ph709-15
... planet-metallicity correlation at all stellar masses; this argues that the high metallicities of stars with planets is not likely due to convective envelope "pollution." BUT: Neptune-mass planets form preferentially around metal-poor stars, in contrast to stars with giant planets 3) Some planet have ...
... planet-metallicity correlation at all stellar masses; this argues that the high metallicities of stars with planets is not likely due to convective envelope "pollution." BUT: Neptune-mass planets form preferentially around metal-poor stars, in contrast to stars with giant planets 3) Some planet have ...
Massive Star Formation - Max-Planck
... formation of planets around stars in such clusters. Two main classes of massive star formation theory are under active study, Core Accretion and Competitive Accretion. In Core Accretion, the initial conditions are self-gravitating, centrally concentrated cores that condense with a range of masses fr ...
... formation of planets around stars in such clusters. Two main classes of massive star formation theory are under active study, Core Accretion and Competitive Accretion. In Core Accretion, the initial conditions are self-gravitating, centrally concentrated cores that condense with a range of masses fr ...
The destruction and survival of polycyclic aromatic hydrocarbons in
... The observed emission can be explained in models of an irradiated disk (Habart et al. 2004; Visser et al. 2007; Dullemond et al. 2007a). The infrared space observatory (ISO) looked at a few of the much fainter T Tauri stars, but without a clear PAH detection (Siebenmorgen et al. 2000). In the Evans ...
... The observed emission can be explained in models of an irradiated disk (Habart et al. 2004; Visser et al. 2007; Dullemond et al. 2007a). The infrared space observatory (ISO) looked at a few of the much fainter T Tauri stars, but without a clear PAH detection (Siebenmorgen et al. 2000). In the Evans ...
THREE Li-RICH K GIANTS - Indian Institute of Astrophysics
... the spectra by a standard procedure using ATLAS model atmospheres computed using the ‘‘no convective overshoot’’ option (see Robert L. Kurucz’s Web site2). The effective temperature (Teff) was obtained from the requirement that all Fe i lines give the same abundance independent of the lower state’s ...
... the spectra by a standard procedure using ATLAS model atmospheres computed using the ‘‘no convective overshoot’’ option (see Robert L. Kurucz’s Web site2). The effective temperature (Teff) was obtained from the requirement that all Fe i lines give the same abundance independent of the lower state’s ...
L53 He I 1.083 mm EMISSION AND ABSORPTION IN DG TAURI
... contamination from the extended jet and allow us to study the emission-line regions closest to the star. In addition to the target, an A-type bright standard was observed at similar air masses to correct for telluric absorption. The flat fields were made by combining many exposures of the spectrogra ...
... contamination from the extended jet and allow us to study the emission-line regions closest to the star. In addition to the target, an A-type bright standard was observed at similar air masses to correct for telluric absorption. The flat fields were made by combining many exposures of the spectrogra ...
First detection of helium emissions in RR Lyrae⋆
... that a shock wave moving throughout the atmosphere during the rising light of each pulsation cycle can explain the presence of emission lines in the population II Cepheids. The first shock model was proposed by Whitney (1956), but the prediction of the occurrence of He I emission lines was discussed ...
... that a shock wave moving throughout the atmosphere during the rising light of each pulsation cycle can explain the presence of emission lines in the population II Cepheids. The first shock model was proposed by Whitney (1956), but the prediction of the occurrence of He I emission lines was discussed ...
Carbon-enhanced metal-poor stars: a window on AGB
... classify our sample CEMP-s stars in three groups based on the observed abundance of europium. In CEMP−s/r stars the europium-toiron ratio is more than ten times higher than in the Sun, whereas it is lower than this threshold in CEMP−s/nr stars. No measurement of europium is currently available for C ...
... classify our sample CEMP-s stars in three groups based on the observed abundance of europium. In CEMP−s/r stars the europium-toiron ratio is more than ten times higher than in the Sun, whereas it is lower than this threshold in CEMP−s/nr stars. No measurement of europium is currently available for C ...
Kinematic signature of an intermediate
... & Hamilton (2002) presented scenarios for the capture of clusters by their host galaxies and accretion in the galactic disk in order to explain the observed bright X-ray sources. Our goal in this paper is to study the globular cluster NGC 6388. This cluster is located 11.6 kpc away from the Sun, in ...
... & Hamilton (2002) presented scenarios for the capture of clusters by their host galaxies and accretion in the galactic disk in order to explain the observed bright X-ray sources. Our goal in this paper is to study the globular cluster NGC 6388. This cluster is located 11.6 kpc away from the Sun, in ...
