The 100-billion-body problem A full-scale computer simulation of the
... from O(N 2 ) to O(N log N), a huge improvement. For 1011 stars, the number of force evaluations per time step falls from 1022 to as few as 1013. The tradeoff between speed and accuracy can be fine-tuned by adjusting the crossover point between individual and aggregated force computations. To observe ...
... from O(N 2 ) to O(N log N), a huge improvement. For 1011 stars, the number of force evaluations per time step falls from 1022 to as few as 1013. The tradeoff between speed and accuracy can be fine-tuned by adjusting the crossover point between individual and aggregated force computations. To observe ...
Chapter 10 Late evolution of low- and intermediate
... After the H-burning shell is reignited, the He-burning shell that lies underneath it becomes geometrically thin. Nuclear burning in such a thin shell is thermally unstable, for the reasons discussed in Sect. 6.5.2. This gives rise to periodic thermal pulses of the He-burning shell. What happens duri ...
... After the H-burning shell is reignited, the He-burning shell that lies underneath it becomes geometrically thin. Nuclear burning in such a thin shell is thermally unstable, for the reasons discussed in Sect. 6.5.2. This gives rise to periodic thermal pulses of the He-burning shell. What happens duri ...
Photometric variability of the Pre
... effect of color reversal (or co-called ”blueing”) was described in many studies (Bibo & The (1990), Grinin et al. (1994)). According to the model of dust clumps obscuration the observed color reversal is caused by the scattered light from the small dust grains. Normally the star becomes redder when ...
... effect of color reversal (or co-called ”blueing”) was described in many studies (Bibo & The (1990), Grinin et al. (1994)). According to the model of dust clumps obscuration the observed color reversal is caused by the scattered light from the small dust grains. Normally the star becomes redder when ...
Lecture 9: Supernovae
... faded quickly until June 1987. Then it settled into a much slower fade, of about 1% a day, for two years. This corresponds exactly to the laboratory-measured half-life of 56 Co (77 days), which is the result of the (rapid) decay of 56 Ni which is produced in the blast. We could even determine the ma ...
... faded quickly until June 1987. Then it settled into a much slower fade, of about 1% a day, for two years. This corresponds exactly to the laboratory-measured half-life of 56 Co (77 days), which is the result of the (rapid) decay of 56 Ni which is produced in the blast. We could even determine the ma ...
A. Big Bang Theory: A Failure from the Beginning
... prediction that the Universe should contain particular abundances of the lightest elements: hydrogen, deuterium, and helium ... Detailed calculations predicted that the present Universe should contain about 75% of its mass in the form of hydrogen and 25% as helium-4 with about one part in a million ...
... prediction that the Universe should contain particular abundances of the lightest elements: hydrogen, deuterium, and helium ... Detailed calculations predicted that the present Universe should contain about 75% of its mass in the form of hydrogen and 25% as helium-4 with about one part in a million ...
arXiv:astro-ph/0703091v1 5 Mar 2007
... uncertainties. This uniformity was probably not predictable a priori, since n-capture abundances in r-process-rich low metallicity stars reflect contributions from a single supernova or a small number of supernova events, while the solar system (hereafter, SS) abundances result from many generations ...
... uncertainties. This uniformity was probably not predictable a priori, since n-capture abundances in r-process-rich low metallicity stars reflect contributions from a single supernova or a small number of supernova events, while the solar system (hereafter, SS) abundances result from many generations ...
Models of red giants in the CoRoT asteroseismology fields
... as described above, and AV = 0. These results are presented in Figs. 1 and 2. The radii determined with PARAM have the best precision thanks to the Bayesian approach and the use of priors on stellar evolutionary tracks. In most cases, masses and radii determined using different methods agree within s ...
... as described above, and AV = 0. These results are presented in Figs. 1 and 2. The radii determined with PARAM have the best precision thanks to the Bayesian approach and the use of priors on stellar evolutionary tracks. In most cases, masses and radii determined using different methods agree within s ...
here - Stars `r` Us!
