- ID:
- ivo://CDS.VizieR/J/ApJ/682/1029
- Title:
- Abundances in OGLE-2007-BLG-349S
- Short Name:
- J/ApJ/682/1029
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present an abundance analysis based on high-dispersion and high signal-to-noise ratio Keck spectra of a very highly microlensed Galactic bulge dwarf, OGLE-2007-BLG-349S, with Teff~5400K. The amplification at the time the spectra were taken ranged from 350 to 450. This bulge star is highly enhanced in metallicity with [Fe/H]=+0.51+/-0.09dex. The abundance ratios for the 28 species of 26 elements for which features could be detected in the spectra are almost all solar. In particular, there is no evidence for enhancement of any of the {alpha}-elements, including O and Mg. We conclude that the high [Fe/H] seen in this star, when combined with the equally high [Fe/H] derived in previous detailed abundance analysis of two other Galactic bulge dwarfs, both also highly magnified by microlensing, implies that the median metallicity in the Galactic bulge is very high. We thus infer that many previous estimates of the metallicity distribution in the Galactic bulge have substantially underestimated the mean Fe metallicity there due to sample bias, and suggest a candidate mechanism for such. If our conjecture proves valid, it may be necessary to update the calibrations for the algorithms used by many groups to interpret spectra and broadband photometry of the integrated light of very metal-rich old stellar populations, including luminous elliptical galaxies.
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- ID:
- ivo://CDS.VizieR/J/ApJ/824/75
- Title:
- Abundances in 23 open clusters. I.
- Short Name:
- J/ApJ/824/75
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Neutron-capture elements, those with Z>35, are the least well understood in terms of nucleosynthesis and formation environments. The rapid neutron-capture, or r-process, elements are formed in the environments and/or remnants of massive stars, while the slow neutron-capture, or s-process, elements are primarily formed in low-mass AGB stars. These elements can provide much information about Galactic star formation and enrichment, but observational data are limited. We have assembled a sample of 68 stars in 23 open clusters that we use to probe abundance trends for six neutron-capture elements (Eu, Gd, Dy, Mo, Pr, and Nd) with cluster age and location in the disk of the Galaxy. In order to keep our analysis as homogeneous as possible, we use an automated synthesis fitting program, which also enables us to measure multiple (3-10) lines for each element. We find that the pure r-process elements (Eu, Gd, and Dy) have positive trends with increasing cluster age, while the mixed r- and s-process elements (Mo, Pr, and Nd) have insignificant trends consistent with zero. Pr, Nd, Eu, Gd, and Dy have similar, slight (although mostly statistically significant) gradients of ~0.04dex/kpc. The mixed elements also appear to have nonlinear relationships with R_GC_.
- ID:
- ivo://CDS.VizieR/J/A+A/572/A82
- Title:
- Abundances in outer parts of Fornax dSph
- Short Name:
- J/A+A/572/A82
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present radial velocities and [Fe/H] abundances for 340 stars in the Fornax dwarf spheroidal from R~16000 spectra. The targets were obtained in the outer parts of the galaxy. Our sample shows a wide range in [Fe/H], between -0.5 and -3.0dex, in which we detect three subgroups. Removal of stars belonging to the most metal-rich population produces a truncated metallicity distribution function that is identical to Sculptor, indicating that these systems shared a similar early evolution. The derived age-metallicity relation shows a fast increase in [Fe/H] at early ages, after which the enrichment flattens significantly for stars younger than ~8Gyr. Additionally, the data indicate a strong population of stars around 4Gyr, followed by a second rapid enrichment in [Fe/H]. Our dynamical analysis reveals an increasing velocity dispersion with decreasing [Fe/H] from sigma_sys_=7.5km/s to 14km/s. The large velocity dispersion at low metallicities is possibly the result of a non-Gaussian velocity distribution among stars older than ~8Gyr. Our sample also includes members from the Fornax globular clusters H2 and H5. In agreement with past studies we find [Fe/H]=-2.04+/-0.04 and a mean radial velocity RV=59.36+/-0.31km/s for H2 and [Fe/H]=-2.02+/-0.11 and RV=59.39+/-0.44km/s for H5. Overall, we find high complexity in the chemical and dynamical properties, with signatures that additionally vary with galactocentric distance.
- ID:
- ivo://CDS.VizieR/J/A+A/500/1089
- Title:
- Abundances in planetary nebulae
- Short Name:
- J/A+A/500/1089
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present new spectroscopic data (90 objects) and derived plasma diagnostics and abundances of a sample of planetary nebulae in the direction of the Galactic center. The spectra were obtained in 2001/2002 with the 4-m class telescope at the Cerro Tololo Interamerican Observatory and the European Southern Observatory.
