Late stages of the evolution of A-type stars on the main sequence: comparison between observed chemical abundances and diffusion models for 8 Am stars of the Praesepe cluster

Fossati, L.; Bagnulo, S.; Monier, Richard; Khan, S. A.; Kochukhov, O.; Landstreet, J. D.; Wade, G. A.; Weiß, W. W.

doi:10.1051/0004-6361:20078320

Cited by 83 publications

(150 citation statements)

References 52 publications

(99 reference statements)

Supporting

Mentioning

135

Contrasting

Order By: Relevance

“…Unfortunately, however, no lines of this element are suitable for measurement in our spectra of either system. Nevertheless, the overall abundance pattern in both SW CMa and HW CMa is quite similar to that found in many other studies of Am stars (see, e.g., Okyudo & Sadakane 1990;Hui-Bon-Hoa 2000;Yushchenko et al 2004;Iliev et al 2006;Fossati et al 2007;Gebran et al 2008Gebran et al , 2010.…”

Section: Radial Velocities and Spectroscopic Orbitsupporting

confidence: 65%

Absolute dimensions of eclipsing binaries

Torres

Clausen

Bruntt

et al. 2012

A&A

View full text Add to dashboard Cite

Context. Accurate physical properties of eclipsing stars provide important constraints on models of stellar structure and evolution, especially when combined with spectroscopic information on their chemical composition. Empirical calibrations of the data also lead to accurate mass and radius estimates for exoplanet host stars. Finally, accurate data for unusual stellar subtypes, such as Am stars, also help to unravel the cause(s) of their peculiarities. Aims. We aim to determine the masses, radii, effective temperatures, detailed chemical composition and rotational speeds for the Am-type eclipsing binaries SW CMa (A4-5m) and HW CMa (A6m) and compare them with similar normal stars. Methods. Accurate radial velocities from the Digital Speedometers of the Harvard-Smithsonian Center for Astrophysics were combined with previously published uvby photometry to determine precise physical parameters for the four stars. A detailed abundance analysis was performed from high-resolution spectra obtained with the Nordic Optical Telescope (La Palma). Results. We find the masses of the (relatively evolved) stars in SW CMa to be 2.10 and 2.24 M , with radii of 2.50 and 3.01 R , while the (essentially zero-age) stars in HW CMa have masses of 1.72 and 1.78 M , radii of 1.64 and 1.66 R -all with errors well below 2%. Detailed atmospheric abundances for one or both components were determined for 14 elements in SW CMa (

show abstract

Section: Radial Velocities and Spectroscopic Orbitsupporting

confidence: 65%

Absolute dimensions of eclipsing binaries

Torres

Clausen

Bruntt

et al. 2012

A&A

View full text Add to dashboard Cite

show abstract

“…Recent studies have obtained abundance determinations for numerous A and F stars of open clusters for a number of chemical species (Burkhart & Coupry 2000;Hui-Bon-Hoa 2000;Monier 2005;Fossati et al 2007; in an effort to confront relatively well constrained stars to current evolutionary models. The advantage of observing cluster stars is that they generally have the same age and initial metallicity, which greatly facilitates a comparison with models.…”

Section: Astrophysical Contextmentioning

confidence: 99%

“…In terms of stellar age, this upswing only lasts 3 Myr before the star starts its descent onto the red giant branch. While it has very little effect on surface abundances, models were chosen at this age in order to be A&A 521, A62 (2010) Burkhart & Coupry (2000); diamonds, Fossati et al (2007). Curves correspond to models listed at the top of the figure.…”

Section: Open Cluster Starsmentioning

confidence: 99%

AmFm and lithium gap stars

Vick

Michaud

Richer

et al. 2010

A&A

102

View full text Add to dashboard Cite

Aims. A thorough study of the effects of mass loss on internal and surface abundances of A and F stars is carried out in order to constrain mass loss rates for these stars, as well as further elucidate some of the processes which compete with atomic diffusion. Methods. Self-consistent stellar evolution models of 1.3 to 2.5 M stars including atomic diffusion and radiative accelerations for all species within the OPAL opacity database were computed with mass loss and compared to observations as well as previous calculations with turbulent mixing. Results. Models with unseparated mass loss rates between 5 × 10 −14 and 10 −13 M yr −1 reproduce observations for many cluster AmFm stars as well as Sirius A and o Leonis. These models also explain cool Fm stars, but not the Hyades lithium gap. Like turbulent mixing, these mass loss rates reduce surface abundance anomalies; however, their effects are very different with respect to internal abundances. For most of the main-sequence lifetime of an A or F star, surface abundances in the presence of such mass loss depend on separation which takes place between log ΔM/M * = −6 and −5. Conclusions. The current observational constraints do not allow us to conclude that mass loss is to be preferred over turbulent mixing (induced by rotation or otherwise) in order to explain the AmFm phenomenon. Internal concentration variations which could be detectable through asteroseismic tests should provide further information. If atomic diffusion coupled with mass loss are to explain the Hyades Li gap, the wind would need to be separated.

show abstract

“…We derived a microturbulence velocity (ξ)= 2 ± 1 km/s by minimising the standard deviation of weak and strong lines of both Fe I and Fe II, in the same way as described by Fossati et al (2007). We also calculated ξ=2.6 km/s from the relation given by Pace et al (2006): ξ = −4.7 log(T e f f ) + 20.9 km/s.…”

Section: Atmospheric Parameters and Abundance Analysismentioning

confidence: 99%

A spectroscopic study of DD UMa: Ursa Major group member and candidate for BRITE

Elmaslı¹,

Fossati²,

Folsom³

et al. 2012

New Astronomy

Self Cite

View full text Add to dashboard Cite

The Ursa Major group is a nearby stellar supercluster which, while not gravitationally bound, is defined by co-moving members. DD UMa is a δ Scuti star whose membership in the Ursa Major group is unclear.The objective of this study is to confirm the membership of DD UMa in the Ursa Major group, as well as perform a detailed spectral analysis of the star. Since DD UMa is a low-amplitude δ Scuti star, we performed a frequency analysis. We determined fundamental parameters, chemical abundances, and derive a mass and age for the star.For this study we observed DD UMa at the Okayama Astrophysical Observatory with the high-resolution spectrograph HIDES, between the 27 th of February and the 4 th March, 2009. Additional observations were extracted from the ELODIE archive in order to expand our abundance analysis. Group membership of DD UMa was assessed by examining the velocity of the star in Galactic coordinates. Pulsational frequencies were determined by examining line profile variability in the HIDES spectra. Stellar fundamental parameters and chemical abundances were derived by fitting synthetic spectra to both the HIDES and ELODIE observations. DD UMa is found to be a member of the extended stream of the Ursa Major group, based on the space motion of the star. This is supported by the chemical abundances of the star being consistent with those of Ursa Major group members. The star is found to be chemically solar, with T e f f = 7450 ± 150 K and log g = 3.98 ± 0.2. We found pulsational frequencies of 9.4 c/d and 15.0 c/d. While these frequencies are insufficient to perform an asteroseismic study, DD UMa is a good bright star candidate for future study by the BRITE-constellation.

show abstract

Late stages of the evolution of A-type stars on the main sequence: comparison between observed chemical abundances and diffusion models for 8 Am stars of the Praesepe cluster

Cited by 83 publications

References 52 publications

Absolute dimensions of eclipsing binaries

Absolute dimensions of eclipsing binaries

AmFm and lithium gap stars

A spectroscopic study of DD UMa: Ursa Major group member and candidate for BRITE

Contact Info

Product

Resources

About