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We present a chemo-dynamical analysis for 27 near main-sequence turnoff metal-poor stars, including 20 stars analysed for the first time. The sample spans a range in [Fe/H] from −2.5 to −3.6, with 44 per cent having [Fe/H]<−2.9. We derived chemical abundances for 17 elements, including strontium and barium. We derive Li abundances for the sample, which are in good agreement with the 'Spite Plateau' value. The lighter elements (Z < 30) generally agree well with those of other low-metallicity halo stars. This broadly indicates chemically homogeneous gas at the earliest times. We used the [Sr/Ba] versus [Ba/Fe] diagram to classify metal-poor stars into five populations based on their observed ratios. We find HE 0232 − 3755 to be a likely main r -process star, and HE 2214 − 6127 and HE 2332 − 3039 to be limited- r stars. CS30302-145, HE 2045 − 5057, and CD −24°17504 plausibly originated in long-disrupted early dwarf galaxies. We also find that the derived [Sr/H] and [Ba/H] values for CD −24°17504 are not inconsistent with the predicted yields of the s -process in massive rotating low-metallicity stars models. Further theoretical explorations will be helpful to better understand the earliest mechanisms and time scales of heavy element production for comparison with these and other observational abundance data. Finally, we investigate the orbital histories of our stars. Most display halo-like kinematics although three stars (CS 29504-018, HE 0223 − 2814, and HE 2133 − 0421) appear to be disc-like in nature. This confirms the extragalactic origin for CS 30302-145, HE 2045 − 5057, and, in particular, CD −24°17504 which likely originated from a small accreted stellar system as one of the oldest stars. [ABSTRACT FROM AUTHOR]

We present metallicities for red giant stars in the globular cluster NGC 6273 based on intermediate resolution GMOS-S spectra of the calcium triplet region. For the 42 radial velocity members with reliable calcium triplet line strength measurements, we obtain metallicities, [Fe/H], using calibrations established from standard globular clusters. We confirm the presence of an intrinsic abundance dispersion identified by Johnson et al. The total range in [Fe/H] is ~1.0 dex and after taking into account the measurement errors, the intrinsic abundance dispersion is σint[Fe/H] = 0.17 dex. Among the Galactic globular clusters, the abundance dispersion in NGC 6273 is only exceeded by ω Cen, which is regarded as the remnant of a disrupted dwarf galaxy, and M54, which is the nuclear star cluster of the Sagittarius dwarf galaxy. If these three globular clusters share the same formation mechanism, then NGC 6273 may also be the remnant nucleus of a disrupted dwarf galaxy. [ABSTRACT FROM AUTHOR]

We measure the C+N+O abundance sum in red giant stars in two Galactic globular clusters, NGC 1851 and NGC 6752. NGC 1851 has a split subgiant branch which could be due to different ages or C+N+O content while NGC 6752 is representative of the least complex globular clusters. For NGC 1851 and NGC 6752, we obtain average values of A(C+N+O) = 8.16 ± 0.10 (σ = 0.34) and 7.62 ± 0.02 (σ = 0.06), respectively. When taking into account the measurement errors, we find a constant C+N+O abundance sum in NGC 6752. The C+N+O abundance dispersion is only 0.06 dex, and such a result requires that the source of the light element abundance variations does not increase the C+N+O sum in this cluster. For NGC 1851, we confirm a large spread in C+N+O. In this cluster, the anomalous RGB has a higher C+N+O content than the canonical RGB by a factor of 4 (∼0.6 dex). This result lends further support to the idea that the two subgiant branches in NGC 1851 are roughly coeval, but with different CNO abundances. [ABSTRACT FROM AUTHOR]

We present results of an analysis of high-resolution spectra ( R∼ 50 000), obtained with the Subaru Telescope High Dispersion Spectrograph, of two carbon-enhanced metal-poor (CEMP) stars selected from the Hamburg/European Southern Observatory prism survey, HE 1305+0007 and HE 1152−0355, and of the classical CH star HD 5223. All these stars have relatively low effective temperatures (4000–4750 K) and high carbon abundances, which result in the presence of very strong molecular carbon bands in their spectra. The stellar atmospheric parameters for these stars indicate that they all have surface gravities consistent with a present location on the red giant branch, and metallicities of (HE 1305+0007, HD 5223) and (HE 1152−0355). In addition to their large enhancements of carbon ( and +0.6, respectively), all three stars exhibit strong enhancements of the s-process elements relative to iron. HE 1305+0007 exhibits a large enhancement of the third-peak s-process element, lead, with , as well as a high abundance of the r-process element europium, . The second-peak s-process elements, Ba, La, Ce, Nd and Sm, are found to be more enhanced than the first-peak s-process elements Zr, Sr and Y. Thus, HE 1305+0007 joins the growing class of the so-called ‘Lead stars’, and also the class of objects that exhibit the presence of both r- and s-process elements, the CEMP- r/ s stars. The large enhancements of neutron-capture ( n-capture) elements exhibited by HE 1152−0355 and HD 5223 are more consistent with the abundance patterns generally noticed in CH stars, essentially arising from pure s-process nucleosynthesis. The elemental abundance distributions observed in these stars are discussed in light of existing theories of CH star formation, as well as the suggested formation scenarios of the CEMP- r/ s group. [ABSTRACT FROM AUTHOR]

This is the second in a series of papers presenting a new calculation of the mass of the Galaxy based on radial velocities and distances for a sample of faint field blue horizontal-branch (BHB) stars. We present accurate BV CCD photometry and spectra for 142 candidate A-type stars selected from photometry of UK Schmidt telescope plates in six high-Galactic-latitude fields. Classification of these candidates produces a sample of 60 BHB stars at distances of 11–52 kpc from the Sun (mean 28 kpc), with heliocentric line-of-sight velocities accurate to 15 km s−1, and distance errors <10 per cent. We provide a summary table listing coordinates and velocities of these stars. The measured dispersion of the radial component of the Galactocentric velocity for this sample is 108 ± 10 km s−1, in agreement with a recent study of the distant halo by Sirko and coworkers. Measurements of the Ca ii K line indicate that nearly all the stars are metal-poor with a mean with dispersion 0.5. Subsequent papers will describe a second survey of BHBs to heliocentric distances and present a new estimate of the mass of the Galaxy. [ABSTRACT FROM AUTHOR]

A correction to the article "The Radial Velocity Dispersion Profile of the Galactic Halo: Constraining the Density Profile of the Dark Halo of the Milky Way," in the previous issue is presented.