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Beyond the iron group: Heavy metals in hot subdwarfs
... appear to be unidentified. While analysing our HST/STIS spectra we noticed that the wavelengths of two very strong unmatched lines corresponded very well with the resonance doublet of Ge . The region around the line at 1189.028 Å is shown in Fig. 2 (the other line is at 1229.840 Å). There are no s ...
... appear to be unidentified. While analysing our HST/STIS spectra we noticed that the wavelengths of two very strong unmatched lines corresponded very well with the resonance doublet of Ge . The region around the line at 1189.028 Å is shown in Fig. 2 (the other line is at 1229.840 Å). There are no s ...
The physics of high-mass star formation
... IMF high-mass stars are rare: N(1 MO) = 100 N(10 MO) large distance: >400 pc, typically a few kpc formation in clusters confusion ...
... IMF high-mass stars are rare: N(1 MO) = 100 N(10 MO) large distance: >400 pc, typically a few kpc formation in clusters confusion ...
closed-box model
... the Universe, while all metals (except for a very small fraction of Li) were produced through nucleosynthesis (nuclear burning) in stars. ...
... the Universe, while all metals (except for a very small fraction of Li) were produced through nucleosynthesis (nuclear burning) in stars. ...
The Hα Balmer line as an effective temperature criterion
... of Texas for the northern stars, and at ESO (FEROS spectrograph) for the southern stars. However, owing to instrumental difficulties1 , we removed the southern stars from our program. The Sun and the ten stars of the S4N catalogue with a measured angular diameter of accuracy higher than 2 percent, con ...
... of Texas for the northern stars, and at ESO (FEROS spectrograph) for the southern stars. However, owing to instrumental difficulties1 , we removed the southern stars from our program. The Sun and the ten stars of the S4N catalogue with a measured angular diameter of accuracy higher than 2 percent, con ...
Lectures 6-8: Solar nebula theory
... Step 5: Geometric and gravitational accretion o Objects formed by geometric accretion are called planetesimals: act as seeds for planet formation. o At first, planetesimals were closely packed. o Then coalesced into larger objects, forming clumps few km across in few million years. o Once plane ...
... Step 5: Geometric and gravitational accretion o Objects formed by geometric accretion are called planetesimals: act as seeds for planet formation. o At first, planetesimals were closely packed. o Then coalesced into larger objects, forming clumps few km across in few million years. o Once plane ...
Beyond the iron group: heavy metals in hot subdwarfs
... The analysis of the UV spectra of sdBs is complicated by the large number of absorption lines caused by iron-group elements. The wavelengths of these lines in the Kurucz database in some cases can be quite inaccurate, especially at bluer wavelengths. This can mean that some lines in the spectrum app ...
... The analysis of the UV spectra of sdBs is complicated by the large number of absorption lines caused by iron-group elements. The wavelengths of these lines in the Kurucz database in some cases can be quite inaccurate, especially at bluer wavelengths. This can mean that some lines in the spectrum app ...
Star-Planet Interactions
... and differences with the Sun-planet interactions. In the Solar system, planets are located√in a region where the velocity of the solar wind vw is greater than the local Alfven velocity vA = B/ µρ, where B is the magnetic field in the interplanetary space, µ the permeability of the plasma, and ρ its ...
... and differences with the Sun-planet interactions. In the Solar system, planets are located√in a region where the velocity of the solar wind vw is greater than the local Alfven velocity vA = B/ µρ, where B is the magnetic field in the interplanetary space, µ the permeability of the plasma, and ρ its ...
PDF file - Research in Astronomy and Astrophysics
... HH objects, they originate from optically visible young low mass stars, which apparently suffer very low extinction and are not embedded in opaque molecular cloud cores; (b) probably due to impacts from the strong radiation field encountered, the jets are predominantly one-sided or highly asymmetric ...
... HH objects, they originate from optically visible young low mass stars, which apparently suffer very low extinction and are not embedded in opaque molecular cloud cores; (b) probably due to impacts from the strong radiation field encountered, the jets are predominantly one-sided or highly asymmetric ...
TO THE STATISTICS OF DOUBLE STARS It was indicated by a
... It was indicated by a number of authors, that the study of distribution law of elements of double stars orbits, as well as of other statistical interrelations for these objects, can give interesting results for cosmogony in general and for the age problem of our star system in particular. However, a ...
... It was indicated by a number of authors, that the study of distribution law of elements of double stars orbits, as well as of other statistical interrelations for these objects, can give interesting results for cosmogony in general and for the age problem of our star system in particular. However, a ...
On the origin of stars with and without planets
... et al. (2009), where the authors discussed several possible explanations of the solar “peculiar” abundances when compared to the solar twins. Most of the discussed possible effects (e.g., supernova pollution, early dust separation, etc.) however are not expected to have a dependence on age and can in ...
