AN EXPERT COMPUTER PROGRAM FOR CLASSIFYING STARS
... successful in temperature classification, but luminosity classification has never been entirely satisfactory except in limited regions of the HR diagram. STARMIND, which admittedly is a preliminary attempt to apply fuzzy logic to MK classification, produces only one-dimensional spectral types (no lu ...
... successful in temperature classification, but luminosity classification has never been entirely satisfactory except in limited regions of the HR diagram. STARMIND, which admittedly is a preliminary attempt to apply fuzzy logic to MK classification, produces only one-dimensional spectral types (no lu ...
REVIEW Early star-forming galaxies and the reionization of the Universe
... fesc. The rate dnion/dt is therefore fundamentally tied to the abundance and detailed astrophysics of early stars and galaxies. The recombination rate depends on the IGM temperature and the physical hydrogen density, which decreases with time according to the universal expansion factor, a23, and is ...
... fesc. The rate dnion/dt is therefore fundamentally tied to the abundance and detailed astrophysics of early stars and galaxies. The recombination rate depends on the IGM temperature and the physical hydrogen density, which decreases with time according to the universal expansion factor, a23, and is ...
The evolution of close binaries with white dwarf components
... expansion of the stellar envelope to giant dimensions. For low- and intermediate-mass stars (M . 8M⊙ ) the stellar radius increases by a factor of about 10-100 compared to the mainsequence radius. When the density and the temperature in the core become sufficiently high, core helium burning is ignited ...
... expansion of the stellar envelope to giant dimensions. For low- and intermediate-mass stars (M . 8M⊙ ) the stellar radius increases by a factor of about 10-100 compared to the mainsequence radius. When the density and the temperature in the core become sufficiently high, core helium burning is ignited ...
The effect of dark matter capture on binary stars
... most of its energy from WIMP-WIMP annihilation. This would have dramatic effects in the star’s structure and evolution, greatly prolonging its life. The possibility of directly observing stars powered by WIMP annihilation is the driving force behind this project. In this project I have modelled coll ...
... most of its energy from WIMP-WIMP annihilation. This would have dramatic effects in the star’s structure and evolution, greatly prolonging its life. The possibility of directly observing stars powered by WIMP annihilation is the driving force behind this project. In this project I have modelled coll ...
Pulsars - Arecibo Observatory
... for super-dense matter The exact dimensions of neutron stars are not known – this quantity is almost impossible to observe. This happens because at the center of a neutron star, the density is of the order of 1 billion tons cm–3, i.e., tens to hundreds of times larger than in atomic nuclei. There ...
... for super-dense matter The exact dimensions of neutron stars are not known – this quantity is almost impossible to observe. This happens because at the center of a neutron star, the density is of the order of 1 billion tons cm–3, i.e., tens to hundreds of times larger than in atomic nuclei. There ...
doctoral thesis (Dissertation)
... temperature and thus the thermal pressure was provided by J. Jeans. The higher the temperature, the higher is the critical mass, because the thermal pressure counteracts the gravitational contraction. If the mass exceeds the so-called Jeans mass, the collapse to a first proto-star happens relatively ...
... temperature and thus the thermal pressure was provided by J. Jeans. The higher the temperature, the higher is the critical mass, because the thermal pressure counteracts the gravitational contraction. If the mass exceeds the so-called Jeans mass, the collapse to a first proto-star happens relatively ...
APS Neutrino Study
... solar, reactor, proton decay, and high energy neutrino telescopes to observe neutrinos from the next supernova explosion and participate in a worldwide monitoring system. Furthermore, future large-volume detectors should consider the detection of supernova neutrinos an important science goal and pla ...
... solar, reactor, proton decay, and high energy neutrino telescopes to observe neutrinos from the next supernova explosion and participate in a worldwide monitoring system. Furthermore, future large-volume detectors should consider the detection of supernova neutrinos an important science goal and pla ...
A STRONGLY MAGNETIZED PULSAR WITHIN THE GRASP OF THE MILKY... SUPERMASSIVE BLACK HOLE Rea ,
... Among the large variety of Galactic neutron stars, magnetars constitute the most energetic and unpredictable class (Mereghetti 2008). They are X-ray pulsars rotating at relatively long periods (0.3–12 s, with Ṗ ∼ 10−15 –10−10 s s−1 ), and persistent X-ray luminosities of LX ∼ 1033 –1035 erg s−1 . T ...
... Among the large variety of Galactic neutron stars, magnetars constitute the most energetic and unpredictable class (Mereghetti 2008). They are X-ray pulsars rotating at relatively long periods (0.3–12 s, with Ṗ ∼ 10−15 –10−10 s s−1 ), and persistent X-ray luminosities of LX ∼ 1033 –1035 erg s−1 . T ...
ppt - ciera
... exchange encounters with a third more massive MS star “used up” PB early in the cluster history 1-2 : A more massive MS star exchanges into a MS-MS binary 3 : the primary evolves off the MS and fills its Roche lobe 4: the secondary gains mass from the primary becoming a BSS ...
