Lithium abundances for 185 main-sequence stars
... 1997) as described by Chen et al. (2000). For the more distant stars we adopt a spectroscopic gravity obtained by requiring that Fe i and Fe ii lines provide the same iron abundance. Metallicities were taken from Chen et al. (2000), Nissen & Schuster (1997), and Edvardsson et al. (1993). For a few s ...
... 1997) as described by Chen et al. (2000). For the more distant stars we adopt a spectroscopic gravity obtained by requiring that Fe i and Fe ii lines provide the same iron abundance. Metallicities were taken from Chen et al. (2000), Nissen & Schuster (1997), and Edvardsson et al. (1993). For a few s ...
Carbon-enhanced metal-poor stars: a window on AGB
... enhanced abundances of elements produced by the slow neutron-capture process (s-elements). The origin of the peculiar chemical abundances of these CEMP-s stars is believed to be accretion in the past of enriched material from a primary star in the asymptotic giant branch (AGB) phase of its evolution ...
... enhanced abundances of elements produced by the slow neutron-capture process (s-elements). The origin of the peculiar chemical abundances of these CEMP-s stars is believed to be accretion in the past of enriched material from a primary star in the asymptotic giant branch (AGB) phase of its evolution ...
Introduction to Cosmology - Experimental Elementary Particle
... the standard unit of power used in astronomy. The Sun’s luminosity (that is, the rate at which it radiates away energy in the form of light) is 1 L¯ = 3.8 × 1026 watts. The total luminosity of our Galaxy is Lgal = 3.6 × 1010 L¯ . For times much longer than a second, astronomers use the year (yr), de ...
... the standard unit of power used in astronomy. The Sun’s luminosity (that is, the rate at which it radiates away energy in the form of light) is 1 L¯ = 3.8 × 1026 watts. The total luminosity of our Galaxy is Lgal = 3.6 × 1010 L¯ . For times much longer than a second, astronomers use the year (yr), de ...
Georges Lemaître, The beginning of the world from
... past, the universe would have proceeded from a state of zero entropy. Eddington had wondered whether the moment of zero entropy could mark the beginning of the world, a concept that he had personal reasons to discard. Lemaître disagreed and pointed out that entropy is a measurement of proper time, a ...
... past, the universe would have proceeded from a state of zero entropy. Eddington had wondered whether the moment of zero entropy could mark the beginning of the world, a concept that he had personal reasons to discard. Lemaître disagreed and pointed out that entropy is a measurement of proper time, a ...
$^{13} $ CO/C $^{18} $ O Gradients Across the Disks of Nearby
... ratio as a function of the surface density of star formation, ΣSFR . Again, NGC 628 appears as an outlier, while the other targets with resolved gradients show decreasing 13 CO/C18 O with increasing ΣSFR . As discussed below, the sense of this trend is what is expected if massive star nucleosynthesi ...
... ratio as a function of the surface density of star formation, ΣSFR . Again, NGC 628 appears as an outlier, while the other targets with resolved gradients show decreasing 13 CO/C18 O with increasing ΣSFR . As discussed below, the sense of this trend is what is expected if massive star nucleosynthesi ...
Cosmic Topology: A Brief Overview
... emitted by cosmic sources follows geodesics, the immediate observational consequence of a spatially closed universe is that light from distant objects can reach a given observer along more than one path — the sky may show multiple images of radiating sources [cosmic objects or cosmic microwave backg ...
... emitted by cosmic sources follows geodesics, the immediate observational consequence of a spatially closed universe is that light from distant objects can reach a given observer along more than one path — the sky may show multiple images of radiating sources [cosmic objects or cosmic microwave backg ...
A Simple Model for r-Process Scatter and Halo Evolution
... 3. The placement of a star between these extremes quantifies a admixture of nucleosynthesis sources recorded in the star. Thus, (a) at the very earliest times, when single SN events are really all that contaminate a given star, the r/Fe scatter should only populate the extremes. (b) At later times, ...
... 3. The placement of a star between these extremes quantifies a admixture of nucleosynthesis sources recorded in the star. Thus, (a) at the very earliest times, when single SN events are really all that contaminate a given star, the r/Fe scatter should only populate the extremes. (b) At later times, ...
Chemical Composition of Selected Metal Poor Stars
... of Big Bang nucleosynthesis, to understand the earliest episodes of star formation (or star formation history of our galaxy) and regarding the first heavy element producing objects. The study of their chemical composition, serve as a tool to constrain the model of stellar nucleosynthesis, yields of ...
... of Big Bang nucleosynthesis, to understand the earliest episodes of star formation (or star formation history of our galaxy) and regarding the first heavy element producing objects. The study of their chemical composition, serve as a tool to constrain the model of stellar nucleosynthesis, yields of ...
