A 25 micron search for Vega-like disks around main
... After the initial discoveries by IRAS, the search and analysis of Vega-like disks in the infrared has received a substantial boost with the availability of data from the Infrared Space Observatory (ISO, Kessler et al. 1996). ISO has improved on IRAS in several important ways. Firstly, the number of ...
... After the initial discoveries by IRAS, the search and analysis of Vega-like disks in the infrared has received a substantial boost with the availability of data from the Infrared Space Observatory (ISO, Kessler et al. 1996). ISO has improved on IRAS in several important ways. Firstly, the number of ...
Oxygen, magnesium and chromium isotopic ratios of
... grains have substantial Mg isotopic anomalies. They have excesses in 26Mg, primarily from the decay of 26Al, as well as excesses and deficits in 25Mg. We present the results of new model calculations of the evolution of Mg and Al isotopic ratios in the envelopes of AGB stars for a range of masses (1 ...
... grains have substantial Mg isotopic anomalies. They have excesses in 26Mg, primarily from the decay of 26Al, as well as excesses and deficits in 25Mg. We present the results of new model calculations of the evolution of Mg and Al isotopic ratios in the envelopes of AGB stars for a range of masses (1 ...
The history of a discovery - Institut d`Astrophysique Spatiale
... – F. Low The Infrared-Galaxy Phenomenon 1970 (ApJ 159, L173) – 50-300 µm observations of the Galactic center and NGC1068 and M82 (2 1012 and 6 1011 Lo) by Franck Low and H. Aumann 1970, (ApJ 162, L79) – in 1972 the Fundamental panel of ESRO (not yet ESA !) asked me a report on what can space observa ...
... – F. Low The Infrared-Galaxy Phenomenon 1970 (ApJ 159, L173) – 50-300 µm observations of the Galactic center and NGC1068 and M82 (2 1012 and 6 1011 Lo) by Franck Low and H. Aumann 1970, (ApJ 162, L79) – in 1972 the Fundamental panel of ESRO (not yet ESA !) asked me a report on what can space observa ...
X-ray Observations of Cosmic Accelerators Greg Madejski SLAC/KIPAC
... (fragmentation of the accretion disk plasma) -> Flares come from dissipation of gravitational energy What is the origin of the hot plasma? Observed X-ray spectra (up to at least 100 keV) indicate that accretion disks must be sites of vigorous particle acceleration - Most likely associated with “plas ...
... (fragmentation of the accretion disk plasma) -> Flares come from dissipation of gravitational energy What is the origin of the hot plasma? Observed X-ray spectra (up to at least 100 keV) indicate that accretion disks must be sites of vigorous particle acceleration - Most likely associated with “plas ...
Understanding Mass-Loss and the Late Evolution of Intermediate
... New Mexico, first light in 2010), with resolutions ranging from 0.1 to 100, can be used to probe the launch regions of CFWs in late AGB stars and PPNs, in particular the disk temperature, geometry and density structure. Direct imaging, with space-based telescopes such as HST and JWST will remain uns ...
... New Mexico, first light in 2010), with resolutions ranging from 0.1 to 100, can be used to probe the launch regions of CFWs in late AGB stars and PPNs, in particular the disk temperature, geometry and density structure. Direct imaging, with space-based telescopes such as HST and JWST will remain uns ...
Formation of Massive Stars
... appreciable UV flux and (possibly) a strong wind modifying the surrounding conditions, structure, & chemistry At this stage the star ionizes its surroundings, giving rise to a small region of ionized gas, usually referred as the ultracompact HII (UCHII) region phase ...
... appreciable UV flux and (possibly) a strong wind modifying the surrounding conditions, structure, & chemistry At this stage the star ionizes its surroundings, giving rise to a small region of ionized gas, usually referred as the ultracompact HII (UCHII) region phase ...
Circumstellar medium around rotating massive stars at solar metallicity
... At higher mass, the phase of a slow and dense wind progressively disappears. The star exhibits a very fast and relatively dense wind during the last few 100 000 years before the final collapse. The different and time-dependent mass-loss histories have a strong impact on the power injected in the ISM ...
... At higher mass, the phase of a slow and dense wind progressively disappears. The star exhibits a very fast and relatively dense wind during the last few 100 000 years before the final collapse. The different and time-dependent mass-loss histories have a strong impact on the power injected in the ISM ...
Evolution and colors of helium-core white dwarf stars with high
... requires evolutionary calculations. In particular, it requires computing full evolutionary sequences of white dwarfs with supersolar metallicity progenitors. However, a detailed study of the evolutionary properties of He-core white dwarfs resulting from progenitors with extreme metallicity does not ...
... requires evolutionary calculations. In particular, it requires computing full evolutionary sequences of white dwarfs with supersolar metallicity progenitors. However, a detailed study of the evolutionary properties of He-core white dwarfs resulting from progenitors with extreme metallicity does not ...
IDENTIFICATION OF MAIN-SEQUENCE STARS WITH MID
... Evidence for planets around nearby stars is now overwhelming, with over 120 planets in 100+ planetary systems,14 most found using high-resolution stellar spectroscopy capable of detecting Doppler shifts in the parent star. However, the process or processes by which these planets form is still unknow ...
