2020MNRAS.492.3143T -
Mon. Not. R. Astron. Soc., 492, 3143-3155 (2020/March-1)
Rotation and spots in normal A and Am/Fm stars.
TRUST O., JURUA E., DE CAT P. and JOSHI S.
Abstract (from CDS):
Frequency analysis of long-term ultraprecise photometry can lead to precise values of rotation frequencies of rotating stars with `hump and spike' features in their periodograms. Using these features, we computed the rotation frequencies and amplitudes. The corresponding equatorial rotational velocity (V_{{rot}}) and spot size were estimated. On fitting the autocorrelation functions of the light curves with the appropriate model, we determined the star-spot decay time-scale. The V_{rot} agrees well with the projected rotational velocity (ν ∼sin i) in the literature. Considering a single circular and black spot, we estimate its radius from the amplitude of the `spike'. No evidence for a significant difference in the average `spike' amplitude and spot radius was found for Am/Fm and normal A stars. Indeed, we derived an average value of ∼ 21± 2 and ∼ 19± 2 ppm for the photometric amplitude and of 1.01 ± 0.13 and 1.16 ± 0.12 R_ E for the spot radius (where R_E is the Earth radius), respectively. We do find a significant difference for the average spot decay time-scale, which amounts to 3.6 ± 0.2 and 1.5 ± 0.2 d for Am/Fm and normal A stars, respectively. In general, spots on normal A stars are similar in size to those on Am/Fm stars, and both are weaker than previously estimated. The existence of the `spikes' in the frequency spectra may not be strongly dependent on the appearance of star-spots on the stellar surface. In comparison with G, K, and M stars, spots in normal A and Am/Fm stars are weak, which may indicate the presence of a weak magnetic field.
Abstract Copyright:
© 2020 The Author(s) Published by Oxford University Press on behalf of the Royal Astronomical Society
Journal keyword(s):
stars: chemically peculiar - stars: general - stars: rotation
VizieR on-line data:
<Available at CDS (J/MNRAS/492/3143): tablea1.dat tablea2.dat>
CDS comments:
KIC 4557097 is a probable misprint for KIC 4567097.
Simbad objects:
174
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