MODEST-1: Integrating stellar evolution and stellar dynamics

Hut, Piet; Shara, Michael M.; Aarseth, Sverre J.; Klessen, Ralf S.; Lombardi, James C.; Makino, Junichiro; McMillan, Stephen L. W.; Pols, O. R.; Teuben, Peter; Webbink, R. F.

doi:10.1016/s1384-1076(02)00229-4

Cited by 38 publications

(32 citation statements)

References 89 publications

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“…Globular cluster parameters from Harris (1996, updated Feb. 2003 be 11.5 ± 2.6 Gyr (Carretta et al 2000). This core collapse must have been delayed by an internal energy source to explain the GC longevity, and binaries could play this role (see Hut et al 1992Hut et al , 2003, for a review). In the core, binaries are subject to encounters and hard binaries become harder while transfering their energy to passing stars.…”

Section: Introductionmentioning

confidence: 99%

XMM-Newtonobservations of the Galactic globular clusters NGC 2808 and NGC 4372

Servillat¹,

Webb²,

Barret³

2007

A&A

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Aims. Galactic globular clusters harbour binary systems that are detected as faint X-ray sources. These close binaries are thought to play an important role in the stability of the clusters by liberating energy and delaying the inevitable core collapse of globular clusters. The inventory of close binaries and their identification is therefore essential. Methods. We present XMM-Newton observations of two Galactic globular clusters: NGC 2808 and NGC 4372. We use X-ray spectral and variability analysis combined with ultra-violet observations made with the XMM-Newton optical monitor and published data from the Hubble Space Telescope to identify sources associated with the clusters. We compare the results of our observations with estimates from population synthesis models. Results. Five sources out of 96 are likely to be related to NGC 2808. Nine sources are found in the field of view of NGC 4372, none being located inside its half-mass radius. We find one quiescent neutron star low mass X-ray binary candidate in the core of NGC 2808, and propose that the majority of the central sources in NGC 2808 are cataclysmic variables. An estimation leads to 20±10 cataclysmic variables with luminosity above 4.25 × 10 31 erg s −1 . Millisecond pulsars could also be present in the core of NGC 2808, and some sources outside the half-mass radius could possibly be linked to the cluster.

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Section: Introductionmentioning

confidence: 99%

XMM-Newtonobservations of the Galactic globular clusters NGC 2808 and NGC 4372

Servillat¹,

Webb²,

Barret³

2007

A&A

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“…Elson et al 1987;Hut et al 1992Hut et al , 2003, and references therein). In the core, binaries are subject to encounters and hard binaries become harder while transferring their energy to passing stars.…”

Section: Introductionmentioning

confidence: 99%

Combined Chandra, XMM-Newton, and Hubble Space Telescope observations of the Galactic globular cluster NGC 2808

Servillat¹,

Dieball

Webb³

et al. 2008

A&A

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Aims. Using new Chandra X-ray observations and existing XMM-Newton X-ray and Hubble far ultraviolet observations, we aim to detect and identify the faint X-ray sources belonging to the Galactic globular cluster NGC 2808 in order to understand their role in the evolution of globular clusters. Methods. We present a Chandra X-ray observation of the Galactic globular cluster NGC 2808. We classify the X-ray sources associated with the cluster by analysing their colours and variability. Previous observations with XMM-Newton and far ultraviolet observations with the Hubble Space Telescope are re-investigated to help identify the Chandra sources associated with the cluster. We compare our results to population synthesis models and observations of other Galactic globular clusters. Results. We detect 113 sources, of which 16 fall inside the half-mass radius of NGC 2808 and are concentrated towards the cluster core. From statistical analysis, these 16 sources are very likely to be linked to the cluster. We detect short-term (1 day) variability in X-rays for 7 sources, of which 2 fall inside the half-mass radius, and long-term (28 months) variability for 10 further sources, of which 2 fall inside the half-mass radius. Ultraviolet counterparts are found for 8 Chandra sources in the core, of which 2 have good matching probabilities and have ultraviolet properties expected for cataclysmic variables. We find one likely neutron star-quiescent low-mass X-ray binary and 8 cataclysmic variable candidates in the core of NGC 2808. The other sources are cataclysmic variable candidates, but some could possibly be active binaries or millisecond pulsars. We find a possible deficit of X-ray sources compared to 47 Tuc which could be related to the metallicity content and the complexity of the evolution of NGC 2808.

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“…[14] and references therein). The selection of systems and their initial and final conditions made in such studies are typically astrophysically-motivated; the considered systems are often too complex to make a general conclusions about the phase diagrams and phase transitions in such systems.…”

Section: Introductionmentioning

confidence: 99%

Collapses and explosions in self-gravitating systems

Ispolatov

Karttunen²

2003

Phys. Rev. E

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Collapse and reverse to collapse explosion transition in self-gravitating systems are studied by molecular dynamics simulations. A microcanonical ensemble of point particles confined to a spherical box is considered; the particles interact via an attractive soft Coulomb potential. It is observed that the collapse in the particle system indeed takes place when the energy of the uniform state is put near or below the metastability-instability threshold (collapse energy), predicted by the mean-field theory. Similarly, the explosion in the particle system occurs when the energy of the core-halo state is increased above the explosion energy, where according to the mean field predictions the core-halo state becomes unstable. For a system consisting of 125 -500 particles, the collapse takes about 10 5 single particle crossing times to complete, while a typical explosion is by an order of magnitude faster. A finite lifetime of metastable states is observed. It is also found that the meanfield description of the uniform and the core-halo states is exact within the statistical uncertainty of the molecular dynamics data.

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MODEST-1: Integrating stellar evolution and stellar dynamics

Cited by 38 publications

References 89 publications

XMM-Newtonobservations of the Galactic globular clusters NGC 2808 and NGC 4372

XMM-Newtonobservations of the Galactic globular clusters NGC 2808 and NGC 4372

Combined Chandra, XMM-Newton, and Hubble Space Telescope observations of the Galactic globular cluster NGC 2808

Collapses and explosions in self-gravitating systems

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