Finding high-redshift dark stars with the James Webb Space
... of the gravitationally-contracted dark matter. The strategy is not optimised for dealing with the stellar evolution after formation, because it relies on either full hydrodynamic simulations (Natarajan et al. 2009; Ripamonti et al. 2009, 2010) or analytical approximations to them (Spolyar et al. 200 ...
... of the gravitationally-contracted dark matter. The strategy is not optimised for dealing with the stellar evolution after formation, because it relies on either full hydrodynamic simulations (Natarajan et al. 2009; Ripamonti et al. 2009, 2010) or analytical approximations to them (Spolyar et al. 200 ...
A Second Shell in the Fornax dSph Galaxy
... significantly larger than the first, located 1.3◦ north-west from the centre of Fornax, outside the nominal tidal radius. Moreover, the distribution of Fornax RGB stars reveals two lobes extending to the spatial limit of our survey, and aligned with the minor axis and with the two shells. These resu ...
... significantly larger than the first, located 1.3◦ north-west from the centre of Fornax, outside the nominal tidal radius. Moreover, the distribution of Fornax RGB stars reveals two lobes extending to the spatial limit of our survey, and aligned with the minor axis and with the two shells. These resu ...
Evolved, single, slowly rotating... but magnetically active
... Its spectral classification of G8 suggests a sufficiently deep outer convection zone for photospheric starspots and their magnetic fields to develop, although a search for optical flares in the Johnson U-band did not reveal any detectable events (Henry & Newsom 1996). The usual interpretation that t ...
... Its spectral classification of G8 suggests a sufficiently deep outer convection zone for photospheric starspots and their magnetic fields to develop, although a search for optical flares in the Johnson U-band did not reveal any detectable events (Henry & Newsom 1996). The usual interpretation that t ...
Rainbows with carbon nanotubes
... (solid lines) radial velocities of S2 star (top), as well as the corresponding O-C residuals (bottom). The left panel shows the results in the case of NTT/VLT observations and Yukawa gravity potential with Λ = 2.59· 103 AU, while the right panel shows the results for NTT/VLT+Keck combined observatio ...
... (solid lines) radial velocities of S2 star (top), as well as the corresponding O-C residuals (bottom). The left panel shows the results in the case of NTT/VLT observations and Yukawa gravity potential with Λ = 2.59· 103 AU, while the right panel shows the results for NTT/VLT+Keck combined observatio ...
Chemical analysis of 24 dusty (pre-) main
... of CNO lines and the non-LTE (local thermodynamic equilibrium) sensitivity of especially nitrogen implies that the uncertainties on the CNO abundances are sometimes critical for assessing whether selective depletion occurs; in all cases at most a few lines are available for the determination of the ...
... of CNO lines and the non-LTE (local thermodynamic equilibrium) sensitivity of especially nitrogen implies that the uncertainties on the CNO abundances are sometimes critical for assessing whether selective depletion occurs; in all cases at most a few lines are available for the determination of the ...
The Local Bubble
... more elusive. First of all, it is more dif• Develop internal structures after ~8(see ficult to localize, as there are most likely no dense clouds inside the LB, which can be used instability for shadowing experiments, thus allowing us to separate back- and foreground emission. • Interacting shells d ...
... more elusive. First of all, it is more dif• Develop internal structures after ~8(see ficult to localize, as there are most likely no dense clouds inside the LB, which can be used instability for shadowing experiments, thus allowing us to separate back- and foreground emission. • Interacting shells d ...
Does feedback help or hinder star formation? The effect of
... Clouds (GMCs). As dense gas cores within these clouds collapse into stars, they begin to emit heat into its surrounding gaseous nursery. This energy will affect the efficiency of the future star formation or may stop it completely if the cloud is dispersed. Such interplay between the parent cloud an ...
... Clouds (GMCs). As dense gas cores within these clouds collapse into stars, they begin to emit heat into its surrounding gaseous nursery. This energy will affect the efficiency of the future star formation or may stop it completely if the cloud is dispersed. Such interplay between the parent cloud an ...
Theoretical Predictions for Mass Loss Rates: Rotation & Pulsation
... • Wind acceleration determined by a combination of magnetic flux-tube geometry, gradual Alfvén-wave reflection, and outward wave pressure. Theoretical Predictions for Mass Loss Rates: Rotation & Pulsation ...
