HS 0702+6043: a star showing both short-period
 <i>p</i>-mode  and long-period <i>g</i>-mode oscillations

Schuh, S.; Huber, J.; Dreizler, S.; Heber, U.; O'Toole, S. J.; Green, E. M.; Fontaine, G.

doi:10.1051/0004-6361:200500210

Cited by 112 publications

(110 citation statements)

References 22 publications

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“…A few stars belong to both classes and are called hybrid (or sdBV rs ) pulsators, showing both p-and g-modes (e.g., Schuh et al 2006; see also the review by Charpinet et al 2009). …”

Section: Introductionmentioning

confidence: 99%

CoRoT opens a new era in hot B subdwarf asteroseismology

Charpinet¹,

Green

Baglin

et al. 2010

A&A

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Context. The asteroseismic exploitation of long period, g-mode hot B subdwarf (sdB) pulsators has been a long sought objective undermined, thus far, by the difficulty of obtaining sufficiently precise and continuous time series data from the ground. Aims. Fast photometry from space appears to be the only means of gathering the appropriate asteroseismic data for this type of star. We explore this possibility with the CoRoT (COnvection, ROtation, and planetary Transits) satellite. Methods. We obtained ∼24 days of high quality, nearly continuous photometric data with CoRoT during a short run (SRa03) dedicated to the long period sdB pulsator KPD 0629−0016. We analysed the frequency (period) content of the CoRoT time series by combining Fourier analysis, nonlinear least squares fitting, and prewhitening techniques. Results. Our study has led to the detection of a large number of g-mode pulsations in KPD 0629−0016, with 17 frequencies clearly identified in addition to 7 possible (although more uncertain) peaks emerging above the mean noise level (estimated at ∼57 ppm). This is more than is typically detected for sdB stars from the ground and, more importantly, the frequencies of all uncovered g-modes are, for the first time, reliably measured. This paves the way for a detailed asteroseismic analysis of this star. The oscillations are found in the 90−400 μHz frequency range with a dominant mode at 205.29 μHz (P = 1.353 h) of amplitude 0.246% of the mean brightness, i.e., typical of mid-radial order g-mode pulsations. Conclusions. These photometric observations of KPD 0629−0016 demonstrate that g-mode sdB pulsators have rich oscillation spectra that are accessible to current space-based facilities. CoRoT opens up a new era in asteroseismology of hot B subdwarf stars.

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“…A few stars belong to both classes and are called hybrid (or sdBV rs ) pulsators, showing both p-and g-modes (e.g., Schuh et al 2006; see also the review by Charpinet et al 2009). …”

Section: Introductionmentioning

confidence: 99%

CoRoT opens a new era in hot B subdwarf asteroseismology

Charpinet¹,

Green

Baglin

et al. 2010

A&A

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“…Especially interesting are the sdB pulsators that exhibit both p-and g-mode pulsations. Three of these so-called hybrid pulsators have been found at the intersection of the V361 Hya and V1093 Her stars (Oreiro et al 2005;Baran et al 2005;Schuh et al 2006;Lutz et al 2008).…”

Section: Introductionmentioning

confidence: 99%

Impact of helium diffusion and helium-flash-induced carbon production on gravity-mode pulsations in subdwarf B stars

Nelemans²,

Aerts

et al. 2009

A&A

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Context. Realistic stellar models are essential to the forward modelling approach in asteroseismology. For practicality however, certain model assumptions are also required. For example, in the case of subdwarf B stars, one usually starts with zero-age horizontal branch structures without following the progenitor evolution. Aims. We analyse the effects of common assumptions in subdwarf B models on the g-mode pulsational properties. We investigate if and how the pulsation periods are affected by the H-profile in the core-envelope transition zone. Furthermore, the effects of Cproduction and convective mixing during the core helium flash are evaluated. Finally, we reanalyse the effects of stellar opacities on the mode excitation in subdwarf B stars. Methods. We computed detailed stellar evolutionary models of subdwarf B stars, and their non-adiabatic pulsational properties. Atomic diffusion of H and He is included consistently during the evolution calculations. The number fractions of Fe and Ni are gradually increased by up to a factor of 10 around log T = 5.3. This is necessary for mode excitation and to approximate the resulting effects of radiative levitation. We performed a pulsational stability analysis on a grid of subdwarf B models constructed with OPAL and OP opacities. Results. We find that helium settling causes a shift in the theoretical blue edge of the g-mode instability domain to higher effective temperatures. This results in a closer match to the observed instability strip of long-period sdB pulsators, particularly for l ≤ 3 modes. We show further that the g-mode spectrum is extremely sensitive to the H-profile in the core-envelope transition zone. If atomic diffusion is efficient, details of the initial shape of the profile become less important in the course of evolution. Diffusion broadens the chemical gradients, and results in less effective mode trapping and different pulsation periods. Furthermore, we report on the possible consequences of the He-flash for the g-modes. The outer edge of a flash-induced convective region introduces an additional chemical transition in the stellar models, and the corresponding spike in the Brünt-Väisälä frequency produces a complicated mode trapping signature in the period spacings.

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“…In addition, a few stars are found to be hybrid pulsators showing both kind of modes simultaneously (Schuh et al 2006). In all cases, the oscillations are caused by an opacity (κ-)effect involving iron-group elements and radiative levitation to enrich sufficiently the driving region in the stellar envelope.…”

Section: Pulsations In Hot Subdwarfsmentioning

confidence: 98%

Pulsations in hot subdwarf stars: recent advances and prospects for testing stellar physics

et al. 2015

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Abstract. The evolved, core helium burning, extreme horizontal branch stars (also known as hot B subdwarfs) host several classes of pulsators showing either p-or g-modes, or both. They offer particularly favorable conditions for probing with asteroseismology their internal structure, thus constituting arguably the most interesting seismic window for this intermediate stage of stellar evolution. G-modes in particular have the power to probe deep inside these stars, down to the convective He-burning core boundary where uncertain physics (convection, overshooting, semi-convection) is at work. Space data recently obtained with CoRoT and Kepler are offering us the possibility to probe these regions in detail and possibly shed new light on how these processes shape the core structure. In this short paper, we present the most recent advances that have taken place in this field and we provide hints of the foreseen future achievements of hot subdwarf asteroseismology.

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HS 0702+6043: a star showing both short-period p-mode and long-period g-mode oscillations

Cited by 112 publications

References 22 publications

CoRoT opens a new era in hot B subdwarf asteroseismology

CoRoT opens a new era in hot B subdwarf asteroseismology

Impact of helium diffusion and helium-flash-induced carbon production on gravity-mode pulsations in subdwarf B stars

Pulsations in hot subdwarf stars: recent advances and prospects for testing stellar physics

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