- ID:
- ivo://CDS.VizieR/J/A+A/427/231
- Title:
- Abundances in planetary nebulae
- Short Name:
- J/A+A/427/231
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present new spectroscopic data (43 objects) and derived plasma diagnostics and abundances (164 objects) of a sample of planetary nebulae in the direction of the Galactic center. The spectra were obtained in July 2000 with the 1.9-m telescope at the South African Astronomical Observatory. The spectral coverage was 3500-7000{AA} with an average resolution of 1000.
- ID:
- ivo://CDS.VizieR/J/A+A/494/591
- Title:
- Abundances in planetary nebulae
- Short Name:
- J/A+A/494/591
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present new plasma diagnostics and abundances of a sample of planetary nebulae located in the Galactic bulge (168 objects), the Galactic inner disk (61 objects) and in the LMC (110 objects).
- ID:
- ivo://CDS.VizieR/J/ApJS/218/25
- Title:
- Abundances in PNe. III: Se and Kr
- Short Name:
- J/ApJS/218/25
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- The detection of neutron(n)-capture elements in several planetary nebulae (PNe) has provided a new means of investigating s-process nucleosynthesis in low-mass stars. However, a lack of atomic data has inhibited accurate trans-iron element abundance determinations in astrophysical nebulae. Recently, photoionization (PI) and recombination data were determined for Se and Kr, the two most widely detected n-capture elements in nebular spectra. We have incorporated these new data into the photoionization code Cloudy (Ferland et al. 2013RMxAA..49..137F). To test the atomic data, numerical models were computed for 15 PNe that exhibit emission lines from multiple Kr ions. We found systematic discrepancies between the predicted and observed emission lines that are most likely caused by inaccurate PI and recombination data. These discrepancies were removed by adjusting the Kr^+^-Kr^3+^ PI cross sections within their cited uncertainties and the dielectronic recombination rate coefficients by slightly larger amounts. From grids of models spanning the physical conditions encountered in PNe, we derive new, broadly applicable ionization correction factor (ICF) formulae for calculating Se and Kr elemental abundances. The ICFs were applied to our previous survey of near-infrared [KrIII] and [SeIV] emission lines in 120 PNe. The revised Se and Kr abundances are 0.1-0.3dex lower than former estimates, with average values of [Se/(O,Ar)]=0.12+/-0.27 and [Kr/(O,Ar)]=0.82+/-0.29, but correlations previously found between their abundances and other nebular and stellar properties are unaffected. We also find a tendency for high-velocity PNe that can be associated with the Galactic thick disk to exhibit larger s-process enrichments than low-velocity PNe belonging to the thin-disk population.
- ID:
- ivo://CDS.VizieR/J/PASJ/59/1127
- Title:
- Abundances in 5 post-AGB candidates
- Short Name:
- J/PASJ/59/1127
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- A detailed non-LTE study on the abundances of C, N, O, S, and Zn was carried out for five F-G supergiants of suspected post-AGB candidates with IR excesses (HD 112374, HD 148743, HD 161796, HD 163506, and HD 187203), since these volatile elements can provide the key to inferring the original metallicity as well as an evolution-induced change due to mixing, given that they are free from depletion caused by dust-gas separation.
- ID:
- ivo://CDS.VizieR/J/ApJ/682/1217
- Title:
- Abundances in red giants in 7 globular clusters
- Short Name:
- J/ApJ/682/1217
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present a technique that applies spectral synthesis to medium-resolution spectroscopy (MRS; R~6000) in the red (6300{AA}<{lambda}<9100{AA}) to measure [Fe/H] and [{alpha}/Fe] of individual red giant stars over a wide metallicity range. We apply our technique to 264 red giant stars in seven Galactic globular clusters and demonstrate that it reproduces the metallicities and {alpha}-enhancements derived from high-resolution spectroscopy (HRS). The MRS technique excludes the three CaII triplet lines and instead relies on a plethora of weaker lines. Unlike empirical metallicity estimators, such as the equivalent width of the CaII triplet, the synthetic method presented here is applicable over an arbitrarily wide metallicity range and is independent of assumptions about the {alpha}-enhancement.
