- ID:
- ivo://CDS.VizieR/J/A+A/607/A91
- Title:
- CS 29497-004 abundances
- Short Name:
- J/A+A/607/A91
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We report an abundance analysis for the highly r-process-enhanced (r-II) star CS 29497-004, a very metal-poor giant with solar system Teff=5013K and [Fe/H]=-2.85, whose nature was initially discovered in the course of the HERES project. Our analysis is based on high signal-to-noise ratio, high-resolution (R~75000) VLT/UVES spectra and MARCS model atmospheres under the assumption of local thermodynamic equilibrium, and obtains abundance measurements for a total of 46 elements, 31 of which are neutron-capture elements. As is the case for the other ~25 r-II stars currently known, the heavy-element abundance pattern of CS 29497-004 well-matches a scaled solar system second peak r-process-element abundance pattern. We confirm our previous detection of Th, and demonstrate that this star does not exhibit an "actinide boost". Uranium is also detected (log{epsilon}(U)=-2.20+/-0.30), albeit with a large measurement error that hampers its use as a precision cosmochronometer. Combining the various elemental chronometer pairs that are available for this star, we derive a mean age of 12.2+/-3.7Gyr using the theoretical production ratios from published waiting-point approximation models. We further explore the high-entropy wind model (Farouqi et al., 2010ApJ...712.1359F) production ratios arising from different neutron richness of the ejecta (Ye), and derive an age of 13.7+/-4.4Gyr for a best-fitting Ye=0.447. The U/Th nuclei-chronometer is confirmed to be the most resilient to theoretical production ratios and yields an age of 16.5+/-6.6Gyr. Lead (Pb) is also tentatively detected in CS 29497-004, at a level compatible with a scaled solar r-process, or with the theoretical expectations for a pure r-process in this star.
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Search Results
- ID:
- ivo://CDS.VizieR/J/AJ/134/229
- Title:
- CT1T2 Photometry of red giants in 2 globulars
- Short Name:
- J/AJ/134/229
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present Washington photometry of the giant branches of the relatively metal-rich globular cluster NGC 6388 and compare it with 47 Tuc. By examining the spatial distribution of stellar colors across the red giant branch and using spectroscopic data on several bright giants, we found that NGC 6388's center is affected by differential reddening of at least {DELTA}E(B-V)~0.1. Most of the width of the red giant branch is caused by that differential reddening. The southeastern outer regions of the cluster seem to be less affected by variable dust extinction, and we find that NGC 6388 is slightly more metal-rich than 47 Tuc, with a distinct asymptotic giant branch. We have put an upper limit on possible variations in [Fe/H] for NGC 6388, finding that it must be less than ~0.2dex. It is unlikely that such a small range in metallicity could be responsible for the blue horizontal branch and blue tail stars in a cluster with a metallicity similar to the more massive 47 Tuc, which only exhibits a red horizontal branch.
- ID:
- ivo://CDS.VizieR/J/A+A/566/A120
- Title:
- 3D dust extinction in Milky Way bulge
- Short Name:
- J/A+A/566/A120
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Three dimensional interstellar extinction maps provide a powerful tool for stellar population analysis. However, until now, these 3D maps were rather limited by sensitivity and spatial resolution. We use data from the VISTA Variables in the Via Lactea survey together with the Besancon stellar population synthesis model of the Galaxy to determine interstellar extinction as a function of distance in the Galactic bulge covering -10<l<10 and -10<b<5. We adopted a recently developed method to calculate the colour excess. First we constructed the H-Ks vs. Ks and J-Ks vs. Ks colour-magnitude diagrams based on the VVV catalogues that matched 2MASS. Then, based on the temperature-colour relation for M giants and the distance-colour relations, we derived the extinction as a function of distance. The observed colours were shifted to match the intrinsic colours in the Besancon model as a function of distance iteratively. This created an extinction map with three dimensions: two spatial and one distance dimension along each line of sight towards the bulge. We present a 3D extinction map that covers the whole VVV area with a resolution of 6'x6', for J-Ks and H-Ks using distance bins of 0.5-1.0kpc. The high resolution and depth of the photometry allows us to derive extinction maps for a range of distances up to 10kpc and up to 30 magnitudes of extinction in AV (3.0mag in AKs). Integrated maps show the same dust features and consistent values as other 2D maps. We discuss the spatial distribution of dust features in the line of sight, which suggests that there is much material in front of the Galactic bar, specifically between 5-7kpc. We compare our dust extinction map with the high-resolution ^12^CO maps (NANTEN2) towards the Galactic bulge, where we find a good correlation between ^12^CO and A_V_. We determine the X factor by combining the CO map and our dust extinction map. Our derived average value X=2.5+/-0.47x10^20^/(cm^2^.K.km/s) is consistent with the canonical value of the Milky Way. The X-factor decreases with increasing extinction.
