scholarly journals Binary-binary collisions involving main-sequence stars, white dwarfs, and neutron stars in globular clusters

1994 ◽  
Author(s):  
Peter J. T. Leonard ◽  
Melvyn B. Davies
Keyword(s):  
Neutron Stars ◽  
Globular Clusters ◽  
White Dwarfs ◽  
Main Sequence ◽  
Main Sequence Stars ◽  
Binary Collisions

scholarly journals The gravitational wave background signal from tidal disruption events

2020 ◽  
Vol 498 (1) ◽  
pp. 507-516 ◽  
Author(s):  
Martina Toscani ◽  
Elena M Rossi ◽  
Giuseppe Lodato
Keyword(s):  
Black Holes ◽  
Gravitational Wave ◽  
Globular Clusters ◽  
White Dwarfs ◽  
Main Sequence ◽  
Big Bang ◽  
The Other ◽  
Main Sequence Stars ◽  
Background Signal ◽  
Tidal Disruption

ABSTRACT In this paper, we derive the gravitational wave stochastic background from tidal disruption events (TDEs). We focus on both the signal emitted by main-sequence stars disrupted by supermassive black holes (SMBHs) in galaxy nuclei and on that from disruptions of white dwarfs by intermediate-mass black holes (IMBHs) located in globular clusters. We show that the characteristic strain hc’s dependence on frequency is shaped by the pericenter distribution of events within the tidal radius and under standard assumptions hc∝f−1/2. This is because, the TDE signal is a burst of gravitational waves at the orbital frequency of the closest approach. In addition, we compare the background characteristic strains with the sensitivity curves of the upcoming generation of space-based gravitational wave interferometers: the Laser Interferometer Space Antenna (LISA), TianQin, ALIA, the DECI-hertz inteferometer Gravitational wave Observatory (DECIGO), and the Big Bang Observer (BBO). We find that the background produced by main-sequence stars might be just detected by BBO in its lowest frequency coverage, but it is too weak for all the other instruments. On the other hand, the background signal from TDEs with white dwarfs will be within reach of ALIA, and especially of DECIGO and BBO, while it is below the LISA and TianQin sensitive curves. This background signal detection will not only provide evidence for the existence of IMBHs up to redshift z ∼ 3, but it will also inform us on the number of globular clusters per galaxy and on the occupation fraction of IMBHs in these environments.

scholarly journals Pulsars in Globular Clusters

2007 ◽  
Vol 3 (S246) ◽  
pp. 291-300 ◽  
Author(s):  
Scott M. Ransom
Keyword(s):  
Equation Of State ◽  
Neutron Stars ◽  
Globular Clusters ◽  
Main Sequence ◽  
Galactic Disk ◽  
Nuclear Density ◽  
Millisecond Pulsars ◽  
Eccentric Orbits ◽  
The Masses ◽  
Current Record

AbstractGlobular clusters produce orders of magnitude more millisecond pulsars per unit mass than the Galactic disk. Since the first cluster pulsar was uncovered 20 years ago, at least 138 have been identified – most of which are binary millisecond pulsars. Because their origins involve stellar encounters, many of the systems are exotic objects that would never be observed in the Galactic disk. Examples include pulsar-main sequence binaries, extremely rapid rotators (including the current record holder), and millisecond pulsars in highly eccentric orbits. These systems are allowing new probes of the interstellar medium, the equation of state of material at supra-nuclear density, the masses of neutron stars, and globular cluster dynamics.

scholarly journals The importance of helium and metals diffusion in stars

1997 ◽  
Vol 189 ◽  
pp. 355-360
Author(s):  
Charles R. Proffitt
Keyword(s):  
Sound Speed ◽  
Globular Clusters ◽  
Main Sequence ◽  
Chemical Elements ◽  
Substantial Reduction ◽  
Solar Interior ◽  
Relative Importance ◽  
Main Sequence Stars ◽  
Gravitational Settling ◽  
Hydrodynamic Processes

Comparisons between models of the solar interior and sound speed profiles derived from inversions of helioseismic data have demonstrated that it is essential to include the effects of gravitational settling when calculating the structure and evolution of the Sun. Including settling should also be necessary for models of metal poor main-sequence stars and results in a substantial reduction in the ages derived for globular clusters.In many cases it is clear that competing hydrodynamic processes, such as mass loss or rotationally driven mixing, will limit the effectiveness of gravitational separation of chemical elements. However, the quantitative details and even the relative importance of the different processes in various types of stars remains poorly understood.