... et al. (2009), where the authors discussed several possible explanations of the solar “peculiar” abundances when compared to the solar twins. Most of the discussed possible effects (e.g., supernova pollution, early dust separation, etc.) however are not expected to have a dependence on age and can in ...
ASTRONOMY AND ASTROPHYSICS How many low
... = 1.26, Lambert et al. 1980) observed in this spectroscopic binary is another indication that this star did not suffer any extramixing on the RGB. It corresponds to the expected post-dilution Li for a star more massive than 1.7-2M! (see Charbonnel & Vauclair 1992). This is consistent with the observ ...
... = 1.26, Lambert et al. 1980) observed in this spectroscopic binary is another indication that this star did not suffer any extramixing on the RGB. It corresponds to the expected post-dilution Li for a star more massive than 1.7-2M! (see Charbonnel & Vauclair 1992). This is consistent with the observ ...
Astronomy 100—Exam 3
... C. the length and curvature of their spiral arms. D. the time it takes individual stars to orbits the center. E. None of the above —- galaxies don’t rotate. 11. An astronomer now living in another galaxy far away from ours would see A. some of the most distant galaxies coming toward her and some goi ...
... C. the length and curvature of their spiral arms. D. the time it takes individual stars to orbits the center. E. None of the above —- galaxies don’t rotate. 11. An astronomer now living in another galaxy far away from ours would see A. some of the most distant galaxies coming toward her and some goi ...
Stellar Spectroscopy during Exoplanet Transits
... sin i = 1 if the star rotates in same plane as transiting planet Sufficiently similar to Sun for same spectral identifications. Somewhat hotter, lines somewhat weaker, less blending. Large planet: Bloated hot Jupiter, R = 1.38 RJup. More vigorous convection for line differences to be detectable? ...
... sin i = 1 if the star rotates in same plane as transiting planet Sufficiently similar to Sun for same spectral identifications. Somewhat hotter, lines somewhat weaker, less blending. Large planet: Bloated hot Jupiter, R = 1.38 RJup. More vigorous convection for line differences to be detectable? ...
Major Themes of “ The First Stars ”
... But by this time there may also be dust, ionizing radiation, the CMB, cosmic rays, B fields. . so ab initio simulation is too hard. To cut the knot of theory, we need observations! ...
... But by this time there may also be dust, ionizing radiation, the CMB, cosmic rays, B fields. . so ab initio simulation is too hard. To cut the knot of theory, we need observations! ...
Dynamics
... 105 stars, a massive elliptical galaxy contains in excess of 1012 stars. In addition to being much more massive than globular clusters, elliptical galaxies are physically larger too. In fact, a massive elliptical galaxy may have several thousand globular clusters bound to it, with ample space for th ...
... 105 stars, a massive elliptical galaxy contains in excess of 1012 stars. In addition to being much more massive than globular clusters, elliptical galaxies are physically larger too. In fact, a massive elliptical galaxy may have several thousand globular clusters bound to it, with ample space for th ...
Space astrometry 3: Gaia: scientific rationale, principles, and data analysis
... each star are then established by least-squares • the data set is a compromise for projection effects • also requires solving for satellite attitude (gyros, torque models, etc), as well as instrument calibration terms (evolve only slowly with time), and slit ambiguities • also corrected for aberrati ...
... each star are then established by least-squares • the data set is a compromise for projection effects • also requires solving for satellite attitude (gyros, torque models, etc), as well as instrument calibration terms (evolve only slowly with time), and slit ambiguities • also corrected for aberrati ...
NEUTRON STARS AND PULSARS Discovery Were it not for
... theory is needed both because the crust on neutron stars is made of iron and nickel nuclei, and the pressure in the interior is so great that nuclei are torn apart into their individual nucleons. A considerable fraction of the nucleons themselves are likely transformed into other types of particles ...
... theory is needed both because the crust on neutron stars is made of iron and nickel nuclei, and the pressure in the interior is so great that nuclei are torn apart into their individual nucleons. A considerable fraction of the nucleons themselves are likely transformed into other types of particles ...
FP11: DRAKE et al. - Astronomical Institute WWW Homepage
... The ambipolar diffusion of hydrogen which affects much more strongly light ionized particles may enhance significantly the Li abundance and might also enhance the 6Li/7Li isotopic ratio (Babel & Michaud 1991; Babel 1993). Another probable mechanism could be Li production by spallation reactions on t ...
... The ambipolar diffusion of hydrogen which affects much more strongly light ionized particles may enhance significantly the Li abundance and might also enhance the 6Li/7Li isotopic ratio (Babel & Michaud 1991; Babel 1993). Another probable mechanism could be Li production by spallation reactions on t ...
New layout
... Origins of Structure in the Universe, points out CFHT will cease to be a front line observatory around 2005. While Canada has a part of the Gemini telescopes, that by itself is not enough to keep the nation at the forefront of astronomical research. The report can be downloaded from http://www.casca ...
