Modelling the Ultra-Faint Dwarf Galaxies and Tidal
... Before(A), while (B) Both models show high velocity dispersion after dissolution [c] C:&no density enhancement, low , C Mean vrad is patchy with gradient (B) vs. constant within object (D) gradient in vrad D ...
... Before(A), while (B) Both models show high velocity dispersion after dissolution [c] C:&no density enhancement, low , C Mean vrad is patchy with gradient (B) vs. constant within object (D) gradient in vrad D ...
A Very Dense Low-Mass Molecular Condensation in Taurus
... spectra with a larger line width. Therefore, this wing is probably due to outflow. The asymmetry of the wing is also consistent with this. As discussed above, MC 27 is unique among the starless condensations in Taurus. Especially, it has the largest density of ~ 106 c m - 3 , significantly higher th ...
... spectra with a larger line width. Therefore, this wing is probably due to outflow. The asymmetry of the wing is also consistent with this. As discussed above, MC 27 is unique among the starless condensations in Taurus. Especially, it has the largest density of ~ 106 c m - 3 , significantly higher th ...
masses of star clusters in the nuclei of bulgeless spiral galaxies
... not covered by our data. However, we also investigated two other regions of the observed spectrum, namely 6385–6525 and 4380–4800 8, which are also free of telluric lines and do have other metal lines. The measured velocity dispersions agree to within 15% for those clusters where the S/N of the meta ...
... not covered by our data. However, we also investigated two other regions of the observed spectrum, namely 6385–6525 and 4380–4800 8, which are also free of telluric lines and do have other metal lines. The measured velocity dispersions agree to within 15% for those clusters where the S/N of the meta ...
a fresh catch of massive binaries in the cygnus ob2 association
... the Spitzer 4.5 μm, and the Spitzer 8.0 μm bands, respectively. White labels denote previously known binary systems, while magenta labels highlight the newly discovered systems reported herein. Numeration follows the system of Massey & Thompson (1991), with “S” additionally indicating the numeration ...
... the Spitzer 4.5 μm, and the Spitzer 8.0 μm bands, respectively. White labels denote previously known binary systems, while magenta labels highlight the newly discovered systems reported herein. Numeration follows the system of Massey & Thompson (1991), with “S” additionally indicating the numeration ...
The role of tidal interactions in star formation
... 2001). Even in the context of standard accretion disc models, a binary companion may play an important role by limiting the growth in radius of the disc and thus preventing the accretion time from becoming too long (Calvet et al. 2000); in this case most of the angular momentum of the system must go ...
... 2001). Even in the context of standard accretion disc models, a binary companion may play an important role by limiting the growth in radius of the disc and thus preventing the accretion time from becoming too long (Calvet et al. 2000); in this case most of the angular momentum of the system must go ...
Infrared colours, distance determination and absolute magnitudes of
... 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 ...
... 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 ...
The Final Version of the White Paper is available.
... The characterization of exoplanets is one of the outstanding key science cases for HIRES. The focus will be on characterizing exo-planet atmospheres over a wide range of masses, from Neptune-like down to Earth-like including those in the habitable zones, in terms of chemical composition, stratificat ...
... The characterization of exoplanets is one of the outstanding key science cases for HIRES. The focus will be on characterizing exo-planet atmospheres over a wide range of masses, from Neptune-like down to Earth-like including those in the habitable zones, in terms of chemical composition, stratificat ...
RADIO OBSERVATIONS RELATED TO STAR FORMATION P. G.
... procedure; we introduce the review of observations (Sect. II) by outlining a working hypothesis for the evolutionary sequence of Ο and Β stars. This sequence is based on radio and IR observations of the giant HII region W3 (reviewed by Mezger and Wink, 1974) and on model calculations of dust-filled ...
... procedure; we introduce the review of observations (Sect. II) by outlining a working hypothesis for the evolutionary sequence of Ο and Β stars. This sequence is based on radio and IR observations of the giant HII region W3 (reviewed by Mezger and Wink, 1974) and on model calculations of dust-filled ...
