The CoRoT B-type binary HD 50230: a prototypical hybrid pulsator with g-mode period and p-mode frequency spacings

Degroote, P.; Aerts, C.; Michel, E.; Briquet, Maryline; Pápics, P. I.; Amado, P. J.; Mathias, P.; Poretti, E.; Rainer, M.; Lombaert, R.; Hillen, M.; Morel, Thierry; Auvergne, M.; Baglin, A.; Baudin, F.; Catala, C.; Samadi, R.

doi:10.1051/0004-6361/201118548

Cited by 47 publications

(67 citation statements)

References 30 publications

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“…Such STFTs allow to decide whether we are dealing with multi mode beating of stable phase-coherent non-radial pulsation modes (see, e.g., Fig. 5 in Degroote et al, 2012) and/or a dominant base frequency due to rotational modulation (Degroote et al, 2011), or rather variability produced by a stochastic phenomenon. Examples of the latter can be found in Tkachenko et al (2012, Fig.…”

Section: Frequency Analysismentioning

confidence: 99%

Low-frequency photospheric and wind variability in the early-B supergiant HD 2905

Diaz

Aerts

Urbaneja

et al. 2018

A&A

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Context. Despite the important advances in space asteroseismology during the last decade, the early phases of evolution of stars with masses above ∼15 M (including the O stars and their evolved descendants, the B supergiants) have been only vaguely explored up to now. This is due to the lack of adequate observations for a proper characterization of the complex spectroscopic and photometric variability occurring in these stars. Aims. Our goal is to detect, analyze and interpret variability in the early-B type supergiant HD 2905 (κ Cas, B1 Ia) using long-term, ground based, high resolution spectroscopy. Methods. We gather a total of 1141 high-resolution spectra covering some 2900 days with three different high-performance spectrographs attached to 1 -2.6m telescopes at the Canary Islands observatories. We complement these observations with the Hipparcos light curve, which includes 160 data points obtained during a time span of ∼1200 days. We investigate spectroscopic variability of up to 12 diagnostic lines by using the zero and first moments of the line profiles. We perform a frequency analysis of both the spectroscopic and photometric dataset using Scargle periodograms. We obtain single snapshot and time-dependent information about the stellar parameters and abundances by means of the fastwind stellar atmosphere code. Results. HD 2905 is a spectroscopic variable with peak-to-peak amplitudes in the zero and first moments of the photospheric lines of up to 15% and 30 km s −1 , respectively. The amplitude of the line-profile variability is correlated with the line formation depth in the photosphere and wind. All investigated lines present complex temporal behavior indicative of multi-periodic variability with timescales of a few days to several weeks. No short-period (hourly) variations are detected. The Scargle periodograms of the Hipparcos light curve and the first moment of purely photospheric lines reveal a low-frequency amplitude excess and a clear dominant frequency at ∼0.37 d −1 . In the spectroscopy, several additional frequencies are present in the range 0.1 -0.4 d −1 . These may be associated with heat-driven gravity modes, convectively-driven gravity waves, or sub-surface convective motions. Additional frequencies are detected below 0.1 d −1 . In the particular case of Hα, these are produced by rotational modulation of a non-spherically symmetric stellar wind. Conclusions. Combined long-term uninterrupted space photometry with high-precision spectroscopy is the best strategy to unravel the complex low-frequency photospheric and wind variability of B supergiants. 3D simulations of waves and of convective motions in the sub-surface layers can shed light on a unique interpretation of the variability.

