- ID:
- ivo://CDS.VizieR/J/ApJ/887/91
- Title:
- Equivalent widths of giants in the GC NGC3201
- Short Name:
- J/ApJ/887/91
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- The Hubble Space Telescope (HST) UV Legacy Survey of Galactic Globular Clusters (GCs) has investigated multiple stellar populations by means of the "chromosome map" (ChM) diagnostic tool that maximizes the separation between stars with different chemical compositions. One of the most challenging features revealed by ChM analysis is the apparent inhomogeneity among stars belonging to the first population, a phenomenon largely attributed to He variations. However, this explanation is not supported by uniformity in the p-capture elements of these stars. The HST survey has revealed that the GC NGC 3201 shows exceptionally wide coverage in the {Delta}_F275W,F814W_ parameter of the ChM. We present a chemical abundance analysis of 24 elements in 18 giants belonging to the first population of this GC and having a wide range in {Delta}_F275W,F814W_. As far as the p-capture elements are concerned, the chemical abundances are typical of first-generation (1G) stars, as expected from the location of our targets in the ChM. Based on radial velocities and chemical abundance arguments, we find that the three stars with the lowest {Delta}_F275W,F814W_ values are binary candidates. This suggests that at least those stars could be explained with binarity. These results are consistent with evidence inferred from multiband photometry that evolved blue stragglers (BSs) populate the bluest part of the 1G sequence in the ChM. The remaining 15 spectroscopic targets show a small range in the overall metallicity by ~0.10dex, with stars at higher {Delta}_F275W,F814W_ values having higher absolute abundances. We suggest that a small variation in metals and binarity governs the color spread of the 1G in the ChM and that evolved BSs contribute to the bluest tail of the 1G sequence.
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Search Results
- ID:
- ivo://CDS.VizieR/J/A+A/435/657
- Title:
- Equivalent widths of 5 giants in 47 Tuc
- Short Name:
- J/A+A/435/657
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- High resolution spectra of 5 giants, including a horizontal branch star, of the metal-rich globular cluster 47 Tucanae were obtained with the UVES spectrograph at the 8m VLT UT2-Kueyen telescope. The atmospheric parameters (Teff, logg, [Fe/H], vt) were derived from VIJK photometry and spectroscopic data based on Fe I and Fe II lines.
- ID:
- ivo://CDS.VizieR/J/ApJ/798/110
- Title:
- Equivalent widths of LAMOST metal-poor stars
- Short Name:
- J/ApJ/798/110
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We report on early results from a pilot program searching for metal-poor stars with LAMOST and follow-up high-resolution observation acquired with the MIKE spectrograph attached to the Magellan II telescope. We performed detailed abundance analysis for eight objects with iron abundances [Fe/H]<-2.0, including five extremely metal-poor (EMP; [Fe/H]<-3.0) stars with two having [Fe/H]<-3.5. Among these objects, three are newly discovered EMP stars, one of which is confirmed for the first time with high-resolution spectral observations. Three program stars are regarded as carbon-enhanced metal-poor (CEMP) stars, including two stars with no enhancement in their neutron-capture elements, which thus possibly belong to the class of CEMP-no stars; one of these objects also exhibits significant enhancement in nitrogen, and is thus a potential carbon and nitrogen-enhanced metal-poor star. The [X/Fe] ratios of the sample stars generally agree with those reported in the literature for other metal-poor stars in the same [Fe/H] range. We also compared the abundance patterns of individual program stars with the average abundance pattern of metal-poor stars and find only one chemically peculiar object with abundances of at least two elements (other than C and N) showing deviations larger than 0.5 dex. The distribution of [Sr/Ba] versus [Ba/H] agrees that an additional nucleosynthesis mechanism is needed aside from a single r-process. Two program stars with extremely low abundances of Sr and Ba support the prospect that both main and weak r-processes may have operated during the early phase of Galactic chemical evolution. The distribution of [C/N] shows that there are two groups of carbon-normal giants with different degrees of mixing. However, it is difficult to explain the observed behavior of the [C/N] of the nitrogen-enhanced unevolved stars based on current data.
- ID:
- ivo://CDS.VizieR/J/A+A/425/671
- Title:
- Equivalent widths of 10 metal-poor halo stars
- Short Name:
- J/A+A/425/671
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We presented the observed information of ten metal-poor halo stars with the metallicity range -2.3<[Fe/H]< -1.4 and derived their stellar parameters, acquired some elemental abundances relative to iron and discussed the relation between the abundance ratio and the metallicity. The stars were observed using the 6m telescope of the Special Astrophysical Observatory with the ECHELLE spectrometer PFES equipped with the CCD (1040x1160 pixels, pixel size 16x16{mu}m). The spectral wavelength coverage is of 430-798nm with the resolving power of 15000 and the signal-to-noise ratio is about 200. It was found that oxygen abundances are nearly constant at a level of 0.6dex for our metal-poor halo stars when the non-LTE correction is considered. The alpha-elements (Mg, Si, Ca and Ti) are overabundant relative to Fe and decrease with increasing metallicity. We also obtained a significant underabundant non-LTE [Na/Fe] ratio from NaI D lines which have large deviation from LTE assumption. Scandium is marginally overabundant with respect to iron and tends to decrease with increasing metallicity like the alpha-elements. Nearly solar value of [Cr/Fe] ratio and underabundant [Mn/Fe] ratio are obtained.
