SPB stars in the open SMC cluster NGC 371 - AstrophysicsReport as inadecuate

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Abstract: Pulsation in beta Cep and SPB stars are driven by the kappa mechanism whichdepends critically on the metallicity. It has therefore been suggested thatbeta Cep and SPB stars should be rare in the Magellanic Clouds which have lowermetallicities than the solar neighborhood. To test this prediction we haveobserved the open SMC cluster NGC 371 for 12 nights in order to search for betaCep and SPB stars. Surprisingly, we find 29 short-period B-type variables inthe upper part of the main sequence, many of which are probably SPB stars. Thisresult indicates that pulsation is still driven by the kappa mechanism even inlow metallicity environments. All the identified variables have periods longerthan the fundamental radial period which means that they cannot be beta Cepstars. Within an amplitude detection limit of 5 mmag no stars in the top of theHR-diagram show variability with periods shorter than the fundamental radialperiod. So if beta Cep stars are present in the cluster they oscillate withamplitudes below 5 mmag, which is significantly lower than the mean amplitudeof beta Cep stars in the Galaxy. We see evidence that multimode pulsation ismore common in the upper part of the main sequence than in the lower. We havealso identified 5 eclipsing binaries and 3 periodic pulsating Be stars in thecluster field.

Author: C. Karoff, T. Arentoft, L. Glowienka, C. Coutures, T. B. Nielsen, G. Dogan, F. Grundahl, H. Kjeldsen

Source: https://arxiv.org/


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