Nuclear astrophysics: the unfinished quest for the origin of the
... technetium isotopes have rather short half-lives on a Galactic time scale, the obvious conclusion was that technetium must have been produced in the observed stars and thus nucleosynthesis must still be going on in the Universe. Shortly after, two seminal papers that provided the theoretical framewo ...
... technetium isotopes have rather short half-lives on a Galactic time scale, the obvious conclusion was that technetium must have been produced in the observed stars and thus nucleosynthesis must still be going on in the Universe. Shortly after, two seminal papers that provided the theoretical framewo ...
IR-excesses around nearby Lambda Boo stars are caused by debris
... found around stars of ∼1 Gyr in age, subgiants, and even white dwarfs (Bonsor et al. 2014a; Matthews et al. 2014b). If the mechanism were internal, A stars would need to have a very specific criteria for initiating and ceasing a Lambda Boo-like phase, independent of age and stellar evolution. In ord ...
... found around stars of ∼1 Gyr in age, subgiants, and even white dwarfs (Bonsor et al. 2014a; Matthews et al. 2014b). If the mechanism were internal, A stars would need to have a very specific criteria for initiating and ceasing a Lambda Boo-like phase, independent of age and stellar evolution. In ord ...
properties and evolution of disks around pre-main
... all stars of spectral type approximately in the range A–B that lie on PMS evolutionary tracks in the HR diagram. This criterion is applied very loosely to stars earlier than about B2, which remain on the zero-age main sequence (ZAMS) only for a very short time. The current sample includes stars of m ...
... all stars of spectral type approximately in the range A–B that lie on PMS evolutionary tracks in the HR diagram. This criterion is applied very loosely to stars earlier than about B2, which remain on the zero-age main sequence (ZAMS) only for a very short time. The current sample includes stars of m ...
Interpretation of the Helix Planetary Nebula using Hydro
... by factors ≈ ×6 − 10. Because stars form from planets, the first stars must be small and early. Large ≥ 2M population III stars forming from 106 M Jeans mass gas clouds in CDM halos never happened and neither did re-ionization of the gas-epoch back to a second plasmaepoch. CDM halos never happened ...
... by factors ≈ ×6 − 10. Because stars form from planets, the first stars must be small and early. Large ≥ 2M population III stars forming from 106 M Jeans mass gas clouds in CDM halos never happened and neither did re-ionization of the gas-epoch back to a second plasmaepoch. CDM halos never happened ...
Blue horizontal branch stars in the Sloan Digital Sky Survey:
... plates used herein that were subsequently identified as stars by Brightstars, which is accurate enough that quasars and galaxies are virtually nonexistent in the sample. (Throughout this paper all magnitudes are corrected for Galactic extinction using the maps of Schlegel, Finkbeiner, & Davis (1998) ...
... plates used herein that were subsequently identified as stars by Brightstars, which is accurate enough that quasars and galaxies are virtually nonexistent in the sample. (Throughout this paper all magnitudes are corrected for Galactic extinction using the maps of Schlegel, Finkbeiner, & Davis (1998) ...
STELLAR STRUCTURE AND EVOLUTION
... luminosity and a colour index (B − V or V − I) as a measure for the effective temperature. It is left as an exercise to identify various types of stars and evolution phases in this HRD, such as the main sequence, red giants, the horizontal branch, white dwarfs, etc. Star clusters provide an even cle ...
... luminosity and a colour index (B − V or V − I) as a measure for the effective temperature. It is left as an exercise to identify various types of stars and evolution phases in this HRD, such as the main sequence, red giants, the horizontal branch, white dwarfs, etc. Star clusters provide an even cle ...
Chapter 2 Mass Transfer in Binary Systems
... For stars with deep surface convective zones (lying on or near the giant branch, or on the lower main sequence), and degenerate stars, the variation of the radius of a star with deep convective envelope depends on its mass as R M. If mass is lost, the star expands, and cannot maintain within it ...
... For stars with deep surface convective zones (lying on or near the giant branch, or on the lower main sequence), and degenerate stars, the variation of the radius of a star with deep convective envelope depends on its mass as R M. If mass is lost, the star expands, and cannot maintain within it ...
the discovery of a massive cluster of red supergiants with glimpse
... high-mass stars), and the duration of the star formation burst that produced the cluster, in that the stars must have formed in a relatively short period to have reached the same evolved state simultaneously. Figer et al. (2006) and Davies et al. (2007) use an evolved initial mass function (IMF) to ...
