scholarly journals The binary content of multiple populations in NGC 3201

2020 ◽  
Vol 635 ◽  
pp. A65 ◽  
Author(s):  
S. Kamann ◽  
B. Giesers ◽  
N. Bastian ◽  
J. Brinchmann ◽  
S. Dreizler ◽  
...  
Keyword(s):  
Globular Cluster ◽  
Binary Stars ◽  
Globular Clusters ◽  
Relaxation Times ◽  
Stellar Populations ◽  
Multiple Populations ◽  
Cluster Centre

We investigate the binary content of the two stellar populations that coexist in the globular cluster NGC 3201. Previous studies of binary stars in globular clusters have reported higher binary fractions in their first populations (P1, having field-like abundances) compared to their second populations (P2, having anomalous abundances). This is interpreted as evidence for the latter forming more centrally concentrated. In contrast to previous studies, our analysis focusses on the cluster centre, where comparable binary fractions between the populations are predicted because of short relaxation times. However, we find that even in the centre of NGC 3201, the observed binary fraction of P1 is higher (23.1 ± 6.2)% compared to (8.2 ± 3.5)% in P2. Our results are difficult to reconcile with a scenario in which the populations only differ in their initial concentrations, but instead suggests that the populations also formed with different fractions of binary stars.

scholarly journals The Hubble Space Telescope UV Legacy Survey of Galactic globular clusters – XXI. Binaries among multiple stellar populations

2019 ◽  
Vol 492 (4) ◽  
pp. 5457-5469
Author(s):  
A P Milone ◽  
E Vesperini ◽  
A F Marino ◽  
J Hong ◽  
R van der Marel ◽  
...  
Keyword(s):  
Numerical Simulations ◽  
Binary Stars ◽  
Globular Clusters ◽  
First Generation ◽  
Hubble Space Telescope ◽  
Dynamical Evolution ◽  
Stellar Populations ◽  
Multiple Populations ◽  
Space Telescope ◽  
Significant Difference

Abstract A number of scenarios for the formation of multiple populations in globular clusters (GCs) predict that second generation (2G) stars form in a compact and dense subsystem embedded in a more extended first-generation (1G) system. If these scenarios are accurate, a consequence of the denser 2G formation environment is that 2G binaries should be more significantly affected by stellar interactions and disrupted at a larger rate than 1G binaries. The fractions and properties of binary stars can thus provide a dynamical fingerprint of the formation epoch of multiple-population GCs and their subsequent dynamical evolution. We investigate the connection between binaries and multiple populations in five GCs, NGC 288, NGC 6121 (M 4), NGC 6352, NGC 6362, and NGC 6838 (M 71). To do this, we introduce a new method based on the comparison of Hubble Space Telescope observations of binaries in the F275W, F336W, F438W, F606W, and F814W filters with a large number of simulated binaries. In the inner regions probed by our data, we do not find large differences between the local 1G and the 2G binary incidences in four of the studied clusters, the only exception being M 4 where the 1G binary incidence is about three times larger than the 2G incidence. The results found are in general agreement with the results of simulations predicting significant differences in the global 1G and 2G incidences and in the local values in the clusters’ outer regions but similar incidences in the inner regions. The significant difference found in M 4 is consistent with simulations with a larger fraction of wider binaries. Our analysis also provides the first evidence of mixed (1G–2G) binaries, a population predicted by numerical simulations to form in a cluster’s inner regions as a result of stellar encounters during which one component of a binary is replaced by a star of a different population.

Globular cluster tidal interactions and mergers in the Galactic disc

2019 ◽  
Vol 14 (S351) ◽  
pp. 442-446
Author(s):  
Alessandra Mastrobuono-Battisti ◽  
Sergey Khoperskov ◽  
Paola Di Matteo ◽  
Misha Haywood
Keyword(s):  
Globular Cluster ◽  
Iron Content ◽  
Globular Clusters ◽  
Dynamical Evolution ◽  
Stellar Populations ◽  
Cluster System ◽  
Galactic Disc ◽  
Tidal Interactions ◽  
Globular Cluster System ◽  
Shed Light

AbstractThe Galactic globular cluster system went and is still going through dynamical processes that require to be explored in detail. Here we illustrate how primordial massive globular clusters born in the Milky Way’s disc evolved by stripping material from each other or even merging very early during their lives. These processes might explain the puzzling presence of star-by-star spreads in iron content observed in massive globular clusters and should be taken into account when studying globular cluster stellar populations. In this context, we show how the direct comparison between the predictions provided by our direct N-body simulations and observations can shed light on the origin and chemo-dynamical evolution of globular clusters.

scholarly journals The s-process enriched star HD 55496: origin from a globular cluster or from the tidal disruption of a dwarf galaxy?