- ID:
- ivo://CDS.VizieR/J/MNRAS/469/4578
- Title:
- Deep learning classification in asteroseismology
- Short Name:
- J/MNRAS/469/4578
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- In the power spectra of oscillating red giants, there are visually distinct features defining stars ascending the red giant branch from those that have commenced helium core burning. We train a 1D convolutional neural network by supervised learning to automatically learn these visual features from images of folded oscillation spectra. By training and testing on Kepler red giants, we achieve an accuracy of up to 99 per cent in separating helium-burning red giants from those ascending the red giant branch. The convolutional neural network additionally shows capability in accurately predicting the evolutionary states of 5379 previously unclassified Kepler red giants, by which we now have greatly increased the number of classified stars.
- ID:
- ivo://CDS.VizieR/J/ApJ/711/573
- Title:
- Detailed abundances in a halo stellar stream
- Short Name:
- J/ApJ/711/573
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present the results of a detailed abundance analysis of one of the confirmed building blocks of the Milky Way stellar halo, a kinematically coherent metal-poor stellar stream. We have obtained high-resolution and high signal-to-noise spectra of 12 probable stream members using the Magellan Inamori Kyocera Echelle spectrograph on the Magellan-Clay Telescope at Las Campanas Observatory and the 2dCoude spectrograph on the Smith Telescope at McDonald Observatory. We have derived abundances or upper limits for 51 species of 46 elements in each of these stars. The stream members show a range of metallicity (-3.4<[Fe/H]<-1.5) but are otherwise chemically homogeneous, with the same star-to-star dispersion in [X/Fe] as the rest of the halo. This implies that, in principle, a significant fraction of the Milky Way stellar halo could have formed from accreted systems like the stream. The stream stars show minimal evolution in the {alpha} or Fe-group elements over the range of metallicity. This stream is enriched with material produced by the main and weak components of the rapid neutron-capture process and shows no evidence for enrichment by the slow neutron-capture process.
- ID:
- ivo://CDS.VizieR/J/MNRAS/449/3889
- Title:
- Detailed abundances of 15 stars in NGC 4833
- Short Name:
- J/MNRAS/449/3889
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We have observed 15 red giant stars in the relatively massive, metal-poor globular cluster NGC 4833 using the Magellan Inamori Kyocera Echelle spectrograph at Magellan. We calculate stellar parameters for each star and perform a standard abundance analysis to derive abundances of 43 species of 39 elements, including 20 elements heavier than the iron group. We derive <[Fe/H]>=-2.25+/-0.02 from FeI lines and <[Fe/H]>=-2.19+/-0.013 from FeII lines. We confirm earlier results that found no internal metallicity spread in NGC 4833, and there are no significant star-to-star abundance dispersions among any elements in the iron group (19=<Z=<30). We recover the usual abundance variations among the light elements C, N, O, Na, Mg, Al, and possibly Si. The heavy-element distribution reflects enrichment by r-process nucleosynthesis ([Eu/Fe]=+0.36+/-0.03), as found in many other metal-poor globular clusters. We investigate small star-to-star variations found among the neutron-capture elements, and we conclude that these are probably not real variations. Upper limits on the Th abundance, log{epsilon} (Th/Eu)<-0.47+/-0.09, indicate that NGC 4833, like other globular clusters where Th has been studied, did not experience a so-called actinide boost.
- ID:
- ivo://CDS.VizieR/J/A+A/372/85
- Title:
- Detected sources at 12{mu}m in 47 Tuc
- Short Name:
- J/A+A/372/85
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- The present paper investigates the properties of the dust mass loss in stars populating the giant branch of the globular cluster 47 Tuc, by combining ISOCAM and DENIS data. Raster maps of 5 fields covering areas ranging from 4x4 to 15x15arcmin^2^ at different distances from the center of the cluster have been obtained with ISOCAM at 11.5{mu}m (LW10 filter). The covered fields include most of the red variables known in this cluster. A detection threshold of about 0.2 mJy is achieved, allowing us to detect giant stars at 11.5{mu}m all the way down to the horizontal branch. No dust-enshrouded asymptotic giant branch stars have been found in the observed fields, contrary to the situation encountered in LMC/SMC globular clusters with larger turnoff masses. The color index [12]-[2] (based on the ISO 11.5{mu}m flux and on the DENIS K_S_ magnitude) is used as a diagnostic of dust emission (and hence dust mass loss). Its evolution with luminosity along the giant branch reveals that dust mass loss is only present in V3 (the only cluster Mira variable observed in the present study) and in V18, a star presenting intermittent variability. This conclusion confirms the importance of stellar pulsations in the dust formation and ensuing mass loss.
