The search for consistency between nebular and massive-star abundances has been a longstanding problem. I briefly review what has been done regarding this topic, also presenting a recent study focused on the Orion nebula: the O and Si stellar abundances resulting from a detailed and fully consistent spectroscopic analysis of the group of B stars associated with the Orion nebula are compared with the most recent nebular gas-phase results.

We present results from comparisons of elemental abundances and dust content between damped Lyman-alpha (DLA) absorbers and gamma-ray-burst (GRB) afterglows, as determined by absorption-line spectroscopy. Our sample of DLA absorbers includes the results from 76 quasar spectra taken with the HIRES spectrograph of the Keck observatory, from which we obtain a sample of 38 DLA absorbers in the redshift range 2 < z < 4. The GRB absorption lines were obtained in collaboration with the Caltech Carnegie NOAO GRB collaboration, in which rapid spectroscopy is obtained from newly discovered GRBs, to obtain high-quality optical spectra. We present results of O, N, C, Si, Zn, Cr, and C II*/C II ratios from a “core sample” of 15 of the best of the DLA absorbers, and detailed analysis of GRB 051111 and GRB 050505, which are at redshifts of z = 1.549 and 4.275, respectively. From our analysis we can see trends in the DLA dust content, and in [C/H], [N/H] and [O/H] values as a function of DLA redshift, as well as evidence for dust formation and highly excited dense gas within the disks of GRB host galaxies.

Recent progress in the study of the various proposed SN Ia-progenitor scenarios is reviewed. We discuss the effects of rotation on the evolution of SN Ia progenitors, in particular the stabilization of helium-shell burning and the increase of the Chandrasekhar limit. The latter may have been confirmed by a recent analysis of an overluminous SN 2003fg. For the evolution of CO white dwarf mergers, we discuss new arguments in favor of obtaining Type-Ia SNe from those systems, in contrast to the previous consensus. We onsensus. We address the issue of SN Ia delay times, and the dependence of average SN Ia properties on the type of host galaxy, in the light of recent observations and progenitor models, and derive implications for SN Ia yields.

This review summarizes the properties of the stellar population in bulges observed in nearby and distant spiral galaxies. Particular emphasis is placed on comparison with elliptical galaxies, when possible. The sample-selection criteria and choices in data analysis are addressed when they may be involved in discrepancies among published results.

We argue that the discrepancies observed in H ii regions between abundances derived from optical recombination lines (ORLs) and collisionally excited lines (CELs) might well be the signature of a scenario of the enrichment of the interstellar medium (ISM) proposed by Tenorio-Tagle (1996). In this scenario, the fresh oxygen released during massive supernova explosions is confined within the hot superbubbles as long as supernovae continue to explode. Only after the last massive supernova explosion does the metal-rich gas start to cool down and fall onto the galaxy in the form of metal-rich droplets. Full mixing of these metal-rich droplets and the ISM occurs during photoionization by the next generations of massive stars. During this process, the metal-rich droplets give rise to strong recombination lines of the metals, leading to the observed ORL–CEL discrepancy.

Several spectroscopic studies have shown that stars with giant planets are particularly metal-rich compared with average field stars. In this paper we review the most recent results concerning the study of the chemical abundances of planet-host stars. Abundance distributions for several elements are presented or discussed, including those of iron-peak and alpha-elements, and the light elements lithium (both 7Li and 6Li) and beryllium. The impact of these results on the theories of planet formation and evolution is discussed.

From stellar-evolution models and from observations of Wolf–Rayet stars it is known that massive stars are releasing metal-enriched gas during their Wolf–Rayet phase by means of strong stellar winds. Although H ii-region spectra serve as diagnostics to determine the present-day chemical composition of the interstellar medium, it is not yet reliably known to what extent the diagnostic H ii gas is already contaminated by chemically processed stellar-wind matter. In a recent paper, we therefore analyzed our models of radiation-driven and wind-blown H ii bubbles around an isolated 85M⊙ star of originally Solar metallicity with respect to its chemical abundances. Although the hot stellar-wind bubble (SWB) is enriched with 14N during the WN phase and even more so with 12C and 16O during the WC phase of the star, we found that at the end of the stellar lifetime the mass ratios of the traced elements N and O in the warm ionized gas are insignificantly higher than Solar, whereas an enrichment of 22% above Solar is found for C. The transport of enriched elements from the hot SWB to the cool gas occurs mainly by means of mixing of hot gas with cooler at the back side of the SWB shell.