2019 ◽  
Vol 488 (1) ◽  
pp. 482-494 ◽  
Author(s):  
C B Pereira ◽  
N A Drake ◽  
F Roig
Keyword(s):  
Globular Cluster ◽  
Binary Stars ◽  
Globular Clusters ◽  
Dwarf Galaxy ◽  
Dynamical Analysis ◽  
Element Abundance ◽  
Tidal Disruption ◽  
Abundance Pattern ◽  
Retrograde Motion ◽  
Process Elements

Abstract We present a new abundance analysis of HD 55496, previously known as a metal-poor barium star. We found that HD 55496 has a metallicity [Fe/H]  = −1.55 and is s-process enriched. We find that HD 55496 presents four chemical peculiarities: (i) a Na–O abundance anticorrelation; (ii) it is aluminium rich; (iii) it is carbon poor for an s-process enriched star, and (iv) the heavy second s-process peak elements, such as Ba, La, Ce, and Nd, present smaller abundances than the light s-process elements, such as Sr, Y, and Zr, which is not usually observed among the chemically peculiar binary stars at this metallicity. The heavy-element abundance pattern suggests that the main source of the neutrons is the 22Ne(α,n)25Mg reaction. Taking all these abundance evidences together into consideration strongly suggests that HD 55496 is a ‘second-generation of globular cluster stars’ formed from gas already strongly enriched in s-process elements and now is a field halo object. Our dynamical analysis, however, indicates that the past encounter probabilities with the known globular clusters are very low ($\le \!6{{\ \rm per\ cent}}$). This evidence, together with the retrograde motion, points to a halo intruder possibly originated from the tidal disruption of a dwarf galaxy.

scholarly journals The predicted properties of helium-enriched globular cluster progenitors at high redshift

2020 ◽  
Vol 496 (3) ◽  
pp. 3222-3234
Author(s):  
David M Nataf ◽  
Shunsaku Horiuchi ◽  
Guglielmo Costa ◽  
Rosemary F G Wyse ◽  
Yuan-Sen Ting ◽  
...  
Keyword(s):  
Adaptive Optics ◽  
Globular Cluster ◽  
Globular Clusters ◽  
Hubble Space Telescope ◽  
High Redshift ◽  
Cluster Formation ◽  
Stellar Populations ◽  
Space Telescope ◽  
James Webb Space Telescope ◽  
Galactic Astronomy

ABSTRACT Globular cluster progenitors may have been detected by Hubble Space Telescope, and are predicted to be observable with James Webb Space Telescope (JWST) and ground-based extremely large telescopes with adaptive optics. This has the potential to elucidate the issue of globular cluster formation and the origins of significantly helium-enriched subpopulations, a problem in Galactic astronomy with no satisfactory theoretical solution. Given this context, we use model stellar tracks and isochrones to investigate the predicted observational properties of helium-enriched stellar populations in globular cluster progenitors. We find that, relative to helium-normal populations, helium-enriched (ΔY = +0.12) stellar populations similar to those inferred in the most massive globular clusters, are expected, modulo some rapid fluctuations in the first ∼30 Myr, to be brighter and redder in the rest frame. At fixed age, stellar mass, and metallicity, a helium-enriched population is predicted to converge to being ∼0.40 mag brighter at $\lambda \approx 2.0\, {\mu \rm m}$, and to be 0.30-mag redder in the JWST–NIRCam colour (F070W − F200W), and to actually be fainter for $\lambda \lesssim 0.50 \, {\mu \rm m}$. Separately, we find that the time-integrated shift in ionizing radiation is a negligible $\sim \!5{{\ \rm per\ cent}}$, though we show that the Lyman-α escape fraction could end up higher for helium-enriched stars.

scholarly journals Binaries in Globular Clusters

1998 ◽  
Vol 11 (2) ◽  
pp. 616-621 ◽  
Author(s):  
S. L. W. Mcmillan ◽  
C. Pryor ◽  
E. S. Phinney
Keyword(s):  
Kinetic Energy ◽  
Globular Cluster ◽  
Binary Stars ◽  
Formation Process ◽  
Globular Clusters ◽  
The Other ◽  
Energy Distributions ◽  
Other Hand ◽  
Mass Segregation ◽  
Three Body