Evolutionary and pulsational properties of white dwarf stars
... of relativity and quantum statistical mechanics, which yielded another key breakthrough, i.e., the existence of a limiting mass, where gravitational forces overwhelm degenerate electron pressure, and above which no stable white dwarf can exist. This limiting mass, also known as the Chandrasekhar lim ...
... of relativity and quantum statistical mechanics, which yielded another key breakthrough, i.e., the existence of a limiting mass, where gravitational forces overwhelm degenerate electron pressure, and above which no stable white dwarf can exist. This limiting mass, also known as the Chandrasekhar lim ...
AN INITIAL MASS FUNCTION STUDY OF THE DWARF Please share
... of producing ionizing photons (>15–20 M ) have disappeared. For example, SB99 models using the parameters listed above show that the Hα luminosity at 8 Myr is only 2.5% of LHα at 2 Myr. Therefore, it is necessary to exclude all clusters >8 Myr in order to keep objects in which the H ii region is st ...
... of producing ionizing photons (>15–20 M ) have disappeared. For example, SB99 models using the parameters listed above show that the Hα luminosity at 8 Myr is only 2.5% of LHα at 2 Myr. Therefore, it is necessary to exclude all clusters >8 Myr in order to keep objects in which the H ii region is st ...
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... Despite their co-location in the Hertzsprung-Russell (HR) diagram (cf. Clark et al. 2005b, Aret et al. 2012), it is currently unknown whether sgB[e] stars and luminous blue variables (LBVs) may be physically identified with one another. As their name suggests, LBVs are massive evolved stars that are ...
... Despite their co-location in the Hertzsprung-Russell (HR) diagram (cf. Clark et al. 2005b, Aret et al. 2012), it is currently unknown whether sgB[e] stars and luminous blue variables (LBVs) may be physically identified with one another. As their name suggests, LBVs are massive evolved stars that are ...
grains of
... Micron-sized grains settle in about 105 years at 1 AU, although grains grow during their journey to the midplane => reduce the settling time-scale ...
... Micron-sized grains settle in about 105 years at 1 AU, although grains grow during their journey to the midplane => reduce the settling time-scale ...
chemical compositions of rv tauri stars and related objects
... single stars; in fact, RVa objects are known to have binary companions, e.g., AC Her (see van Winckel et al. 1998) and RU Cen (see Maas, van Winckel, & Waelkens 2002). From a comprehensive study of RV Tauri binaries, van Winckel et al. (1999); Maas et al. (2002) proposed that the RV Tauri photometri ...
... single stars; in fact, RVa objects are known to have binary companions, e.g., AC Her (see van Winckel et al. 1998) and RU Cen (see Maas, van Winckel, & Waelkens 2002). From a comprehensive study of RV Tauri binaries, van Winckel et al. (1999); Maas et al. (2002) proposed that the RV Tauri photometri ...
Star Formation and Dynamics in the Galactic Centre
... The first attempts to estimate the mass enclosed in the central parsec are radial velocity measurements of ionized gas located in the structure which is known as minispiral (Lacy et al. 1980). On the other hand, the radial velocity of ionized gas may be affected by a plethora of processes besides gr ...
... The first attempts to estimate the mass enclosed in the central parsec are radial velocity measurements of ionized gas located in the structure which is known as minispiral (Lacy et al. 1980). On the other hand, the radial velocity of ionized gas may be affected by a plethora of processes besides gr ...
On the absolute age of the globular cluster M71
... used a new approach based on the ColorColor-Magnitude-Diagram (CCMD) shown in the left panel of Fig.1 (Di Cecco et al. in preparation). In particular, we reconstructed a 3D ridgeline in the u0 − g0 , g0 − r0 , r0 CCMD and we considered the candidate cluster stars those located within the ridgeline±2 ...
... used a new approach based on the ColorColor-Magnitude-Diagram (CCMD) shown in the left panel of Fig.1 (Di Cecco et al. in preparation). In particular, we reconstructed a 3D ridgeline in the u0 − g0 , g0 − r0 , r0 CCMD and we considered the candidate cluster stars those located within the ridgeline±2 ...
Nuclear reactions and stellar processes
... The formation of elements heavier than A = 4 takes place inside stars at fairly high densities and temperatures. Such conditions are necessary to allow nuclei to interact and to overcome the Coulomb barrier. The different nucleosynthesis steps [9] are characterized by the subsequent phases of stella ...
... The formation of elements heavier than A = 4 takes place inside stars at fairly high densities and temperatures. Such conditions are necessary to allow nuclei to interact and to overcome the Coulomb barrier. The different nucleosynthesis steps [9] are characterized by the subsequent phases of stella ...
mass and temperature of the twa 7 debris disk
... Two models that are able to fit the observed emission spectrum are shown in Figure 2. In both models the dust has a range of temperatures; however, there are two different physical motivations behind the origin of this range. In model 3 (dotted line of Fig. 2), the dust is assumed to all lie at the ...
