Theoretical instability strips for<i>δ</i>Scuti and<i>γ</i> Doradus stars

Dupret, Marc‐Antoine; Grigahcène, A.; Garrido, R.; Gabriel, M.; Scuflaire, R.

doi:10.1051/0004-6361:20031740

Cited by 184 publications

(198 citation statements)

References 17 publications

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“…Theoretical calculations by Dupret et al (2004) also successfully reproduced the observed instability strip of the γ-Doradus stars, at least as it was known before the observations made by Kepler. Indeed, recently the Kepler satellite detected a large number of hybrid δ Scuti -γ Doradus pulsators lying on the left side of the blue edge of γ Doradus (Balona and Dziembowski, 2011;Balona, 2014), as shown in Fig.…”

Section: Convective Flux Blocking Mechanismsupporting

confidence: 67%

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Stellar oscillations - II - The non-adiabatic case

Samadi

Belkacem

Sonoi

2015

EAS Publications Series

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Abstract. A leap forward has been performed due to the space-borne missions, MOST, CoRoT and Kepler. They provided a wealth of observational data, and more precisely oscillation spectra, which have been (and are still) exploited to infer the internal structure of stars. While an adiabatic approach is often sufficient to get information on the stellar equilibrium structures it is not sufficient to get a full understanding of the physics of the oscillation. Indeed, it does not permit one to answer some fundamental questions about the oscillations, such as: What are the physical mechanisms responsible for the pulsations inside stars? What determines the amplitudes? To what extent the adiabatic approximation is valid? All these questions can only be addressed by considering the energy exchanges between the oscillations and the surrounding medium.This lecture therefore aims at considering the energetical aspects of stellar pulsations with particular emphasis on the driving and damping mechanisms. To this end, the full non-adiabatic equations are introduced and thoroughly discussed. Two types of pulsation are distinguished, namely the self-excited oscillations that result from an instability and the solar-like oscillations that result from a balance between driving and damping by turbulent convection. For each type, the main physical principles are presented and illustrated using recent observations obtained with the ultra-high precision photometry space-borne missions (MOST, CoRoT and Kepler). Finally, we consider in detail the physics of scaling relations, which relates the seismic global indices with the global stellar parameters and gave birth to the development of statistical (or ensemble) asteroseismology. Indeed, several of these relations rely on the same cause: the physics of non-adiabatic oscillations.

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Section: Convective Flux Blocking Mechanismsupporting

confidence: 67%

“…4.3) must be considered. Dupret et al (2004) calculations based on TDC finally confirmed the effectiveness of the convective flux blocking mechanism (see also Dupret et al, 2005).…”

Section: Convective Flux Blocking Mechanismmentioning

confidence: 65%

Stellar oscillations - II - The non-adiabatic case

Samadi

Belkacem

Sonoi

2015

EAS Publications Series

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“…The dot-dash line is a model for a star with an initial mass of 1.0M ⊙ in a binary system with a 0.9M ⊙ companion, orbital separation of 4.8R ⊙ and metallicity Z=0.008. The instability strip for δ-Scuti-type pulsations with radial order k = 4 is indicated by light-grey shading (Dupret et al 2004).…”

Section: Discussionmentioning

confidence: 99%

WASP 1628+10 – an EL CVn-type binary with a very low mass stripped red giant star and multiperiodic pulsations

Maxted¹,

Serenelli²,

Marsh³

et al. 2014

Monthly Notices of the Royal Astronomical Society

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The star 1SWASP J162842.31+101416.7 (WASP 1628+10) is one of several EL CVntype stars recently identified using the WASP database, i.e., an eclipsing binary star in which an A-type dwarf star (WASP 1628+10 A) eclipses the remnant of a disrupted red giant star (WASP 1628+10 B). We have measured the masses, radii and luminosities of the stars in WASP 1628+10 using photometry obtained in three bands (u', g', r') with the Ultracam instrument and medium-resolution spectroscopy. The properties of the remnant are well-matched by models for stars in a rarely-observed state evolving to higher effective temperatures at nearly constant luminosity prior to becoming a very low-mass white dwarf composed almost entirely of helium, i.e., we confirm that WASP 1628+10 B is a pre-He-WD. WASP 1628+10 A appears to be a normal A2 V star with a mass of 1.36 ± 0.05M ⊙ . By fitting models to the spectrum of this star around the Hγ line we find that it has an effective temperature T eff,A = 7500 ± 200 K and a metallicity [Fe/H] = −0.3±0.3. The mass of WASP 1628+10 B is only 0.135±0.02M ⊙ . The effective temperature of this pre-He-WD is approximately 9200 K. The Ultracam photometry of WASP 1628+10 shows variability at several frequencies around 40 cycles per day, which is typical for δ Sct-type pulsations often observed in early A-type stars like WASP 1628+10 A. We also observe frequencies near 114 cycles/day and 129 cycles/day, much higher than the frequencies normally seen in δ Sct stars. Additional photometry through the primary eclipse will be required to confirm that these higher frequencies are due to pulsations in WASP 1628+10 B. If confirmed, this would be only the second known example of a pre-He-WD showing high-frequency pulsations.

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“…Fig. 2 shows the log T eff versus log L/L diagram of our programme stars (Table 1) together with the borders of the δ Scuti and γ Doradus instability strips taken from Breger & Pamyatnykh (1998) and Dupret et al (2004), respectively. Four stars (HD 23392, HD 36726, HD 261904 and HD 294253) are well outside the instability strips whereas HD 90821 is just on the edge.…”

Section: Discussionmentioning

confidence: 99%

λ Bootis stars in the SuperWASP survey

Paunzen¹,

Skarka²,

Walczak³

et al. 2015

Mon. Not. R. Astron. Soc.

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We have analysed around 170 000 individual photometric WASP (Wide Angle Search for Planets) measurements of 15 well-established λ Bootis stars to search for variability. The λ Bootis stars are a small group of late-B to early-F, Pop I, stars that show moderate to extreme (surface) underabundances (up to a factor 100) of most Fe-peak elements, but solar abundances of lighter elements (C, N, O and S). They are excellent laboratories for the study of fundamental astrophysical processes such as diffusion, meridional circulation, stellar winds and accretion in the presence of pulsation. From the 15 targets, 8 are variable and 7 are apparently constant with upper limits between 0.8 and 3.0 mmag. We present a detailed time-series analysis and a comparison with previously published results. From an asteroseismologic study, we conclude that the found chemical peculiarities are most probably restricted to the surface.

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Theoretical instability strips forδScuti andγ Doradus stars

Cited by 184 publications

References 17 publications

Stellar oscillations - II - The non-adiabatic case

Stellar oscillations - II - The non-adiabatic case

WASP 1628+10 – an EL CVn-type binary with a very low mass stripped red giant star and multiperiodic pulsations

λ Bootis stars in the SuperWASP survey

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