Why the globular cluster NGC 6752 contains no sodium-rich second-generation AGB stars

We present an elemental abundance analysis of high-resolution spectra for five giant stars spatially located within the innermost regions of the bulge globular cluster NGC 6522 and derive Fe, Mg, Al, C, N, O, Si, and Ce abundances based on H-band spectra taken with the multi-object APOGEE-north spectrograph from the SDSS-IV Apache Point Observatory Galactic Evolution Experiment (APOGEE) survey. Of the five cluster candidates, two previously unremarked stars are confirmed to have second-generation (SG) abundance patterns, with the basic pattern of depletion in C and Mg simultaneous with enrichment in N and Al as seen in other SG globular cluster populations at similar metallicity. In agreement with the most recent optical studies, the NGC 6522 stars analyzed exhibit (when available) only mild overabundances of the s-process element Ce, contradicting the idea that NGC 6522 stars are formed from gas enriched by spinstars and indicating that other stellar sources such as massive AGB stars could be the primary polluters of intra-cluster medium. The peculiar abundance signatures of SG stars have been observed in our data, confirming the presence of multiple generations of stars in NGC 6522.

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Hydrodynamic simulations of second generation star formation in a young globular cluster

Proceedings of the International Astronomical Union ◽

10.1017/s1743921319006732 ◽

2019 ◽

Vol 14 (S351) ◽

pp. 269-272

Author(s):

Francesco Calura

Keyword(s):

Star Formation ◽

Globular Cluster ◽

Second Generation ◽

Three Dimensional ◽

Asymptotic Giant Branch ◽

Central Density ◽

Agb Stars ◽

Hydrodynamic Simulations ◽

Numerical Studies

AbstractI will present results obtained by means of three-dimensional hydrodynamic simulations of the formation of second generation (SG) stars in a young globular cluster (GC). Our setup includes the mass return from Asymptotic Giant branch (AGB) stars, the accretion of pristine gas as well as star formation of SG stars, three ingredients which have never been simultaneously taken into account in previous 3D numerical studies of GC formation. The cluster is set in motion with respect to a distribution of gas and allowed to accrete mass from it. Formation of SG stars occurs out of the gas shed by AGB stars and from the gas accreted during the motion of the cluster. We consider two models characterised by different densities of the external gas. In both cases, we find that a very compact SG subsystem with central density > 105M⊙/pc3 forms in the innermost regions of the cluster.

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Metallicity, pulsation and mass loss in globular cluster low-mass AGB stars

10.1063/1.3099256 ◽

2009 ◽

Author(s):

Iain McDonald ◽

Jacco Th. van Loon ◽

Martha L. Boyer ◽

Eric Stempels

Keyword(s):

Mass Loss ◽

Globular Cluster ◽

Agb Stars ◽

Low Mass

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Are Galactic globular cluster AGB stars rich or poor in Sodium? Sodium abundance of AGB and RGB stars in NGC 2808

Proceedings of the International Astronomical Union ◽

10.1017/s1743921316008681 ◽

2015 ◽

Vol 12 (S316) ◽

pp. 361-362

Author(s):

Yue Wang ◽

Francesca Primas ◽

Corinne Charbonnel ◽

Mathieu Van der Swaelmen ◽

William Chantereau ◽

...

Keyword(s):

Spectroscopic Study ◽

Globular Cluster ◽

Main Sequence ◽

Significant Fraction ◽

Agb Stars ◽

2Nd Generation ◽

Red Giant ◽

Sodium Abundance

AbstractA spectroscopic study comparing the [Na/Fe] distributions of RGB and AGB stars in the Galactic globular cluster (GC) NGC 6752 found that there was no Na-rich, 2nd-generation star along the early-AGB of this cluster. This came as a surprise since in this GC, as well as other Galactic GCs studied so far, 1st- and 2nd-generation stars have usually been found from the main sequence turnoff up to the red giant branch. To investigate whether the failure of a significant fraction of stars to ascend the AGB also happens to other GCs, we studied a sample of AGB and RGB stars in NGC 2808 observed at the ESO/VLT with FLAMES. Contrary to NGC 6752, we find that the AGB and RGB stars we studied in NGC 2808 have comparable [Na/Fe] dispersions.