... Two models that are able to fit the observed emission spectrum are shown in Figure 2. In both models the dust has a range of temperatures; however, there are two different physical motivations behind the origin of this range. In model 3 (dotted line of Fig. 2), the dust is assumed to all lie at the ...
Master Thesis - Sterrenkunde RU Nijmegen
... iron and nickel. Fusing iron and nickel does not produce any energy, and thus the pressure drops. This causes the star to implode, which release enormous amounts of potential energy, which heats up the outer parts of the star. The star explodes as a supernova and the core either end up as a neutron ...
... iron and nickel. Fusing iron and nickel does not produce any energy, and thus the pressure drops. This causes the star to implode, which release enormous amounts of potential energy, which heats up the outer parts of the star. The star explodes as a supernova and the core either end up as a neutron ...
EXTREMELY EXTENDED DUST SHELLS AROUND EVOLVED
... 8.2 Basic observed parameters (distance, luminosity, pulsation period, mass loss rates and expansion velocities) for six target oxygen-rich intermediatemass stars found in literature that were used in calculations. . . . . . 177 8.3 Target evolved oxygen-rich intermediate-mass stars imaged by Infra ...
... 8.2 Basic observed parameters (distance, luminosity, pulsation period, mass loss rates and expansion velocities) for six target oxygen-rich intermediatemass stars found in literature that were used in calculations. . . . . . 177 8.3 Target evolved oxygen-rich intermediate-mass stars imaged by Infra ...
In Pursuit of the Least Luminous Galaxies
... distribution, and clustering scale of dark matter. What was initially viewed as a problem now provides an opportunity to simultaneously learn about dark matter and galaxy formation physics. Many studies have invoked simple models of galaxy formation within low-mass dark matter halos to successfully ...
... distribution, and clustering scale of dark matter. What was initially viewed as a problem now provides an opportunity to simultaneously learn about dark matter and galaxy formation physics. Many studies have invoked simple models of galaxy formation within low-mass dark matter halos to successfully ...
" Galaxy," Defined
... of galaxy that does not depend on a cold dark matter model of the universe: A galaxy is a gravitationally bound collection of stars whose properties cannot be explained by a combination of baryons and Newton’s laws of gravity. After exploring several possible observational diagnostics of this defini ...
... of galaxy that does not depend on a cold dark matter model of the universe: A galaxy is a gravitationally bound collection of stars whose properties cannot be explained by a combination of baryons and Newton’s laws of gravity. After exploring several possible observational diagnostics of this defini ...
pdf-file - Max-Planck-Institut für Astronomie
... radiation pressure. Thus, the star formation scenario for low- and high-mass stars could in principle be the same (e.g., Keto 2007), suggesting that high-mass star formation could be a scaled-up version of the low-mass star formation process. In this paper, we aim to construct a global model (with t ...
... radiation pressure. Thus, the star formation scenario for low- and high-mass stars could in principle be the same (e.g., Keto 2007), suggesting that high-mass star formation could be a scaled-up version of the low-mass star formation process. In this paper, we aim to construct a global model (with t ...
Physical Properties of Wolf-Rayet Stars
... red supergiants (RSG), according to a comparison between the current temperature calibration of RSG and stellar models that allow for mass loss and rotation (e.g., Levesque et al. 2005). Consequently, some single WR stars are post-red supergiants (RSGs) within a fairly limited mass range of probably ...
... red supergiants (RSG), according to a comparison between the current temperature calibration of RSG and stellar models that allow for mass loss and rotation (e.g., Levesque et al. 2005). Consequently, some single WR stars are post-red supergiants (RSGs) within a fairly limited mass range of probably ...
![arXiv:1210.2471v1 [astro-ph.EP] 9 Oct 2012 Exoplanet Detection](http://s1.studyres.com/store/data/015975823_1-e4b4b3613f38bbff39746aa9bc12073b-300x300.png)
arXiv:1210.2471v1 [astro-ph.EP] 9 Oct 2012 Exoplanet Detection
... Exoplanet detection is essentially the extreme limit of binary star characterization, and so it is unsurprising that the terminology and formalism of planetary orbits derives from that of binaries. Conservation of momentum requires that as a planet orbits a distant star, the star executes a smaller, ...
... Exoplanet detection is essentially the extreme limit of binary star characterization, and so it is unsurprising that the terminology and formalism of planetary orbits derives from that of binaries. Conservation of momentum requires that as a planet orbits a distant star, the star executes a smaller, ...
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.