Hyades dynamics from<i>N</i>-body simulations: Accuracy of astrometric radial velocities from Hipparcos

Madsen, S.N.

doi:10.1051/0004-6361:20030147

Cited by 16 publications

(16 citation statements)

References 59 publications

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“…In ρ-Oph, for example, the typical core-to-core velocity dispersion is found to be less than 0.4 km s −1 (André et al 2007). The typical stellar velocity dispersion measured in nearby T Tauri associations or open star clusters is similar: ∼0.3 km s −1 for the Hyades (Madsen 2003), ∼0.5−0.6 km s −1 for Coma Berenices, Pleiades, and Praesepe (Madsen et al 2002), and below ∼1 km s −1 for α Per (Makarov 2006), Lupus (Makarov 2007), and the subgroups in Taurus (Jones & Herbig 1979;Bertout & Genova 2006). It only gets above 1 km s −1 for the more massive clusters and OB associations (Madsen et al 2002).…”

Section: Are T Tauri Disks Accreting?mentioning

confidence: 61%

Accretion-driven turbulence as universal process: galaxies, molecular clouds, and protostellar disks

Klessen¹,

Hennebelle²

2010

A&A

318

353

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Context. Even though turbulent motions are found everywhere in astrophysical systems, the origin of this turbulence is poorly understood. When cosmic structures form, they grow in mass via accretion from their surrounding environment. Aims. We propose that accretion is able to drive internal turbulent motions in a wide range of astrophysical objects and study this process in the case of galaxies, molecular clouds, and protoplanetary disks. Methods. We use a combination of numerical simulations and analytical arguments to predict the level of turbulence as a function of the accretion rate, the dissipation scale, and the density contrast, and compare our models with observational data. Results. We find that in Milky Way type galaxies the observed level of turbulence in the interstellar medium can be explained by accretion, provided that the galaxies gain mass at a rate comparable to the rate at which they form stars. This process is particularly relevant in the extended outer disks beyond the star-forming radius. For it to drive turbulence in dwarf galaxies, the accretion rate needs to exceed the star formation rate by a large factor, so we expect other sources to dominate. We also calculate the rate at which molecular clouds grow in mass when they build up from the atomic component of the galactic gas and find that their internal turbulence is likely to be driven by accretion as well. It is the very process of cloud formation that excites turbulent motions on small scales by establishing the turbulent cascade. In the case of T Tauri disks, we show that accretion can drive subsonic turbulence if the rate at which gas falls onto the disk is comparable to the rate at which disk material accretes onto the central star. This also explains the observed relation of accretion rate and stellar mass,Ṁ ∝ M 1.8 . The efficiency required to convert infall motion into turbulence is a few percent in all three cases. Conclusions. We conclude that accretion-driven turbulence is a universal concept with far-reaching implications for a wide range of astrophysical objects.

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Section: Are T Tauri Disks Accreting?mentioning

confidence: 61%

Accretion-driven turbulence as universal process: galaxies, molecular clouds, and protostellar disks

Klessen¹,

Hennebelle²

2010

A&A

318

353

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“…To do this, we considered the 3D structure of the cluster by using the equatorial coordinates of the stars and G17 parallaxes. Then, we analyzed a few subsample selections of stars within a 3-10 pc radius from the cluster centre, namely between the cluster core and its tidal radius (Madsen 2003). We used the Hyades central coordinates provided in G17.…”

Section: M02mentioning

confidence: 99%

Spectroscopic and astrometric radial velocities: Hyades as a benchmark

Leão

Pasquini²,

Ludwig

et al. 2018

Monthly Notices of the Royal Astronomical Society

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We study the accuracy of spectroscopic RVs by comparing spectroscopic and astrometric RVs for stars of the Hyades open cluster. Rather accurate astrometric RVs are available for the Hyades' stars, based on Hipparcos and on the first Gaia data release. We obtained HARPS spectra for a large sample of Hyades stars, and we homogeneously analysed them. After cleaning the sample from binaries, RV variables, and outliers, 71 stars remained. The distribution of the observed RV difference (spectroscopic -astrometric) is skewed and depends on the star right ascension. This is consistent with the Hyades cluster rotating at 42.3 m s −1 pc −1 . The two Hyades giants in the sample show, as predicted by gravitational redshift (GR), a spectroscopic RV that is blue-shifted with respect to the dwarfs, and the empirical GR slope is of 626 ± 131 m s −1 , in agreement with the theoretical prediction. The difference between spectroscopic and astrometric RVs is very close to zero, within the uncertainties. In particular, the mean difference is of −33 m s −1 and the median is of −16 m s −1 when considering the Gaia-based RVs (corrected for cluster rotation), with a σ of 347 m s −1 , very close to the expected cluster velocity dispersion. We also determine a new value of the cluster centroid spectroscopic RV: 39.36 ± 0.26 km s −1 . The spectroscopic RV measurements are expected, from simulations, to depend on stellar rotation, but our data do not confirm these predictions. We finally discuss the other phenomena that can influence the RV difference, such as cluster expansion, stellar activity, general relativity, and Galactic potential. Clusters within the reach of current telescopes are expected to show differences of several hundreds m s −1 , depending on their position in the Galaxy.

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“…Published studies have employed encounter rate techniques in static cluster backgrounds, Fokker-Planck and Monte Carlo models and direct N -body simulations — e.g., [51, 54, 334, 372, 383, 402, 405, 421, 429, 438, 458, 95, 93, 94, 96, 289, 163, 155, 159, 253, 252, 130, 244, 132, 131, 72, 387, 390, 386, 315, 232, 231, 229]. These models can, if properly interpreted, provide a wealth of information about stellar populations in globular clusters.…”

Section: Dynamical Evolutionmentioning

confidence: 99%

Relativistic Binaries in Globular Clusters

Benacquista¹,

Downing

2013

Living Rev. Relativ.

196

130

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Galactic globular clusters are old, dense star systems typically containing 104–106 stars. As an old population of stars, globular clusters contain many collapsed and degenerate objects. As a dense population of stars, globular clusters are the scene of many interesting close dynamical interactions between stars. These dynamical interactions can alter the evolution of individual stars and can produce tight binary systems containing one or two compact objects. In this review, we discuss theoretical models of globular cluster evolution and binary evolution, techniques for simulating this evolution that leads to relativistic binaries, and current and possible future observational evidence for this population. Our discussion of globular cluster evolution will focus on the processes that boost the production of tight binary systems and the subsequent interaction of these binaries that can alter the properties of both bodies and can lead to exotic objects. Direct N-body integrations and Fokker-Planck simulations of the evolution of globular clusters that incorporate tidal interactions and lead to predictions of relativistic binary populations are also discussed. We discuss the current observational evidence for cataclysmic variables, millisecond pulsars, and low-mass X-ray binaries as well as possible future detection of relativistic binaries with gravitational radiation.

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Hyades dynamics fromN-body simulations: Accuracy of astrometric radial velocities from Hipparcos

Cited by 16 publications

References 59 publications

Accretion-driven turbulence as universal process: galaxies, molecular clouds, and protostellar disks

Accretion-driven turbulence as universal process: galaxies, molecular clouds, and protostellar disks

Spectroscopic and astrometric radial velocities: Hyades as a benchmark

Relativistic Binaries in Globular Clusters

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