scholarly journals Chemical abundance analysis of red giant branch stars in the globular cluster E3

2018 ◽  
Vol 616 ◽  
pp. A181 ◽  
Author(s):  
L. Monaco ◽  
S. Villanova ◽  
G. Carraro ◽  
A. Mucciarelli ◽  
C. Moni Bidin
Keyword(s):  
Radial Velocity ◽  
Globular Cluster ◽  
Globular Clusters ◽  
Abundance Ratio ◽  
Chemical Abundance ◽  
Chemical Abundances ◽  
Multiple Populations ◽  
Red Giant ◽  
A Minor ◽  
Giant Branch Stars

Context. Globular clusters are known to host multiple stellar populations, which are a signature of their formation process. The globular cluster E3 is one of the few low-mass globulars that is thought not to host multiple populations. Aims. We investigate red giant branch stars in E3 with the aim of providing a first detailed chemical inventory for this cluster, we determine its radial velocity, and we provide additional insights into the possible presence of multiple populations in this cluster. Methods. We obtained high-resolution FLAMES-UVES/VLT spectra of four red giant branch stars likely members of E3. We performed a local thermodynamic equilibrium abundance analysis based on one-dimensional plane parallel ATLAS9 model atmospheres. Abundances were derived from line equivalent widths or spectrum synthesis. Results. We measured abundances of Na and of iron peak (Fe, V, Cr, Ni, Mn), α(Mg, Si, Ca, Ti), and neutron capture elements (Y, Ba, Eu). The mean cluster heliocentric radial velocity, metallicity, and sodium abundance ratio are νhelio = 12.6 ± 0.4 km s−1(σ = 0.6 ± 0.2 km s−1), [Fe/H] = −0.89 ± 0.08 dex, and [Na/Fe] = 0.18 ± 0.07 dex, respectively. The low Na abundance with no appreciable spread is suggestive of a cluster dominated by first-generation stars in agreement with results based on lower resolution spectroscopy. The low number of stars observed does not allow us to rule out a minor population of second-generation stars. The observed chemical abundances are compatible with the trends observed in Milky Way stars.

scholarly journals Searching for multiple populations in Ruprecht 106

2021 ◽  
Author(s):  
H Frelijj ◽  
S Villanova ◽  
C Muñoz ◽  
J G Fernández-Trincado
Keyword(s):  
Globular Cluster ◽  
Stellar Population ◽  
Atmospheric Parameters ◽  
Photometric Analysis ◽  
Dynamical Study ◽  
Multiple Populations ◽  
Red Giant ◽  
Definition Of ◽  
Energy Plane ◽  
Giant Branch Stars

Abstract More than a decade has passed since the definition of Globular Cluster (GC) changed, and now we know that they host Multiple Populations (MPs). But few GCs do not share that behaviour and Ruprecht 106 is one of these clusters. We analyzed thirteen member red giant branch stars using spectra in the wavelength range 6120-6405 Å obtained through the GIRAFFE Spectrograph, mounted at UT2 telescope at Paranal, as well as the whole cluster using C, V, R and I photometry obtained through the Swope telescope at Las Campanas. Atmospheric parameters were determined from the photometry to determine Fe and Na abundances. A photometric analysis searching for MPs was also carried out. Both analyses confirm that Ruprecht 106 is indeed one on the few GCs to host Simple Stellar Population, in agreement with previous studies. Finally, a dynamical study concerning its orbits was carried out to analyse the possible extragalactic origin of the Cluster. The orbital integration indicates that this GC belongs to the inner halo, while an Energy plane shows that it cannot be accurately associated with any known extragalactic progenitor.

scholarly journals Observational Aspects of Slow Variables in Globular Clusters

1973 ◽  
Vol 21 ◽  
pp. 131-144
Author(s):  
M. W. Feast
Keyword(s):  
Radial Velocity ◽  
Compact Group ◽  
Globular Cluster ◽  
Globular Clusters ◽  
Magellanic Cloud ◽  
Small Magellanic Cloud ◽  
Mira Variables ◽  
Period Effects ◽  
Slow Variables ◽  
Red Giant

