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

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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H-band discovery of additional second-generation stars in the Galactic bulge globular cluster NGC 6522 as observed by APOGEE and Gaia

Astronomy and Astrophysics ◽

10.1051/0004-6361/201834391 ◽

2019 ◽

Vol 627 ◽

pp. A178 ◽

Cited By ~ 9

Author(s):

J. G. Fernández-Trincado ◽

O. Zamora ◽

Diogo Souto ◽

R. E. Cohen ◽

F. Dell’Agli ◽

...

Keyword(s):

Globular Cluster ◽

Second Generation ◽

Elemental Abundance ◽

Agb Stars ◽

Giant Stars ◽

Abundance Patterns ◽

Evolution Experiment ◽

Band Spectra ◽

Stellar Sources ◽

Process Element

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

Astronomy and Astrophysics ◽

10.1051/0004-6361/201322422 ◽

2013 ◽

Vol 557 ◽

pp. L17 ◽

Cited By ~ 27

Author(s):

Corinne Charbonnel ◽

William Chantereau ◽

Thibaut Decressin ◽

Georges Meynet ◽

Daniel Schaerer

Keyword(s):

Globular Cluster ◽

Second Generation ◽

Agb Stars

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Globular cluster abundances: the role of asymptotic giant branch stars

Proceedings of the International Astronomical Union ◽

10.1017/s1743921309991013 ◽

2009 ◽

Vol 5 (S266) ◽

pp. 161-168

Author(s):

Amanda I. Karakas

Keyword(s):

Globular Cluster ◽

Globular Clusters ◽

Asymptotic Giant Branch ◽

Asymptotic Giant Branch Stars ◽

Agb Stars ◽

Modelling Uncertainties ◽

Low Metallicity ◽

Abundance Anomalies ◽

Giant Branch Stars

AbstractOne of the more popular theories to account for the abundance anomalies in globular cluster stars is the ‘self-pollution scenario,’ where the polluters were a previous generation of intermediate-mass asymptotic giant branch (AGB) stars. This idea has proved attractive because: (i) the hot-bottom burning experienced by these objects qualitatively provides an ideal proton-capture environment to produce helium and convert C and O to N, Ne to Na and Mg to Al, and (ii) the slow winds from these stars allow their retention by the cluster's gravitational potential. New stellar yields from low-metallicity AGB models are presented and compared to abundances derived in globular clusters. We also discuss external pollution and inhomogeneous-pollution models that use AGB stars as polluters. Current models of AGB stars cannot match all observational features of globular cluster stars. However, stellar modelling uncertainties are considerable and suggest AGB stars should not be ruled out just yet.

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A catalogue of oxygen-rich pulsating giants in the Galactic halo and the Sagittarius stream

Astronomy and Astrophysics ◽

10.1051/0004-6361/201834089 ◽

2019 ◽

Vol 626 ◽

pp. A112

Author(s):

N. Mauron ◽

L. P. A. Maurin ◽

T. R. Kendall

Keyword(s):

Northern Hemisphere ◽

Globular Cluster ◽

Reasonable Agreement ◽

Galactic Halo ◽

Radial Velocities ◽

Distance Scale ◽

Asymptotic Giant Branch ◽

Agb Stars ◽

Rr Lyrae ◽

M Stars

To construct a catalogue of oxygen-rich (M) asymptotic giant branch (AGB) stars in the halo, complementing the catalogues of carbon-rich (C) stars, previous lists of Miras and SRa semi-regulars located in the northern hemisphere are merged and cleaned of various defects. After putting aside known C stars, characteristics such as colours and periods indicate that most of the remaining objects are M stars. Distances are obtained through the period-luminosity relation. By considering their position in the sky, stars lying at |Z| > 5 kpc are confirmed to be in majority in the Sgr tidal arms. The M stars are more numerous than C ones. Our distance scale is supported by two cool variables located in the Pal 4 globular cluster. Along the Sgr arms, there is reasonable agreement on distances of our objects with recent RR Lyrae distances. A few stars may be as distant as 150 kpc, with possibly four at the trailing arm apocentre, and two in the A16 sub-structure, angularly close to two C stars. Ninety radial velocities are collected from Gaia and other sources. A catalogue with 417 M pulsating AGB stars is provided. This catalogue contains ∼260 stars in the halo with |Z| > 5 kpc. Their Ks magnitudes range from 8 up to 13. For comparison, the catalogue also provides ∼150 stars in the disc having 5 < Ks < 8.

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