THE CHEMICAL COMPOSITION AND AGE OF THE METAL
... (½Fe=H ¼ 2:9; Cayrel et al. 2001). Westin et al. (2000) were able to obtain third r-process peak element abundances with the Hubble Space Telescope (HST), along with thorium, in the UMP (½Fe=H ¼ 3:0) star HD 115444. This was the first halo star with reliable abundance data on the heaviest stable ...
... (½Fe=H ¼ 2:9; Cayrel et al. 2001). Westin et al. (2000) were able to obtain third r-process peak element abundances with the Hubble Space Telescope (HST), along with thorium, in the UMP (½Fe=H ¼ 3:0) star HD 115444. This was the first halo star with reliable abundance data on the heaviest stable ...
Krypton in presolar mainstream SiC grains from AGB stars
... (4.737±0.021 mb, 30 keV). Its production by the s−process depends on the 85 Kr neutron channel. 85 Kr is an unstable isotope, characterised by a ground state, 85 Krg (t1/2 = 10.76 yr), and an isomeric state, 85 Krm (t1/2 = 4.48 h). About 50 % of the neutron capture of 84 Kr feeds 85 Krm (Bao et al. ...
... (4.737±0.021 mb, 30 keV). Its production by the s−process depends on the 85 Kr neutron channel. 85 Kr is an unstable isotope, characterised by a ground state, 85 Krg (t1/2 = 10.76 yr), and an isomeric state, 85 Krm (t1/2 = 4.48 h). About 50 % of the neutron capture of 84 Kr feeds 85 Krm (Bao et al. ...
Imaging and spectroscopy of ejected common envelopes
... we are viewing this object in cross-section, and in some respects there is some resemblance between this nebula and the central parts of Abell 63. In fact, under suitable scaling the object takes on the appearance of a figure eight with the central star situated at the junction of the two halves of ...
... we are viewing this object in cross-section, and in some respects there is some resemblance between this nebula and the central parts of Abell 63. In fact, under suitable scaling the object takes on the appearance of a figure eight with the central star situated at the junction of the two halves of ...
The chemical composition of two supergiants in the dwarf
... are too distant for detailed analysis of their red giant branch (=RGB, stars that can sample ages >1 Gyr). It is possible to observe and analyse the spectra of their bright, young massive stars though, since they continue to form stars today. These stars will reflect the integrated star formation hi ...
... are too distant for detailed analysis of their red giant branch (=RGB, stars that can sample ages >1 Gyr). It is possible to observe and analyse the spectra of their bright, young massive stars though, since they continue to form stars today. These stars will reflect the integrated star formation hi ...
THE HOBBY-EBERLY TELESCOPE CHEMICAL ABUNDANCES OF
... plateau (Spite & Spite 1982) Li abundance characteristic of most warm, metal-poor turnoff and subgiant stars. A wide spectrum of Spite plateau /primordial Li abundances has been inferred from recent studies of these stars: log "(Li) ¼ 2:37 (with an observational scatter of 0.05Y0.06 dex; Meléndez & ...
... plateau (Spite & Spite 1982) Li abundance characteristic of most warm, metal-poor turnoff and subgiant stars. A wide spectrum of Spite plateau /primordial Li abundances has been inferred from recent studies of these stars: log "(Li) ¼ 2:37 (with an observational scatter of 0.05Y0.06 dex; Meléndez & ...
The effect of helium sedimentation on galaxy cluster masses and
... Context. Recent theoretical studies predict that the inner regions of galaxy clusters may have an enhanced helium abundance due to sedimentation over the cluster lifetime. If sedimentation is not suppressed (e.g., by tangled magnetic fields), this may significantly affect the cluster mass estimates. ...
... Context. Recent theoretical studies predict that the inner regions of galaxy clusters may have an enhanced helium abundance due to sedimentation over the cluster lifetime. If sedimentation is not suppressed (e.g., by tangled magnetic fields), this may significantly affect the cluster mass estimates. ...
arXiv:astro-ph/0703091v1 5 Mar 2007
... isotopes: first, a generally sharp rise to a maximum followed by a more gradual decline – if log nn < 20 abundance runs were to be displayed in Figure 2, then the rising portions of the curves would be more apparent for the lightest isotopes (A = 100 and 120). The details of the curves are dependent ...
... isotopes: first, a generally sharp rise to a maximum followed by a more gradual decline – if log nn < 20 abundance runs were to be displayed in Figure 2, then the rising portions of the curves would be more apparent for the lightest isotopes (A = 100 and 120). The details of the curves are dependent ...
