On the<i>λ</i> Bootis spectroscopic binary hypothesis

Stütz, Ch.; Paunzen, E.

doi:10.1051/0004-6361:20066195

Cited by 13 publications

(18 citation statements)

References 22 publications

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“…Stütz & Paunzen (2006) Venn & Lambert (1990), though those authors derived slightly different T eff (8750 K) and log g (4.0) compared to our values of 8495 K and 3.90. λ Boo exhibits absorption near λ 4479 Å (Fig. 4).…”

Section: λ Boo = Hd 125162contrasting

confidence: 91%

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The composite-spectrum binary hypothesis does not explain theλBootis stars

Griffin

Gray

Corbally³

2012

A&A

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The existence of the λ Boo type as a class of chemically-peculiar stars in its own right has taxed numerous researchers, and has challenged spectroscopists to produce a model which is plausible, comprehensive and predictive. Stars which are recognized as members of the λ Boo class have late-B to early-F spectral types, and exhibit (often substantially) low abundances of Fe-peak elements although elements such as C, N, O and S may have more nearly solar abundances. Since less than 2% of objects within the relevant spectral-type domain appear to be λ Boo stars their existence has demanded rather special conditions, and has triggered opinion that this group may not in fact exist but that each case can be explained as an unrecognized binary. In this paper we examine those claims by monitoring 10 stars, listed in the literature as possible λ Boo stars but said to be "likely candidates" for composite-spectrum binaries, by employing high-dispersion spectroscopy in an intermittent observing programme designed to reveal the sort of line-profile changes that should be detectable if each object were really a pair of similar stars in an SB2 system. We also monitor two other stars: HR 7903, said to be a binary (but is more like an Ap star), and λ Boo itself. The sample includes 1 possible, 1 marginal and 4 definite λ Boo classifications. In addition, we derive the physical properties of the 12 stars by photometric and spectroscopic synthesis, and measure their radial velocities. Three of the sample show small line-profile variations, but not of the sort that can be attributed to the presence of a companion star; they are the suspected Ap star HR 7903, HR 6878 (which exhibits spectrum peculiarities very similar to those of HR 7903 but has not previously been classified as Bp or Ap), and λ Aql, whose rapid spectrum variations resemble those observed in spotted or CP stars. None of the stars shows any evidence to suggest that it could be a composite-spectrum binary.

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Section: λ Boo = Hd 125162contrasting

confidence: 91%

“…As in 21 LMi, the photospheric K line is strong enough to mask any small absorption feature that might also be present. Stütz & Paunzen (2006) also found no evidence for binarity from their statistical study of photometric indices.…”

Section: Lmi = Hd 87696mentioning

confidence: 95%

The composite-spectrum binary hypothesis does not explain theλBootis stars

Griffin

Gray

Corbally³

2012

A&A

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“…We then used state-of-the-art pulsation models to characterize the (in)stability properties. From this analysis we conclude that if the stars are still on the main sequence, which is the most accepted hypothesis (Stütz & Paunzen 2006), they are not intrinsically metal-weak. If they are beyond the terminal-age main sequence, the results are ambiguous.…”

Section: O N C L U S I O Nmentioning

confidence: 66%

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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“…A recent discussion of this hypothesis was presented by Stütz & Paunzen (2006). They concluded that at least some of these types of stars could be unsolved binary systems.…”

Section: Tablementioning

confidence: 99%

THE CHEMICAL COMPOSITION OFρPUPPIS AND THE SIGNS OF ACCRETION IN THE ATMOSPHERES OF B–F-TYPE STARS

Yushchenko

Gopka

Kang

et al. 2015

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We investigated the chemical composition of ρ Pup using high-resolution spectral observations taken from the Very Large Telescope and the IUE archives and also spectra obtained at the 1.8 m telescope of the Bohyunsan observatory in Korea. The abundances of 56 chemical elements and the upper limits of Li and Be abundances were determined. The abundance pattern of ρ Pup was found to be similar to that of Am-type stars. The possibility of the influence of the accretion of interstellar gas and dust on the abundance patterns of B-F-type stars is discussed. The plots of the relative abundances of chemical elements in the atmospheres of ρ Pup and δ Sct versus the second ionization potentials of these elements show the correlations. The discontinuities at 13.6 and 24.6 eV-the ionization potentials of hydrogen and helium, respectively, are also exhibited in these plots. These discontinuities can be explained by interaction of the atoms of interstellar gas, mainly hydrogen and helium atoms, with the atoms of stellar photospheres (so-called charge-exchange reactions). Note that only the jumps near 13.6 and 24.6 eV were pointed out in previous investigations of relative abundances versus the second ionization potentials for Am-type stars. The dependencies of the relative abundances of chemical elements on the second ionization potentials of these elements were investigated using the published abundance patterns of B-F-type stars. The correlations of relative and absolute abundances of chemical elements, second ionization potentials, and projected rotational velocities are clearly detected for stars with effective temperatures between 7,000 and 12,000 K. If the correlation of relative abundances and second ionization potentials can be explained by the accretion of interstellar gas on the stellar surfaces, the investigation of these correlations can provide valuable information on the density and velocities of interstellar gas in different regions of the Galaxy and also on the influence of this phenomenon on stellar evolution. The dependencies of the relative abundances of chemical elements on the condensation temperatures of these elements were also found in the atmospheres of ρ Pup, δ Sct, and other B-F-type stars. Ten possible λ Boo-type stars were detected. The effective temperatures of these objects are between 10,900 and 14,000 K.

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On theλ Bootis spectroscopic binary hypothesis

Cited by 13 publications

References 22 publications

The composite-spectrum binary hypothesis does not explain theλBootis stars

The composite-spectrum binary hypothesis does not explain theλBootis stars

λ Bootis stars in the SuperWASP survey

THE CHEMICAL COMPOSITION OFρPUPPIS AND THE SIGNS OF ACCRETION IN THE ATMOSPHERES OF B–F-TYPE STARS

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