... high-mass stars), and the duration of the star formation burst that produced the cluster, in that the stars must have formed in a relatively short period to have reached the same evolved state simultaneously. Figer et al. (2006) and Davies et al. (2007) use an evolved initial mass function (IMF) to ...
Constraining planet structure from stellar chemistry: the cases of
... Methods. We use high resolution spectra to derive stellar parameters and chemical abundances for Fe, Si, Mg, O, and C in three stars hosting low mass, rocky planets: CoRoT-7, Kepler-10, and Kepler-93. These planets follow the same line along the mass-radius diagram, pointing toward a similar composi ...
... Methods. We use high resolution spectra to derive stellar parameters and chemical abundances for Fe, Si, Mg, O, and C in three stars hosting low mass, rocky planets: CoRoT-7, Kepler-10, and Kepler-93. These planets follow the same line along the mass-radius diagram, pointing toward a similar composi ...
Stellar Evolution - Astrophysics
... these scaling relations relating them to L, M and R are therefore extremely important. Teff is the most important parameter which is immediately apparent from an inspection of stellar energy distributions or spectra; it determines (roughly) the wavelength at which the maximum flux density occurs and ...
... these scaling relations relating them to L, M and R are therefore extremely important. Teff is the most important parameter which is immediately apparent from an inspection of stellar energy distributions or spectra; it determines (roughly) the wavelength at which the maximum flux density occurs and ...
The Massive Star Population of Cygnus OB2
... The Massive Star Population of Cygnus OB2 Wright et al. (2010b) found the lower-mass IMF to be in agreement with the Salpeter value. Work over the past decade has assembled the data needed to form a much fuller view of the OB population in Cyg OB2, thanks to a combination of new spectroscopic surve ...
... The Massive Star Population of Cygnus OB2 Wright et al. (2010b) found the lower-mass IMF to be in agreement with the Salpeter value. Work over the past decade has assembled the data needed to form a much fuller view of the OB population in Cyg OB2, thanks to a combination of new spectroscopic surve ...
Maximum Mass Restraint of Neutron Stars
... question is if these superfluids have unique EOS and if the interactions between lower layers of the star via these vortex properties are significant enough to take into account when determining the overall EOS. Most papers on the topic agree that it would not affect neutron star mass significantly ...
... question is if these superfluids have unique EOS and if the interactions between lower layers of the star via these vortex properties are significant enough to take into account when determining the overall EOS. Most papers on the topic agree that it would not affect neutron star mass significantly ...
Variability in the CoRoT photometry of three hot O
... Fig. 2. Detrended CoRoT light curves, covering the full 34.3 days of the observing run. Each observation is represented by a dot. Flagged data are not plotted. Top: HD 46223, middle: HD 46150, bottom: HD 46966. As a further test, we also redo the analysis on the observed data after rebinning over a ...
... Fig. 2. Detrended CoRoT light curves, covering the full 34.3 days of the observing run. Each observation is represented by a dot. Flagged data are not plotted. Top: HD 46223, middle: HD 46150, bottom: HD 46966. As a further test, we also redo the analysis on the observed data after rebinning over a ...
The mass, temperature and distance of the white dwarf in V 471 Tauri
... system has been the origin of the 555-s X-ray pulsations discovered by EXOSATobservations (Jensen et al. 1986) and subsequently also observed at optical wavelengths, but with much lower amplitude, by Robinson, Clemens & Hine (1988) (9.7 x 10-4 cf. =0.2: see Jensen et al.). Two alternative explanatio ...
... system has been the origin of the 555-s X-ray pulsations discovered by EXOSATobservations (Jensen et al. 1986) and subsequently also observed at optical wavelengths, but with much lower amplitude, by Robinson, Clemens & Hine (1988) (9.7 x 10-4 cf. =0.2: see Jensen et al.). Two alternative explanatio ...
Core-Halo Age Gradients and Star Formation in the Orion Nebula
... While considerable insights have been gained regarding the formation of stars on small scales, the formation of rich stellar clusters dominated by OB stars is quite uncertain. Debate has waged for decades over the relative importance of rapid ‘top-down’ fragmentation or a slower ‘bottom-up’ process ...
