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 ...
PowerPoint Presentation - 21. Galaxy Evolution
... • What are active galactic nuclei and quasars? • The nature of quasars was once hotly debated. What evidence supports the idea that they are the active galactic nuclei of distant galaxies? • What do we think is the source of power for active galactic nuclei? ...
... • What are active galactic nuclei and quasars? • The nature of quasars was once hotly debated. What evidence supports the idea that they are the active galactic nuclei of distant galaxies? • What do we think is the source of power for active galactic nuclei? ...
JC Beamín1,2, RA Mendez3,2, RL Smart4, R. Jara3, R
... We were able to obtain spectroscopic follow up observations for several tens of sources and the results were discussed in Beamín et al. 2015, Gromadzki et al. 2016, most of them K-M dwarfs. Among our discoveries two of them are particularly interesting an unusually blue L dwarf at 18.6 pc (revised d ...
... We were able to obtain spectroscopic follow up observations for several tens of sources and the results were discussed in Beamín et al. 2015, Gromadzki et al. 2016, most of them K-M dwarfs. Among our discoveries two of them are particularly interesting an unusually blue L dwarf at 18.6 pc (revised d ...
... because the accretion rate in these systems is probably higher than in a DN in quiescence, the likelihood is that the fraction of the K-band light contributed by the secondary is much less than in the quiescent DNe. For example, only 30 per cent of the light comes from the secondary in IX Vel (Haug ...
Behavior of Li abundances in solar-analog stars
... ages/masses were estimated from stellar evolutionary tracks, and the width of the macrobroadening (rotation plus macroturbulence) function as well as Li abundances (ALi ) were established by spectrum-fitting analyses. Results. The resulting ALi vs. T eff relation revealed a characteristic inverse-tri ...
... ages/masses were estimated from stellar evolutionary tracks, and the width of the macrobroadening (rotation plus macroturbulence) function as well as Li abundances (ALi ) were established by spectrum-fitting analyses. Results. The resulting ALi vs. T eff relation revealed a characteristic inverse-tri ...
The effect of helium sedimentation on galaxy cluster masses and
... Context. Recent theoretical studies predict that the inner regions of galaxy clusters may have an enhanced helium abundance due to sedimentation over the cluster lifetime. If sedimentation is not suppressed (e.g., by tangled magnetic fields), this may significantly affect the cluster mass estimates. ...
... Context. Recent theoretical studies predict that the inner regions of galaxy clusters may have an enhanced helium abundance due to sedimentation over the cluster lifetime. If sedimentation is not suppressed (e.g., by tangled magnetic fields), this may significantly affect the cluster mass estimates. ...
Kepler-1647b: The Largest And Longest-Period Kepler
... We report the discovery of a new Kepler transiting circumbinary planet (CBP). This latest addition to the stillsmall family of CBPs defies the current trend of known short-period planets orbiting near the stability limit of binary stars. Unlike the previous discoveries, the planet revolving around th ...
... We report the discovery of a new Kepler transiting circumbinary planet (CBP). This latest addition to the stillsmall family of CBPs defies the current trend of known short-period planets orbiting near the stability limit of binary stars. Unlike the previous discoveries, the planet revolving around th ...
Stars: Intro & Classification Astronomy 1 — Elementary Astronomy LA Mission College
... Star A has an absolute magnitude of -8.1 and belongs to spectral class B8. Star B has an absolute magnitude of 11.2 and also belongs to spectral class B8. Which star has the higher temperature? ...
... Star A has an absolute magnitude of -8.1 and belongs to spectral class B8. Star B has an absolute magnitude of 11.2 and also belongs to spectral class B8. Which star has the higher temperature? ...
Radial Velocity - Yale Exoplanet
... an important limitation of the RV technique for individual to the observer, k is the unit vector pointing from the obsystems, this fact does not have a large impact on statisti- server to the source in the rest frame of the observer, and c cal studies of exoplanet populations. Because inclination is ...
... an important limitation of the RV technique for individual to the observer, k is the unit vector pointing from the obsystems, this fact does not have a large impact on statisti- server to the source in the rest frame of the observer, and c cal studies of exoplanet populations. Because inclination is ...
Gaia - STScI
... Bright stars will give rigid tie between LSST and Gaia. Faint stars (down to 26th and beyond) will deliver the new science. Gaia has 2 fields of regard in same focal plane. At some star density, confusion will degrade accuracy. LSST has bigger images but a single field of regard. LSST can do differe ...
