- ID:
- ivo://CDS.VizieR/J/ApJ/679/1549
- Title:
- Spectroscopy of metal-poor star CS 17435-00532
- Short Name:
- J/ApJ/679/1549
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present the first detailed abundance analysis of the metal-poor giant HKII 17435-00532. This star was observed as part of the University of Texas long-term project Chemical Abundances of Stars in the Halo (CASH). A spectrum was obtained with the High Resolution Spectrograph (HRS) on the Hobby-Eberly Telescope with a resolving power of R~15000. Our analysis reveals that this star may be located on the red giant branch, red horizontal branch, or early asymptotic giant branch. We find that this metal-poor ([Fe/H]=-2.2) star has an unusually high lithium abundance [log{epsilon}(Li)=+2.1], mild carbon ([C/Fe]=+0.7) and sodium ([Na/Fe]=+0.6) enhancement, as well as enhancement of both s-process ([Ba/Fe]=+0.8) and r-process ([Eu/Fe]=+0.5) material.
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- ID:
- ivo://CDS.VizieR/J/AJ/144/168
- Title:
- Spectroscopy of Scl 1019417 and UMi 20103
- Short Name:
- J/AJ/144/168
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- The most metal-poor stars in dwarf spheroidal galaxies (dSphs) can show the nucleosynthetic patterns of one or a few supernovae (SNe). These SNe could have zero metallicity, making metal-poor dSph stars the closest surviving links to Population III stars. Metal-poor dSph stars also help to reveal the formation mechanism of the Milky Way (MW) halo. We present the detailed abundances from Keck/HIRES spectroscopy for two very metal-poor stars in two MW dSphs. One star, in the Sculptor dSph, has [FeI/H]=-2.40. The other star, in the Ursa Minor dSph, has [FeI/H]=-3.16. Both stars fall in the previously discovered low-metallicity, high-[{alpha}/Fe] plateau. Most abundance ratios of very metal-poor stars in these two dSphs are largely consistent with very metal-poor halo stars. However, the abundances of Na and some r-process elements lie at the lower end of the envelope defined by inner halo stars of similar metallicity. We propose that the metallicity dependence of SN yields is the cause. The earliest SNe in low-mass dSphs have less gas to pollute than the earliest SNe in massive halo progenitors. As a result, dSph stars at -3<[Fe/H]<-2 sample SNe with [Fe/H]{Lt}-3, whereas halo stars in the same metallicity range sample SNe with [Fe/H]~-3. Consequently, enhancements in [Na/Fe] and [r/Fe] were deferred to higher metallicity in dSphs than in the progenitors of the inner halo.
- ID:
- ivo://CDS.VizieR/J/ApJ/708/560
- Title:
- Spectroscopy of UMa II and Coma Ber
- Short Name:
- J/ApJ/708/560
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present spectra of six metal-poor stars in two of the ultra-faint dwarf galaxies orbiting the Milky Way (MW), Ursa Major II, and Coma Berenices obtained with the Keck/High Resolution Echelle Spectrometer (HIRES). These observations include the first high-resolution spectroscopic observations of extremely metal-poor ([Fe/H]<-3.0) stars not belonging to the MW halo field star population. We obtain abundance measurements and upper limits for 26 elements between carbon and europium. The entire sample of stars spans a range of -3.2<[Fe/H]<-2.3, and we confirm that each galaxy contains a large intrinsic spread of Fe abundances. A comparison with MW halo stars of similar metallicities reveals substantial agreement between the abundance patterns of the ultra-faint dwarf galaxies and the MW halo for the light, {alpha}, and iron-peak elements (C to Zn). The abundances of neutron-capture elements (Sr to Eu) in the ultra-faint dwarf galaxies are extremely low, consistent with the most metal-poor halo stars, but not with the typical halo abundance pattern at [Fe/H]>~-3.0. Not only are our results broadly consistent with a galaxy formation model that predicts that massive dwarf galaxies are the source of the metal-rich component ([Fe/H]>-2.5) of the MW halo, but they also suggest that the faintest known dwarfs may be the primary contributors to the metal-poor end of the MW halo metallicity distribution.