scholarly journals A high-spectral-resolution study of abundances and isotopic composition of BHB stars in NGC 6397 and NGC 6752

2009 ◽  
Vol 5 (S266) ◽  
pp. 421-421
Author(s):  
S. Hubrig ◽  
F. Castelli ◽  
G. De Silva ◽  
J. F. González ◽  
Y. Momany ◽  
...  
Keyword(s):  
Globular Clusters ◽  
Main Sequence ◽  
High Spectral Resolution ◽  
Horizontal Branch ◽  
Main Sequence Stars ◽  
Chemical Abundances ◽  
Chemically Peculiar ◽  
Abundance Anomalies ◽  
Isotopic Anomalies ◽  
Resolution Study

AbstractLarge abundance anomalies have previously been detected in horizontal-branch B-type stars. We present the first high-resolution study of isotopic anomalies and chemical abundances in six horizontal-branch B-type stars in the globular clusters NGC 6397 and NGC 6752, carried out with UVES on the VLT and compare them to those observed in chemically peculiar main-sequence stars.

scholarly journals Observations of blue straggler stars in globular clusters

2006 ◽  
Vol 2 (14) ◽  
pp. 438-439
Author(s):  
Francesco R. Ferraro ◽  
Barbara Lanzoni
Keyword(s):  
Globular Clusters ◽  
Binary Systems ◽  
Stellar Population ◽  
Main Sequence ◽  
Formation Mechanisms ◽  
Main Sequence Stars ◽  
Blue Stragglers ◽  
Photometric And Spectroscopic Observations ◽  
Blue Straggler ◽  
Dynamical Simulations

AbstractBlue stragglers stars (BSS) define a sparsely populated sequence extending to higher luminosity than the turnoff point of normal main sequence stars in the color magnitude diagrams of stellar aggregates, thus mimicking a rejuvenated (more massive) stellar population. The nature of these stars has been a puzzle for many years and their formation mechanism is not completely understood, yet. Two mechanisms have been proposed to produce BSS: (i) the mass transfer in binary systems; and ((ii) the merger of two stars induced by stellar interactions. In this contribution we schematically report on the main properties of BSS in globular clusters (GCs) in the light of the most recent photometric and spectroscopic observations. These results, combined with dynamical simulations, indicate that both the proposed formation mechanisms play an important role in the production of BSS in GCs.

scholarly journals Collisions of Main-Sequence Stars and the Formation of Blue Stragglers in Globular Clusters

1996 ◽  
Vol 468 ◽  
pp. 797 ◽  
Author(s):  
James C., Jr. Lombardi ◽  
Frederic A. Rasio ◽  
Stuart L. Shapiro
Keyword(s):  
Globular Clusters ◽  
Main Sequence ◽  
Main Sequence Stars ◽  
Blue Stragglers

scholarly journals Observational signatures of lithium depletion in the metal-poor globular cluster NGC6397

2009 ◽  
Vol 5 (S268) ◽  
pp. 263-268 ◽  
Author(s):  
Karin Lind ◽  
Francesca Primas ◽  
Corinne Charbonnel ◽  
Frank Grundahl ◽  
Martin Asplund
Keyword(s):  
Globular Cluster ◽  
Globular Clusters ◽  
Main Sequence ◽  
Galactic Halo ◽  
Main Sequence Stars ◽  
Surface Evolution ◽  
Halo Stars ◽  
Systematic Uncertainties ◽  
Low Mass ◽  
Lithium Depletion

AbstractThe “stellar” solution to the cosmological lithium problem proposes that surface depletion of lithium in low-mass, metal-poor stars can reconcile the lower abundances found for Galactic halo stars with the primordial prediction. Globular clusters are ideal environments for studies of the surface evolution of lithium, with large number statistics possible to obtain for main sequence stars as well as giants. We discuss the Li abundances measured for >450 stars in the globular cluster NGC 6397, focusing on the evidence for lithium depletion and especially highlighting how the inferred abundances and interpretations are affected by early cluster self-enrichment and systematic uncertainties in the effective temperature determination.

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