... Bright stars will give rigid tie between LSST and Gaia. Faint stars (down to 26th and beyond) will deliver the new science. Gaia has 2 fields of regard in same focal plane. At some star density, confusion will degrade accuracy. LSST has bigger images but a single field of regard. LSST can do differe ...
The Magic of Star Dust - Exploring Exotic Nuclei
... with a big bang that created a soup of objects, among which were the massive ones called nucleons. The soup contained both positively charged nucleons called ‘protons’ and electrically neutral ones called ‘neutrons’. As the universe cooled and expanded the hadrons coalesced together to form more com ...
... with a big bang that created a soup of objects, among which were the massive ones called nucleons. The soup contained both positively charged nucleons called ‘protons’ and electrically neutral ones called ‘neutrons’. As the universe cooled and expanded the hadrons coalesced together to form more com ...
Unravelling the Origin and Evolution of Our Galaxy
... Earth). The systems have some surprising properties: two thirds of these giant planets are orbiting their host stars much closer than Mercury orbits the Sun (0.39 astronomical units), some having periods as short as 3 days. More than one third have significantly elliptical orbits, with e > 0.3, comp ...
... Earth). The systems have some surprising properties: two thirds of these giant planets are orbiting their host stars much closer than Mercury orbits the Sun (0.39 astronomical units), some having periods as short as 3 days. More than one third have significantly elliptical orbits, with e > 0.3, comp ...
Radio emissions from terrestrial planets around white dwarfs
... tends to mildly overestimate the density, and therefore the drag, in comparison to the Soker (1992) model, particularly during the last pulses and collapse to a proto-white dwarf. We note here that the approximate expression for the density profile (Eq. (12) in Soker & Livio 1994), used in this cont ...
... tends to mildly overestimate the density, and therefore the drag, in comparison to the Soker (1992) model, particularly during the last pulses and collapse to a proto-white dwarf. We note here that the approximate expression for the density profile (Eq. (12) in Soker & Livio 1994), used in this cont ...
Moving Beyond Chi-Squared in Nuclei and Neutron Stars
... can be checked and verified by comparing to data. In the case of nuclear mass fitting described above, the likelihood function is a product of Nd Gaussian probability distributions for each data point. The neutron star case is handled similarly (c.f. Eq. 31 in Ref. [3]): the likelihood function is a ...
... can be checked and verified by comparing to data. In the case of nuclear mass fitting described above, the likelihood function is a product of Nd Gaussian probability distributions for each data point. The neutron star case is handled similarly (c.f. Eq. 31 in Ref. [3]): the likelihood function is a ...
hal.archives-ouvertes.fr - HAL-ENS
... MHz). This artefact, usually called “specular reflection”, is exactly removed when using the position-switch mode of observation, whereas, in the frequency-switch mode, it can be kept down to 0.15 K by selecting an offset equal to a multiple of 536 kHz. In principle, there is no stray radiation for ...
... MHz). This artefact, usually called “specular reflection”, is exactly removed when using the position-switch mode of observation, whereas, in the frequency-switch mode, it can be kept down to 0.15 K by selecting an offset equal to a multiple of 536 kHz. In principle, there is no stray radiation for ...
ASTR 330: The Solar System Dr Conor Nixon Fall 2006
... become a star? • A true star is at least 70 Jupiter Masses (MJ). This is the minimum mass required to compress the core sufficiently to ignite true hydrogen fusion, the chain of adding protons together to make helium, which powers stars. • However, between 13 and 70 MJ, an object can fuse deuterium ...
... become a star? • A true star is at least 70 Jupiter Masses (MJ). This is the minimum mass required to compress the core sufficiently to ignite true hydrogen fusion, the chain of adding protons together to make helium, which powers stars. • However, between 13 and 70 MJ, an object can fuse deuterium ...
Highligh in Physics 2005
... FU Orionis objects are a small class of young stellar objects undergoing periods of enhanced disk accretion activity (outbursts). While T Tauri stars usually have rather low accretion rates (of the order of 10-8 M/yr), during the outburst the accretion rate can reach a few times 10-4 M/yr. Even if ...
... FU Orionis objects are a small class of young stellar objects undergoing periods of enhanced disk accretion activity (outbursts). While T Tauri stars usually have rather low accretion rates (of the order of 10-8 M/yr), during the outburst the accretion rate can reach a few times 10-4 M/yr. Even if ...
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.