Kepler observations of the variability in B-type stars

Balona, L. A.; Pigulski, A.; Cat, P. De; Handler, G.; Gutiérrez‐Soto, J.; Engelbrecht, C. A.; Frescura, F. A. M.; Briquet, Maryline; Cuypers, J.; Daszyńska‐Daszkiewicz, J.; Degroote, P.; Dukes, R. J.; García, R. A.; Green, E. M.; Heber, U.; Kawaler, S. D.; Lehmann, H.; Leroy, B.; Molenda‐Żakowicz, J.; Neiner, C.; Noels, A.; Nuspl, J.; Østensen, R. H.; Pricopi, D.; Roxburgh, I. W.; Salmon, Sébastien; Smith, M. A.; Suárez, J. C.; Suran, M. D.; Szabo, Robert M.; Uytterhoeven, K.; Christensen‐Dalsgaard, J.; Kjeldsen, H.; Caldwell, Douglas A.; Girouard, Forrest R.; Sanderfer, Dwight T.

doi:10.1111/j.1365-2966.2011.18311.x

Cited by 148 publications

(210 citation statements)

References 78 publications

(121 reference statements)

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“…They are known as β Cep/SPB hybrids (e.g. De Cat et al 2007;Pigulski & Pojmanski 2008;Handler 2009;Balona et al 2011;Degroote et al 2012b;Pápics et al 2012). …”

Section: Oscillation Spectra Of Early-type Starsmentioning

confidence: 99%

Seismic models of O and B stars with Kurucz’s opacity data

Cugier

2014

A&A

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Aims. We investigated seismic models of O and B stars calculated with the new Kurucz opacities implemented in the Opacity Project (OP) and Rogers & Iglesias OPAL opacity tables (OPAL). Methods. We studied the problem using Dziembowski's computer codes for linear, nonadiabatic, and nonradial oscillations. We considered seismic models of main sequence (MS) stars for different chemical compositions of elements in the mass-range 9 ≤ M ≤ 70 M . Results. The new opacity bump at lg T ≈ 5.06 that occurs in Kurucz's data influences evolutionary tracks mainly for M ≥ 30 M and markedly changes the driving zone for pulsations of stars in the whole mass range studied. We obtained no unstable oscillation modes for models corresponding to the abundance parameter Z ≤ 0.013 and only unstable low-frequency g-modes for 0.013 < Z ≤ 0.021. Conclusions. The opacity bump at lg T ≈ 5.3 should be significantly larger than the opacity bump at lg T ≈ 5.06 to drive pulsations of B stars in low-degree p-modes. Models with an increased OPAL (or OP) opacity bump at lg T ≈ 5.3 by a factor of about 1.7 have sufficiently large driving zones to excite modes in the β Cephei frequency-domain for 0.003 ≤ Z ≤ 0.021. These values of Z are in a good agreement with those derived spectroscopically for stars in the Galaxy and Magellanic Clouds.

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“…They are known as β Cep/SPB hybrids (e.g. De Cat et al 2007;Pigulski & Pojmanski 2008;Handler 2009;Balona et al 2011;Degroote et al 2012b;Pápics et al 2012). …”

Section: Oscillation Spectra Of Early-type Starsmentioning

confidence: 99%

Seismic models of O and B stars with Kurucz’s opacity data

Cugier

2014

A&A

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“…Tkachenko et al (2013) determined atmospheric parameters from high resolution spectra for 69 stars in the Kepler data set that have γ Dor g-mode pulsations. Balona et al (2011b) similarly provided visual descriptions of 48 B stars in the Kepler data. Following the lead of these papers, McNamara, Jackiewicz & McKeever (2012) classified the light curves of 252 B stars in the Kepler data, describing many of the stars as 'Fg', meaning that they show frequency groups in their amplitude spectra.…”

Section: Introductionmentioning

confidence: 99%

A unifying explanation of complex frequency spectra of γ Dor, SPB and Be stars: combination frequencies and highly non-sinusoidal light curves

Kurtz¹,

Shibahashi²,

Murphy³

et al. 2015

Monthly Notices of the Royal Astronomical Society

150

199

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There are many Slowly Pulsating B (SPB) stars and γ Dor stars in the Kepler Mission data set. The light curves of these pulsating stars have been classified phenomenologically into stars with symmetric light curves and with asymmetric light curves. In the same effective temperature ranges as the γ Dor and SPB stars, there are variable stars with downward light curves that have been conjectured to be caused by spots. Among these phenomenological classes of stars, some show 'frequency groups' in their amplitude spectra that have not previously been understood. While it has been recognised that nonlinear pulsation gives rise to combination frequencies in a Fourier description of the light curves of these stars, such combination frequencies have been considered to be a only a minor constituent of the amplitude spectra. In this paper we unify the Fourier description of the light curves of these groups of stars, showing that many of them can be understood in terms of only a few base frequencies, which we attribute to g mode pulsations, and combination frequencies, where sometimes a very large number of combination frequencies dominate the amplitude spectra. The frequency groups seen in these stars are thus tremendously simplified. We show observationally that the combination frequencies can have amplitudes greater than the base frequency amplitudes, and we show theoretically how this arises. Thus for some γ Dor and SPB stars combination frequencies can have the highest observed amplitudes. Among the B stars are pulsating Be stars that show emission lines in their spectra from occasional ejection of material into a circumstellar disk. Our analysis gives strong support to the understanding of these pulsating Be stars as rapidly rotating SPB stars, explained entirely by g mode pulsations.

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“…One example is the B-type main sequence pulsators, which exhibit both pressure and high-order gravity modes, e.g., ν Eridani , 12 Lacertae (Handler et al 2006), γ Pegasi (Handler et al 2009). There are also bags of such pulsators identified from the space data from Kepler and CoRoT missions (e.g., Degroote et al 2009, Balona et al 2011, 2015a. However, so far none of the pulsational models can account for their oscillation spectra.…”

Section: Introductionmentioning

confidence: 99%

Interpretation of the BRITE oscillation data of the hybrid pulsator ν Eridani: a call for the modification of stellar opacities

Daszyńska‐Daszkiewicz

Pamyatnykh

Walczak

et al. 2016

Mon. Not. R. Astron. Soc.

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The analysis of the BRITE oscillation spectrum of the main sequence early B-type star ν Eridani is presented. Only models with the modified mean opacity profile can account for the observed frequency ranges as well as for the values of some individual frequencies. The number of the κ modified seismic models is constrained by the nonadiabatic parameter f , which is very sensitive to the opacity changes in the subphotospheric layers where the pulsations are driven. We present an example of the model that satisfies all the above conditions. It seems that the OPLIB opacities are preferred over those from the OPAL and OP projects. Moreover, we discuss additional consequences of the opacity modification, namely, an enhancement of the efficiency of convection in the Z-bump as well as an occurrence of close radial modes which is a kind of avoided-crossing phenomenon common for nonradial modes in standard main sequence models.

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Kepler observations of the variability in B-type stars

Cited by 148 publications

References 78 publications

Seismic models of O and B stars with Kurucz’s opacity data

Seismic models of O and B stars with Kurucz’s opacity data

A unifying explanation of complex frequency spectra of γ Dor, SPB and Be stars: combination frequencies and highly non-sinusoidal light curves

Interpretation of the BRITE oscillation data of the hybrid pulsator ν Eridani: a call for the modification of stellar opacities

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