Stellar Population Effects on the Inferred Photon Density at
... removal of the hydrogen envelope in primary stars - forming more hot helium or Wolf-Rayet stars; the transfer of mass to secondary stars increasing their mass and rejuvenating them; and finally the generation of massive stars from stellar mergers (Eldridge et al. 2008). The first of these, enhanced ma ...
... removal of the hydrogen envelope in primary stars - forming more hot helium or Wolf-Rayet stars; the transfer of mass to secondary stars increasing their mass and rejuvenating them; and finally the generation of massive stars from stellar mergers (Eldridge et al. 2008). The first of these, enhanced ma ...
Document
... is composed of perhaps a few hundred billion stars plus many different types of gas, dust, planets, and so on. In the directions in which we see the Milky Way in the sky, we are looking through the relatively thin, pancake-like disk of matter that forms a major part of our Milky Way Galaxy. ...
... is composed of perhaps a few hundred billion stars plus many different types of gas, dust, planets, and so on. In the directions in which we see the Milky Way in the sky, we are looking through the relatively thin, pancake-like disk of matter that forms a major part of our Milky Way Galaxy. ...
Wind-Blown Bubbles around Evolved Stars
... physical processes can be included.2 The first, spherically symmetric, numerical studies included radiative cooling and were able to follow the transition between the initial fully adiabatic stage to the stage where the swept-up interstellar medium cools radiatively (Falle, 1975). Subsequent numeric ...
... physical processes can be included.2 The first, spherically symmetric, numerical studies included radiative cooling and were able to follow the transition between the initial fully adiabatic stage to the stage where the swept-up interstellar medium cools radiatively (Falle, 1975). Subsequent numeric ...
Winds from clusters with non-uniform stellar distribution
... in which the distribution of stars (i.e., the number of stars per unit volume) within the cluster is spherically symmetric, has a power-law radial dependence, and drops discontinuously to zero at the outer radius of the cluster. We carry out comparisons between an analytic model (in which the stars ...
... in which the distribution of stars (i.e., the number of stars per unit volume) within the cluster is spherically symmetric, has a power-law radial dependence, and drops discontinuously to zero at the outer radius of the cluster. We carry out comparisons between an analytic model (in which the stars ...
Spectral classification of O–M stars on the basis of UBV photometry
... direction. The practice of research of interstellar light absorption (e.g. Urasin et al. 1989) proves that for construction of such a dependence towards the Galactic periphery it is enough to know magnitudes and spectra of stars up to V = 15 mag only. Of course this absorption curve like the one sho ...
... direction. The practice of research of interstellar light absorption (e.g. Urasin et al. 1989) proves that for construction of such a dependence towards the Galactic periphery it is enough to know magnitudes and spectra of stars up to V = 15 mag only. Of course this absorption curve like the one sho ...
Parent stars of extrasolar planets III: ρ1 Cancri Revisited
... 3.1.1. Model atmosphere selection and Fe abundances The final model atmosphere parameters were arrived at iteratively, approached slightly differently and conducted independently by each of us (GG and ADV). We employed slightly different versions of the line list (differing by four Fe I lines), yet ...
... 3.1.1. Model atmosphere selection and Fe abundances The final model atmosphere parameters were arrived at iteratively, approached slightly differently and conducted independently by each of us (GG and ADV). We employed slightly different versions of the line list (differing by four Fe I lines), yet ...
a wide-field survey for variable stars
... 1555/1554). Over 400 light-years away, at the edge of a molecular cloud, both star and nebula are seen to vary significantly in brightness but not necessarily at the same time, adding to the mystery of the intriguing region. T Tauri stars are now generally recognized as young (less than a few millio ...
... 1555/1554). Over 400 light-years away, at the edge of a molecular cloud, both star and nebula are seen to vary significantly in brightness but not necessarily at the same time, adding to the mystery of the intriguing region. T Tauri stars are now generally recognized as young (less than a few millio ...
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.