... Origins of Structure in the Universe, points out CFHT will cease to be a front line observatory around 2005. While Canada has a part of the Gemini telescopes, that by itself is not enough to keep the nation at the forefront of astronomical research. The report can be downloaded from http://www.casca ...
Search for giant planets in M67 - III. Excess of hot Jupiters in dense
... frequency of HJs in M67, Hyades, and Praesepe, we may argue that the frequency of HJs depends on stellar metallicity, mass, or on dynamical history, and therefore environment. The dependence of planet frequency on stellar metallicity is complex: even if established very early (Johnson et al. 2010; U ...
... frequency of HJs in M67, Hyades, and Praesepe, we may argue that the frequency of HJs depends on stellar metallicity, mass, or on dynamical history, and therefore environment. The dependence of planet frequency on stellar metallicity is complex: even if established very early (Johnson et al. 2010; U ...
double shell–burning
... carbon in a shell around the carbon core, and hydrogen fuses to helium in a shell around the helium layer. • This double shell–burning stage never reaches equilibrium—fusion rate periodically spikes upward in a series of thermal pulses. • With each spike, convection dredges carbon up from core and t ...
... carbon in a shell around the carbon core, and hydrogen fuses to helium in a shell around the helium layer. • This double shell–burning stage never reaches equilibrium—fusion rate periodically spikes upward in a series of thermal pulses. • With each spike, convection dredges carbon up from core and t ...
11.1 Introduction
... The interstellar medium is a complex environment, worthy of its own lecture course. For our present purposes, suffice to say that among the various components of the ISM, it is the Giant Molecular Clouds that are associated with sites of star formation. Images taken at near-infrared wavelengths (λ ...
... The interstellar medium is a complex environment, worthy of its own lecture course. For our present purposes, suffice to say that among the various components of the ISM, it is the Giant Molecular Clouds that are associated with sites of star formation. Images taken at near-infrared wavelengths (λ ...
Interpretation of the Helix Planetary Nebula using Hydro
... fraction of the 14 hour Leonid stand-down period taking photographs with the full array of HST cameras including the newly installed wide angle Advanced Camera for Surveys (ACS). As the closest PNe to earth with one of the hottest known central white dwarf stars (120,000 K) and close (dMe) X-ray com ...
... fraction of the 14 hour Leonid stand-down period taking photographs with the full array of HST cameras including the newly installed wide angle Advanced Camera for Surveys (ACS). As the closest PNe to earth with one of the hottest known central white dwarf stars (120,000 K) and close (dMe) X-ray com ...
1 From Molecular Clouds to the Origin of Life
... In current scenarios of low mass star formation a protostar with an accretion disk and strong mass outflow is formed after gravitational collapse of a molecular cloud on a time-scale of 104-105 years [33, 34]. In its early evolutionary phases this protostar is still embedded in its placental cloud m ...
... In current scenarios of low mass star formation a protostar with an accretion disk and strong mass outflow is formed after gravitational collapse of a molecular cloud on a time-scale of 104-105 years [33, 34]. In its early evolutionary phases this protostar is still embedded in its placental cloud m ...
Planetary nebula
![](https://commons.wikimedia.org/wiki/Special:FilePath/NGC6543.jpg?width=300)
A planetary nebula, often abbreviated as PN or plural PNe, is a kind of emission nebula consisting of an expanding glowing shell of ionized gas ejected from old red giant stars late in their lives. The word ""nebula"" is Latin for mist or cloud and the term ""planetary nebula"" is a misnomer that originated in the 1780s with astronomer William Herschel because when viewed through his telescope, these objects appeared to him to resemble the rounded shapes of planets. Herschel's name for these objects was popularly adopted and has not been changed. They are a relatively short-lived phenomenon, lasting a few tens of thousands of years, compared to a typical stellar lifetime of several billion years.A mechanism for formation of most planetary nebulae is thought to be the following: at the end of the star's life, during the red giant phase, the outer layers of the star are expelled by strong stellar winds. Eventually, after most of the red giant's atmosphere is dissipated, the exposed hot, luminous core emits ultraviolet radiation to ionize the ejected outer layers of the star. Absorbed ultraviolet light energises the shell of nebulous gas around the central star, appearing as a bright coloured planetary nebula at several discrete visible wavelengths.Planetary nebulae may play a crucial role in the chemical evolution of the Milky Way, returning material to the interstellar medium from stars where elements, the products of nucleosynthesis (such as carbon, nitrogen, oxygen and neon), have been created. Planetary nebulae are also observed in more distant galaxies, yielding useful information about their chemical abundances.In recent years, Hubble Space Telescope images have revealed many planetary nebulae to have extremely complex and varied morphologies. About one-fifth are roughly spherical, but the majority are not spherically symmetric. The mechanisms which produce such a wide variety of shapes and features are not yet well understood, but binary central stars, stellar winds and magnetic fields may play a role.