Photometric and magnetic variability of the late AP star HD 3980

Details Photometric and magnetic variability of the late AP star HD 3980 Photometric and magnetic variability of the late AP star HD 3980

Jan 1980

adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=1980a%26a....81..323m&link_type=abstract

Astronomy and Astrophysics, vol. 81, no. 3, Jan. 1980, p. 323-327. Research supported by the Oesterreichishcher Fonds zur Foerd

Astronomy and Astrophysics

Astrophysics

12

Late Stars, Luminous Intensity, Magnetic Variations, Stellar Luminosity, Stellar Spectrophotometry, Variable Stars, A Stars, Magnetic Fields, Zeeman Effect

Scientific paper

HD 3980, a late type Ap star has been observed in differential photometry (comparison: HD 4150) in the system at two epochs (Oct. 1974 and July/August 1978) and additionally with the g1 and g2 filters as described by Maitzen (1976). These measurements enable us, together with the data by Vogt and Faundex (1979) and Seggewiss and Maitzen (1979), to derive precise elements of the light variation: JD (primary min in υ) = 2442314d.48 + 3d.9516 E.
We note a striking similarity with the light curves and the flux distribution found for HD 98088 (Maitzen, 1973): a very outstanding variation of 0m13 occurs only in the Strömgren-υ pass band and exhibits two different minima separated in phase by 0.5. Towards longer wavelengths the amplitudes decrease to about zero at Strömgren-γ. In addition, like for HD 98088 the published spectral classification (A 9p) does not match the gradient of the continuum flux nor the hydrogen line strength, which both indicate a much earlier type (A 3 V).
With the accurate elements of the photometric variation we can phase the Zeeman spectroscopy obtained by us on La Silla from 1970 to 1972. It turns out that the Zeeman plates show a reversal of magnetic polarity every second day with an amplitude of about 2 kG, and that all but one of the spectra were taken after either the positive or negative crossover. More Zeeman observations are suggested in order to complete the magnetic curve (= Heff) and to establish the possible presence of an unusual strong magnetic field as inferred by Wood (1978).

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