Heavy Remnants in Globular Cluster Cores

1984 ◽  
Vol 88 ◽  
pp. 393-396
Author(s):  
M. Mayor ◽  
G. Meylan
Keyword(s):  
Globular Cluster ◽  
Velocity Dispersion ◽  
Radial Velocities ◽  
The Core ◽  
Random Motions ◽  
Cluster Cores

With a mean precision of 0.6 km/s per measurement, the radial velocities of 169 giants in 47 Tue (published in Mayor et al., 1983) added to the further measures of 25 stars in the core, have permitted the determination of rotation V(r,z) and velocity dispersion σ(r) in this globular cluster. With a mean precison of 0.9 km/s per measurement, the radial velocities of 298 giants in ω Cen (to be published in Mayor et al., 1985), distributed up to the centre, have also permitted the determination of V(r,z) and σ(r) (for both clusters, see Meylan and Mayor, 1984).The ratios νo/σo of ordered to random motions and the ellipticities of ω Cen and 47 Tue point to a global isotropy of the velocity dispersion.

Current Programs of Local Galactic Structure and Evolution

1984 ◽  
Vol 88 ◽  
pp. 171-176
Author(s):  
J. Andersen ◽  
B. Nordström
Keyword(s):  
Radial Velocity ◽  
Velocity Dispersion ◽  
Progress Report ◽  
Radial Velocities ◽  
Bright Star ◽  
Star Catalogue ◽  
Metal Abundance ◽  
F Stars ◽  
Near Future

AbstractWe present a progress report on some current radial-velocity observing programs aiming to provide complete data for selected samples of stars covering the whole sky. The velocities are based on ESO coudé spectra as well as CORAVEL observations obtained in both hemispheres. As a first step, the Bright Star Catalogue has been completed in radial velocities ( ~1500 stars or ~l/3 of the southern BS stars). Currently, we are approaching completion of some 4000 dwarf F stars from Olsen’s (1983) uvbyß photometric survey. The data will be used to study the velocity dispersion of these stars as a function of age and metal abundance from a kinematically unbiased sample. They will also provide a basis for an improved determination of Kz. Extension of the program to the G dwarfs is planned for the near future.

scholarly journals Central kinematics of the Galactic globular cluster M80

2021 ◽  
Author(s):  
Fabian Göttgens ◽  
Sebastian Kamann ◽  
Holger Baumgardt ◽  
Stefan Dreizler ◽  
Benjamin Giesers ◽  
...  
Keyword(s):  
Black Holes ◽  
Globular Cluster ◽  
Surface Brightness ◽  
Velocity Dispersion ◽  
Radial Velocities ◽  
Intermediate Mass ◽  
Field Mode ◽  
Radial Profiles ◽  
Integral Field Spectrograph ◽  
Integral Field

Abstract We use spectra observed with the integral-field spectrograph MUSE to reveal the central kinematics of the Galactic globular cluster Messier 80 (M80, NGC 6093). Using observations obtained with the recently commissioned narrow-field mode of MUSE, we are able to analyse 932 stars in the central 7.5 arcsec by 7.5 arcsec of the cluster for which no useful spectra previously existed. Mean radial velocities of individual stars derived from the spectra are compared to predictions from axisymmetric Jeans models, resulting in radial profiles of the velocity dispersion, the rotation amplitude, and the mass-to-light ratio. The new data allow us to search for an intermediate-mass black hole (IMBH) in the centre of the cluster. Our Jeans model finds two similarly probable solutions around different dynamical cluster centres. The first solution has a centre close to the photometric estimates available in the literature and does not need an IMBH to fit the observed kinematics. The second solution contains a location of the cluster centre that is offset by about 2.4 arcsec from the first one and it needs an IMBH mass of $4600^{+1700}_{-1400}~\text{M}_\odot {}$. N-body models support the existence of an IMBH in this cluster with a mass of up to 6000 M⊙ in this cluster, although models without an IMBH provide a better fit to the observed surface brightness profile. They further indicate that the cluster has lost nearly all stellar-mass black holes. We further discuss the detection of two potential high-velocity stars with radial velocities of 80 to 90 km s−1 relative to the cluster mean.

