Pulsations of the Oe Star ζ Ophiuchi from
                    <i>MOST</i>
                    Satellite Photometry and Ground-based Spectroscopy

Walker, G. A. H.; Kuschnig, R.; Matthews, J. M.; Reegen, P.; Kallinger, T.; Kambe, Eiji; Saio, Hideyuki; Harmanec, P.; Guenther, D. B.; Moffat, A. F. J.; Ruciński, S. M.; Sasselov, Dimitar; Weiß, W. W.; Bohlender, D.; Božić, H.; Hashimoto, Osamu; Koubský, P.; Mann, R. G.; Ruždjak, Domagoj; Škoda, Petr; Šlechta, M.; Sudar, D.; Wolf, M.; Yang, Sean

doi:10.1086/430254

Cited by 70 publications

(64 citation statements)

References 15 publications

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“…We can compare the position in the HR diagram of our stars, HD 47129 (Mahy et al 2011), HD 46149 (Degroote et al 2010), HD 46202 (Briquet et al 2011) and ζ Oph (Walker et al 2005) to theoretical predictions of the β Cep and SPB instability strip. Zdravkov & Pamyatnykh (2008) present the theoretical strip for models up to 40 M for a metallicity Z = 0.02.…”

Section: Pulsations and Red Noisementioning

confidence: 89%

“…HD 46202 (O9 V) shows clear β Cep-like pulsations (Briquet et al 2011). Observations with the MOST (Microvariability and Oscillations of Stars) satellite of the O9.5 V star ζ Oph also show β Cep-type pulsations (Walker et al 2005). Among the early B-type stars, pulsation frequencies are easily found: Degroote et al (2009a) present a study of 358 candidate B-star pulsators, showing numerous classical SPBs (slowly-pulsating B stars).…”

Section: Pulsations and Red Noisementioning

confidence: 97%

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Variability in the CoRoT photometry of three hot O-type stars

Blomme

Mahy

Catala

et al. 2011

A&A

108

121

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Context. The detection of pulsational frequencies in stellar photometry is required as input for asteroseismological modelling. The second short run (SRa02) of the CoRoT mission has provided photometric data of unprecedented quality and time-coverage for a number of O-type stars. Aims. We analyse the CoRoT data corresponding to three hot O-type stars, describing the properties of their light curves and search for pulsational frequencies, which we then compare to theoretical model predictions. Methods. We determine the amplitude spectrum of the data, using the Lomb-Scargle and a multifrequency HMM-like technique. Frequencies are extracted by prewhitening, and their significance is evaluated under the assumption that the light curve is dominated by red noise. We search for harmonics, linear combinations, and regular spacings among these frequencies. We use simulations with the same time sampling as the data as a powerful tool to judge the significance of our results. From the theoretical point of view, we use the MAD non-adiabatic pulsation code to determine the expected frequencies of excited modes. Results. A substantial number of frequencies is listed, but none can be convincingly identified as being connected to pulsations. The amplitude spectrum is dominated by red noise. Theoretical modelling shows that all three O-type stars can have excited modes, but the relation between the theoretical frequencies and the observed spectrum is not obvious. Conclusions. The dominant red noise component in the hot O-type stars studied here clearly points to a different origin than the pulsations seen in cooler O stars. The physical cause of this red noise is unclear, but we speculate on the possibility of sub-surface convection, granulation, or stellar wind inhomogeneities being responsible.

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Section: Pulsations and Red Noisementioning

confidence: 89%

Section: Pulsations and Red Noisementioning

confidence: 97%

Variability in the CoRoT photometry of three hot O-type stars

Blomme

Mahy

Catala

et al. 2011

A&A

108

121

View full text Add to dashboard Cite

show abstract

“…This mainly concerns early-type stars such as δ Scuti, which can reach projected equatorial velocities (v sin i) of 200 km s −1 (Rodríguez et al 2000), β Cephei stars (v sin i < ∼ 300 km s −1 , Stankov & Handler 2005), and ζ Oph stars (v sin i < ∼ 400 km s −1 , Balona & Dziembowski 1999). Interestingly, the star ζ Oph (v sin i = 380 km s −1 ) has been observed by MOST and WIRE, thus revealing the presence of 19 different pulsation modes (Walker et al 2005;Bruntt, private communication).…”

Section: Introductionmentioning

confidence: 90%

Regular patterns in the acoustic spectrum of rapidly rotating stars

Reese

Lignières

Rieutord

2008

A&A

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Context. Rapid rotation modifies the structure of the frequency spectrum of pulsating stars, thus making mode identification difficult. Aims. We look for new forms of organisation for the frequency spectrum that can provide a basis for mode identification at high rotation rates. Methods. Acoustic modes in uniformly rotating polytropic models of stars are computed using a numerical code that fully takes the effects of rotation (centrifugal distortion and Coriolis acceleration) into account. All low-degree modes, = 0 to 3, with radial orders n = 1−10 and 21−25 for N = 3 polytropic models and n = 1−10 for N = 1.5 polytropic models are followed from a zero rotation rate up to 59% of the break-up velocity. Results. We find an empirical formula that gives a good description of the high-frequency range of the computed acoustic spectrum for high rotation rates. Differences between this formula and complete eigenmode calculations are shown to be substantially smaller than those obtained with a 3rd order perturbative method valid at low rotation rates.

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“…The β Cephei-type pulsations were, however, found in O-type stars (e.g. Walker et al 2005;Pigulski & Pojmanski 2008), and oscillations with periods of the order of one day were commonly present, as was first predicted by Vogt & Penrod (1983) from observed variability of line profiles detected by Walker et al (1979). CoRoT observations show further examples of the variability of O stars and several frequencies in light curves were found, which were not predicted to be unstable modes by the OPAL and OP seismic models (cf.…”

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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Pulsations of the Oe Star ζ Ophiuchi from MOST Satellite Photometry and Ground-based Spectroscopy

Cited by 70 publications

References 15 publications

Variability in the CoRoT photometry of three hot O-type stars

Variability in the CoRoT photometry of three hot O-type stars

Regular patterns in the acoustic spectrum of rapidly rotating stars

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

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