$^{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 ...
The occurrence of nitrogen-enhanced metal
... for masses larger than 1.2 M , the large CEMP fraction cannot be explained. However, they also found that efficient dredgeup in lower-mass AGB stars (0.8–1.2 M ) can substantially increase the expected CEMP fraction to within the observed range. Therefore the question of whether CEMP stars provide e ...
... for masses larger than 1.2 M , the large CEMP fraction cannot be explained. However, they also found that efficient dredgeup in lower-mass AGB stars (0.8–1.2 M ) can substantially increase the expected CEMP fraction to within the observed range. Therefore the question of whether CEMP stars provide e ...
evolución química de la nube grande de magallanes.
... Understanding how our Galaxy and other galaxies formed is one of the big questions in Astronomy and is the principal motivation for this thesis. The two most widely accepted scenarios for Galaxy formation, in particular the halo, for the purpose of this work, are ’The Monolithic Collapse Model’ and ...
... Understanding how our Galaxy and other galaxies formed is one of the big questions in Astronomy and is the principal motivation for this thesis. The two most widely accepted scenarios for Galaxy formation, in particular the halo, for the purpose of this work, are ’The Monolithic Collapse Model’ and ...
Krypton in presolar mainstream SiC grains from AGB stars
... sources: by 13 C(α,n)16 O and by 22 Ne(α,n)25 Mg (see Pignatari et al. 2005b for details). The other i Kr/82 Kr isotopic ratios are only slightly affected by the above uncertainties. To conclude, it is difficult to obtain a well established estimate for the 86 Kr/82 Kr ratio from AGB models, and at ...
... sources: by 13 C(α,n)16 O and by 22 Ne(α,n)25 Mg (see Pignatari et al. 2005b for details). The other i Kr/82 Kr isotopic ratios are only slightly affected by the above uncertainties. To conclude, it is difficult to obtain a well established estimate for the 86 Kr/82 Kr ratio from AGB models, and at ...
Chapter 5 - Leiden Observatory
... We present an update to the software package SeBa [Portegies Zwart & Verbunt, 1996; Nelemans et al., 2001c] for fast stellar and binary evolution computations. Stars are evolved from the zero-age main sequence (ZAMS) until remnant formation and beyond. Stars are parametrised by mass, radius, luminos ...
... We present an update to the software package SeBa [Portegies Zwart & Verbunt, 1996; Nelemans et al., 2001c] for fast stellar and binary evolution computations. Stars are evolved from the zero-age main sequence (ZAMS) until remnant formation and beyond. Stars are parametrised by mass, radius, luminos ...
Investigating the Effects of Milky Way Globular Clusters
... Dark matter is believed to be matter that gives off so little light, if any at all, that we are unable to detect its presence (Weintraub 261). However, scientists have been able to infer its existence from numerous observations and calculations surrounding the nature of the Milky Way galaxy, oth ...
... Dark matter is believed to be matter that gives off so little light, if any at all, that we are unable to detect its presence (Weintraub 261). However, scientists have been able to infer its existence from numerous observations and calculations surrounding the nature of the Milky Way galaxy, oth ...
A Theory of Extrasolar Giant Planets
... MJ and close in age to 4.5 Gyr. However, as we discuss below, Black's formulas become very inaccurate at earlier ages and at larger masses. The scope of this paper is as follows. Our lower mass limit is the mass of Saturn (0.3 MJ ), and our upper mass limit is 15 MJ , which takes us to objects which ...
... MJ and close in age to 4.5 Gyr. However, as we discuss below, Black's formulas become very inaccurate at earlier ages and at larger masses. The scope of this paper is as follows. Our lower mass limit is the mass of Saturn (0.3 MJ ), and our upper mass limit is 15 MJ , which takes us to objects which ...
Three Binary Millisecond Pulsars in NGC 6266
... data are reprocessed, with dedispersion at the DM value of the newly discovered pulsar. The resulting time series is then subjected to a fully coherent search for Doppler-distorted signals over a large range of acceleration values. Applying this extremely CPU-intensive procedure to NGC 6266, explori ...
... data are reprocessed, with dedispersion at the DM value of the newly discovered pulsar. The resulting time series is then subjected to a fully coherent search for Doppler-distorted signals over a large range of acceleration values. Applying this extremely CPU-intensive procedure to NGC 6266, explori ...
Early Star-Forming Galaxies and the Reionisation of the Universe
... forming galaxies is the Lyman α emission line at rest wavelength of 121.6nm, produced internally by gas heated by young stars. The observability of Lyman α emission is sensitive to the ionisation state of the IGM, as the observed line strength can be attenuated by intervening neutral hydrogen. The ...
... forming galaxies is the Lyman α emission line at rest wavelength of 121.6nm, produced internally by gas heated by young stars. The observability of Lyman α emission is sensitive to the ionisation state of the IGM, as the observed line strength can be attenuated by intervening neutral hydrogen. The ...