On the velocity dispersion in the core of the globular cluster M15

1994 ◽  
Vol 426 ◽  
pp. 192 ◽  
Author(s):  
P. Dubath ◽  
G. Meylan ◽  
M. Mayor
Keyword(s):  
Globular Cluster ◽  
Velocity Dispersion ◽  
The Core

scholarly journals Low Luminosity Globular Cluster X-Ray Sources

1988 ◽  
Vol 126 ◽  
pp. 685-686
Author(s):  
Paul Hertz
Keyword(s):  
Stellar Evolution ◽  
Globular Cluster ◽  
Globular Clusters ◽  
Main Sequence ◽  
Compact Object ◽  
Compact Objects ◽  
Close Binary ◽  
X Ray ◽  
The Core ◽  
Cluster Cores

Two classes of globular cluster X-ray sources are known. Each consists of compact objects accreting material from a close binary companion. The brighter class has a neutron star primary, and the low luminosity class has a white dwarf primary. These sources formed by tidal capture of the compact object by a main sequence dwarf in the core of the globular cluster. Their presence and number has implications on the end points of stellar evolution in globular clusters and on the formation of binaries in cluster cores.

Galactic orbits of stars

1966 ◽  
Vol 25 ◽  
pp. 93-97
Author(s):  
Richard Woolley
Keyword(s):  
Globular Cluster ◽  
Potential Field ◽  
High Velocity ◽  
Velocity Vector ◽  
Variable Stars ◽  
The Sun ◽  
Proper Motions ◽  
Rr Lyrae ◽  
The Galaxy

It is now possible to determine proper motions of high-velocity objects in such a way as to obtain with some accuracy the velocity vector relevant to the Sun. If a potential field of the Galaxy is assumed, one can compute an actual orbit. A determination of the velocity of the globular clusterωCentauri has recently been completed at Greenwich, and it is found that the orbit is strongly retrograde in the Galaxy. Similar calculations may be made, though with less certainty, in the case of RR Lyrae variable stars.

Imaging of ribosomal RNA-protein interactions by dark-field STEM

1989 ◽  
Vol 47 ◽  
pp. 250-251
Author(s):  
M. Boublik ◽  
V. Mandiyan ◽  
S. Tumminia ◽  
J.F. Hainfeld ◽  
J.S. Wall
Keyword(s):  
Nucleic Acid ◽  
16S Rrna ◽  
Dark Field ◽  
Radius Of Gyration ◽  
Central Domain ◽  
The Core ◽  
16S Rna ◽  
30S Subunit ◽  
Core Particles

Success in protein-free deposition of native nucleic acid molecules from solutions of selected ionic conditions prompted attempts for high resolution imaging of nucleic acid interactions with proteins, not attainable by conventional EM. Since the nucleic acid molecules can be visualized in the dark-field STEM mode without contrasting by heavy atoms, the established linearity between scattering cross-section and molecular weight can be applied to the determination of their molecular mass (M) linear density (M/L), mass distribution and radius of gyration (RG). Determination of these parameters promotes electron microscopic imaging of biological macromolecules by STEM to a quantitative analytical level. This technique is applied to study the mechanism of 16S rRNA folding during the assembly process of the 30S ribosomal subunit of E. coli. The sequential addition of protein S4 which binds to the 5'end of the 16S rRNA and S8 and S15 which bind to the central domain of the molecule leads to a corresponding increase of mass and increased coiling of the 16S rRNA in the core particles. This increased compactness is evident from the decrease in RG values from 114Å to 91Å (in “ribosomal” buffer consisting of 10 mM Hepes pH 7.6, 60 mM KCl, 2 m Mg(OAc)2, 1 mM DTT). The binding of S20, S17 and S7 which interact with the 5'domain, the central domain and the 3'domain, respectively, continues the trend of mass increase. However, the RG values of the core particles exhibit a reverse trend, an increase to 108Å. In addition, the binding of S7 leads to the formation of a globular mass cluster with a diameter of about 115Å and a mass of ∽300 kDa. The rest of the mass, about 330 kDa, remains loosely coiled giving the particle a “medusa-like” appearance. These results provide direct evidence that 16S RNA undergoes significant structural reorganization during the 30S subunit assembly and show that its interactions with the six primary binding proteins are not sufficient for 16S rRNA coiling into particles resembling the native 30S subunit, contrary to what has been reported in the literature.

