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dc.contributor.authorTrust, Otto
dc.contributor.authorJurua, Edward
dc.contributor.authorCat, Peter De
dc.contributor.authorJoshi, Santosh
dc.date.accessioned2022-10-26T06:26:56Z
dc.date.available2022-10-26T06:26:56Z
dc.date.issued2020
dc.identifier.citationTrust, O., Jurua, E., De Cat, P., & Joshi, S. (2020). Rotation and spots in normal A and Am/Fm stars. Monthly Notices of the Royal Astronomical Society, 492(3), 3143-3155.en_US
dc.identifier.urihttp://ir.must.ac.ug/xmlui/handle/123456789/2584
dc.description.abstractFrequency 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 (Vrot) 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 Vrot 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 RE for the spot radius (where RE 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.en_US
dc.description.sponsorshipInternational Science Program (ISP) of Uppsala Universityen_US
dc.language.isoen_USen_US
dc.publisherMonthly Notices of the Royal Astronomical Societyen_US
dc.subjectStarsen_US
dc.subjectChemically peculiar – starsen_US
dc.subjectGeneral – starsen_US
dc.subjectRotation – starspots.en_US
dc.titleRotation and spots in normal A and Am/Fm starsen_US
dc.typeArticleen_US


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