A Detection Method for Small Kuiper Belt Objects: The Search for
... (i) a perfectly circular object and (ii) the star is a point source. We thus discuss the following two provisoes: What about an irregularly shaped object? Of course, we do not expect to deal with perfect spherical objects in the Kuiper belt, while we need to model a random occultation with an isotro ...
... (i) a perfectly circular object and (ii) the star is a point source. We thus discuss the following two provisoes: What about an irregularly shaped object? Of course, we do not expect to deal with perfect spherical objects in the Kuiper belt, while we need to model a random occultation with an isotro ...
STELLAR STRUCTURE AND EVOLUTION
... of heavy elements (Z) apparently increases with time. This is the result of chemical enrichment by subsequent stellar generations. The study of chemical evolution has led to the hypothesis of a ‘Population III’ consisting of the first generation of stars formed after the Big Bang, containing only hy ...
... of heavy elements (Z) apparently increases with time. This is the result of chemical enrichment by subsequent stellar generations. The study of chemical evolution has led to the hypothesis of a ‘Population III’ consisting of the first generation of stars formed after the Big Bang, containing only hy ...
Chapter 17 - Astronomy
... absolutely exact. What scientists attempt to do is to be aware of how inexact their measurements are. 2. Calculating the likely error is a common practice in all natural sciences. Scientists thus attempt to be specific about their inexactness. 3. A scientist tries to be aware of the assumptions invo ...
... absolutely exact. What scientists attempt to do is to be aware of how inexact their measurements are. 2. Calculating the likely error is a common practice in all natural sciences. Scientists thus attempt to be specific about their inexactness. 3. A scientist tries to be aware of the assumptions invo ...
RUPRECHT 147: THE OLDEST NEARBY OPEN CLUSTER AS A
... studies of the Sun and stellar clusters. A few “benchmark” clusters form the basis of our understanding of stellar evolution, and the effects of abundance, age, and mass on stars. When fully characterized with precise ages, distances, and metallicities, these clusters become touchstones for similar ...
... studies of the Sun and stellar clusters. A few “benchmark” clusters form the basis of our understanding of stellar evolution, and the effects of abundance, age, and mass on stars. When fully characterized with precise ages, distances, and metallicities, these clusters become touchstones for similar ...
Zhu Qualifier Solutions - University of Toronto Astronomy
... 3.1.5. How do you determine an a present-day mass function (PDMF) from an IMF? 3.2. Question 2 3.2.1. What Orbits are Allowed in an Axisymmetric Potential? 3.2.2. How did each population of stars gain their particular orbit? 3.2.3. Orbits in Elliptical Galaxies 3.2.4. What are the different populati ...
... 3.1.5. How do you determine an a present-day mass function (PDMF) from an IMF? 3.2. Question 2 3.2.1. What Orbits are Allowed in an Axisymmetric Potential? 3.2.2. How did each population of stars gain their particular orbit? 3.2.3. Orbits in Elliptical Galaxies 3.2.4. What are the different populati ...
SPITZER/MIPS 24 µm OBSERVATIONS OF GALAXY CLUSTERS
... at 0.02 ≤ z ≤ 0.83 that have a total of 1315 spectroscopically confirmed members. The core of our sample is composed of five clusters spanning the entire redshift range with large spectroscopic membership, uniform multifilter optical photometry and deep SST/MIPS imaging1 . For the part of the analys ...
... at 0.02 ≤ z ≤ 0.83 that have a total of 1315 spectroscopically confirmed members. The core of our sample is composed of five clusters spanning the entire redshift range with large spectroscopic membership, uniform multifilter optical photometry and deep SST/MIPS imaging1 . For the part of the analys ...
distribution and properties of a sample of massive young stars
... earliest stages of their evolution are therefore hidden behind many magnitudes of visual extinction, only observable at infrared (IR) and millimetre wavelengths. Moreover, massive stars are known to form exclusively in clusters (e.g. de Wit et al. 2004), which makes it difficult to attribute derived ...
... earliest stages of their evolution are therefore hidden behind many magnitudes of visual extinction, only observable at infrared (IR) and millimetre wavelengths. Moreover, massive stars are known to form exclusively in clusters (e.g. de Wit et al. 2004), which makes it difficult to attribute derived ...
a0041_Spectral Analysis and Classification of Herbig A
... diagram. The presence of continua and emission lines formed outside the photosphere complicate traditional spectral classification schemes used for early-type stars. Several efforts have been made in the past to classify HAeBe stars, applying qualitative and quantitative spectral classification sche ...
... diagram. The presence of continua and emission lines formed outside the photosphere complicate traditional spectral classification schemes used for early-type stars. Several efforts have been made in the past to classify HAeBe stars, applying qualitative and quantitative spectral classification sche ...
Stars as cosmological tools: giving light to Dark Matter
... the matter in the Universe exists in an undiscovered form, known as Dark Matter (DM), dierent from any other type of matter. Despite the extensive eorts dedicated to investigate the DM problem, the identi cation of its nature remains elusive. In this Thesis we propose a complementary approach to p ...