- ID:
- ivo://CDS.VizieR/J/AJ/103/1987
- Title:
- Stars of very low metal abundance
- Short Name:
- J/AJ/103/1987
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Spectroscopic observations for 1044 stars located primarily in the southern Galactic hemisphere are reported; the stars were chosen from a list of candidate metal-deficient stars discovered in the HK objective-prism survey. Radial velocities and line indices based on the equivalent widths of Ca II, K, H-gamma and H-delta, and the CH G band are reported. Estimates of metallicity for 874 stars with derived abundances less than -0.5 are presented.
- ID:
- ivo://CDS.VizieR/J/AJ/90/2089
- Title:
- Stars of very low metal abundance. I
- Short Name:
- J/AJ/90/2089
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- An objective-prism and a narrowband interference filter have been used in combination on the Curtis Schmidt telescope at CTIO to conduct a search for extremely metal-poor stars. The filter restricts the bandpass to the region around the H and K lines of CaII; the metal-poor candidates are those stars with weak or absent H and K. Slit spectra (1 A resolution) of some 450 candidates are used to measure equivalent widths of the CaII K line and Balmer features. A calibration of the K-line strength for giants in the metal-poor globular cluster NGC 6397 and field dwarfs and giants of known metallicity is used to identify survey candidates with metal abundance [Fe/H]<=-2.0; a list of 134 such stars is presented. UBV photometry is used to distinguish between two groups of metal-poor stars: a group with objects near the main-sequence turnoff, on the subgiant branch, and on the giant branch; and a second group with objects on the red horizontal branch (RHB) and asymptotic giant branch (AGB). The RHB-AGB stars exhibit the well-known weak G-band effect; three CH-strong objects are identified among the subgiants.
- ID:
- ivo://CDS.VizieR/J/AJ/147/136
- Title:
- Stars of very low metal abundance. VI. Abundances
- Short Name:
- J/AJ/147/136
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present radial velocities, equivalent widths, model atmosphere parameters, and abundances or upper limits for 53 species of 48 elements derived from high resolution optical spectroscopy of 313 metal-poor stars. A majority of these stars were selected from the metal-poor candidates of the HK Survey of Beers, Preston, and Shectman. We derive detailed abundances for 61% of these stars for the first time. Spectra were obtained during a 10yr observing campaign using the Magellan Inamori Kyocera Echelle spectrograph on the Magellan Telescopes at Las Campanas Observatory, the Robert G. Tull Coude Spectrograph on the Harlan J. Smith Telescope at McDonald Observatory, and the High Resolution Spectrograph on the Hobby-Eberly Telescope at McDonald Observatory. We perform a standard LTE abundance analysis using MARCS model atmospheres, and we apply line-by-line statistical corrections to minimize systematic abundance differences arising when different sets of lines are available for analysis. We identify several abundance correlations with effective temperature. A comparison with previous abundance analyses reveals significant differences in stellar parameters, which we investigate in detail. Our metallicities are, on average, lower by {approx}0.25dex for red giants and {approx}0.04dex for subgiants. Our sample contains 19 stars with [Fe/H]<=-3.5, 84 stars with [Fe/H]<=-3.0, and 210 stars with [Fe/H]<=-2.5. Detailed abundances are presented here or elsewhere for 91% of the 209 stars with [Fe/H]<=-2.5 as estimated from medium resolution spectroscopy by Beers, Preston, and Shectman. We will discuss the interpretation of these abundances in subsequent papers.
- ID:
- ivo://CDS.VizieR/J/A+A/398/363
- Title:
- Statistical properties of exoplanets II
- Short Name:
- J/A+A/398/363
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Table2 file is an extended version of table 2 in the paper. It contains the stellar parameters as well as the number of FeI and FeII lines used (and the rms around the mean value) in the analysis, the spectrograph used, and the derived stellar masses for each star. Velocity files contains the U, V, and W space velocities for the planet host stars used in Figs. 9 and 10.