Models of red giants in the CoRoT asteroseismology fields
... 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 standard uncertainty. However, this is not a very stringent test since the typical uncertainties are ∼9% for the radii and ∼22% for the ...
... 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 standard uncertainty. However, this is not a very stringent test since the typical uncertainties are ∼9% for the radii and ∼22% for the ...
8) consequence of the new theory about the
... For the next aproximate 400 – 600 billion years the universe will still expand to a sphere with a radius of about 8 - 10 billion light years. This expansion, already decelerating from the current approximate 650 km/sec -> 0 km/sec, will continue until all H2 in the universe has totally fused by nucl ...
... For the next aproximate 400 – 600 billion years the universe will still expand to a sphere with a radius of about 8 - 10 billion light years. This expansion, already decelerating from the current approximate 650 km/sec -> 0 km/sec, will continue until all H2 in the universe has totally fused by nucl ...
astro-ph/9505110 PDF
... in our Galaxy is decoupled from that of carbon and oxygen. One possible interpretation of the trend in C/O is that the most metal-poor galaxies are young and dominated by the products of early enrichment by massive stars, while more metal-rich galaxies show increasing, delayed contributions of carbo ...
... in our Galaxy is decoupled from that of carbon and oxygen. One possible interpretation of the trend in C/O is that the most metal-poor galaxies are young and dominated by the products of early enrichment by massive stars, while more metal-rich galaxies show increasing, delayed contributions of carbo ...
A self-consistent empirical model atmosphere, abundance and
... α Circini (HD 128898, HR 5463, HIP 71908) for our investigation. This star is the brightest of about 40 currently known rapidly oscillating Ap (roAp) stars and is one of the most promising objects for detailed asteroseismic investigation. It pulsates in several non-radial oscillation modes (Kurtz et ...
... α Circini (HD 128898, HR 5463, HIP 71908) for our investigation. This star is the brightest of about 40 currently known rapidly oscillating Ap (roAp) stars and is one of the most promising objects for detailed asteroseismic investigation. It pulsates in several non-radial oscillation modes (Kurtz et ...
Rapid neutral–neutral reactions at low temperatures
... et al. (1994) and Bettens, Lee & Herbst (1995), the latter referring to their network as the ‘new neutral–neutral model (nnnm)’. In these networks, the small number of low-temperature studies then extant was generalized based on the chemical intuition of the authors. In general, the models failed to ...
... et al. (1994) and Bettens, Lee & Herbst (1995), the latter referring to their network as the ‘new neutral–neutral model (nnnm)’. In these networks, the small number of low-temperature studies then extant was generalized based on the chemical intuition of the authors. In general, the models failed to ...
Confronting predictions of the galaxy stellar mass function with
... We investigate the evolution of the galaxy stellar mass function at high redshift (z ≥ 5) using a pair of large cosmological hydrodynamical simulations: MassiveBlack and MassiveBlack-II. By combining these simulations, we can study the properties of galaxies with stellar masses greater than 108 M h ...
... We investigate the evolution of the galaxy stellar mass function at high redshift (z ≥ 5) using a pair of large cosmological hydrodynamical simulations: MassiveBlack and MassiveBlack-II. By combining these simulations, we can study the properties of galaxies with stellar masses greater than 108 M h ...
The Chemical Composition of Exoplanet
... signal-to-noise to resolve these absorption features. RV measurements require highresolution spectra for the initial exoplanet discoveries, so high-resolution datasets (of appropriate quality for this analysis) already exist for many known planetary systems. Therefore, this method provides a simple ...
... signal-to-noise to resolve these absorption features. RV measurements require highresolution spectra for the initial exoplanet discoveries, so high-resolution datasets (of appropriate quality for this analysis) already exist for many known planetary systems. Therefore, this method provides a simple ...
The isotopic mixture of barium in the metal-poor
... occur in the helium and carbon shells of massive stars in their hydrostatic burning phases. The r-process is likely associated with the deep interior of Type II supernovae. Since massive stars dying as Type II supernovae evolve faster than the stars that populate and evolve from the AGB, one anticip ...
... occur in the helium and carbon shells of massive stars in their hydrostatic burning phases. The r-process is likely associated with the deep interior of Type II supernovae. Since massive stars dying as Type II supernovae evolve faster than the stars that populate and evolve from the AGB, one anticip ...
Nucleus Chapter 1
... With a very powerful telescope, a vast number of galaxies can be observed, stretching out to such distances that the light coming from the very furthest would have been travelling for most of the time since the Universe was born. That was about 15 billion years ago and so they are the better part of ...
... With a very powerful telescope, a vast number of galaxies can be observed, stretching out to such distances that the light coming from the very furthest would have been travelling for most of the time since the Universe was born. That was about 15 billion years ago and so they are the better part of ...