- ID:
- ivo://CDS.VizieR/J/AJ/110/2319
- Title:
- Abundances in RR Lyr variables
- Short Name:
- J/AJ/110/2319
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We have used moderately high-resolution, high S/N spectra to study the chemical composition of ten field ab-type RR Lyrae stars. Variables having accurate photometric and radial-velocity data were selected, in order to derive a precise estimate of the atmospheric parameters independently of excitation and ionization equilibria. A new temperature scale was determined from literature "Infrared Flux Method" measures of subdwarfs and the Kurucz (1992) (priv. com.) model atmospheres, and used to calibrate colors for both dwarfs and RR Lyraes. Photometric reddening estimates for the program stars were carefully examined, and compared with other determinations. The applicability of Kurucz (1992) (priv. com.) model atmospheres in the analysis of RR Lyraes at minimum light was analyzed: we found that they are able to reproduce colors, excitation, and ionization equilibria as well as the wings of Halpha. The comparison solar abundances were carefully determined. From a new analysis of weak Fe I lines with accurate gfs [Bard & Kock, A&A, 282, 1014 (1994)] we derived log epsilon(Fe)_Sun=7.52, in agreement with the Fe abundances determined from meteorites and Fe II lines. We derived abundances for 21 species. Main results are: The metal abundances of the program stars span the range -2.50<[Fe/H]<+0.17. Lines of most elements are found to form in LTE conditions. Fe lines satisfy very well the excitation and ionization equilibria. A comparison with statistical equilibrium computations shows that rather large collisional cross sections are required to reproduce observations. If these cross sections are then used in the analysis of the formation of Fe lines in subdwarfs and RGB stars, no significant departures from LTE are found for these stars, thus validating the very numerous LTE analyses. RR Lyraes share the typical abundance pattern of other stars of similar [Fe/H]: alpha-elements are overabundant by ~0.4dex and Mn is underabundant by ~0.6dex in stars with [Fe/H]<-1. Solar scaled abundances are found for most of the other species, except for the low Ba abundance in the extremely metal-poor star X Ari ([Fe/H]~-2.5). Significant departures from LTE are found for a few species: Nd II, Ce II, Y II, and Sc II are severely underabundant (~0.5dex) in metal-rich variables; Ti I and Cr I are slightly (~0.1-0.2dex) underabundant in metal-poor stars. These effects are attributed to overionization. We suggest that the photoionization of the alkaline earth-like ions is due to Lyman lines emission produced by the shock waves that propagate in the atmosphere of these variables [Fokin (1992MNRAS.256...26F)]. Departures from LTE were considered in detail in the derivation of abundances for the light elements (O and Na). Significant corrections were required for the O I IR triplet and the Na D lines. The resulting pattern reproduces that observed in less evolved field stars. We did not find any evidence for an O-Na anticorrelation among these field HB stars, suggesting that the environment is likely to be responsible for the anticorrelation found in metal-poor globular cluster stars [Sneden et al. =1992AJ....104.2121S]. We used our new [Fe/H] abundances, as well as values from Butler and co-workers (corrected to our system), and from high- resolution spectroscopy of globular clusters giants, to obtain a revised calibration of the low-resolution metallicity index Delta(S) [Preston =1959ApJ...130..507P]: [Fe/H]=-0.194(+/-0.011)Delta(S)-0.08(+/-0.18). Our new metallicity scale is stretched on both low and high metallicity ends with respect to Butler's [1975ApJ...200...68B]. The error in [Fe/H] by Delta(S) observations is 0.16dex, well of the same order of high-resolution metallicity determinations. The slope of the calibration obtained considering only stars with 4<Delta(S)<10 is slightly smaller than that obtained using all stars. While this difference is only barely significant, it might point out the presence of a nonlinearity of the Delta(S) vs [Fe/H] relation, as suggested by Manduca [ApJ, 245, 258 (1981)]. The new [Fe/H] values were used to update the metallicity calibration of the Ca II K line index [Clementini et al. =1991AJ....101.2168C]. Using the present new metallicities, and W'(K) values and relative errors from Clementini et al. (1991), a least-squares fit weighted both in W'(K) and [Fe/H] gives [Fe/H]=0.65(+/-0.17)W'(K)-3.49(+/-0.39). Finally, our new metallicity scale was used to revise the metallicity dependence of the absolute magnitude of RR Lyrae stars, M_V. Using M_V values from Fernley [1994A&A...284L..16F] for the field stars, and estimates from Liu & Janes [1990ApJ...360..561L] and Storm et al. [1994A&A...290..443S] for the cluster variables, we found M_V=0.20(+/-0.03) [Fe/H]+1.06(+/-0.04) and M_V=0.19(+/-0.03)[Fe/H]+0.96(+/-0.04), the last being obtained by using M_V estimates derived for a value of the conversion factor between observed and true pulsation velocity p=1.38 (Fernley 1994). The adoption of the new metallicity scale does not yield significant changes in the slope or zero point of the M_V vs [Fe/H] relation. Observations do not rule out the possibility that the slope of the M_V vs [Fe/H] relation might be different for metal-poor and metal-rich variables. However, a larger sample of Baade-Wesselink M_V determinations is required to definitely settle this question.
