Heavy calcium in CP stars

被引:21
作者
Cowley, C. R. [1 ]
Hubrig, S.
Castelli, F.
Gonzalez, J. F.
Wolff, B.
机构
[1] Univ Michigan, Dept Astron, Ann Arbor, MI 48109 USA
[2] European So Observ, Santiago 19, Chile
[3] Osserv Astron Trieste, INAF, I-34131 Trieste, Italy
[4] Complejo Astron El Leoncito, RA-5400 San Juan, Argentina
[5] European So Observ, D-85748 Garching, Germany
关键词
stars : atmospheres; stars : chemically peculiar; stars : magnetic fields;
D O I
10.1111/j.1365-2966.2007.11719.x
中图分类号
P1 [天文学];
学科分类号
0704 ;
摘要
Large wavelength shifts of infrared triplet lines of Ca II have been observed in the spectra of HgMn and magnetic Ap stars. They have been attributed to the heavy calcium isotopes, including Ca-48. One member of the triplet, lambda 8542, had been either unavailable, or of poor quality in earlier spectra. The present material shows conclusively that the stellar lambda 8542 shifts are consistent with an interpretation in terms of Ca-48. We find no relation between isotopic shifts of the Ca II triplet lines, and those of Hg II lambda 3984. There is a marginal indication that the shifts are anticorrelated with the surface field strengths of the magnetic stars. We see sparse evidence for Ca-48 in other chemically peculiar stars, for example, Am stars, metal-poor stars or chemically peculiar red giants. However, the sample is still very small, and the wavelengths of all three triplet lines, including those in the Sun, show slight positive shifts with respect to terrestrial positions. Some profiles of the Ca II infrared triplet in the magnetic stars show extensive wings beyond a well-defined core. We can obtain reasonable fits to these profiles using a stratified calcium abundance similar to that used by previous workers. There is no indication that either the stratification or the Zeeman effect significantly disturbs the measurement of isotope shifts.
引用
收藏
页码:1579 / 1587
页数:9
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