The Atmospheres of A-Type Subdwarfs and 95 Leonis.

Chamberlain, Joseph W.; Aller, L. H.

doi:10.1086/145451

Cited by 110 publications

(77 citation statements)

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“…Concerning A-type subdwarfs, there is no clear evidence for their existence. Besides some historical papers on this topic (Chamberlain & Aller 1951;Greenstein 1954), we found only two A-type subdwarfs with trigonometric parallaxes in SIMBAD (corresponding to distances >180 pc). One of those (HD 224927) is a close binary with an A-type primary, whereas the other (HD 161817) is classified as a horizontal branch star.…”

Section: Introductionmentioning

confidence: 66%

An ancient F-type subdwarf from the halo crossing the Galactic plane

Scholz

Heber

Heuser

et al. 2015

A&A

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Aims. We selected the bluest object, WISE J0725−2351, from Luhman's new high proper motion (HPM) survey based on observations with the Wide-field Infrared Survey Explorer (WISE) for spectroscopic follow-up observations. Our aim was to unravel the nature of this relatively bright (V ∼ 12, J ∼ 11) HPM star (µ = 267 mas/yr). Methods. We obtained low-and medium-resolution spectra with the European Southern Observatory (ESO) New Technology Telescope (NTT)/EFOSC2 and Very Large Telescope (VLT)/X-Shooter instruments, investigated the radial velocity and performed a quantitative spectral analysis that allowed us to determine physical parameters. The fit of the spectral energy distribution based on the available photometry to low-metallicity model spectra and the similarity of our target to a metal-poor benchmark star (HD 84937) allowed us to estimate the distance and space velocity. Results. As in the case of HD 84937, we classified WISE J0725−2351 as sdF5: or a metal-poor turnoff star with [Fe/H] = −2.0 ± 0.2, T eff = 6250 ± 100 K, log g = 4.0 ± 0.2, and a possible age of about 12 Gyr. At an estimated distance of more than 400 pc, its proper motion translates to a tangential velocity of more than 500 km s −1 . Together with its constant (on timescales of hours, days, and months) and large radial velocity (about +240 km s −1 ), the resulting Galactic restframe velocity is about 460 km s −1 , implying a bound retrograde orbit for this extreme halo object that currently crosses the Galactic plane at high speed.

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Section: Introductionmentioning

confidence: 66%

An ancient F-type subdwarf from the halo crossing the Galactic plane

Scholz

Heber

Heuser

et al. 2015

A&A

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“…At the time of the writing of B 2 FH no member of a globular cluster had been analyzed in detail for its chemical composition. Multicolor photometry and low resolution spectroscopy had strongly suggested that globular cluster stars were metal deficient, probably similar to the subdwarfs analyzed by Chamberlain and Aller (1951). Using spectra obtained by Greenstein with the then new 200 inch telescope and exposures of up to three full nights, Helfer et al (1959) found metal deficiencies of a factor of 20 and 200, as compared with the sun for stars in M13 and M92.…”

Section: B O Depletion and The Enhancement Of Na And Almentioning

confidence: 83%

“…Due to blending of absorption lines and molecular bands a quantiative comparison of carbon and oxygen red giants was not possible. More recently the subdwarfs had been found to be metal-poor by factors more than 10 (Chamberlain and Aller, 1951), and the heavy element stars such as the Ba II stars and S stars were known to show abundance excesses of certain species by factors near 10 ( . Of great importance was the discovery of Tc in S stars (Merrill, 1952) since the longest lived isotope of Tc has a half-life of 4ϫ10 6 years and Cameron (1955) had shown that 99 Tc, with a half-life of only 3ϫ10 5 years was the most easily produced isotope.…”

Section: B the Astronomical Background In 1957mentioning

confidence: 99%

Synthesis of the elements in stars: forty years of progress

et al. 1997

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Forty years ago Burbidge, Burbidge, Fowler, and Hoyle combined what we would now call fragmentary evidence from nuclear physics, stellar evolution and the abundances of elements and isotopes in the solar system as well as a few stars into a synthesis of remarkable ingenuity. Their review provided a foundation for forty years of research in all of the aspects of low energy nuclear experiments and theory, stellar modeling over a wide range of mass and composition, and abundance studies of many hundreds of stars, many of which have shown distinct evidence of the processes suggested by B 2 FH. In this review we summarize progress in each of these fields with emphasis on the most recent developments. [S0034-6861(97)

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“…, on the entry m column Notes on individual stars: (10) , BPS 1269A: The T e and log g values derived from Breger's model atmosphere calibration were extrapolated from his grid. HD 19445: Chamberlain and Aller (1951) give T e = 6300, log g = 4.8. Cohen and Strom f1968) give T = 5800, log g = 4.0, while Cayrel (1968) gives T g = 6300 and questions the trigonometric parallax: the star should be fainter to be on the main sequence.…”

Section: Analysis and Discussionmentioning

confidence: 99%

A survey for small-amplitude variability among population II stars.

McMillan¹,

Breger²,

Ferland³

et al. 1976

PASP

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A search for small-amplitude variability among members of old stellar populations reveals no variability >0 ,?1 01 among 15 metal-deficient or high-velocity F-and G-type subdwarfs, 13 old-disk main-sequence F stars, four cluster blue stragglers, and seven blue horizontal-branch field stars. Variability was detected in two A-type stars: A metal-deficient main-sequence A star, BDS 1269A = HD 15165 is shown to have 8 Scuti-like variability, and the variability of the high-velocity field blue straggler HD 100363 reported by Eggen (1971) is confirmed. The high-velocity sdAp star GD-210, a suspected variable, showed no amplitude > 0 ,p 017 for three hours.T eff and logg of ten high-velocity, short-period variables are similar to those of the 8 Scuti stars with Uff ^ 7800° K, although the low-mass variables in the sample probably do not share the same evolutionary history as the higher-mass field blue stragglers.

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The Atmospheres of A-Type Subdwarfs and 95 Leonis.

Cited by 110 publications

References 0 publications

An ancient F-type subdwarf from the halo crossing the Galactic plane

An ancient F-type subdwarf from the halo crossing the Galactic plane

Synthesis of the elements in stars: forty years of progress

A survey for small-amplitude variability among population II stars.

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