- ID:
- ivo://CDS.VizieR/J/A+A/550/A62
- Title:
- DIBs from Baade's window bulge clump giants
- Short Name:
- J/A+A/550/A62
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Interstellar (IS) absorption lines or diffuse bands are usually extracted from early-type star spectra because they are characterized by smooth continua. However, this introduces a strong limitation on the number of available targets, and reduces potential studies of the IS matter and the use of absorptions for cloud mapping. We have developed a new and automated fitting method appropriate to interstellar (IS) absorptions in the spectra of cool stars that possess stellar atmospheric parameters. We applied this method to the extraction of three diffuse interstellar bands (DIBs) in high resolution VLT FLAMES/GIRAFFE spectra of red-clump stars from the bulge. By combining all stellar synthetic spectra, HITRAN-LBLRTM atmospheric transmission spectra and diffuse band empirical absorption profiles, we determined the 6196.0, 6204.5, and 6283.8{AA} DIB strength toward the 219 target stars and discuss the sources of uncertainties. To test the sensitivity of the DIB extraction, we compared all three results and compared the DIB equivalent widths (EWs) with the reddening derived from an independent extinction map based on OGLE photometric data. We also derived the three independent color excess estimates based on the DIB strengths and average linear correlation coefficients previously established in the solar neighborhood and compared with the OGLE photometric results.
- ID:
- ivo://CDS.VizieR/J/A+A/619/A13
- Title:
- 28 distant globular clusters CaT metallicities
- Short Name:
- J/A+A/619/A13
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- In an earlier paper we presented the first part of a project to obtain metallicities and radial velocities of Galactic globular clusters from multiobject spectroscopy of their member stars using the ESO Very Large Telescope. In this paper we add metallicities and radial velocities for a new sample of 28 globular clusters, including in particular globular clusters in the MW halo and the Galactic bulge. Together with our previous results, this study brings the number of globular clusters with homogeneous measurements to ~69% of those listed in the W. Harris' catalogue. As in our previous work, we have used the CaII triplet lines to derive metallicities and radial velocities. For most of the clusters in this study, this is the first analysis based on spectroscopy of individual member stars. The metallicities derived from the CaII triplet are then compared to the results of our parallel study based on spectral fitting in the optical region and the implications for different calibrations of the CaII triplet line strengths are discussed.
- ID:
- ivo://CDS.VizieR/J/A+A/650/A146
- Title:
- Distant, pulsating red giants in southern halo
- Short Name:
- J/A+A/650/A146
- Date:
- 22 Feb 2022
- Publisher:
- CDS
- Description:
- To investigate the asymptotic giant branch (AGB) population in the Galactic halo, we search for pulsating AGB stars at a heliocentric distance over 50kpc. Our research is based on the Catalina Southern Survey (CSS) catalogue of variables, comprising 1286 long-period variables (LPVs) with declination less than -20{deg}. We first focus on the 77 stars in the cap abs(b)>30deg for which spectral M-type or C-type classification can be derived from Hamburg-ESO objective prism spectra. Most of these are oxygen-rich (M-type) and very few are carbon rich. The periods are in the range 100-500 days, and CSS amplitudes are up to 3mag. In this small sample, no halo AGB star is fainter than Ks0=12.5. This may be due to the scarcity of AGBs in the outer halo, or insufficient instrumental depth. Leaving aside spectral information, we then searched for even fainter pulsators (Ks>12.5) in the entire CSS catalogue. Gaia astrometry makes it possible to identify some contaminants. Our final result is the identification of ten candidate distant LPVs. If these ten stars obey the fundamental mode K-band period luminosity relation used for Miras and small-amplitude Miras, their distances are between 50 and 120kpc from the Sun. In a diagram showing distance versus Gaia tangential velocity, these ten stars have positions similar to those of other objects in the halo, such as globular clusters and dwarf galaxies. We also detect some underluminous AGBs that deserve further study. A detailed catalogue of the 77 high-latitude M or C stars will be made available at the CDS.