... exchange encounters with a third more massive MS star “used up” PB early in the cluster history 1-2 : A more massive MS star exchanges into a MS-MS binary 3 : the primary evolves off the MS and fills its Roche lobe 4: the secondary gains mass from the primary becoming a BSS ...
Polaris B, an optical companion of Polaris (alpha UMi) system
... A comparison of chemical abundances of the both components displays some interesting features. At about an equal (within the limits of mean errors) iron, α−, Fe-group (excepting manganese) and s-process elements abundances for the both stars, Polaris B demonstrates solar carbon content, thereas Ceph ...
... A comparison of chemical abundances of the both components displays some interesting features. At about an equal (within the limits of mean errors) iron, α−, Fe-group (excepting manganese) and s-process elements abundances for the both stars, Polaris B demonstrates solar carbon content, thereas Ceph ...
Section IV High-Energy Astrophysics and Cosmology
... where MBH is the mass of a black hole, f is a virial parameter that defines the geometry, velocity field and orientation of BLR, RBLR is the radius of BLR and VBLR is the velocity dispersion that is usually measured as the full width of the emission line at a half of height in the radiation spectrum ...
... where MBH is the mass of a black hole, f is a virial parameter that defines the geometry, velocity field and orientation of BLR, RBLR is the radius of BLR and VBLR is the velocity dispersion that is usually measured as the full width of the emission line at a half of height in the radiation spectrum ...
The MORGANA model for the rise of galaxies and active nuclei
... We present the Model for the Rise of Galaxies and Active Nuclei (MORGANA), a new code for the formation and evolution of galaxies and active galactic nuclei (AGNs). Starting from the merger trees of dark matter (DM) haloes and a model for the evolution of substructure within the haloes, the complex ...
... We present the Model for the Rise of Galaxies and Active Nuclei (MORGANA), a new code for the formation and evolution of galaxies and active galactic nuclei (AGNs). Starting from the merger trees of dark matter (DM) haloes and a model for the evolution of substructure within the haloes, the complex ...
Why do naked singularities form in gravitational collapse?
... discovered where the gravitational collapse of a massive matter cloud results in the development of a naked singularity [1]. The final outcome of gravitational collapse in general relativity is an issue of great importance and interest from the perspective of black hole physics as well as its astrop ...
... discovered where the gravitational collapse of a massive matter cloud results in the development of a naked singularity [1]. The final outcome of gravitational collapse in general relativity is an issue of great importance and interest from the perspective of black hole physics as well as its astrop ...
Abstract Title of Dissertation: BLACK HOLE DYNAMICS AND GRAVITATIONAL RADIATION IN GALACTIC NUCLEI
... combination of the two masses of the binary members. The vertical line shows Mchirp for two 10 M! BHs, which demonstrates that BH-BH mergers from this mechanism are of low mass. ...
... combination of the two masses of the binary members. The vertical line shows Mchirp for two 10 M! BHs, which demonstrates that BH-BH mergers from this mechanism are of low mass. ...
Stellar evolution
Stellar evolution is the process by which a star changes during its lifetime. Depending on the mass of the star, this lifetime ranges from a few million years for the most massive to trillions of years for the least massive, which is considerably longer than the age of the universe. The table shows the lifetimes of stars as a function of their masses. All stars are born from collapsing clouds of gas and dust, often called nebulae or molecular clouds. Over the course of millions of years, these protostars settle down into a state of equilibrium, becoming what is known as a main-sequence star.Nuclear fusion powers a star for most of its life. Initially the energy is generated by the fusion of hydrogen atoms at the core of the main-sequence star. Later, as the preponderance of atoms at the core becomes helium, stars like the Sun begin to fuse hydrogen along a spherical shell surrounding the core. This process causes the star to gradually grow in size, passing through the subgiant stage until it reaches the red giant phase. Stars with at least half the mass of the Sun can also begin to generate energy through the fusion of helium at their core, whereas more-massive stars can fuse heavier elements along a series of concentric shells. Once a star like the Sun has exhausted its nuclear fuel, its core collapses into a dense white dwarf and the outer layers are expelled as a planetary nebula. Stars with around ten or more times the mass of the Sun can explode in a supernova as their inert iron cores collapse into an extremely dense neutron star or black hole. Although the universe is not old enough for any of the smallest red dwarfs to have reached the end of their lives, stellar models suggest they will slowly become brighter and hotter before running out of hydrogen fuel and becoming low-mass white dwarfs.Stellar evolution is not studied by observing the life of a single star, as most stellar changes occur too slowly to be detected, even over many centuries. Instead, astrophysicists come to understand how stars evolve by observing numerous stars at various points in their lifetime, and by simulating stellar structure using computer models.In June 2015, astronomers reported evidence for Population III stars in the Cosmos Redshift 7 galaxy at z = 6.60. Such stars are likely to have existed in the very early universe (i.e., at high redshift), and may have started the production of chemical elements heavier than hydrogen that are needed for the later formation of planets and life as we know it.