New grids of ATLAS9 atmospheres I: Influence of convection treatments on model structure and on observable quantities

Heiter, U.; Kupka, F.; Veer-Menneret, C. van 't; Barban, C.; Weiß, W. W.; Goupil, M. J.; Schmidt, Wolfgang; Katz, David; Garrido, R.

doi:10.1051/0004-6361:20020788

Cited by 158 publications

(194 citation statements)

References 29 publications

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“…In the proper treatment of the CGM, the convection length scale Λ is the distance to the convection/radiation regime boundary. This mimics the increase in the convective efficiency with depth (Heiter et al 2002) and the associated smooth change in the thermal gradient. However, this treatment is not handled by our code where Λ = α cgm H p .…”

Section: Introductionmentioning

confidence: 66%

Surface convection and red-giant radius measurements

Piau

Kervella

Dib

et al. 2011

A&A

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Phenomenological models of convection adopt characteristic length scales that are chosen to fit solar or stellar observations. We investigate whether changes in these length scales are required between the Sun and low mass stars on the red giant branch (RGB). The question is addressed jointly in the frameworks of the mixing length theory and the full spectrum of turbulence model. For both models, the convective length scale is assumed to be a fixed fraction of the local pressure scale height. We use constraints provided by the observed effective temperatures and linear radii independently. We consider a sample of 38 nearby giants and subgiants for which surface temperatures and luminosities are known accurately and the radii are determined by interferometry to better than 10%. We computed dedicated models for the few cases where the stellar masses were determined by asteroseismological measurements. First we calibrated the solar models. With the same physics, we then computed RGB models for masses between 0.9 M and 2.5 M and metallicities ranging from [Fe/H] = −0.34 to solar. The evolution is followed up to 10 3 L . Special attention is given to the opacities and the non-grey atmosphere models used as boundary conditions for which the model of convection is the same as in the interior. For both the mixing length theory and the full spectrum of turbulence models, the characteristic solar length scale for convection has to be slightly reduced to fit the lower edge of the observed RGB. The corresponding models also agree more closely with the expected mass distribution on the RGB and the seismic constraints. These results are robust regardless of effective temperatures determined spectroscopically or radii determined interferometrically are used.

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Section: Introductionmentioning

confidence: 66%

Surface convection and red-giant radius measurements

Piau

Kervella

Dib

et al. 2011

A&A

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“…The method and the VWA software have been described in detail by Bruntt et al (2002Bruntt et al ( , 2004 and the method compared to the classical EW method by Bikmaev et al (2002). The abundance analysis relies on atomic parameters from the VALD database (Kupka et al 1999;Piskunov et al 1995) and uses modified ATLAS9 atmospheric models from interpolation in the grid published by Heiter et al (2002). The least blended atomic lines are selected automatically by VWA but additional lines can be chosen manually.…”

Section: Abundance Analysis: Methodsmentioning

confidence: 99%

Binarity, activity and metallicity among late-type stars

Dall¹,

Bruntt²,

Strassméier

2005

A&A

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We present the first in a series of papers that attempt to investigate the relation between binarity, magnetic activity, and chemical surface abundances of cool stars. In the current paper, we lay out and test two abundance analysis methods and apply them to two well-known, active, single stars, HD 27536 (G8IV-III) and HD 216803 (K5V), presenting photospheric fundamental parameters and abundances of Li, Al, Ca, Si, Sc, Ti, V, Cr, Fe, Co and Ni. The abundances from the two methods agree within the errors for all elements except calcium in HD 216803, which means that either method yields the same fundamental model parameters and the same abundances. Activity is described by the radiative loss in the Ca ii H and K lines with respect to the bolometric luminosity, through the activity index R HK . Binarity is established by very precise radial velocity (RV) measurements using HARPS spectra. The spectral line bisectors are examined for correlations between RV and bisector shape to distinguish between the effects of stellar activity and unseen companions. We show that HD 27536 exhibit RV variations mimicking the effect of a low-mass (m ∼ 4 M J ) companion in a relatively close (a ∼ 1 AU) orbit. The variation is strongly correlated with the activity, and consistent with the known photometric period P = 306.9 d, demonstrating a remarkable coherence between R HK and the bisector shape, i.e. between the photosphere and the chromosphere. We discuss the complications involved in distinguishing between companion and activity induced RV variations.

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“…We have used the software package sme ("Spectroscopy Made Easy", Valenti & Piskunov 1996) version 412 beta to fit synthetic spectra based on Kurucz' atlas9 model atmospheres (Heiter et al 2002) to the disentangled spectra of WASP 1628+10 A and WASP 1628+10 B. Atomic and molecular line data were obtained from the Vienna Atomic Line Database version VALD3 4 .…”

Section: Effective Temperature Estimatesmentioning

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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New grids of ATLAS9 atmospheres I: Influence of convection treatments on model structure and on observable quantities

Cited by 158 publications

References 29 publications

Surface convection and red-giant radius measurements

Surface convection and red-giant radius measurements

Binarity, activity and metallicity among late-type stars

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

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