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The Helium contribution from massive AGBs

Proceedings of the International Astronomical Union ◽

10.1017/s1743921310003996 ◽

2009 ◽

Vol 5 (S268) ◽

pp. 147-152

Author(s):

Paolo Ventura

Keyword(s):

Interstellar Medium ◽

Globular Clusters ◽

Second Generation ◽

The Self ◽

Agb Stars ◽

Two Populations

AbstractThe helium produced by AGB and super-AGB stars is a key quantity to understand whether these objects may have been the main polluters of the interstellar medium within globular clusters, and originate a second generation of stars with a chemistry showing the imprinting of their ejecta. Helium is the most important element for this topic, as any difference in the original helium between the two populations would determine clearly distinguishable features both in the morphology of the Horizontal Branches and in the Main Sequences. We present the helium yields from massive AGB stars, and show that the results are rather robust, being approximately independent of the various uncertainties that affect the description of the evolution of these stars. The implications for the self-enrichment scenario are discussed and commented.

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Two Luminous Post-AGB Stars in the Galactic Globular Cluster M19

The Astronomical Journal ◽

10.3847/1538-3881/abdbb3 ◽

2021 ◽

Vol 161 (3) ◽

pp. 125

Author(s):

Howard E. Bond ◽

Brian D. Davis ◽

Michael H. Siegel ◽

Robin Ciardullo

Keyword(s):

Globular Cluster ◽

Agb Stars

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Massive stars in globular clusters: drivers of chemical and dynamical evolution

Proceedings of the International Astronomical Union ◽

10.1017/s1743921311010465 ◽

2010 ◽

Vol 6 (S272) ◽

pp. 227-232

Author(s):

Thibault Decressin

Keyword(s):

Globular Cluster ◽

Globular Clusters ◽

Second Generation ◽

Massive Stars ◽

Dynamical Evolution ◽

Strong Impact ◽

Low Velocity ◽

Cluster Evolution ◽

The One ◽

Mechanical Mass

AbstractMassive stars have a strong impact on globular cluster evolution. First providing they rotate initially fast enough they can reach the break-up velocity during the main sequence and a mechanical mass-loss will eject matter from the equator at low velocity. Rotation-induced mixing will also bring matter from the convective core to the surface. From this ejected matter loaded in H-burning material a second generation of stars will born. The chemical pattern of these second generation stars are similar to the one observed for stars in globular cluster with abundance anomalies in light elements. Then during the explosion as supernovae the massive stars will also clear the cluster of the remaining gas. If this gas expulsion process acts on short timescale it can strongly modify the dynamical properties of clusters by ejecting preferentially first generation stars.

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ALMA reveals sunburn: CO dissociation around AGB stars in the globular cluster 47 Tucanae

Monthly Notices of the Royal Astronomical Society ◽

10.1093/mnras/stv1968 ◽

2015 ◽

Vol 453 (4) ◽

pp. 4325-4337 ◽

Cited By ~ 11

Author(s):

I. McDonald ◽

A. A. Zijlstra ◽

E. Lagadec ◽

G. C. Sloan ◽

M. L. Boyer ◽

...

Keyword(s):

Globular Cluster ◽

Agb Stars ◽

Co Dissociation

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An extreme paucity of second population AGB stars in the ‘normal’ globular cluster M4

Monthly Notices of the Royal Astronomical Society Letters ◽

10.1093/mnrasl/slw073 ◽

2016 ◽

Vol 460 (1) ◽

pp. L69-L73 ◽

Cited By ~ 23

Author(s):

B. T. MacLean ◽

S. W. Campbell ◽

G. M. De Silva ◽

J. Lattanzio ◽

V. D'Orazi ◽

...

Keyword(s):

Globular Cluster ◽

Agb Stars

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Dynamical implications of multiple stellar populations

Proceedings of the International Astronomical Union ◽

10.1017/s1743921307011258 ◽

2006 ◽

Vol 2 (14) ◽

pp. 436-437

Author(s):

Alison I. Sills ◽

Jonathan M. Downing

Keyword(s):

Star Formation ◽

Globular Cluster ◽

Globular Clusters ◽

Stellar Populations ◽

The Self ◽

Asymptotic Giant Branch ◽

Agb Stars ◽

Early Generation ◽

Single Burst

AbstractWe investigate some implications of having two star formation episodes in globular clusters, rather than the traditional single-burst approximation. Evidence for more than one stellar generation is accumulating in observations of abundances of elements lighter than iron in globular cluster stars, and is thought to imply some self-enrichment of the globular cluster gas. In particular, we explore models based on the assumption that the self-enrichment comes from an early generation of asymptotic giant branch (AGB) stars.

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