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Section: Frequency Analysismentioning

confidence: 99%

Low-frequency photospheric and wind variability in the early-B supergiant HD 2905

Diaz

Aerts

Urbaneja

et al. 2018

A&A

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“…For HD 46328 we only show one tenth of the data for visibility reasons. and 12, turned out to be of insufficient resolution and signalto-noise to capture the line-profile variability of such lowamplitude pulsations (Degroote et al 2012).…”

Section: The Measured Line-profile Variationsmentioning

confidence: 99%

On the use of the Fourier transform to determine the projected rotational velocity of line-profile variable B stars

Aerts

Simón‐Díaz

Groot

et al. 2014

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Context. The Fourier transform method is a popular tool for deriving the rotational velocities of stars from their spectral line profiles. However, its domain of validity does not include line-profile variables with time-dependent profiles. Aims. We investigate the performance of the method for such cases, by interpreting the line-profile variations of spotted B stars and of pulsating B stars, as if their spectral lines were caused by uniform surface rotation along with macroturbulence. Methods. We perform time-series analysis and harmonic least-squares fitting of various line diagnostics and of the outcome of several implementations of the Fourier transform method. Results. We find that the projected rotational velocities derived from the Fourier transform vary appreciably during the pulsation cycle whenever the pulsational and rotational velocity fields have similar magnitudes. The macroturbulent velocities derived while ignoring the pulsations can vary by tens of km s −1 during the pulsation cycle. The temporal behaviour of the deduced rotational and macroturbulent velocities are in antiphase with each other. The rotational velocity is in phase with the second moment of the line profiles. Conclusions. The application of the Fourier method to stars with considerable pulsational line broadening may lead to an appreciable spread in the values of the rotation velocity, and, by implication, of the deduced value of the macroturbulence. These two quantities should therefore not be derived from single snapshot spectra if the aim is to use them as a solid diagnostic evaluating stellar evolution models of slow-to-moderate rotators.

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“…In an attempt to give better estimates of the fundamental parameters of HD 43317, the parameters were determined from multicolour photometry following the method described in Degroote et al (2012). We used UV (ANS, TD1, Wesselius et al 1982Wesselius et al , 1980Thompson et al 1978), optical (Geneva, Johnson, Hipparcos, Tycho, Stromgren, Rufener 1988Rufener & Nicolet 1988;Mermilliod 1986;Høg et al 2000;Hauck & Mermilliod 1998), and near-infrared (2MASS, Wise, Cutri et al 2003Cutri et al , 2011Wright et al 2010) photometry.…”

Section: Sed-fittingmentioning

confidence: 99%

Gravito-inertial and pressure modes detected in the B3 IV CoRoT target HD 43317

Pápics

Briquet

Baglin

et al. 2012

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Context. OB stars are important building blocks of the Universe, but we have only a limited sample of them well understood enough from an asteroseismological point of view to provide feedback on the current evolutionary models. Our study adds one special case to this sample, with more observational constraints than for most of these stars. Aims. Our goal is to analyse and interpret the pulsational behaviour of the B3 IV star HD 43317 using the CoRoT light curve along with the ground-based spectroscopy gathered by the HARPS instrument. This way we continue our efforts to map the β Cep and SPB instability strips. Methods. We used different techniques to reveal the abundances and fundamental stellar parameters from the newly-obtained highresolution spectra. We used various time-series analysis tools to explore the nature of variations present in the light curve. We calculated the moments and used the pixel-by-pixel method to look for line profile variations in the high-resolution spectra. Results. We find that HD 43317 is a single fast rotator (v rot ≈ 50% v crit ) and hybrid SPB/β Cep-type pulsator with Solar metal abundances. We interpret the variations in photometry and spectroscopy as a result of rotational modulation connected to surface inhomogeneities, combined with the presence of both g and p mode pulsations. We detect a series of ten consecutive frequencies with an almost constant period spacing of 6339 s as well as a second shorter sequence consisting of seven frequencies with a spacing of 6380 s. The dominant frequencies fall in the regime of gravito-inertial modes.

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The CoRoT B-type binary HD 50230: a prototypical hybrid pulsator with g-mode period and p-mode frequency spacings

Cited by 47 publications

References 30 publications

Low-frequency photospheric and wind variability in the early-B supergiant HD 2905

Low-frequency photospheric and wind variability in the early-B supergiant HD 2905

On the use of the Fourier transform to determine the projected rotational velocity of line-profile variable B stars

Gravito-inertial and pressure modes detected in the B3 IV CoRoT target HD 43317

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