... the matter in the Universe exists in an undiscovered form, known as Dark Matter (DM), dierent from any other type of matter. Despite the extensive eorts dedicated to investigate the DM problem, the identi cation of its nature remains elusive. In this Thesis we propose a complementary approach to p ...
Debris discs around M stars: non-existence versus non
... Motivated by the reported dearth of debris discs around M stars, we use survival models to study the occurrence of planetesimal discs around them. These survival models describe a planetesimal disc with a small number of parameters, determine if it may survive a series of dynamical processes and com ...
... Motivated by the reported dearth of debris discs around M stars, we use survival models to study the occurrence of planetesimal discs around them. These survival models describe a planetesimal disc with a small number of parameters, determine if it may survive a series of dynamical processes and com ...
1 C. An expanded description of the work being done on the
... The telescope has always been an important tool for scientists, allowing astronomers to observe distant objects. It seems to represent the way in which our perspective of the Universe has changed drastically over the last 400 years, with the rise of science showing us just how insignificant we are. ...
... The telescope has always been an important tool for scientists, allowing astronomers to observe distant objects. It seems to represent the way in which our perspective of the Universe has changed drastically over the last 400 years, with the rise of science showing us just how insignificant we are. ...
The binary fractions in the massive young Large Magellanic Cloud
... yield high detection efficiency, since it only depends on a single set of observations. In principle, one does not need to adopt many physical assumptions either; the approach is only based on our understanding of stellar evolution. This also allows us to simulate artificial observations for compari ...
... yield high detection efficiency, since it only depends on a single set of observations. In principle, one does not need to adopt many physical assumptions either; the approach is only based on our understanding of stellar evolution. This also allows us to simulate artificial observations for compari ...
CHARACTERIZING THE COOL KOIs. III. KOI 961: A SMALL STAR
... we acquired a K-band spectrum of KOI 961 as part of a survey of low-mass KOIs. The spectrum confirmed that it is a dwarf and not a giant based on the shallowness of the CO absorption band, and we reported an effective temperature of 3200 ± 50 K and an overall metallicity ([M/H]) of −0.33 ± 0.12 usin ...
... we acquired a K-band spectrum of KOI 961 as part of a survey of low-mass KOIs. The spectrum confirmed that it is a dwarf and not a giant based on the shallowness of the CO absorption band, and we reported an effective temperature of 3200 ± 50 K and an overall metallicity ([M/H]) of −0.33 ± 0.12 usin ...
View/Open - University of Hertfordshire
... distinguish between members of NGC 6822 and foreground stars in the Milky Way and that the analysis tools available could be used to obtain useful velocity results from the spectra. This led to the discovery of a rotating population of intermediate age stars in the halo of NGC 6822, which constitute ...
... distinguish between members of NGC 6822 and foreground stars in the Milky Way and that the analysis tools available could be used to obtain useful velocity results from the spectra. This led to the discovery of a rotating population of intermediate age stars in the halo of NGC 6822, which constitute ...
Downloadable Full Text
... phase; this approximation seems justified in light of the other theoretical uncertainties for this phase of the evolution. In order to study the range of possible progenitor stars for the Regulus inner binary system, we considered primary stars of mass M10 3 M , and secondaries of any mass less t ...
... phase; this approximation seems justified in light of the other theoretical uncertainties for this phase of the evolution. In order to study the range of possible progenitor stars for the Regulus inner binary system, we considered primary stars of mass M10 3 M , and secondaries of any mass less t ...
Planetary nebula
A planetary nebula, often abbreviated as PN or plural PNe, is a kind of emission nebula consisting of an expanding glowing shell of ionized gas ejected from old red giant stars late in their lives. The word ""nebula"" is Latin for mist or cloud and the term ""planetary nebula"" is a misnomer that originated in the 1780s with astronomer William Herschel because when viewed through his telescope, these objects appeared to him to resemble the rounded shapes of planets. Herschel's name for these objects was popularly adopted and has not been changed. They are a relatively short-lived phenomenon, lasting a few tens of thousands of years, compared to a typical stellar lifetime of several billion years.A mechanism for formation of most planetary nebulae is thought to be the following: at the end of the star's life, during the red giant phase, the outer layers of the star are expelled by strong stellar winds. Eventually, after most of the red giant's atmosphere is dissipated, the exposed hot, luminous core emits ultraviolet radiation to ionize the ejected outer layers of the star. Absorbed ultraviolet light energises the shell of nebulous gas around the central star, appearing as a bright coloured planetary nebula at several discrete visible wavelengths.Planetary nebulae may play a crucial role in the chemical evolution of the Milky Way, returning material to the interstellar medium from stars where elements, the products of nucleosynthesis (such as carbon, nitrogen, oxygen and neon), have been created. Planetary nebulae are also observed in more distant galaxies, yielding useful information about their chemical abundances.In recent years, Hubble Space Telescope images have revealed many planetary nebulae to have extremely complex and varied morphologies. About one-fifth are roughly spherical, but the majority are not spherically symmetric. The mechanisms which produce such a wide variety of shapes and features are not yet well understood, but binary central stars, stellar winds and magnetic fields may play a role.