Spectrographic observations of three suspected Delta Scuti variables

Details Spectrographic observations of three suspected Delta Scuti variables Spectrographic observations of three suspected Delta Scuti variables

May 1978

adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=1978a%26a....66...37a&link_type=abstract

Astronomy and Astrophysics, vol. 66, no. 1-2, May 1978, p. 37-43. Consiglio Nazionale delle Ricerche

Astronomy and Astrophysics

Astrophysics

11

Astronomical Spectroscopy, Cepheid Variables, Early Stars, Stellar Spectra, H Beta Line, Hydrogen, Radial Velocity, Spectral Line Width, Tables (Data)

Scientific paper

Spectrograms obtained with a dispersion of 35 A/mm at H-gamma are analyzed for three suspected Delta Scuti variables of type A2 V: Sigma And, Theta Peg, and 2 Lyn. These three stars are found to exhibit large-amplitude short-period variations in radial velocity that differ from line to line, definite regular variations in equivalent width with probable larger periods, and smaller short-period variations in equivalent width that are somehow phased with the radial-velocity variations. Tentative periodogram analyses of the hydrogen lines are performed, indicating possible chromospheric effects, and the observed asymmetry of the Ca II K lines in the descending branch of the radial-velocity curves is taken as a further indication of transient phenomena. The pulsation constant is estimated to be in excess of 0.30, which suggests fundamental-mode pulsation for the three stars. It is noted that all three stars exhibit some characteristics similar to those of 'unusual' and Ap variables and that 2 Lyn also shows certain Am characteristics, which could indicate crossing from the Am to the Delta Scuti zone, as predicted by turbulent-mixing theory.

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