- ID:
- ivo://CDS.VizieR/J/ApJ/769/57
- Title:
- Equivalent widths of metal-poor stars
- Short Name:
- J/ApJ/769/57
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- It is well established that stellar effective temperatures determined from photometry and spectroscopy yield systematically different results. We describe a new, simple method to correct spectroscopically derived temperatures ("excitation temperatures") of metal-poor stars based on a literature sample with -3.3<[Fe/H]<-2.5. Excitation temperatures were determined from Fe I line abundances in high-resolution optical spectra in the wavelength range of ~3700-7000{AA}, although shorter wavelength ranges, up to 4750-6800{AA}, can also be employed, and compared with photometric literature temperatures. Our adjustment scheme increases the temperatures up to several hundred degrees for cool red giants, while leaving the near-main-sequence stars mostly unchanged. Hence, it brings the excitation temperatures in good agreement with photometrically derived values. The modified temperature also influences other stellar parameters, as the Fe I-Fe II ionization balance is simultaneously used to determine the surface gravity, while also forcing no abundance trend on the absorption line strengths to obtain the microturbulent velocity. As a result of increasing the temperature, the often too low gravities and too high microturbulent velocities in red giants become higher and lower, respectively. Our adjustment scheme thus continues to build on the advantage of deriving temperatures from spectroscopy alone, independent of reddening, while at the same time producing stellar chemical abundances that are more straightforwardly comparable to studies based on photometrically derived temperatures. Hence, our method may prove beneficial for comparing different studies in the literature as well as the many high-resolution stellar spectroscopic surveys that are or will be carried out in the next few years.
- ID:
- ivo://CDS.VizieR/J/MNRAS/435/3667
- Title:
- Equivalent widths of 6 NGC5694 stars
- Short Name:
- J/MNRAS/435/3667
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present the results of the analysis of high-resolution spectra obtained with UVES-FLAMES at the Very Large Telescope for six red giant branch stars in the outer-halo metal-poor ([Fe/H]I=-1.98 and [Fe/H]II=-1.83) Galactic globular cluster NGC 5694, which has been suggested as a possible incomer by Lee et al. based on the anomalous chemical composition of a single cluster giant. We obtain accurate abundances for a large number of elements and we find that (a)the six target stars have the same chemical composition within the uncertainties, except for Na and Al; (b) the average cluster abundance of {alpha} elements (with the only exception of Si) is nearly solar, at odds with typical halo stars and globular clusters of similar metallicity; (c) Y, Ba, La and Eu abundances are also significantly lower than in Galactic field stars and star clusters of similar metallicity. Hence, we confirm the Lee et al. classification of NGC 5694 as a cluster of extragalactic origin. We provide the first insight on the Na-O and Mg-Al anticorrelations in this cluster: all the considered stars have very similar abundance ratios for these elements, except one that has significantly lower [Na/Fe] and [Al/Fe] ratios, suggesting that some degree of early self-enrichment has occurred also in this cluster.
- ID:
- ivo://CDS.VizieR/J/MNRAS/422/3527
- Title:
- Equivalent widths of 11 NGC 3680 stars
- Short Name:
- J/MNRAS/422/3527
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present a new abundance analysis of the intermediate-age Galactic open cluster NGC 3680, based on high-resolution, high signal-to-noise ratio VLT/UVES spectroscopic data. Several element abundances are presented for this cluster for the first time, but most notably we derive abundances for the light and heavy s-process elements Y, Ba, La and Nd. The serendipitous measurement of the rare-earth r-process element Gd is also reported. This cluster exhibits a significant enhancement of Na in giants as compared to dwarfs, which may be a proxy for an O to Na anticorrelation as observed in Galactic globular clusters but not open clusters. We also observe a step-like enhancement of heavy s-process elements towards higher atomic number, contrary to expectations from asymptotic giant branch nucleosynthesis models, suggesting that the r process played a significant role in the generation of both La and Nd in this cluster.
- ID:
- ivo://CDS.VizieR/J/A+A/419/1123
- Title:
- Equivalent widths of 3 post-AGB
- Short Name:
- J/A+A/419/1123
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present model atmosphere analyses of high resolution Keck and VLT optical spectra for three evolved stars in globular clusters, viz. ZNG-1 in M10, ZNG-1 in M15 and ZNG-1 in NGC6712. The derived atmospheric parameters and chemical compositions confirm the programme stars to be in the post-Asymptotic Giant Branch (post-AGB) evolutionary phase.
- ID:
- ivo://CDS.VizieR/J/ApJ/613/129
- Title:
- Equivalent widths of QSOs
- Short Name:
- J/ApJ/613/129
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present the results of a search for variability in the equivalent widths (EWs) of narrow, associated (|{Delta}v|<=5000km/s) absorption lines found in the UV spectra of z<=1.5 quasars. The goal of this search was to use variability as a means of identifying absorption lines arising in gas that is intrinsic to the quasar central engine. We have compared archival Hubble Space Telescope (HST) Faint Object Spectrograph (FOS) spectra of quasars with recent spectra obtained as part of our own snapshot survey of the same objects with the Space Telescope Imaging Spectrograph (STIS). The intervals between observations are 4-10yr. We primarily focused on the C IV absorption lines, although we also studied other lines available in the same spectra (e.g., Ly{alpha}, N V, O VI).
- ID:
- ivo://CDS.VizieR/J/PAZh/38/122
- Title:
- Equivalent widths of 14 red giants
- Short Name:
- J/PAZh/38/122
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- The results of a comparative analysis of the elemental abundances in the atmospheres of 14 red giants with high Galactic space velocities are presented. For almost all of the chemical elements considered, the their abundance trends with metallicity correspond to those constructed for thick-disk dwarfs. In the case of sodium, the main factor affecting the [Na/Fe] abundance in the stellar atmosphere for red giants is the surface gravity that characterizes the degree of development of the convective envelope. The difference between the [Na/Fe] abundances in the atmospheres of thin- and thick-disk red giants has been confirmed.
