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C.R. Cowley (Univ. of Michigan), W.P. Bidelman (Case Western Reserve Univ.), S. Hubrig, G. Mathys (European Southern Observatory), D.J. Bord (U. of Mich. Dearborn)
Two chemical elements lighter than bismuth have no isotopes with half-lives longer than 5 million years: the 4d-element technetium and the lanthanide promethium. While 98Tc has a half-life of 4.2 106 years, the longest-lived isotope of Pm, 145Pm, has a half-life of only 17.7 years. The presence of either of these elements in upper main sequence stars would pose a serious problem for our understanding of the chemistry of these stars. It is now generally accepted that the chemical anomalies of numerous subtypes of peculiar B, A, and F stars is a superficial phenomenon caused by chemical separation under the competing influences of radiation pressure and gravity. This theory would have to be supplemented should the presence of these unstable species be confirmed. There is substantial evidence to support the presence of PmI and/or II, and TcI, in HD101065, and PmI and/or II in HD965. HD101065 is a notorious object, well known for the strength of its rare-earth spectra relative to the iron group (see url below for data and references). Hubrig, et al. (ASP Conf. Ser. 279, ed. C. A. Tout and W. Van Hamme, p. 365) noted the similarity of HD965 toPrzybylski's star. Identifications of Tc and Pm in these stars are based on wavelength coincidence statistics (WCS Cowley and Hensberge, ApJ 244. 252. 1081)and traditional line-by-line examinations taking into account laboratory intensities, excitation potentials, and wavelength agreement. Wavelength measurements are available at http://www.astro.lsa.umich.edu/users/cowley/. The highest significances are obtained for HD965 and a list of strong PmI and II from the NIST site (Sansonetti and Martin http://physics.nist.gov/PhysRefData/Handbook/index.html). We found 14 of 39 lines within ±0.02Å, which is a 99.9% confident result. Various tests for PmI and II in HD101065 lead to 99% confidence or better. WCS yields 95-99% confidence for TcI in HD101065.
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The author(s) of this abstract have provided an email address for comments about the abstract: cowley@umich.edu
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Bulletin of the American Astronomical Society, 35#5
© 2003. The American Astronomical Soceity.