... While considerable insights have been gained regarding the formation of stars on small scales, the formation of rich stellar clusters dominated by OB stars is quite uncertain. Debate has waged for decades over the relative importance of rapid ‘top-down’ fragmentation or a slower ‘bottom-up’ process ...
Z - STScI
... Late time tail powered by radioactive 56Ni 56Ni explosively created from Si burning after corecollapse Direct probe of the explosion How Is it related to progenitor mass ? ...
... Late time tail powered by radioactive 56Ni 56Ni explosively created from Si burning after corecollapse Direct probe of the explosion How Is it related to progenitor mass ? ...
Galactic components Structure and kinematics
... These measure directly the bulk of the objects which constitute the target populations (e.g. dwarfs of the galactic Pop.I and Pop.II). These should guarantee “unbiased” results if systematic effects due to the magnitude threshold, photometric accuracy, angular resolution, etc. are properly taken int ...
... These measure directly the bulk of the objects which constitute the target populations (e.g. dwarfs of the galactic Pop.I and Pop.II). These should guarantee “unbiased” results if systematic effects due to the magnitude threshold, photometric accuracy, angular resolution, etc. are properly taken int ...
The MGC - St Andrews Astronomy Group
... • Morphology represents a new research avenue • Elliptical counts could constrain Lambda, if other errors are minimal • Lambda-evolution degeneracy broken via redshifts distributions • With a revised local sample and N(z)s for HST samples ...
... • Morphology represents a new research avenue • Elliptical counts could constrain Lambda, if other errors are minimal • Lambda-evolution degeneracy broken via redshifts distributions • With a revised local sample and N(z)s for HST samples ...
Chapter: The Evolution of Binary Systems
... the donor star has either been transferred to the companion or been lost from the system. The end product will be a hydrogen-exhausted helium star with at most a small hydrogen-rich envelope.3 Mass accretion will also change the structure of the accreting star. If it is still on the main sequence, t ...
... the donor star has either been transferred to the companion or been lost from the system. The end product will be a hydrogen-exhausted helium star with at most a small hydrogen-rich envelope.3 Mass accretion will also change the structure of the accreting star. If it is still on the main sequence, t ...
Star Formation Legacy of the Hubble Space Telescope Outline of Talk
... Currently known disks are relatively distant − Handful at d < 20 pc (Fomalhaut, AU Mic, beta Pic) − other nearby stars TW Hya association (65 pc) − nearest star formation regions (100 - 150 pc) ...
... Currently known disks are relatively distant − Handful at d < 20 pc (Fomalhaut, AU Mic, beta Pic) − other nearby stars TW Hya association (65 pc) − nearest star formation regions (100 - 150 pc) ...
The Science case for the UV and optical cameras
... • The steepness of the AGN luminosity function indicates that most accreting black holes are associated to the least active galaxies. • Theoretical models of low luminosity AGNs can be tested by looking for the characteristic feature of standard disks, i.e. the socalled UV bump. Role of WSO/UV: • De ...
... • The steepness of the AGN luminosity function indicates that most accreting black holes are associated to the least active galaxies. • Theoretical models of low luminosity AGNs can be tested by looking for the characteristic feature of standard disks, i.e. the socalled UV bump. Role of WSO/UV: • De ...
Infrared colours, distance determination and absolute magnitudes of
... of the main sequence, consistent with moderate (",20 per cent) contamination of the secondary light by an accretion disc. We use the K magnitudes to estimate the distances of the stars. We show that most lie within about 400 pc, and only two of the stars in our sample (RU LMi and DO Leo) are convinc ...
... of the main sequence, consistent with moderate (",20 per cent) contamination of the secondary light by an accretion disc. We use the K magnitudes to estimate the distances of the stars. We show that most lie within about 400 pc, and only two of the stars in our sample (RU LMi and DO Leo) are convinc ...
Determining the Stellar Spin Axis Orientation
... telescope. Since each slit orientation delivers only one-dimensional content along that orientation, it is necessary to probe several slit orientations on sky to unravel the full spatial information. Finally, it is common to probe anti-parallel slit orientations. By doing so, instrumental artefacts ...
... telescope. Since each slit orientation delivers only one-dimensional content along that orientation, it is necessary to probe several slit orientations on sky to unravel the full spatial information. Finally, it is common to probe anti-parallel slit orientations. By doing so, instrumental artefacts ...
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.