Nauwkeurige methode voor de aanwasbepaling van het grondvlak met behulp van de Pressler-boor

1968 ◽  
Vol 12 ◽  
Author(s):  
R. Goossens
Keyword(s):  
Basal Area ◽  
Precise Determination ◽  
Maximum Diameter ◽  
Precise Method ◽  
Maximum Radius ◽  
The Core ◽  
Two Parameters

A precise method for the determination of the increment of the  basal area using the PressIer bore. Refering to  previous research showing that the basal area of the corsica pine could be  characterized by an ellips, we present in this paper a precise method for the  determination of the increment of the basal area. In this method we determine  the direction of the maximum diameter, we measure this diameter and we take a  core in one of the points of tangency of the caliper with the measured tree.  The determination of the diameter perpendicular to the maximum diameter  finishes the work wich is to be done in the forest. From the classical  measurements effectuated on the core and from the measured diameters we can  then determine the form (V) and the excentricity (e). Substituting these two  parameters in the formula 2 or 2', we can also calculate the error of a  radius measured on the core with respect to the representative radius, This  error with them allow us to correct the measured value of the minimum or the  maximum radius and we will be able to do a precise determination of the  increment.

scholarly journals Hunting for intermediate-mass black holes in globular clusters: an astrometric study of NGC 6441

2021 ◽  
Vol 503 (1) ◽  
pp. 1490-1506
Author(s):  
Maximilian Häberle ◽  
Mattia Libralato ◽  
Andrea Bellini ◽  
Laura L Watkins ◽  
Jörg-Uwe Pott ◽  
...  
Keyword(s):  
Globular Clusters ◽  
Velocity Dispersion ◽  
Angular Resolution ◽  
Hubble Space Telescope ◽  
High Mass ◽  
High Angular Resolution ◽  
Stellar Kinematics ◽  
Intermediate Mass ◽  
The Core ◽  
Large Telescopes

ABSTRACT We present an astrometric study of the proper motions (PMs) in the core of the globular cluster NGC 6441. The core of this cluster has a high density and observations with current instrumentation are very challenging. We combine ground-based, high-angular-resolution NACO@VLT images with Hubble Space Telescope ACS/HRC data and measure PMs with a temporal baseline of 15 yr for about 1400 stars in the centremost 15 arcsec of the cluster. We reach a PM precision of ∼30 µas yr−1 for bright, well-measured stars. Our results for the velocity dispersion are in good agreement with other studies and extend already existing analyses of the stellar kinematics of NGC 6441 to its centremost region never probed before. In the innermost arcsecond of the cluster, we measure a velocity dispersion of (19.1 ± 2.0) km s−1 for evolved stars. Because of its high mass, NGC 6441 is a promising candidate for harbouring an intermediate-mass black hole (IMBH). We combine our measurements with additional data from the literature and compute dynamical models of the cluster. We find an upper limit of $M_{\rm IMBH} \lt 1.32 \times 10^4\, \textrm{M}_\odot$ but we can neither confirm nor rule out its presence. We also refine the dynamical distance of the cluster to $12.74^{+0.16}_{-0.15}$ kpc. Although the hunt for an IMBH in NGC 6441 is not yet concluded, our results show how future observations with extremely large telescopes will benefit from the long temporal baseline offered by existing high-angular-resolution data.

Formation of an Iron(III) Oxo Cubane Core Fe4(μ4-O)4 from FeCl3 and the Unsymmetrical Tripodal Ligand N[(CH2CH2NH2)(CH2CH2OH)(CH2CH2CH2OH)]

2004 ◽  
Vol 59 (8) ◽  
pp. 855-858 ◽  
Author(s):  
Ekkehardt Hahn ◽  
Christoph Jocher ◽  
Thomas Lügger
Keyword(s):  
Coordination Chemistry ◽  
Structure Determination ◽  
Disodium Salt ◽  
Ferrous Chloride ◽  
Tripodal Ligand ◽  
The Core ◽  
Yellow Precipitate

AbstractThe coordination chemistry of the unsymmetric, aliphatic, tetradentate tripodal ligand N[(CH2CH2NH2)(CH2CH2OH)(CH2CH2CH2OH)] H4-1 with iron chlorides was investigated. The disodium salt of the deprotonated ligand Na2(H2-1) reacts with FeCl3 to yield a yellow precipitate which upon recrystallization from DMSO/CH2Cl2 gives red crystals of the octanuclear iron(III) complex [{FeIIICl(H2-1)}4FeIII4(μ4-O)4Cl4] 2 ・ 4CH2Cl2 containing a central Fe4(μ4-O)4 cubane core. Crystals of 2 ・4DMF were obtained by slow oxidation of the green iron(II) complex obtained from ferrous chloride and Na2(H2-1) after recrystallization from DMF. The structure determination of 2 ・4CH2Cl2 also revealed the presence of the iron(III) oxo cubane core. The core is surrounded by four iron atoms each coordinated by η4-(H2-1)2- and Cl- ligands.

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