An asteroseismic study of the <i>β</i> Cephei star 
<i>β</i> Canis Majoris

Mazumdar, A.; Briquet, Maryline; Desmet, M.; Aerts, C.

doi:10.1051/0004-6361:20064980

Cited by 57 publications

(58 citation statements)

References 34 publications

(54 reference statements)

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“…The typical amount of convective core overshoot required to match observations is about α co = 0.2 and is consistent with measurements for the β Cep stars β CMa (Mazumdar et al 2006) and δ Ceti , as well as for classical Cepheids (Cassisi & Salaris 2011;Neilson et al 2011;Neilson & Langer 2012;Prada Moroni et al 2012) and other stars. However, measurements for other β Cep stars require different amounts of overshoot: θ Oph α co = 0.4 (Briquet et al 2007) 0.28H P (Lovekin & Goupil 2010), HD 129929 α co = 0.1 (Aerts et al 2003), and ν Eridani α co = 0.28 (Suárez et al 2009), among others.…”

Section: Introductionsupporting

confidence: 86%

Period change and stellar evolution ofβCephei stars

Neilson

Ignace

2015

A&A

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The β Cephei stars represent an important class of massive star pulsators that probe the evolution of B-type stars and the transition from main sequence to hydrogen-shell burning evolution. By understanding β Cep stars, we gain insights into the detailed physics of massive star evolution, including rotational mixing, convective core overshooting, magnetic fields, and stellar winds, all of which play important roles. Similarly, modeling their pulsation provides additional information into their interior structures. Furthermore, measurements of the rate of change of pulsation period offer a direct measure of β Cephei stellar evolution. In this work, we compute state-of-the-art stellar evolution models assuming different amounts of initial rotation and convective core overshoot and measure the theoretical rates of period change, that we compare to rates previously measured for a sample of β Cephei stars. The results of this comparison are mixed. For three stars, the rates are too low to infer any information from stellar evolution models, whereas for three other stars the rates are too high. We infer stellar parameters, such as mass and age, for two β Cephei stars: ξ 1 CMa and δ Cet, which agree well with independent measurements. We explore ideas for why models may not predict the higher rates of period change. In particular, period drifts in β Cep stars can artificially lead to overestimated rates of secular period change.

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Section: Introductionsupporting

confidence: 86%

Period change and stellar evolution ofβCephei stars

Neilson

Ignace

2015

A&A

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“…Further details on the data acquisition and reduction procedures can be found in Aerts et al (2004a; ν Eri), Mazumdar et al (2006;β CMa), Saesen et al (2006;ξ 1 CMa), Aerts et al (2004b;V836 Cen), Neiner et al, in prep. (V2052 Oph) and Desmet et al,in prep.…”

Section: Observational Materialsmentioning

confidence: 99%

Abundance analysis of prime B-type targets for asteroseismology

Morel¹,

Butler

Aerts

et al. 2006

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Seismic modelling of the β Cephei stars promises major advances in our understanding of the physics of early B-type stars on (or close to) the main sequence. However, a precise knowledge of their physical parameters and metallicity is a prerequisite for correct mode identification and inferences regarding their internal structure. Here we present the results of a detailed NLTE abundance study of nine prime targets for theoretical modelling: γ Peg, δ Cet, ν Eri, β CMa, ξ 1 CMa, V836 Cen, V2052 Oph, β Cep and DD (12) Lac (hereafter 12 Lac). The following chemical elements are considered: He, C, N, O, Mg, Al, Si, S and Fe. Our curve-of-growth abundance analysis is based on a large number of time-resolved, high-resolution optical spectra covering in most cases the entire oscillation cycle of the stars. Nitrogen is found to be enhanced by up to 0.6 dex in four stars, three of which have severe constraints on their equatorial rotational velocity, ΩR, from seismic or line-profile variation studies: β Cep (ΩR ∼ 26 km s −1 ), V2052 Oph (ΩR ∼ 56 km s −1 ), δ Cet (ΩR < 28 km s −1 ) and ξ 1 CMa (ΩR sin i < ∼ 10 km s −1 ). The existence of core-processed material at the surface of such largely unevolved, slowly-rotating objects is not predicted by current evolutionary models including rotation. We draw attention to the fact that three stars in this subsample have a detected magnetic field and briefly discuss recent theoretical work pointing to the occurrence of diffusion effects in β Cephei stars possibly capable of altering the nitrogen surface abundance. On the other hand, the abundances of all the other chemical elements considered are, within the errors, indistinguishable from the values found for OB dwarfs in the solar neighbourhood. Despite the mild nitrogen excess observed in some objects, we thus find no evidence for a significantly higher photospheric metal content in the studied β Cephei stars compared to non-pulsating B-type stars of similar characteristics.

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“…Using observations by the MOST satellite, Aerts et al (2006) were able to place constraints on the physical parameters of δ Ceti, including constraining the convective core overshoot (α ov = 0.2 ± 0.05). Seismic modeling of β CMa has constrained the core overshoot to α ov = 0.2 ± 0.05, as well as placing constraints on the mass and age of the star (Mazumdar et al 2006).…”

Section: Introductionmentioning

confidence: 99%

Rotation and convective core overshoot inθOphiuchi

Lovekin¹,

Goupil²

2010

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Context. Recent work on several β Cephei stars has succeeded in constraining both their interior rotation profile and their convective core overshoot. In particular, a recent study focusing on θ Ophiuchi has shown that a convective core overshoot parameter of α ov = 0.44 is required to model the observed pulsation frequencies, significantly higher than for other stars of this type. Aims. We investigate the effects of rotation and overshoot in early type main sequence pulsators, such as β Cephei stars, and attempt to use the low order pulsation frequencies to constrain these parameters. This will be applied to a few test models and the β Cephei star θ Ophiuchi. Methods. We use the 2D stellar evolution code ROTORC and the 2D linear adiabatic pulsation code NRO to calculate pulsation frequencies for 9.5 M models evolved to an age of 15.6 Myr. We calculate low order p-modes ( ≤ 2) for models with a range of rotation rates and convective core overshoot parameters. These low order modes are the same range of modes observed in θ Ophiuchi. Results. Using these models, we find that the convective core overshoot has a larger effect on the pulsation frequencies than the rotation, except in the most rapidly rotating models considered. When the differences in radii are accounted for by scaling the frequencies by √ (GM/R(40 • ) 3 ), the effects of rotation diminish, but are not entirely accounted for. Thus, this scaling emphasizes the differences produced by changing the convective core overshoot. We find that increasing the convective core overshoot decreases the large separation, while producing a slight increase in the small separations. We created a model frequency grid which spanned several rotation rates and convective core overshoot values. We used this grid to define a modified χ 2 statistic in order to determine the best fitting parameters from a set of observed frequencies. Using this statistic, we are able to recover the rotation velocity and convective core overshoot for a few test models. We have also performed a "hare and hound" exercise to see how well 1D models can recover these parameters. Finally, we discuss the case of the β Cephei star θ Oph. Using the observed frequencies and a fixed mass and metallicity, we find a lower overshoot than previously determined, with α ov = 0.28 ± 0.05. Our determination of the rotation rate agrees well with both previous work and observations, around 30 km s −1 .

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An asteroseismic study of the β Cephei star β Canis Majoris

Cited by 57 publications

References 34 publications

Period change and stellar evolution ofβCephei stars

Period change and stellar evolution ofβCephei stars

Abundance analysis of prime B-type targets for asteroseismology

Rotation and convective core overshoot inθOphiuchi

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