... a key role in the formation of all the other molecular species. In the cool interstellar medium, this 2H→H2 conversion occurs through surface catalysis (reaction h1 in figure 1), though other reaction mechanisms were important in the dust-free early universe (see below). In high-density environments ...
... a key role in the formation of all the other molecular species. In the cool interstellar medium, this 2H→H2 conversion occurs through surface catalysis (reaction h1 in figure 1), though other reaction mechanisms were important in the dust-free early universe (see below). In high-density environments ...
Document
... determined by this method should be regarded as an estimate – This method has nothing to do with Parallax! ...
... determined by this method should be regarded as an estimate – This method has nothing to do with Parallax! ...
prisma_dic_case_11feb04
... be observed experimentally. The paucity of data on the neutron-rich side is particularly evident for heavy nuclei. The predicted rapid-neutron capture process which is thought to be responsible for the creation of about half the stable elements heavier than tin is also shown for comparison. The thre ...
... be observed experimentally. The paucity of data on the neutron-rich side is particularly evident for heavy nuclei. The predicted rapid-neutron capture process which is thought to be responsible for the creation of about half the stable elements heavier than tin is also shown for comparison. The thre ...
Lecture 29: Ellipticals and Irregulars
... Spectra with O and B star features indicate a young stellar population In addition, lines from nebulae, particularly ionized H regions, can be present as well ...
... Spectra with O and B star features indicate a young stellar population In addition, lines from nebulae, particularly ionized H regions, can be present as well ...
The Cosmos & the Bible - Access Research Network
... Gamow as a natural consequence of a “BigBang” cosmology. • It such a scheme, it is the glow from the time when the universe became transparent, about 100,000 years after its creation. • Other cosmologies have no natural explanation for this phenomenon. ...
... Gamow as a natural consequence of a “BigBang” cosmology. • It such a scheme, it is the glow from the time when the universe became transparent, about 100,000 years after its creation. • Other cosmologies have no natural explanation for this phenomenon. ...
Gamma-ray burst has highest redshift yet seen
... because a GRB’s afterglow fades rapidly after a few hours, the spectra were too noisy to reveal absorption features that could address two cosmologically important issues: the abundance of “metals” (astronomers’ jargon for anything heavier than helium) in this very early star and its galaxy, and the ...
... because a GRB’s afterglow fades rapidly after a few hours, the spectra were too noisy to reveal absorption features that could address two cosmologically important issues: the abundance of “metals” (astronomers’ jargon for anything heavier than helium) in this very early star and its galaxy, and the ...
Fundamental Physics With Cold and Ultra-cold
... (at ILL). Note: over two orders of magnitude improvement may ultimately be possible! ...
... (at ILL). Note: over two orders of magnitude improvement may ultimately be possible! ...
Big Bang and Steady State Theories
... Full marks could be obtained by a clear description of the observation of red-shift of light from galaxies together with either an appreciation of its significance in terms of an expanding universe or some detail about the process. This should lead to a brief description about how this supported the ...
... Full marks could be obtained by a clear description of the observation of red-shift of light from galaxies together with either an appreciation of its significance in terms of an expanding universe or some detail about the process. This should lead to a brief description about how this supported the ...
Krypton in presolar mainstream SiC grains from AGB stars
... at the last third dredge−up episode (25th TP) for an AGB star with initial mass M= 3 M , [Fe/H] = −0.52. The predicted (86 Kr/82 Kr)s ratio is too high with respect to SiC grains observations. This means that, for metallicities ≤ 1/3 Z , the Kr−S predictions in the hot implantation scenario do not ...
... at the last third dredge−up episode (25th TP) for an AGB star with initial mass M= 3 M , [Fe/H] = −0.52. The predicted (86 Kr/82 Kr)s ratio is too high with respect to SiC grains observations. This means that, for metallicities ≤ 1/3 Z , the Kr−S predictions in the hot implantation scenario do not ...
10-25-2007-0000
... The AGATA (Advanced Gamma Tracking Array) array, currently under development, fulfills all the aforementioned requirements. As it is envisaged that the AGATA array will be used in a number of different institutions, (conventional?) alternatives could also be investigated for use at EURISOL. Conversi ...