Binary stars in a globular cluster (hereafter, GC) may be primordial (i.e. formed along with the cluster), or the result of cluster dynamics. “Dynamical” binaries can result from conservative three-body encounters (e.g. Spitzer, 1987) if a third star can carry away enough kinetic energy to leave two others bound, or from dissipative two-body encounters, if two stars happen to pass within a few stellar radii of one other (Fabian, Pringle, & Rees, 1975). Such non-primordial systems are likely to be found primarily in evolved GC cores, both because conditions are more favorable for making them there, and because of mass segregation. Knowledge of the formation process allows reasonable estimates to be made of their mass and energy distributions. The initial spatial, mass, and energy distributions of primordial binaries, on the other hand, are largely unknown.

scholarly journals Observations of multiple populations in star clusters

2008 ◽  
Vol 4 (S258) ◽  
pp. 233-244 ◽  
Author(s):  
Giampaolo Piotto
Keyword(s):  
Globular Clusters ◽  
Star Clusters ◽  
Stellar Populations ◽  
Magellanic Cloud ◽  
Multiple Populations ◽  
Cloud Clusters ◽  
Photometric Observations ◽  
Galactic Globular Clusters

AbstractAn increasing number of photometric observations of multiple stellar populations in Galactic globular clusters is seriously challenging the paradigm of GCs hosting single, simple stellar populations. These multiple populations manifest themselves in a split of different evolutionary sequences as observed in the cluster color-magnitude diagrams. Multiple stellar populations have been identified in Galactic and Magellanic Cloud clusters. In this paper we will summarize the observational scenario.

scholarly journals Dynamical implications of multiple stellar populations

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.

scholarly journals Discovery of rotation axis alignments in Milky Way globular clusters

2020 ◽  
Vol 638 ◽  
pp. L12
Author(s):  
Andrés E. Piatti
Keyword(s):  
Gravitational Field ◽  
Internal Rotation ◽  
Globular Cluster ◽  
Globular Clusters ◽  
Milky Way ◽  
Rotation Axis ◽  
Relaxation Times ◽  
Orbit Inclination ◽  
Inclination Angles ◽  
Rotation Strength

There is an increasing number of recent observational results that show that some globular clusters exhibit internal rotation while they travel along their orbital trajectories around the Milky Way center. Based on these findings, we searched for any relationship between the inclination angles of the globular cluster orbits with respect to the Milky Way plane and those of their rotation. We discovered that the relative inclination, in the sense of inclination of the rotation axis to orbit axis, is a function of the orbit inclination of the globular cluster. Rotation and orbit axes are aligned for an inclination of ∼56°, while the rotation axis inclination is far from the orbit inclination between ∼20° and −20° when the latter increases from 0° up to 90°. We further investigated the origin of this linear relationship and found no correlation with the semimajor axes and eccentricities of the globular cluster orbits, nor with the internal rotation strength, the globular cluster sizes, actual and tidally disrupted masses, or half-mass relaxation times, among others. The uncovered relationship will affect the development of numerical simulations of the internal rotation of globular clusters, our understanding of the interaction of globular clusters with the gravitational field of the Milky Way, and the observational campaigns made to increase the number of globular clusters with detected internal rotation.

scholarly journals FAR-ULTRAVIOLET SURVEYS OF GLOBULAR CLUSTERS: HUNTING FOR THE PRODUCTS OF STELLAR COLLISIONS AND NEAR MISSES

2004 ◽  
Vol 19 (27) ◽  
pp. 2013-2027 ◽  
Author(s):  
CHRISTIAN KNIGGE
Keyword(s):  
Binary Stars ◽  
Globular Clusters ◽  
Dynamical Evolution ◽  
Stellar Populations ◽  
Short Review ◽  
Stellar Systems ◽  
Near Misses ◽  
Close Encounters ◽  
Stellar Collisions ◽  
Far Ultraviolet

Globular clusters are gravitationally bound stellar systems containing on the order of 105 stars. Due to the high stellar densities in the cores of these clusters, close encounters and even physical collisions between stars are inevitable. These dynamical interactions can produce exotic types of single and binary stars that are extremely rare in the galactic field, but which may be important to the dynamical evolution of their host clusters. A common feature of these dynamically-formed stellar populations is that many of their members are relatively hot, and thus bright in the far-ultraviolet (FUV) waveband. In this short review, we describe how space-based FUV observations are being used to find and study these populations.

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