We present a spectrophotometric study of circumnuclear star-forming regions (CNSFRs) in the early-type spiral galaxies NGC 2903, NGC 3351 and NGC 3504, all of them of over Solar metallicity according to standard empirical calibrations. A detailed determination of their abundances is performed after careful subtraction of the very prominent underlying stellar absorption. It is found that most regions exhibit the highest abundances in H II-region-like objects. The relative N/O and S/O abundances are discussed. It is also shown that CNSFRs, as a class, segregate from the disk H II region family, clustering around smaller “softness parameter” – η′ – values, and therefore higher ionizing temperatures.

We present a detailed study on the kinematics of metal-rich stars with and without planets, and their relation with the Hyades, Sirius and Hercules dynamical streams in the Solar neighbourhood. We compare the kinematic behaviour of known planet-host stars with that of the remaining targets belonging to the CORALIE volume-limited sample, in particular its metal-rich population. The high average metallicity of the Hyades stream is confirmed. The planet-host targets exhibit a kinematic behaviour similar to that of the metal-rich comparison subsample, rather than to that of the comparison sample as a whole, thus supporting the hypothesis of a primordial origin for the metal excess observed in stars with known planetary companions. According to the scenarios proposed as an explanation for the dynamical streams, systems with giant planets could have formed more easily in metal-rich inner Galactic regions

We discuss theoretical predictions and observational findings obtained for radiatively driven winds of massive stars, with emphasis on their dependence on metallicity. If these winds are not strongly clumped or the clumping properties are independent of metallicity z, theory and observations agree very well, and mass-loss rates and terminal velocities scale as Ṁ ∝ z0.62±015 and υ∞ ∝ z0.13, respectively. This dependence could be validated only for winds with Solar and subsolar abundances, due to the lack of supersolar-metallicity test cases. The actual values for the mass-loss rates are uncertain, due to unknown clumping properties of the wind, and currently accepted numbers might be overestimated by factors in between ∼2 and 10.

Using the MIKE spectrograph, mounted on the 6.5-m Magellan/Clay telescope at the Las Campanas observatory in Chile, we have obtained highresolution spectra for 60 F and G dwarf stars, all likely members of a density enhancement in the local velocity distribution, referred to as the Hercules stream. By comparing with an existing sample of 102 thin- and thick-disk stars we have used space velocities, detailed elemental abundances, and stellar ages to trace the origin of the Hercules stream. We find that the Hercules-stream stars exhibit a wide spread in stellar ages, metallicities, and element abundances. However, the spreads are not random but separate the Hercules stream into the abundance and age trends outlined by either the thin disk or the thick disk. We hence claim that the major constituents of the Hercules stream actually are thin- and thick-disk stars. These diverse properties of the Hercules stream indicate a dynamical origin, probably caused by the Galactic bar. However, we can at the moment not entirely rule out the possibility that the Hercules stream could be the remnants of a relatively recent merger event.

We study the effect of assuming different formation timescales for the thick and thin disks on the variation of the abundance ratios of several elements with metallicity. We show that, if the thin disk was formed on a onger timescale (≃7 Gyr) than the thick disk (≃0.8 Gyr), the abundance ratio shifts between the thick and thin disk, as a function of the metallicity, can be well explained. Moreover, these observations offer a powerful constraint on stellar yields in general (massive stars, low- and intermediate-mass stars, and SN Ia) and their dependence on metallicity.

Results of several investigations of FGK stars in the Solar neighborhood have suggested that thin-disk stars with an iron abundance similar to that of the Sun appear to have higher abundances of other elements, such as silicon, titanium, and nickel. Offsets could arise if the samples contain stars with ages, mean Galactocentric distances, or kinematics that differ on average from the Solar values. They could also arise due to systematic errors in the abundance determinations, if the samples contain stars that are different from the Sun regarding their atmospheric parameters. We re-examine this issue by studying a sample of 80 nearby stars with Solarlike colors and luminosities. Among these Solar analogs, the objects with Solar iron abundances exhibit Solar abundances of carbon, silicon, calcium, titanium, and nickel.