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Anomalous UV-Extinction and the Effective Temperature of V348 Sgr

Published online by Cambridge University Press:  12 April 2016

D. Schönberner  and
U. Heber
D. Schönberner
Affiliation:
Institut für Theoretische PhysikundSternwarte der Universitat KielOlshausenstr. 40, 2300 Kiel, F.R.G.
U. Heber
Affiliation:
Institut für Theoretische PhysikundSternwarte der Universitat KielOlshausenstr. 40, 2300 Kiel, F.R.G.

Extract

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Our idea of the evolutionary state of the hot R CrB-star V348 Sgr is seriously restricted by our ignorance of its effective temperature. A direct determination from photospheric lines is very difficult, owing to contamination by emission lines. Using Johnson photometry, Houziaux (1968) estimated a spectral type of BO or Bl. This result was, however, based on the assumption that V348 Sgr behaves photometrically as a main sequence star. V348 Sgr appears, however, to be an extreme helium star since hydrogen absorption lines are completely absent (Houziaux, 1968). This conclusion has been strengthened by a study of Heber et al. (1984) in which IUE-spectra (low resolution) of V348 Sgr are compared with those of well-known extreme helium stars. From the similarity between these spectra, it was concluded that V348 Sgr must be a helium supergiant with an effective temperature of about 16000 K, though its (dereddened) spectral flux distribution differs in a peculiar way from that of HD 124448 which has about the same temperature. It should, however, be noted that the dereddening was performed by eliminating the λ = 2200 Å dip with Seaton’s law for the interstellar reddening. Obviously, the latter is not applicable when describing the extinction towards V348 Sgr.

Type
IV Cool Hydrogen Deficient Stars
Information
International Astronomical Union Colloquium , Volume 87: Hydrogen Deficient Stars and Related Objects , 1985 , pp. 217 - 220
Copyright
Copyright © Reidel 1986

References

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