars г CrB, χ Lup and HR 4072. The sharp feature seen near λ1414.4 in the latter three stars is probably Mnll and is also seen in normal stars. The Gall λ1414.44 line varies in strength from star-to-star in the same manner as the blue Gall lines. The absence of the blue Gall lines in cool Mn stars cannot be an excitation effect, since the resonance line is also absent in these stars. Neither can the presence of the blue Gall lines in hotter Mn stars be due to non-LTE effects, because the resonance line is also abnormally strong in these stars. The IUE observations confirm the Ga peculiarity as a genuine abundance anomaly.

Type
Ultraviolet Astronomy-New Results from Recent Space Experiments
Information
Highlights of Astronomy , Volume 5: Highlights of Astronomy. As presented at the XVIIth General Assembly of the IAU, 1979 , 1980 , pp. 277 - 284
Copyright
Copyright © Cambridge University Press 1980

References

Boesgaard, A.M. and Heacox, W.D., 1973, Astrophys. J. 185, L27.Google Scholar
Borsenberger, J., Michaud, G. and Praderie, F., 1979, Astron. Astrophys. (in press).Google Scholar
Cowley, C.R., 1975, Proc. I.A.U. Coll. Nr. 32 (H. Jenkner, W.Weiss and Wood, H., ed.), University of Vienna, 275.Google Scholar
Heacox, W.D., 1979, Astrophys. J. Suppl. (in press).Google Scholar
Jamar, C., Macau-Hercot, D. and Praderie, F., 1978, Astron. Astrophys. 63, 155.Google Scholar
Kurucz, R. and Peytremann, E., 1975, Smithsonian Astrophys. Obs. Special Report Nr. 362.Google Scholar
Michaud, G., 1970, Astrophys. J. 160, 641.Google Scholar
Michaud, G., Reeves, H. and Charland, Y., 1974, Astron. Astrophys. 37, 313.Google Scholar
Praderie, F., Boesgaard, A.M., Milliard, B. and Pitois, M.L., 1977, Astrophys. J. 214, 130.Google Scholar
Vauclair, S., Hardorp, J. and Peterson, D.M., 1979, Astrophys. J. 227, 526.CrossRefGoogle Scholar
White, R.E., Vaughan, A.H., Preston, G.W. and Swings, J.P., 1976, Astrophys. J. 204, 131.CrossRefGoogle Scholar
Wilkinson, P.G. and Andrew, K.L., 1963, J. Opt. Soc. Am. 53, 710.Google Scholar