217 citations · 855 across the 12 of their papers we have counts for
12 papers
A three-dimensional hydrodynamical line profile analysis of iron lines and barium isotopes in HD140283
A. J. Gallagher, H. -G. Ludwig, S. G. Ryan +1
Heavy-elements, i.e. those beyond the iron peak, mostly form via two neutron capture processes: the s- and r-process. Metal-poor stars should contain fewer isotopes that form via t…
The AGB population in IC 1613 using JHK photometry
L. F. Sibbons, S. G. Ryan, M. Irwin +1
A member of the Local Group, IC 1613 is a gas rich irregular dwarf galaxy that appears to have formed stars continuously over the last 10 Gyr and is relatively independent of exter…
The Most Metal-Poor Stars. IV. The Two Populations With [Fe/H] < -3.0
John E. Norris, David Yong, M. S. Bessell +8
We discuss the carbon-normal and carbon-rich populations of Galactic halo stars having [Fe/H] < -3.0, utilizing chemical abundances from high-resolution, high-S/N model-atmosphere…
The Most Metal-Poor Stars. III. The Metallicity Distribution Function and CEMP Fraction
David Yong, John E. Norris, M. S. Bessell +6
We examine the metallicity distribution function (MDF) and fraction of carbon-enhanced metal-poor (CEMP) stars in a sample that includes 86 stars with [Fe/H] < -3.0, based on high-…
The Most Metal-Poor Stars. I. Discovery, Data, and Atmospheric Parameters
John E. Norris, M. S. Bessell, David Yong +7
We report the discovery of 34 stars in the Hamburg/ESO Survey for metal-poor stars and the Sloan Digital Sky Survey that have [Fe/H] < -3.0. Their median and minimum abundances are…
The AGB population of NGC 6822: distribution and the C/M ratio from JHK photometry
L. F. Sibbons, S. G. Ryan, M. -R. L. Cioni M. Irwin +1
NGC 6822 is an irregular dwarf galaxy and part of the Local Group. Its close proximity and apparent isolation provide a unique opportunity to study galactic evolution without any o…
The barium isotopic fractions in five metal-poor stars
A. J. Gallagher, S. G. Ryan, A. Hosford +3
We provide measurements of the Ba isotopic fractions for five metal-poor stars derived with an LTE analysis using 1D model stellar atmospheres. We use high resolution (R\equivλ/Δλ=…
Lithium abundances of halo dwarfs based on excitation temperatures. II. NLTE
A. Hosford, A. E. Garcia Perez, R. Collet +3
One of the most important factors in determining the stellar lithium abundance is the effective temperature. In a previous study by the authors, new effective temperatures Teff for…
Spectroscopic Studies of Extremely Metal-Poor Stars with the Subaru High Dispersion Spectrograph. IV. The alpha-Element-Enhanced Metal-Poor Star BS16934-002
Wako Aoki, Satoshi Honda, Timothy C. Beers +7
A detailed elemental abundance analysis has been carried out for the very metal-poor ([Fe/H]=-2.7) star BS16934-002, which was identified in our previous work as a star exhibiting…
The new record holder for the most iron-poor star: HE 1327-2326, a dwarf or subgiant with [Fe/H]=-5.4
A. Frebel, W. Aoki, N. Christlieb +16
We describe the discovery of HE 1327-2326, a dwarf or subgiant with [Fe/H]}=-5.4. The star was found in a sample of bright metal-poor stars selected from the Hamburg/ESO survey. It…
HE1327-2326, an unevolved star with [Fe/H]<-5.0. I. A Comprehensive Abundance Analysis
W. Aoki, A. Frebel, N. Christlieb +17
We present the elemental abundances of HE1327-2326, the most iron-deficient star known, determined from a comprehensive analysis of spectra obtained with the Subaru Telescope High…
Lithium 6104A in Population II stars
A. Ford, R. D. Jeffries, B. Smalley +5
We have obtained echelle spectroscopy of 14 Population II objects selected from those previously observed by Bonifacio & Molaro (1997). For one object, HD 140283, we obtained exqui…