Related papers: HE 0557-4840 - Ultra-Metal-Poor and Carbon-Rich
The vast majority of the most iron-poor stars in the Galaxy exhibit a strong carbon enhancement, with C/H ratios only about two orders of magnitude below solar. This unusual chemical composition likely reflects the properties of the gas…
We report a detailed abundance analysis for HE0107-5240, a halo giant with [Fe/H]_NLTE=-5.3. This star was discovered in the course of follow-up medium-resolution spectroscopy of extremely metal-poor candidates selected from the digitized…
We present, for the first time, a detailed abundance analysis of the carbon star HE 1104$-$0957 based on high resolution (R${\sim}$ 50\,000) spectra. Our analysis shows that the object is an extremely metal-poor star with [Fe/H] $\sim$…
We discuss the origin of HE0107-5240 which is the most metal poor star yet observed ([Fe/H] = -5.3). Its discovery has an important bearing on the question of the observability of "first generation" stars. In common with other metal-poor…
We present results of an analysis of high-resolution spectra obtained with the Subaru Telescope High Dispersion Spectrograph, of two Carbon-Enhanced Metal-Poor stars, HE 1305+0007 and HE 1152-0355, and of the classical CH star HD 5223. All…
We present an elemental abundance analysis for four newly discovered ultra metal-poor stars from the Hamburg/ESO survey, with $\mathrm{[Fe/H]}\leq-4$. Based on high-resolution, high signal-to-noise spectra, we derive abundances for 17…
We show that the "puzzling" chemical composition observed in the extremely metal poor star HE0107-5240 may be naturally explained by the concurrent pollution of at least two supernovae. In the simplest possible model a supernova of quite…
We report on the discovery of seven low-metallicity stars selected from the Hamburg/ESO Survey, six of which are extremely metal-poor ([Fe/H]<-3.0), with four having [Fe/H]<-3.5. Chemical abundances or upper limits are derived for these…
The two known ``hyper-metal-poor'' (HMP) stars, HE0107-5240 and HE1327-2326, have extremely high enhancements of the light elements C, N, and O relative to Fe and appear to represent a statistically significant excess population relative to…
High-resolution, high-signal-to-noise (<S/N> = 85) spectra have been obtained for five stars -- CD-24:17504, CD-38:245, CS 22172-002, CS 22885-096, and CS 22949-037 -- having [Fe/H] < -3.5 according to previous lower S/N material. LTE…
We present an analysis of high-resolution Keck/HIRES spectroscopic observations of J0815+4729, an extremely carbon-enhanced, iron-poor dwarf star. These high-quality data allow us to derive a metallicity of [Fe/H]$=-5.49{\pm}0.14$ from the…
We present the discovery of HE0144-4657, an ultra metal-poor, CNO-enhanced star dynamically associated with the Helmi Stream disrupted dwarf-galaxy remnant. This star was first identified as a carbon-enhanced, metal-poor star candidate from…
Elemental abundances of extrinsic carbon stars provide insight into the poorly understood origin and evolution of elements in the early Galaxy. In this work, we present the results of a detailed spectroscopic analysis of four potential…
We give an update on our 0Z Survey to find more extremely metal poor (EMP) stars with [Fe/H] < -3 dex through mining the database of the Hamburg/ESO Survey. We present the most extreme such stars we have found from ~1550 moderate resolution…
We present a detailed abundance analysis based on high resolution and high signal-to-noise spectra of eight extremely metal poor (EMP) stars with [Fe/H] < -3.5$ dex, four of which are new. Only stars with 4900 < Teff< 5650 K are included.…
We elaborate the binary scenario for the origin of HE0107-5240, the most metal-poor star yet observed ([Fe/H] = -5.3), using current knowledge of the evolution of extremely metal-poor stars. From the observed C/N value, we estimate the…
We present a detailed chemical abundance analysis of HE 1300+0157, a subgiant with [Fe/H]=-3.9. From a high-resolution, high-S/N Subaru/HDS spectrum we find the star to be enriched in C ([C/Fe]_1D ~ +1.4) and O ([O/Fe]_1D ~ +1.8). With the…
We report on the chemical composition of the very metal-poor ([Fe/H]=-2.9) star LAMOST J1645+4357 that is identified to be a red giant having peculiar abundance ratios by Li et al. (2022). The standard abundance analysis is carried out for…
Two alternative scenarios concerning the origin and evolution of extremely metal-poor halo stars are investigated. The first one assumes that the stars have been completely metal-free initially and produced observed carbon and nitrogen…
In this work, we study the chemical compositions and kinematic properties of six metal-poor stars with [Fe/H] $< -2.5$ in the Galactic halo. From high-resolution (R $\sim$~110,000) spectroscopic observations obtained with the Lick/APF, we…