1,720,975 research outputs found
Dynamical properties of binary stars hosting planets in the Galactic Center
No full textWe present some preliminary results of our work about the close encounter of
binary stars hosting planets on S-type orbits with the Sgr A* supermassive
black hole in the center of our Galaxy
Interaction of Stars Hosting Planets with Sgr A* Black hole
Full text linkWe present some preliminary results of our ongoing project about planetary systems around S-stars in the vicinity of Sgr A* black hole. Since S-stars might have migrated in the Galactic Centre (GC) from elsewhere, they probably still keep their planetary systems throughout their voyage. In this work, we study the destiny of their putative planetary systems after close interaction with the central black hole of our galaxy
PRACE: Partnership for Advanced Computing in Europe
No full textRoberto Capuzzo-Dolcetta è stato nominato membro dell'Access Committee di PRACE (Partnership for Advanced Computing in Europe), progetto europeo che unisce le piu' importanti infrastrutture di calcolo TIER0 per uso scientifico in Europa
Dynamical evolution of globular clusters and its influence on the galactic nucleic activity
No full textDottorato di ricerca in fisica. 12. ciclo. A. a. 1997-98. Relatore Roberto Capuzzo-Dolcetta. Coordinatore Marzio CassandroConsiglio Nazionale delle Ricerche - Biblioteca Centrale - P.le Aldo Moro, 7, Rome; Biblioteca Nazionale Centrale - P.za Cavalleggeri, 1, Florence / CNR - Consiglio Nazionale delle RichercheSIGLEITItal
Elementi di Teoria Classica del Potenziale Gravitazionale
No full textDidactic notes also available via the web site:
astro1.phys.uniroma1.it/dolcetta/dinst/corso.htm
The RR Lyrae projected density distribution from the Galactic centre to the halo
No full textThe projected density distribution of type ab RR Lyrae (RRab) stars was characterised from the innermost regions of the Milky Way to the halo, with the aim of placing constraints on the Galaxy’s evolution. The compiled sample (NRRab = 64 850) stems from fundamental mode RR Lyrae variables identified by the VVV, OGLE, and Gaia surveys. The distribution is well fitted by three power laws over three radial intervals. In the innermost region (R 18%) of the central Galactic region. The radii containing half of the populations (half populations radii) are RH RRab = 6.8° (0.99 kpc), RH RC = 4.2° (0.61 kpc), and RH GCs = 11.9° (1.75 kpc) for the RRab stars, RC giants, and GCs, respectively. Finally, merely ∼1% of the stars have been actually discovered in the innermost region (R < 35 pc) out of the expected (based on our considerations) total number of RRab therein: N ∼ 1562. That deficit will be substantially ameliorated with future space missions like the Nancy Grace Roman Space Telescope (formerly WFIRST)
Classical newtonian gravity
No full textThis book gives an introduction to classical Newtonian gravitation and potential
theories, as pieces of Physics essential for understanding classical mechanics and
particularly relevant for Astrophysics. Among the four fundamental forces of
Physics, gravity has the unique aspect of being an unscreened force which permeates
the whole universe. Moreover, although Einstein’s general relativity provides a more
extended framework for gravity, for most of the practical purposes, both in the field
of pure scientific investigation and in the applicative one, Newtonian gravity
provides much simpler and sufficiently approximated results, whenever applied in
the regime of weak field.
To reach the aim, the book is structured as follows.
In the first chapter, some essential elements of vectorial calculus are recalled,
especially to provide the formalism used in the following chapters.
In the second chapter, classical Newtonian gravity theory for one and a generic
number N of point masses is presented and discussed. The theory for point masses
is naturally extended to the continuous case in the same chapter.
In the third chapter, the paradigmatic case of spherical symmetry in the mass
density distribution (central force) is dealt with the introduction of the useful tool of
qualitative treatment of motion.
In chapter four, the general case of nonsymmetric mass density distribution is
discussed. In this chapter, classical potential theory is presented, with elements of
harmonic theory, which is essential to understand the series development of the
potential development in the discussed in the second part of the chapter.
The short, final, chapter five deals with the specific case of the motion of a
satellite around the Earth.
Examples and exercises are presented throughout the book to clarify aspects
of the theory
Properties of self-gravitating quasi-stationary states
No full textInitially far out-of-equilibrium, self-gravitating systems form quasi-stationary states (QSS) through a collisionless relaxation dynamics. These may arise from a bottom-up aggregation of structures or in a top-down frame; their quasi-equilibrium properties are well described by the Jeans equation and are not universal. These QSS depend on initial conditions. To understand the origin of such dependence, we present the results of numerical experiments of initially cold and spherical systems characterized by various choices of the spectrum of initial density fluctuations. The amplitude of such fluctuations determines whether the system relaxes in a top-down or bottom-up manner. We find that statistical properties of the resulting QSS mainly depend upon the amount of energy exchanged during the formation process. In particular, in the violent top-down collapses the energy exchange is large and the QSS show an inner core with an almost flat density profile and a quasi Maxwell-Boltzmann (isotropic) velocity distribution, while their outer regions display a density profile ρ(r) ∝ r−α (α > 0) with radially elongated orbits. We show analytically that α = 4, in agreement with numerical experiments. In the less violent bottom-up dynamics, the energy exchange is much smaller, the orbits are less elongated, and 0 < α(r) ≤ 4, where the density profile is well fitted by the Navarro-Frenk-White behavior. Such a dynamical evolution is shown by both nonuniform spherical isolated systems and by halos extracted from cosmological simulations. We consider the relation of these results with the core-cusp problem and conclude that this can be solved naturally if galaxies form through a monolithic collapse
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