... • Wind acceleration determined by a combination of magnetic flux-tube geometry, gradual Alfvén-wave reflection, and outward wave pressure. Theoretical Predictions for Mass Loss Rates: Rotation & Pulsation ...
The Extragalactic Group of MPE and USM
... of Massive Galaxies in the FORS Deep and GOODS South fields • Study evolution of galaxies with broadband deep U to K surveys. • LFs, Mass Functions, SFRs do not require spectroscopy but can be derived with accurate photometric redshifts. • Advantage of photo z: no color selection bias, fainter lumin ...
... of Massive Galaxies in the FORS Deep and GOODS South fields • Study evolution of galaxies with broadband deep U to K surveys. • LFs, Mass Functions, SFRs do not require spectroscopy but can be derived with accurate photometric redshifts. • Advantage of photo z: no color selection bias, fainter lumin ...
PPT presentation
... • We find lower limits for O and Ne abundances of 4 PNs beyond 2 effective radii from the center of NGC 4697. The lower limits are a bit below, but near solar values. This is much higher than expected from the gradient as measured from the integrated light spectra. • We cannot say much about the abu ...
... • We find lower limits for O and Ne abundances of 4 PNs beyond 2 effective radii from the center of NGC 4697. The lower limits are a bit below, but near solar values. This is much higher than expected from the gradient as measured from the integrated light spectra. • We cannot say much about the abu ...
Kathy Geise `08 - DU Portfolio
... The stellar atmosphere contains the outermost layers of the star and includes the region from which photons escape the star and become visible. Particles in the stellar atmosphere are not completely ionized and the temperature, pressure and density are much lower than in the interior. Stars are so l ...
... The stellar atmosphere contains the outermost layers of the star and includes the region from which photons escape the star and become visible. Particles in the stellar atmosphere are not completely ionized and the temperature, pressure and density are much lower than in the interior. Stars are so l ...
ASTROPHYSICAL PARAMETERS OF LS 2883 AND IMPLICATIONS FOR THE Y egueruela ,
... In the currently preferred scenario, the cold ultrarelativistic wind of the pulsar interacts with the massive star wind within the binary system. Relativistic electrons are accelerated in a shock region where the pressures of both winds balance. These electrons produce synchrotron radiation and upsc ...
... In the currently preferred scenario, the cold ultrarelativistic wind of the pulsar interacts with the massive star wind within the binary system. Relativistic electrons are accelerated in a shock region where the pressures of both winds balance. These electrons produce synchrotron radiation and upsc ...
Tidal interaction of a rotating 1 vec {M_sun} star with a - UvA-DARE
... by the non-resonant dynamical tide. To explain the observed Pcirc would require a viscosity that is '50 times larger than predicted by simple mixing length estimates. Goodman & Dickson (1998), in their WKB treatment of dynamical tides, considered non-linear damping of excited g-modes near the stella ...
... by the non-resonant dynamical tide. To explain the observed Pcirc would require a viscosity that is '50 times larger than predicted by simple mixing length estimates. Goodman & Dickson (1998), in their WKB treatment of dynamical tides, considered non-linear damping of excited g-modes near the stella ...
Cosmological dynamics with non-minimally coupled scalar field and
... predict that the standard Einstein-Hilbert action should be modified. On the other hand it was shown in many cases that studying generalizations of Einstein’s gravity can give us a deeper understanding of general relativity (GR) itself. On the observational front still remain phenomena that do not f ...
... predict that the standard Einstein-Hilbert action should be modified. On the other hand it was shown in many cases that studying generalizations of Einstein’s gravity can give us a deeper understanding of general relativity (GR) itself. On the observational front still remain phenomena that do not f ...
Can Extra Mixing in RGB and AGB Stars Be Attributed to Magnetic
... the convective layer and then emerge forming the corona; photospheric active regions and sunspots are cross sections of bundles of many flux tubes (“spaghetti model”) and are the roots of coronal loops. Magnetic buoyancy is compensated by complex downflows, providing a sort of asymmetric circulation ...
... the convective layer and then emerge forming the corona; photospheric active regions and sunspots are cross sections of bundles of many flux tubes (“spaghetti model”) and are the roots of coronal loops. Magnetic buoyancy is compensated by complex downflows, providing a sort of asymmetric circulation ...
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.