MK morphological study of AM stars at 66 A/mm

Details MK morphological study of AM stars at 66 A/mm MK morphological study of AM stars at 66 A/mm

Jun 1991

adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=1991japa...12..133s&link_type=abstract

Journal of Astrophysics and Astronomy (ISSN 0250-6335), vol. 12, no. 2, June 1991, p. 133-178.

Astronomy and Astrophysics

Astrophysics

3

A Stars, Metallic Stars, Stellar Luminosity, Stellar Spectra, Dwarf Stars, Giant Stars, Metallicity, Supergiant Stars

Scientific paper

The pseudoluminosity effect in the metallic line A-type stars found by Abt and Morgan (1976) is confirmed in a random sample of 27 Am stars. From a morphological study of their spectra in the wavelength interval 3850-4400 A at a reciprocal dispersion of 66 A/mm, revised spectral types are given on the MK system for their K-line and metallic-line spectra. This shows that: (1) the segregation of weak Am from the Am stars largely agrees with that by Cowley et al. (1969); (2) all the stars in the sample are dwarfs according to their K-line classification; (3) more than 80 percent exhibit the pseudoluminosity effect significantly, with their metallic-line spectra resembling a giant or even a supergiant in the violet (3850-4100 A), and a giant rather than a dwarf in the blue region (4260-4400 A); and (4) in two-thirds of the stars under (3), the Sr II 4077 A line is found to have a markedly brighter luminosity class compared to any region, and in more than one-third of the sample it is comparable to that in Ap stars. Moreover, at least five stars exhibit characteristics which might suggest a spectrum variability; among these, the most striking example is 41 Sex A. The metallic-line spectra of another five stars appear to be similar to A-shell type in different degrees. Less than 20 percent of the sample comprises stars which do not show any significant differential luminosity effect; these stars might have been misclassified or perhaps they are in a quiescent state.

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