the mass-loss return from evolved stars to the large
... Spectrograph spectra from the SAGE and SAGE-Spectroscopy observing programs of two oxygen-rich asymptotic giant branch (O-rich AGB) stars in the Large Magellanic Cloud (LMC) using radiative transfer (RT) models of dust shells around stars. We chose a star from each of the bright and faint O-rich AGB ...
... Spectrograph spectra from the SAGE and SAGE-Spectroscopy observing programs of two oxygen-rich asymptotic giant branch (O-rich AGB) stars in the Large Magellanic Cloud (LMC) using radiative transfer (RT) models of dust shells around stars. We chose a star from each of the bright and faint O-rich AGB ...
Interpretation of the Helix Planetary Nebula using Hydro
... The related Jeans hydrostatic length scale LJHS ≡ [p/ρ2 G]1/2 is given in the equation and has been misinterpreted by Jeans 1902 and others as an indication that pressure itself somehow prevents gravitational condensation on scales smaller than LJ . Although the two scales appear to be equal they ar ...
... The related Jeans hydrostatic length scale LJHS ≡ [p/ρ2 G]1/2 is given in the equation and has been misinterpreted by Jeans 1902 and others as an indication that pressure itself somehow prevents gravitational condensation on scales smaller than LJ . Although the two scales appear to be equal they ar ...
Stellar dust production and composition in the Magellanic Clouds F. Kemper
... in the ISO spectroscopy, and found that, while the spectra all show amorphous silicates, some of them also show the spectral signature of Al2 O3 (alumina). The relative strength of the alumina signature to the spectrum decreases with increasing mass-loss rate, suggestive of a covering of the alumina ...
... in the ISO spectroscopy, and found that, while the spectra all show amorphous silicates, some of them also show the spectral signature of Al2 O3 (alumina). The relative strength of the alumina signature to the spectrum decreases with increasing mass-loss rate, suggestive of a covering of the alumina ...
110 - Institute for Astronomy
... E-mail contact: [email protected] We show that the dearth of brown dwarfs in short-period orbits around Solar-mass stars – the brown dwarf desert – can be understood as a consequence of inward migration within an evolving protoplanetary disc. Brown dwarf secondaries forming at the same time as t ...
... E-mail contact: [email protected] We show that the dearth of brown dwarfs in short-period orbits around Solar-mass stars – the brown dwarf desert – can be understood as a consequence of inward migration within an evolving protoplanetary disc. Brown dwarf secondaries forming at the same time as t ...
UNIVERSITY OF PADUA Master degree in
... Molecular clouds occupy a large range of sizes and densities which is reflected by their evolutionary timescales. It is important to understand the typical timescales that govern molecular clouds in order to understand how molecular clouds evolve. The most relevant timescale is the dynamical time, w ...
... Molecular clouds occupy a large range of sizes and densities which is reflected by their evolutionary timescales. It is important to understand the typical timescales that govern molecular clouds in order to understand how molecular clouds evolve. The most relevant timescale is the dynamical time, w ...
Pan-Planets: Searching for hot Jupiters around cool dwarfs⋆
... The procedure to select the 100 best images is the following: after removing all frames with a masking higher than 50%, we select the 120 images with the best seeing. We determine the weight of each image on the reference frame by determining the PSF FWHM and S/N and reject frames that possess a ver ...
... The procedure to select the 100 best images is the following: after removing all frames with a masking higher than 50%, we select the 120 images with the best seeing. We determine the weight of each image on the reference frame by determining the PSF FWHM and S/N and reject frames that possess a ver ...
The origin of the strongest magnetic fields in dwarfs
... is the evidence that magnetic white dwarfs tend to be more massive and hence less luminous than nonmagnetic white dwarfs. Liebert [16] first summarized the evidence that several nearby magnetic white dwarfs with trigonometric parallaxes have relatively small radii and anomalously high masses and lie ...
... is the evidence that magnetic white dwarfs tend to be more massive and hence less luminous than nonmagnetic white dwarfs. Liebert [16] first summarized the evidence that several nearby magnetic white dwarfs with trigonometric parallaxes have relatively small radii and anomalously high masses and lie ...
ONE- AND MULTI- ZONE MODELS: Chemical properties
... those expected from standard evolutionary models with an initial spike of star formation followed by quiescence. ...
... those expected from standard evolutionary models with an initial spike of star formation followed by quiescence. ...
Observations of Near Infrared Extragalactic Background (NIR_EBL)
... 1. Small neutral fractions at z ~ 6 (1% neutral) 2. Sharp transition at z~6 (end of reionization?) ...
... 1. Small neutral fractions at z ~ 6 (1% neutral) 2. Sharp transition at z~6 (end of reionization?) ...
Detached WD/BD binaries as progenitors of CVs
... • J-H v H-K plot provides an initial selection • Better method: model each WD SED, first with BBs and finally with model atmospheres (DAs only) – Identify WDs with >3 sigma excesses at H and K Dr. Matt Burleigh ...
