Clusters - El Camino College
... Way galaxy as loners, each in their own orbit (like our Sun is). Since open clusters don't contain a lot of stars, they become inconspicuous at distances beyond about a thousand light-years. Most of the naked-eye stars in the Big Dipper are actually part of an open cluster! Open clusters usually app ...
... Way galaxy as loners, each in their own orbit (like our Sun is). Since open clusters don't contain a lot of stars, they become inconspicuous at distances beyond about a thousand light-years. Most of the naked-eye stars in the Big Dipper are actually part of an open cluster! Open clusters usually app ...
this article
... IR-bright. During this SW stage, intense mass loss depletes the remaining hydrogen in the star’s outer envelope, and terminates the AGB phase. The rapid depletion of material from the outer envelope of the star means that while AGB mass loss may last for > 105 yrs, this extremely high mass-loss SW p ...
... IR-bright. During this SW stage, intense mass loss depletes the remaining hydrogen in the star’s outer envelope, and terminates the AGB phase. The rapid depletion of material from the outer envelope of the star means that while AGB mass loss may last for > 105 yrs, this extremely high mass-loss SW p ...
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... • An alternative to searching for galaxies by their emission properties is to search for them by their absorption ...
... • An alternative to searching for galaxies by their emission properties is to search for them by their absorption ...
Lecture 8
... (except black holes), the MACHOs are usually thought of as ordinary substellar objects, such as brown dwarfs or “jupiters”. Ordinary stars can of course also cause a microlensing event, but then we would also see this star. Here we are interested in events where we do not observe light, or any other ...
... (except black holes), the MACHOs are usually thought of as ordinary substellar objects, such as brown dwarfs or “jupiters”. Ordinary stars can of course also cause a microlensing event, but then we would also see this star. Here we are interested in events where we do not observe light, or any other ...
The Galaxy Luminosity Function
... In a cluster, Vs is the same for all L, so ns & φs have the same shape. However, if the sample is apparent magnitude limited, then Vs ↓ as L ↓. (Schechter 1976) ...
... In a cluster, Vs is the same for all L, so ns & φs have the same shape. However, if the sample is apparent magnitude limited, then Vs ↓ as L ↓. (Schechter 1976) ...
Neutron stars - Institut de Physique Nucleaire de Lyon
... The effect of the atmosphere and its partial ionization on the spectrum of thermal radiation of a neutron star with B=1013 G, T= 106 K (the field is normal to the surface, the radiation flux is angle-averaged) ...
... The effect of the atmosphere and its partial ionization on the spectrum of thermal radiation of a neutron star with B=1013 G, T= 106 K (the field is normal to the surface, the radiation flux is angle-averaged) ...
Self-similarity in the chemical evolution of galaxies and the delay
... to actually separate the properties of the old and intermediate age stars on a per galaxy basis. Typical errorbars (precision) on age are 0.2 Gyr and 0.01 dex on [Fe/H] and [α/Fe]1 . The definition of the α-element abundances groups together the elements O, Ne, Mg, Si, S, Ca and Ti (Coelho et al. 20 ...
... to actually separate the properties of the old and intermediate age stars on a per galaxy basis. Typical errorbars (precision) on age are 0.2 Gyr and 0.01 dex on [Fe/H] and [α/Fe]1 . The definition of the α-element abundances groups together the elements O, Ne, Mg, Si, S, Ca and Ti (Coelho et al. 20 ...
(r) and
... However, in most systems, two integrals are not sufficient to fully characterize the stellar orbits. In fact, numerical calculations show that most orbits are not completely described by just two integrals, i.e. they admit a third integral. There is no general expression for this integral of motio ...
... However, in most systems, two integrals are not sufficient to fully characterize the stellar orbits. In fact, numerical calculations show that most orbits are not completely described by just two integrals, i.e. they admit a third integral. There is no general expression for this integral of motio ...
Formation of Massive Stars
... • Massive stars are expected to modify their environment soon after a stellar core has formed since their Kelvin-Helmholtz time scale (< 104 yrs for an O star) is short ( tKH = E/L ~ GM2/LR) (Shu et al. 1987 AARA 25 23) ...
... • Massive stars are expected to modify their environment soon after a stellar core has formed since their Kelvin-Helmholtz time scale (< 104 yrs for an O star) is short ( tKH = E/L ~ GM2/LR) (Shu et al. 1987 AARA 25 23) ...
Stellar Spectroscopy during Exoplanet Transits
... Challenge of extremely high S/N * Retrieving good spectra from behind exoplanet covering 1% of star, requires S/N 10,000 !! ...