AbstractThere are up to 14 known Mira variables in seven globular clusters, though several have not yet been confirmed as radial velocity members. The periods of only 5 are known, all near 200 days. The clusters seem to form a compact group of relatively metal rich clusters. In 3 or 4 cases spectroscopy shows that the giant branches of these clusters penetrate into the M types. The Mira-containing clusters also contain red variables of shorter period and smaller amplitude which are generally also M type stars. Stars apparently evolve to the red of the giant tip as variables of increasing amplitude and period. Effects of TiO blanketing on the (B — V) colours may be anticipated in these clusters.Besides variables at the red giant tip the metal poor globular cluster ω Cen contains variables with strong TiO bands. Photometry, including recent J, H, K, L photometry by Glass shows that these stars are very cool objects. They indicate an extension of the giant branch considerably cooler than previously considered for metal poor clusters.V1, NGC 121 in the Small Magellanic Cloud has a spectrum indicative of an SRd variable. It is not yet clear whether galactic stars similar to this star exist or not.

scholarly journals Observing multiple populations in globular clusters with the ESO archive: NGC 6388 reloaded

2018 ◽  
Vol 614 ◽  
pp. A109 ◽  
Author(s):  
Eugenio Carretta ◽  
Angela Bragaglia
Keyword(s):  
Globular Clusters ◽  
First Generation ◽  
Spectroscopic Properties ◽  
Discrete Groups ◽  
Red Giants ◽  
Single Class ◽  
Multiple Populations ◽  
Telescope Facility ◽  
Red Giant ◽  
Giant Branch Stars

The metal-rich and old bulge globular cluster (GC) NGC 6388 is one of the most massive Galactic GCs (M ~ 106 M⊙). However, the spectroscopic properties of its multiple stellar populations rested only on 32 red giants (only 7 of which observed with UVES, the others with GIRAFFE), given the difficulties in observing a rather distant cluster, heavily contaminated by bulge and disc field stars. We bypassed the problem using the resources of the largest telescope facility ever: the European Southern Observatory (ESO) archive. By selecting member stars identified by other programmes, we derive atmospheric parameters and the full set of abundances for 15 species from high-resolution UVES spectra of another 17 red giant branch stars in NGC 6388. We confirm that no metallicity dispersion is detectable in this GC. About 30% of the stars show the primordial composition of first-generation stars, about 20% present an extremely modified second-generation composition, and 50% have an intermediate composition. The stars are clearly distributed in the Al–O and Na–O planes in three discrete groups. We find substantial hints that more than a single class of polluters is required to reproduce the composition of the intermediate component in NGC 6388. In the heavily polluted component the sum Mg+Al increases as Al increases. The sum Mg+Al+Si is constant, and is the fossil record of hot H-burning at temperatures higher than about 70 MK in the first-generation polluters that contributed to form multiple populations in this cluster.

scholarly journals On The Metal-poor non-Sagittarius Globular Cluster NGC 5053: Orbit, Mg, Al, and Si

2017 ◽  
Vol 13 (S334) ◽  
pp. 370-371
Author(s):  
Baitian Tang
Keyword(s):  
Radial Velocity ◽  
Globular Cluster ◽  
Globular Clusters ◽  
Near Infrared ◽  
Dwarf Galaxy ◽  
Optical Spectra ◽  
Spectral Lines ◽  
Multiple Populations ◽  
Multiple Population ◽  
Similar Location

AbstractMetal-poor globular clusters (GCs) show intriguing Al-Mg and Si-Al correlations, which are important clues to decipher the multiple population phenomenon. NGC 5053 is one of the most metal-poor GCs, and has been suggested to be associated with the Sagittarius dwarf galaxy (Sgr), due to its similar location and radial velocity with one of the Sgr arms. In this work, we simulate the orbit of NGC 5053, and argue against the connection between Sgr and NGC 5053. Meanwhile, Mg, Al, and Si spectral lines, which are difficult to detect in the optical spectra, have been detected in the near-infrared APOGEE spectra. We use three different sets of stellar parameters and codes to derive the Mg, Al, and Si abundances, and we always see a large Al variation, and a substantial Si enhancement. Comparing with other metal-poor GCs, we suggest metallicity may not be the only parameter that controls the multiple populations.

scholarly journals Detailed chemical abundance analysis of the thick disk star cluster Gaia 1

2017 ◽  
Vol 609 ◽  
pp. A13 ◽  
Author(s):  
Andreas Koch ◽  
Terese T. Hansen ◽  
Andrea Kunder
Keyword(s):  
Globular Clusters ◽  
Open Cluster ◽  
Light Element ◽  
Thick Disk ◽  
Chemical Abundance ◽  
Chemical Abundances ◽  
Low Mass ◽  
Red Giant ◽  
Significant Spread ◽  
Detailed Chemical