... • J-H v H-K plot provides an initial selection • Better method: model each WD SED, first with BBs and finally with model atmospheres (DAs only) – Identify WDs with >3 sigma excesses at H and K Dr. Matt Burleigh ...
Telescope Bernard Lyot/Narval The Observatory of Stellar Magnetism
... Program Magnetism in Massive Stars (MiMeS): origins and evolution of magnetic fields in hot stars, Herbig, OB Complex field on Tau Sco (Jardine et al.) ...
... Program Magnetism in Massive Stars (MiMeS): origins and evolution of magnetic fields in hot stars, Herbig, OB Complex field on Tau Sco (Jardine et al.) ...
Kathy Geise `08 - DU Portfolio
... Given an understanding of optical depth, the next task was to develop a model to compare stellar atmospheres of two types of stars, a red giant star and a main sequence star. The model describes six physical parameters for each layer: temperature, gas pressure, radiation pressure, density, opacity a ...
... Given an understanding of optical depth, the next task was to develop a model to compare stellar atmospheres of two types of stars, a red giant star and a main sequence star. The model describes six physical parameters for each layer: temperature, gas pressure, radiation pressure, density, opacity a ...
X-ray Binaries
... of the neutron star mass distribution in HMXBs are found to agree with theoretical expectations of core-collapse supernovae [60]. Constraints on neutron star forming supernovae do seem to be provided by two distinct populations of X-ray pulsars in Be/X-ray binaries; short Pspin pulsars with short or ...
... of the neutron star mass distribution in HMXBs are found to agree with theoretical expectations of core-collapse supernovae [60]. Constraints on neutron star forming supernovae do seem to be provided by two distinct populations of X-ray pulsars in Be/X-ray binaries; short Pspin pulsars with short or ...
The significant contribution of minor mergers to the cosmic star
... Finally, to estimate galaxy environment we employ the environment catalogue of Yang et al. (2007), who use an iterative halo-based group finder to separate the SDSS into structures across a broad dynamical range, spanning clusters to isolated galaxies. The catalogue provides estimates of the mass of ...
... Finally, to estimate galaxy environment we employ the environment catalogue of Yang et al. (2007), who use an iterative halo-based group finder to separate the SDSS into structures across a broad dynamical range, spanning clusters to isolated galaxies. The catalogue provides estimates of the mass of ...
The Be/X-ray transient 4U 0115+ 63/V635 Cassiopeiae
... the line shapes. In spite of this, all the measurements obtained fall in the range v sin i ≈ 240 − 340 km s−1 with most of them concentrated around v sin i = 290 km s−1 and the Balmer lines consistently giving higher values than the He i lines (except Hα). Therefore, allowing for the effect of emiss ...
... the line shapes. In spite of this, all the measurements obtained fall in the range v sin i ≈ 240 − 340 km s−1 with most of them concentrated around v sin i = 290 km s−1 and the Balmer lines consistently giving higher values than the He i lines (except Hα). Therefore, allowing for the effect of emiss ...
Spectral Fingerprints of Earth-like Planets Around FGK Stars
... full FGK spectral range and corresponds roughly to F0V, F2V, F5V, F7V, F9V/G0V, G2V, G8V, K0V, K2V, K4V, K5V, and K7V main sequence stars (following the spectral type classification by Gray, 1992). In this paper, we use ‘‘Earth-like,’’ as applied to our models, to mean using modern Earth’s outgassin ...
... full FGK spectral range and corresponds roughly to F0V, F2V, F5V, F7V, F9V/G0V, G2V, G8V, K0V, K2V, K4V, K5V, and K7V main sequence stars (following the spectral type classification by Gray, 1992). In this paper, we use ‘‘Earth-like,’’ as applied to our models, to mean using modern Earth’s outgassin ...
Binary star progenitors of long GRBs
... of the accreting companion The system is likely to be broke up by the SN kick (80%) The accreting companion becomes a Runaway WR star and travels few hundred pc before producing a Long GRB ...
... of the accreting companion The system is likely to be broke up by the SN kick (80%) The accreting companion becomes a Runaway WR star and travels few hundred pc before producing a Long GRB ...
PPT
... The high metallicity of this cluster makes these effects much more important. To this end, we have followed the entire evolution of 0.5249, 0.5701, 0.593, 0.6096, 0.6323, 0.6598 and 0.7051 M white dwarf sequences which include both physical processes. Our sequences start from stellar models o ...
... The high metallicity of this cluster makes these effects much more important. To this end, we have followed the entire evolution of 0.5249, 0.5701, 0.593, 0.6096, 0.6323, 0.6598 and 0.7051 M white dwarf sequences which include both physical processes. Our sequences start from stellar models o ...
STIS/HST Observations of Large Magellanic Cloud Planetary
... Let us now examine the cases in which the electron density of the PNs is higher than the critical density. In Fig. 4 (top panels) we plot the usual SB vs. Rphot relation, from the observations in the light of [S II]. The critical densities, calculated for a model nebula with Te ~ 10,000 K and Ne ~ 1 ...