... Challenge of extremely high S/N * Retrieving good spectra from behind exoplanet covering 1% of star, requires S/N 10,000 !! ...
a kiloparsec-scale nuclear stellar disk in the milky way
... fields in the mid-plane and off-plane at ∣ b ∣ = 2 (totalling 617 and 1114 stars, respectively). Table 1 lists the fields stacked together and the number of stars used from each field. Figure 2 plots these two stacked APOGEE LOSVDs. The mid-plane stack has a clear second peak at VGSR ~ 220 km s-1, cor ...
... fields in the mid-plane and off-plane at ∣ b ∣ = 2 (totalling 617 and 1114 stars, respectively). Table 1 lists the fields stacked together and the number of stars used from each field. Figure 2 plots these two stacked APOGEE LOSVDs. The mid-plane stack has a clear second peak at VGSR ~ 220 km s-1, cor ...
Reconstructing the evolution of double helium white dwarfs
... white dwarf can be calculated from the core-mass – radius relation given by Iben & Tutukov (1985): R ≈ 103.5 Mc4 ...
... white dwarf can be calculated from the core-mass – radius relation given by Iben & Tutukov (1985): R ≈ 103.5 Mc4 ...
Role of column density in the formation of stars
... formation is determined. For example, in a galaxy such as the Milky Way, the threshold gas surface density occurs at a radius of about 25 kpc, where dark matter is dominant and the gas and dark matter are not strongly radially segregated. A baryon-to-dark-matter ratio equal to the cosmic value of 1/ ...
... formation is determined. For example, in a galaxy such as the Milky Way, the threshold gas surface density occurs at a radius of about 25 kpc, where dark matter is dominant and the gas and dark matter are not strongly radially segregated. A baryon-to-dark-matter ratio equal to the cosmic value of 1/ ...
– 1 – 1. Feedback From The First Stars
... star formation will be halted. Evidence for large scale outflows (“galactic winds”) in local group starbursting dwarfs has been detected through extended soft X-ray emission and imaging diffuse emission in Hα; see, e.g. Properties of Galactic Outflows: Measurements of theFeedback from Star Formation ...
... star formation will be halted. Evidence for large scale outflows (“galactic winds”) in local group starbursting dwarfs has been detected through extended soft X-ray emission and imaging diffuse emission in Hα; see, e.g. Properties of Galactic Outflows: Measurements of theFeedback from Star Formation ...
Dark Matter Concept Questions
... 4. In rural Minnesota, U.S.A., there is a dark matter detector known as the Cryogenic Dark Matter Search (CDMS) located 700 m underground in an abandoned mine. It involves a number of 250 g crystals of germanium (Ge) that are cooled down to just above absolute zero (–273o C). According to the weakly ...
... 4. In rural Minnesota, U.S.A., there is a dark matter detector known as the Cryogenic Dark Matter Search (CDMS) located 700 m underground in an abandoned mine. It involves a number of 250 g crystals of germanium (Ge) that are cooled down to just above absolute zero (–273o C). According to the weakly ...
The binary fraction of the young cluster NGC 1818 in the Large
... means of an artificial-star-test technique, which allows us to estimate the binary fractions in crowded environments. By studying the morphology of their color-magnitude diagrams (CMDs), Romani & Weinberg (1991) determined the observed binary fractions in M92 and M30 at . 9 and . 4%, respectively, f ...
... means of an artificial-star-test technique, which allows us to estimate the binary fractions in crowded environments. By studying the morphology of their color-magnitude diagrams (CMDs), Romani & Weinberg (1991) determined the observed binary fractions in M92 and M30 at . 9 and . 4%, respectively, f ...
SearchCal: a Virtual Observatory tool for searching - HAL-Insu
... the measurement of the visibility amplitudes. Equation 3 shows that the expected accuracy on the target visibility strongly depends on the accuracy of the calibrator visibility. A calibrator is a star for which the visibility is known (or can be predicted) with high accuracy. It should have physical ...
... the measurement of the visibility amplitudes. Equation 3 shows that the expected accuracy on the target visibility strongly depends on the accuracy of the calibrator visibility. A calibrator is a star for which the visibility is known (or can be predicted) with high accuracy. It should have physical ...
CNO and F abundances in the barium star HD 123396
... the low eccentricities arise from tidal circularization (Boffin & Jorissen 1988; Han et al. 1995; Karakas et al. 2000; Izzard et al. 2010). In this context, CNO elements, along with s-process elements, are key tracers of the nucleosynthesis in the previous AGB progenitor, so they provide crucial const ...