... The AGATA (Advanced Gamma Tracking Array) array, currently under development, fulfills all the aforementioned requirements. As it is envisaged that the AGATA array will be used in a number of different institutions, (conventional?) alternatives could also be investigated for use at EURISOL. Conversi ...
How much radioactive nickel does ASASSN
... PISN explosions. The grid of models from Heger & Woosley (2002) shows the results of the simulation of non-rotating zero-metallicity models in the helium-core mass range between 65 M⊙ and 135 M⊙. The initial corresponding mainsequence star mass ranges from 140 M⊙ to 260 M⊙. However, the evolutionary ...
... PISN explosions. The grid of models from Heger & Woosley (2002) shows the results of the simulation of non-rotating zero-metallicity models in the helium-core mass range between 65 M⊙ and 135 M⊙. The initial corresponding mainsequence star mass ranges from 140 M⊙ to 260 M⊙. However, the evolutionary ...
PoS(HTRA-IV)044 - Proceeding of science
... We chose the ProEMT M camera manufactured by Princeton Instruments as the imaging sensor for the instrument. The e2v CCD201B is a back-illuminated, frame-transfer EMCCD with 1024X1024 image pixels (or active area 13.3X13.3 mm). The large image area can cover all of 29 fibre images. The peak Q.E. at ...
... We chose the ProEMT M camera manufactured by Princeton Instruments as the imaging sensor for the instrument. The e2v CCD201B is a back-illuminated, frame-transfer EMCCD with 1024X1024 image pixels (or active area 13.3X13.3 mm). The large image area can cover all of 29 fibre images. The peak Q.E. at ...
Ch16_MilkyWayGalaxy
... • Despite uncertainties, the basic idea of the initial stars being made of pure hydrogen and helium is still true – so where are they • These population III stars may not be observable for three reasons – Only short-lived massive population III stars can form – consequently none are left today – Pop ...
... • Despite uncertainties, the basic idea of the initial stars being made of pure hydrogen and helium is still true – so where are they • These population III stars may not be observable for three reasons – Only short-lived massive population III stars can form – consequently none are left today – Pop ...
Nucleosynthesis
Nucleosynthesis is the process that creates new atomic nuclei from pre-existing nucleons, primarily protons and neutrons. The first nuclei were formed about three minutes after the Big Bang, through the process called Big Bang nucleosynthesis. It was then that hydrogen and helium formed to become the content of the first stars, and this primeval process is responsible for the present hydrogen/helium ratio of the cosmos.With the formation of stars, heavier nuclei were created from hydrogen and helium by stellar nucleosynthesis, a process that continues today. Some of these elements, particularly those lighter than iron, continue to be delivered to the interstellar medium when low mass stars eject their outer envelope before they collapse to form white dwarfs. The remains of their ejected mass form the planetary nebulae observable throughout our galaxy.Supernova nucleosynthesis within exploding stars by fusing carbon and oxygen is responsible for the abundances of elements between magnesium (atomic number 12) and nickel (atomic number 28). Supernova nucleosynthesis is also thought to be responsible for the creation of rarer elements heavier than iron and nickel, in the last few seconds of a type II supernova event. The synthesis of these heavier elements absorbs energy (endothermic) as they are created, from the energy produced during the supernova explosion. Some of those elements are created from the absorption of multiple neutrons (the R process) in the period of a few seconds during the explosion. The elements formed in supernovas include the heaviest elements known, such as the long-lived elements uranium and thorium.Cosmic ray spallation, caused when cosmic rays impact the interstellar medium and fragment larger atomic species, is a significant source of the lighter nuclei, particularly 3He, 9Be and 10,11B, that are not created by stellar nucleosynthesis.In addition to the fusion processes responsible for the growing abundances of elements in the universe, a few minor natural processes continue to produce very small numbers of new nuclides on Earth. These nuclides contribute little to their abundances, but may account for the presence of specific new nuclei. These nuclides are produced via radiogenesis (decay) of long-lived, heavy, primordial radionuclides such as uranium and thorium. Cosmic ray bombardment of elements on Earth also contribute to the presence of rare, short-lived atomic species called cosmogenic nuclides.