Star clusters, particularly those objects in the disk-bulge-halo interface are as yet poorly charted, despite the fact that they carry important information about the formation and the structure of the Milky Way. Here, we present a detailed chemical abundance study of the recently discovered object Gaia 1. Photometry has previously suggested it as an intermediate-age, moderately metal-rich system, although the exact values for its age and metallicity remained ambiguous in the literature. We measured detailed chemical abundances of 14 elements in four red giant members, from high-resolution (R = 25 000) spectra that firmly establish Gaia 1 as an object associated with the thick disk. The resulting mean Fe abundance is −0.62 ± 0.03(stat.)± 0.10(sys.) dex, which is more metal-poor than indicated by previous spectroscopy from the literature, but it is fully in line with values from isochrone fitting. We find that Gaia 1 is moderately enhanced in the α-elements, which allowed us to consolidate its membership with the thick disk via chemical tagging. The cluster’s Fe-peak and neutron-capture elements are similar to those found across the metal-rich disks, where the latter indicate some level of s-process activity. No significant spread in iron nor in other heavy elements was detected, whereas we find evidence of light-element variations in Na, Mg, and Al. Nonetheless, the traditional Na-O and Mg-Al (anti-)correlations, typically seen in old globular clusters, are not seen in our data. This confirms that Gaia 1 is rather a massive and luminous open cluster than a low-mass globular cluster. Finally, orbital computations of the target stars bolster our chemical findings of Gaia 1’s present-day membership with the thick disk, even though it remains unclear which mechanisms put it in that place.

scholarly journals Nucleosynthesis in Red Giant Stars

2002 ◽  
Vol 187 ◽  
pp. 57-69
Author(s):  
Nami Mowlavi
Keyword(s):  
Asymptotic Giant Branch ◽  
Red Giants ◽  
Asymptotic Giant Branch Stars ◽  
Chemical Abundance ◽  
Chemical Abundances ◽  
Giant Stars ◽  
Intermediate Mass Stars ◽  
Standard Models ◽  
Red Giant ◽  
Giant Branch Stars

The production of elements from helium-3 to fluorine in low- and intermediate-mass stars is reviewed and compared to chemical abundances observed at the surface of both red giant branch and asymptotic giant branch stars. It is highlighted that, while the trends predicted by standard models are generally well confirmed, many chemical abundances observed at the surface of red giants require the operation of non-standard mixing in the stellar interior. In addition, chemical abundance predictions from presently available asymptotic giant branch models further suffer from the uncertainties affecting the third dredge-up phenomenon, the source of neutrons and the hot bottom burning process.

scholarly journals Detection of multiple stellar populations in extragalactic massive clusters with JWST

2019 ◽  
Vol 629 ◽  
pp. A40 ◽  
Author(s):  
M. Salaris ◽  
S. Cassisi ◽  
A. Mucciarelli ◽  
D. Nardiello
Keyword(s):  
Globular Clusters ◽  
High Redshift ◽  
Major Change ◽  
Stellar Populations ◽  
Magellanic Clouds ◽  
Chemical Abundances ◽  
Multiple Populations ◽  
Stellar Spectra ◽  
Red Giant ◽  
Massive Clusters

The discovery of multiple stellar populations (multiple in the sense of inhomogeneous chemical abundances, with specific patterns of variations of a few light elements) in Galactic globular clusters and massive intermediate-age and old clusters in the Magellanic Clouds, both through spectroscopy and photometry, has led to a major change in our views about the formation of these objects. To date, none of the proposed scenarios are able to quantitatively explain all the chemical patterns observed in individual clusters. An extension of the study of multiple populations to resolved extragalactic massive clusters beyond the Magellanic Clouds would therefore be welcome, as it would enable the investigation and characterisation of the presence of multiple populations in different environments and age ranges. To this purpose, the James Webb Space Telescope (JWST) can potentially play a major role. On the one hand, the JWST promises direct observations of proto-globular cluster candidates at high redshift, and on the other hand, it can potentially push the sample of resolved clusters with detected multiple populations to larger distances. In this paper we address this second goal. Using theoretical stellar spectra and stellar evolution models, we investigated the effect of multiple population chemical patterns on synthetic magnitudes in the JWST infrared NIRCam filters. We identified the colours (F150W − F460M), (F115W − F460M) and pseudocolours CF150W, F460M, F115W = (F150W − F460M)−(F460M − F115W), CF150W, F277W, F115W = (F150W − F277W)−(F277W − F115W), as diagnostics able to reveal the presence of multiple populations along the red giant branches of old and intermediate-age clusters. Using the available online simulator for the NIRCam detector, we estimated that multiple populations can be potentially detected – depending on the exposure times, exact filter combination used, and extent of the abundance variations and the cluster [Fe/H] – out to a distance of ∼5 Mpc (approximately the distance to the M83 group).