... the low eccentricities arise from tidal circularization (Boffin & Jorissen 1988; Han et al. 1995; Karakas et al. 2000; Izzard et al. 2010). In this context, CNO elements, along with s-process elements, are key tracers of the nucleosynthesis in the previous AGB progenitor, so they provide crucial const ...
An Atlas of Stellar Spectra
... of a group of stars of the same spectral type and luminosity class can be determined with great precision, even when the group consists of a relatively small number of stars. Even for individual stars distances of good accuracy can be derived. A corresponding gain is made in problems concerned with ...
... of a group of stars of the same spectral type and luminosity class can be determined with great precision, even when the group consists of a relatively small number of stars. Even for individual stars distances of good accuracy can be derived. A corresponding gain is made in problems concerned with ...
contributed talk in splinter session
... the field lines that connect beyond the co-rotation radius and provide the spin down torque will be opened up by the shearing effect of the Keplerian velocity of the disk, and so will be unable to exert a torque on the star. The X-wind model solves the angular momentum problem by launching a wind fr ...
... the field lines that connect beyond the co-rotation radius and provide the spin down torque will be opened up by the shearing effect of the Keplerian velocity of the disk, and so will be unable to exert a torque on the star. The X-wind model solves the angular momentum problem by launching a wind fr ...
![The P Cygni supergiant [OMN2000] LS1](http://s1.studyres.com/store/data/014882705_1-5f78b60dc5267f0c5ad35fc8d810ae0e-300x300.png)
The P Cygni supergiant [OMN2000] LS1
... and high wind density causes He ii to recombine to He i very close to the photosphere. In such a situation any He/H ratio may fit the observations with an appropiate scaling of the mass loss rate and a small variation of the stellar temperature; this effect is observed in e.g. HD316285 (see Hillier ...
... and high wind density causes He ii to recombine to He i very close to the photosphere. In such a situation any He/H ratio may fit the observations with an appropiate scaling of the mass loss rate and a small variation of the stellar temperature; this effect is observed in e.g. HD316285 (see Hillier ...
The Milky Way Galaxy
... The Shapley–Curtis debate was the first major public discussion between astronomers as to whether the Milky Way contains all the stars in the universe. Cepheid variable stars are important in determining the distance to other galaxies. Edwin Hubble proved that there are other galaxies far outside of ...
... The Shapley–Curtis debate was the first major public discussion between astronomers as to whether the Milky Way contains all the stars in the universe. Cepheid variable stars are important in determining the distance to other galaxies. Edwin Hubble proved that there are other galaxies far outside of ...
6. Stellar Spectra
... Singly ionized helium lines either in emission or absorption. Strong ultraviolet continuum. He I 4471/He II 4541 increases with type. H and He lines weaken with increasing luminosity. H weak, He I, He II, C III, N III, O III, Si IV. Neutral helium lines in absorption (max at B2). H lines increase wi ...
... Singly ionized helium lines either in emission or absorption. Strong ultraviolet continuum. He I 4471/He II 4541 increases with type. H and He lines weaken with increasing luminosity. H weak, He I, He II, C III, N III, O III, Si IV. Neutral helium lines in absorption (max at B2). H lines increase wi ...
High Energy Phenomena in Supergiant X-ray Binaries - HAL-Insu
... circumstellar medium, by fitting their spectral energy distribution (SED). The main results of this study are that 15 of these IGRs are identified as HMXBs, and among them 12 HMXBs contain massive and luminous early-type companion stars. By combining optical, NIR and MIR photometry, and fitting thei ...
... circumstellar medium, by fitting their spectral energy distribution (SED). The main results of this study are that 15 of these IGRs are identified as HMXBs, and among them 12 HMXBs contain massive and luminous early-type companion stars. By combining optical, NIR and MIR photometry, and fitting thei ...
KELT-7b: A HOT JUPITER TRANSITING A BRIGHT V = 8.54
... radius, the depths of planetary transits of hotter stars are shallower. This is exacerbated by the fact that stars with Teff > 6250 K have lifetimes that are of order the age of the Galactic disk, and thus tend to be significantly evolved. However, there a number of ways in which these challenges are ...
... radius, the depths of planetary transits of hotter stars are shallower. This is exacerbated by the fact that stars with Teff > 6250 K have lifetimes that are of order the age of the Galactic disk, and thus tend to be significantly evolved. However, there a number of ways in which these challenges are ...
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.