... Let us now examine the cases in which the electron density of the PNs is higher than the critical density. In Fig. 4 (top panels) we plot the usual SB vs. Rphot relation, from the observations in the light of [S II]. The critical densities, calculated for a model nebula with Te ~ 10,000 K and Ne ~ 1 ...
The spin-up of contracting red supergiants
... place of a strong mean molecular weight gradient. Both, the entropy and the mean molecular weight gradient, act to strongly suppress any kind of mixing through the hydrogen burning shell source. This concerns chemical mixing as well as the transport of angular momentum (e.g., Zahn 1974; Langer et al ...
... place of a strong mean molecular weight gradient. Both, the entropy and the mean molecular weight gradient, act to strongly suppress any kind of mixing through the hydrogen burning shell source. This concerns chemical mixing as well as the transport of angular momentum (e.g., Zahn 1974; Langer et al ...
Winds from clusters with non-uniform stellar distribution
... in which the distribution of stars (i.e., the number of stars per unit volume) within the cluster is spherically symmetric, has a power-law radial dependence, and drops discontinuously to zero at the outer radius of the cluster. We carry out comparisons between an analytic model (in which the stars ...
... in which the distribution of stars (i.e., the number of stars per unit volume) within the cluster is spherically symmetric, has a power-law radial dependence, and drops discontinuously to zero at the outer radius of the cluster. We carry out comparisons between an analytic model (in which the stars ...
Stellar interactions in dense and sparse star clusters
... clusters (n 103 pc−3 ) the disc frequency seems to be lower in the core (e.g. Balog et al. 2007), it is an open question as to how far interactions with the surrounding stars influence the planet formation in clusters of different densities. Two major mechanisms are potentially able to strongly aff ...
... clusters (n 103 pc−3 ) the disc frequency seems to be lower in the core (e.g. Balog et al. 2007), it is an open question as to how far interactions with the surrounding stars influence the planet formation in clusters of different densities. Two major mechanisms are potentially able to strongly aff ...
plasma/tokamak (alex/steve)new - General Atomics Fusion Education
... Initially, a star will have a huge amount of hydrogen and some helium. Stars of one solar mass or less will fuse hydrogen into helium in a process called the proton-proton chain. Four hydrogen atoms are necessary to produce one atom of helium through this process. In this reaction, two protons are c ...
... Initially, a star will have a huge amount of hydrogen and some helium. Stars of one solar mass or less will fuse hydrogen into helium in a process called the proton-proton chain. Four hydrogen atoms are necessary to produce one atom of helium through this process. In this reaction, two protons are c ...
Main sequence
In astronomy, the main sequence is a continuous and distinctive band of stars that appears on plots of stellar color versus brightness. These color-magnitude plots are known as Hertzsprung–Russell diagrams after their co-developers, Ejnar Hertzsprung and Henry Norris Russell. Stars on this band are known as main-sequence stars or ""dwarf"" stars.After a star has formed, it generates thermal energy in the dense core region through the nuclear fusion of hydrogen atoms into helium. During this stage of the star's lifetime, it is located along the main sequence at a position determined primarily by its mass, but also based upon its chemical composition and other factors. All main-sequence stars are in hydrostatic equilibrium, where outward thermal pressure from the hot core is balanced by the inward pressure of gravitational collapse from the overlying layers. The strong dependence of the rate of energy generation in the core on the temperature and pressure helps to sustain this balance. Energy generated at the core makes its way to the surface and is radiated away at the photosphere. The energy is carried by either radiation or convection, with the latter occurring in regions with steeper temperature gradients, higher opacity or both.The main sequence is sometimes divided into upper and lower parts, based on the dominant process that a star uses to generate energy. Stars below about 1.5 times the mass of the Sun (or 1.5 solar masses (M☉)) primarily fuse hydrogen atoms together in a series of stages to form helium, a sequence called the proton–proton chain. Above this mass, in the upper main sequence, the nuclear fusion process mainly uses atoms of carbon, nitrogen and oxygen as intermediaries in the CNO cycle that produces helium from hydrogen atoms. Main-sequence stars with more than two solar masses undergo convection in their core regions, which acts to stir up the newly created helium and maintain the proportion of fuel needed for fusion to occur. Below this mass, stars have cores that are entirely radiative with convective zones near the surface. With decreasing stellar mass, the proportion of the star forming a convective envelope steadily increases, whereas main-sequence stars below 0.4 M☉ undergo convection throughout their mass. When core convection does not occur, a helium-rich core develops surrounded by an outer layer of hydrogen.In general, the more massive a star is, the shorter its lifespan on the main sequence. After the hydrogen fuel at the core has been consumed, the star evolves away from the main sequence on the HR diagram. The behavior of a star now depends on its mass, with stars below 0.23 M☉ becoming white dwarfs directly, whereas stars with up to ten solar masses pass through a red giant stage. More massive stars can explode as a supernova, or collapse directly into a black hole.