- ID:
- ivo://CDS.VizieR/J/A+A/614/A146
- Title:
- Stellar parameters of NGC3201 RGB stars
- Short Name:
- J/A+A/614/A146
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- The origin of the globular cluster (GC) NGC3201 is under debate. Its retrograde orbit points to an extragalactic origin, but no further chemical evidence supports this idea. Light-element chemical abundances are useful to tag GCs and can be used to shed light in this discussion. Recently it was shown that the CN and CH indices are useful to identify anomalous GCs out of typical Milky Way GCs. A possible origin of anomalous clusters is the merger of two GCs and/or nucleus of a dwarf galaxy. We aim at deriving CN and CH band strengths for red giant stars in NGC3201 and compare with photometric indices and high-resolution spectroscopy and discuss in the context of GC chemical tagging. We measure molecular band indices of S(3839) and G4300 for CN and CH, respectively from low-resolution spectra of red giant stars. Gravity and temperature effects are removed. Photometric indices are used to indicate further chemical information on C+N+O or s-process element abundances, not derived from low-resolution spectra. We found three groups on the CN-CH distribution. A main sequence (S1), a secondary less-populated sequence (S2), and a group of peculiar (pec) CN-weak and CH-weak stars, one of which was previously known. The three groups seem to have different C+N+O and/or s-process element abundances, to be confirmed by high-resolution spectroscopy. These are typical characteristics of anomalous GCs. The CN distribution of NGC3201 is quadrimodal, which is more common in anomalous clusters. However, NGC3201 does not belong to the trend of anomalous GCs in the mass-size relation. NGC3201 shows signs that it can be chemically tagged as anomalous: unusual CN-CH relation, indications that pec-S1-S2 is an increasing sequence of C+N+O or s-process element abundances, and a multimodal CN distribution that seems to correlate with s-process element abundances. The differences are: it has a debatable Fe-spread and it does not follow the trend of mass-size of all anomalous clusters. Three scenarios are postulated here: (i) if the sequence pec-S1-S2 has increasing C+N+O and s-process element abundances, NGC3201 would be the first anomalous GC out of the mass-size relation; (ii) if the abundances are almost constant, NGC3201 would be the first non-anomalous GC with multiple CN-CH anti-correlation groups, or (iii) it would be the first anomalous GC without variations in C+N+O and s-process element abundances. In all cases, the definition of anomalous clusters and the scenario where they have an extragalactic origin must be revised.
- ID:
- ivo://CDS.VizieR/J/ApJS/208/27
- Title:
- Sun and HD 84937 TiII log(gf) and abundances
- Short Name:
- J/ApJS/208/27
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Atomic transition probability measurements for 364 lines of Ti II in the UV through near-IR are reported. Branching fractions from data recorded using a Fourier transform spectrometer (FTS) and a new echelle spectrometer are combined with published radiative lifetimes to determine these transition probabilities. The new results are in generally good agreement with previously reported FTS measurements. Use of the new echelle spectrometer, independent radiometric calibration methods, and independent data analysis routines enables a reduction of systematic errors and overall improvement in transition probability accuracy over previous measurements. The new Ti II data are applied to high-resolution visible and UV spectra of the Sun and metal-poor star HD 84937 to derive new, more accurate Ti abundances. Lines covering a range of wavelength and excitation potential are used to search for non-LTE effects. The Ti abundances derived using Ti II for these two stars match those derived using Ti I and support the relative Ti/Fe abundance ratio versus metallicity seen in previous studies.
- ID:
- ivo://CDS.VizieR/J/PASP/113/1365
- Title:
- Super-metal-rich stars
- Short Name:
- J/PASP/113/1365
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present Lick spectral indices for a complete sample of 139 candidate super-metal-rich stars of different luminosity classes (MK type from I to V). For 91 of these stars we were able to identify, in an accompanying paper, the fundamental atmosphere parameters. This confirms that at least 2/3 of the sample consists of stars with [Fe/H] in excess of +0.1 dex. Optical indices for both observations and fiducial synthetic spectra have been calibrated to the Lick system according to Worthey et al. (1994, Cat. <J/ApJS/94/687>) and include the FeI indices of Fe5015, Fe5270, and Fe5335 and the MgI and MgH indices of Mg_2_ and Mg_b_ at 5180{AA}. The internal accuracy of the observations is found to be {sigma}(Fe5015)=10.32{AA}, {sigma}(Fe5270)=10.19{AA}, {sigma}(Fe5335)=10.22{AA}, {sigma}(Mg_2_)=10.004mag, and {sigma}(Mg_b_)=10.19{AA}. This is about a factor of 2 better than the corresponding theoretical indices from the synthetic spectra, the latter being a consequence of the intrinsic limitations in the input physics, as discussed by Chavez et al. (1997, Cat. <J/A+AS/126/267>).
