Publication details

Stars with discrepant v sin i as derived from Ca II 3933 A and Mg II 4481 A lines. III. Stars with v sin i (3933 A) < v sin i (4481 A)



Year of publication 2013
Type Article in Periodical
Magazine / Source Astrophysical Bulletin
MU Faculty or unit

Faculty of Science

Field Astronomy and astrophysics
Keywords stars: chemically peculiar; stars: rotation
Description Axial rotation of a star plays an important role in its evolution, physical conditions in its atmosphere and the appearance of its spectrum. We analyzed CCD spectra of nine stars for which the projected rotational velocity derived from the Ca II line at 3933 A was remarkably lower than the one derived from the MgII line at 4481 A. We derived effective temperatures and surface gravities using published uvbybeta photometries, and computed synthetic spectra. Comparing the observed line profiles of the two lines with the computed ones, we estimated the values of v sin i. One of the stars, HD 44783, is a Be-star which, besides the narrow absorptions in the spectrum originating in its circumstellar envelope, also has lines of interstellar origin. We also found indications of circumstellar matter in the spectrum of HD 25152. In the spectra of the remaining seven stars the narrow components in the Ca II 3933 A line as well as narrow absorptions in the Na I 5889.951 A (D1) and 5895.924 A (D2) lines are of interstellar origin. In HD 114376 there are two systems of interstellar components, thus disclosing two different interstellar clouds in the direction of the star. In the spectrum of HD 138527 signs of a possible companion were detected, the emission of which contributes 15% to the total light of the system.
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