scholarly journals Chemical abundances in tidally disrupted globular clusters

2009 ◽  
Vol 5 (S266) ◽  
pp. 157-160
Author(s):  
D. Yong ◽  
J. Meléndez ◽  
K. Cunha ◽  
A. I. Karakas ◽  
J. E. Norris ◽  
...  
Keyword(s):  
Globular Cluster ◽  
Preliminary Analysis ◽  
Globular Clusters ◽  
Building Blocks ◽  
Light Elements ◽  
Chemical Abundances ◽  
Chemical Enrichment ◽  
Abundance Variation

AbstractWe present abundance measurements in the tidally disrupted globular cluster NGC 6712. In this cluster, there are large star-to-star variations of the light elements C, N, O, F and Na. While such abundance variations are seen in every well-studied globular cluster, they are not found in field stars and indicate that clusters like NGC 6712 cannot provide many field stars and/or field stars do not form in environments with chemical-enrichment histories like those of NGC 6712. Preliminary analysis of NGC 5466, another tidally disrupted cluster, suggests little (if any) abundance variation for O and Na and the abundance ratios [X/Fe] are comparable to field stars at the same metallicity. Therefore, globular clusters like NGC 5466 may have been Galactic building blocks.

scholarly journals Lithium abundance in lower red giant branch stars of Omega Centauri

2018 ◽  
Vol 618 ◽  
pp. A134 ◽  
Author(s):  
A. Mucciarelli ◽  
M. Salaris ◽  
L. Monaco ◽  
P. Bonifacio ◽  
X. Fu ◽  
...  
Keyword(s):  
High Resolution ◽  
Globular Clusters ◽  
Stellar System ◽  
The Other ◽  
Large Telescope ◽  
Lithium Abundance ◽  
Very Large Telescope ◽  
Red Giant ◽  
Giant Branch Stars ◽  
Branch Star

We present Li, Na, Al, and Fe abundances of 199 lower red giant branch star members of the stellar system Omega Centauri, using high-resolution spectra acquired with FLAMES at the Very Large Telescope. The A(Li) distribution is peaked at A(Li) ∼ 1 dex with a prominent tail towards lower values. The peak of the distribution well agrees with the lithium abundances measured in lower red giant branch stars in globular clusters and Galactic field stars. Stars with A(Li) ∼ 1 dex are found at metallicities lower than [Fe/H] ∼ –1.3 dex but they disappear at higher metallicities. On the other hand, Li-poor stars are found at all metallicities. The most metal-poor stars exhibit a clear Li–Na anti-correlation, where about 30% of the sample have A(Li) lower than ∼0.8 dex, while these stars represent a small fraction of normal globular clusters. Most of the stars with [Fe/H] > –1.6 dex are Li poor and Na rich. The Li depletion measured in these stars is not observed in globular clusters with similar metallicities and we demonstrate that it is not caused by the proposed helium enhancements and/or young ages. Hence, these stars formed from a gas already depleted in lithium. Finally, we note that Omega Centauri includes all the populations (Li-normal/Na-normal, Li-normal/Na-rich, and Li-poor/Na-rich stars) observed, to a lesser extent, in mono-metallic GCs.

scholarly journals Dynamics of Globular Cluster Systems

1983 ◽  
Vol 100 ◽  
pp. 359-364
Author(s):  
K. C. Freeman
Keyword(s):  
Globular Cluster ◽  
Globular Clusters ◽  
Milky Way ◽  
Cluster Formation ◽  
Active Phase ◽  
Chemical Abundance ◽  
Cluster Systems ◽  
Chemical Enrichment ◽  
Wide Range ◽  
The Galaxy

In the Milky Way, the globular clusters are all very old, and we are accustomed to think of them as the oldest objects in the Galaxy. The clusters cover a wide range of chemical abundance, from near solar down to about [Fe/H] ⋍ −2.3. However there are field stars with abundances significantly lower than −2.3 (eg Bond, 1980); this implies that the clusters formed during the active phase of chemical enrichment, with cluster formation beginning at a time when the enrichment processes were already well under way.

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