Pulsations in the late-type Be star HD 50 209 detected by CoRoT

Diago, P. D.; Gutiérrez‐Soto, J.; Auvergne, M.; Fabregat, J.; Hubert, A. M.; Floquet, M.; Frémat, Y.; Garrido, R.; Andrade, L.; Batz, B. de; Emílio, M.; Lara, F. Espinosa; Huat, Anne-Laure; Janot-Pacheco, E.; Leroy, B.; Martayan, Christophe; Neiner, C.; Semaan, T.; Suso, J.; Catala, C.; Poretti, E.; Rainer, M.; Uytterhoeven, K.; Michel, E.; Samadi, R.

doi:10.1051/0004-6361/200911901

Cited by 37 publications

(41 citation statements)

References 22 publications

(35 reference statements)

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“…Various causes for what we see in our periodograms can be eliminated: rotational effects on pulsation can be excluded because our periodograms are very different from those of Be stars (e.g. Diago et al 2009). Spots on the surface of the star would give clearly isolated frequencies (and linear combinations between them).…”

Section: Pulsations and Red Noisementioning

confidence: 99%

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

Blomme

Mahy

Catala

et al. 2011

A&A

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104

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: 99%

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

Blomme

Mahy

Catala

et al. 2011

A&A

Self Cite

104

121

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“…Some others can be identified with the beating frequency of the two stellar frequencies with the highest amplitude or modes with m = 0 (see e.g. Diago et al 2009). Periods that have not been observed during at least 6 cycles (P ≥ T/6) are considered with caution.…”

Section: Long-term Trendmentioning

confidence: 99%

“…The plot shows that, at least at the beginning of the run, the two frequencies exchange their values of power, i.e., the power of F 1 increases when the power of F 2 decreases, and vice versa. Unfortunately, the short duration of the light curve does not allow us to perform a time-frequency analysis, as applied in the study of other Be stars observed during a longer run (see e.g., Diago et al 2009). …”

Section: Analysis Of the Corot Light Curve Of Hd 175869mentioning

confidence: 99%

Low-amplitude variations detected by CoRoT in the B8IIIe star HD 175869

Gutiérrez‐Soto

Floquet²,

Samadi

et al. 2009

A&A

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Context. The origin of the short-term variability in Be stars remains a matter of controversy. Pulsations and rotational modulation are the components of the favored hypothesis. Aims. We present our analysis of CoRoT data of the B8IIIe star HD 175869 observed during the first short run in the center direction (SRC1). Methods. We review both the instrumental effects visible in the CoRoT light curve and the analysis methods used by the CoRoT Be team. We applied these methods to the CoRoT light curve of the star HD 175869. A search for line-profile variations in the spectroscopic data was also performed. We also searched for a magnetic field, by applying the LSD technique to spectropolarimetric data. Results. The light curve exhibits low-amplitude variations of the order of 300 μmag with a double wave shape. A frequency within the range determined for the rotational frequency and 6 of its harmonics are detected. The main frequency and its first harmonic exhibit amplitude variations of a few days. Other significant frequencies of low-amplitude from 25 to a few μmag are also found. The analysis of line profiles from ground-based spectroscopic data does not detect any variation. In addition, no Zeeman signature was found. Conclusions. Inhomogeneities caused by stellar activity in or just above the photosphere are proposed to produce the photometric variability detected by CoRoT in the Be star HD 175869. The hypothesis that non-radial pulsations are the origin of these variations cannot be excluded.

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“…A remarkable finding is the outburst signal detected in the B0.5IVe star HD 49330 (Huat et al 2009), a phenomenon that has not been observed to occur in any of the other observed Be stars, which are of later spectral type. Theoretical work is needed to understand and interpret the observed frequency patterns in the Be pulsators (Neiner et al 2009;Diago et al 2009;Gutiérrez-Soto et al 2009). Progress is hampered by the mathematical complexity of describing the oscillations in these flattened stars, induced by their rapid rotation, often close to their critical velocity.…”

Section: Introductionmentioning

confidence: 99%

Seismic modelling of theβ Cephei star HD 180642 (V1449 Aquilae)

Aerts

Briquet

Degroote

et al. 2011

A&A

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Context. We present modelling of the β Cep star HD 180642 based on its observational properties deduced from CoRoT and groundbased photometry as well as from time-resolved spectroscopy. Aims. We investigate whether present-day state-of-the-art models are able to explain the full seismic behaviour of this star, which has extended observational constraints for this type of pulsator. Methods. We constructed a dedicated database of stellar models and their oscillation modes tuned to fit the dominant radial mode frequency of HD 180642, by means of varying the hydrogen content, metallicity, mass, age, and core overshooting parameter. We compared the seismic properties of these models with those observed. Results. We find models that are able to explain the numerous observed oscillation properties of the star, for a narrow range in mass of 11.4-11.8 M and no or very mild overshooting (with up to 0.05 local pressure scale heights), except for an excitation problem of the = 3, p 1 mode. We deduce a rotation period of about 13 d, which is fully compatible with recent magnetic field measurements. The seismic models do not support the earlier claim of solar-like oscillations in the star. We instead ascribe the power excess at high frequency to non-linear resonant mode coupling between the high-amplitude radial fundamental mode and several of the low-order pressure modes. We report a discrepancy between the seismic and spectroscopic gravity at the 2.5σ level.

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Pulsations in the late-type Be star HD 50 209 detected by CoRoT

Cited by 37 publications

References 22 publications

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

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

Low-amplitude variations detected by CoRoT in the B8IIIe star HD 175869

Seismic modelling of theβ Cephei star HD 180642 (V1449 Aquilae)

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