... Evidence for planets around nearby stars is now overwhelming, with over 120 planets in 100+ planetary systems,14 most found using high-resolution stellar spectroscopy capable of detecting Doppler shifts in the parent star. However, the process or processes by which these planets form is still unknow ...
On the onset of runaway stellar collisions in dense star clusters I
... dynamical friction time-scale is inversely proportional to m. We conclude that dynamical friction is a crucial ingredient in understanding the first collision. In Fig. 4 we compare the time of the first collision, tcoll , with the time-scale on which a star with mass m sinks to the cluster centre fr ...
... dynamical friction time-scale is inversely proportional to m. We conclude that dynamical friction is a crucial ingredient in understanding the first collision. In Fig. 4 we compare the time of the first collision, tcoll , with the time-scale on which a star with mass m sinks to the cluster centre fr ...
On the role of the WNH phase in the evolution of very massive stars
... We propose the new designation “WNH” for luminous Wolf-Rayet (WR) stars of the nitrogen sequence with hydrogen in their spectra. These have been commonly referred to as WNL stars (WN7h, for example), but this new shorthand avoids confusion because there are late-type WN stars without hydrogen and ea ...
... We propose the new designation “WNH” for luminous Wolf-Rayet (WR) stars of the nitrogen sequence with hydrogen in their spectra. These have been commonly referred to as WNL stars (WN7h, for example), but this new shorthand avoids confusion because there are late-type WN stars without hydrogen and ea ...
Chapter 31: Galaxies and the Universe
... the Milky Way is densely speculated that it might also have spiral arms, as many other galaxies populated by stars, many of do. This was very difficult to prove, however, because astronomers which are obscured by dust. have no way to get outside of the galaxy and look down on the disk. Astronomers h ...
... the Milky Way is densely speculated that it might also have spiral arms, as many other galaxies populated by stars, many of do. This was very difficult to prove, however, because astronomers which are obscured by dust. have no way to get outside of the galaxy and look down on the disk. Astronomers h ...
Interpretation of the Helix Planetary Nebula using Hydro
... by factors ≈ ×6 − 10. Because stars form from planets, the first stars must be small and early. Large ≥ 2M population III stars forming from 106 M Jeans mass gas clouds in CDM halos never happened and neither did re-ionization of the gas-epoch back to a second plasmaepoch. CDM halos never happened ...
... by factors ≈ ×6 − 10. Because stars form from planets, the first stars must be small and early. Large ≥ 2M population III stars forming from 106 M Jeans mass gas clouds in CDM halos never happened and neither did re-ionization of the gas-epoch back to a second plasmaepoch. CDM halos never happened ...
Massive Stars in the Arches Cluster 12
... photometry, astrometry, equivalent width, and velocity information. The data are interpreted with a wind/atmosphere code to determine stellar temperatures, luminosities, mass-loss rates, and abundances. We have doubled the number of known emission-line stars, and we have also made the first spectros ...
... photometry, astrometry, equivalent width, and velocity information. The data are interpreted with a wind/atmosphere code to determine stellar temperatures, luminosities, mass-loss rates, and abundances. We have doubled the number of known emission-line stars, and we have also made the first spectros ...
PDF only
... induced by spin interactions within and between atoms and molecules and even within bulk materials. This effect manifests itself in chemical reactions, catalytic processes, conduction processes, photochemical processes, photophysical events and other processes. On the basis of spin induced orbital d ...
... induced by spin interactions within and between atoms and molecules and even within bulk materials. This effect manifests itself in chemical reactions, catalytic processes, conduction processes, photochemical processes, photophysical events and other processes. On the basis of spin induced orbital d ...
Identifying Young far from Giant Stars Molecular Clouds
... features to the stellar spectra. When this boundary material heats up as it accretes onto the star, it radiates, contributing its own continuum to the stellar spectrum. When the material is heated, the electrons in the layer's hydrogen atoms are excited to higher energy levels. However, the electron ...
... features to the stellar spectra. When this boundary material heats up as it accretes onto the star, it radiates, contributing its own continuum to the stellar spectrum. When the material is heated, the electrons in the layer's hydrogen atoms are excited to higher energy levels. However, the electron ...
Abundances of the elements He to Ni in the atmosphere of Sirius A
... be measured precisely on the sky, yielding both the mass ratio and the total mass of the system (van den Bos 1960; Gatewood & Gatewood 1978). The masses of Sirius A and B are MA = (2.12 ± 0.06) M and MB = (1.000 ± 0.016) M . The diameter of Sirius A has been measured interferometrically (Kervella ...
... be measured precisely on the sky, yielding both the mass ratio and the total mass of the system (van den Bos 1960; Gatewood & Gatewood 1978). The masses of Sirius A and B are MA = (2.12 ± 0.06) M and MB = (1.000 ± 0.016) M . The diameter of Sirius A has been measured interferometrically (Kervella ...
Presentation
... If we take values of oscillation parameters suggested by solar ν and atmospheric ν obs., no resonances occur in the core, but they occur in the mantle of SN (C+O shell, He shell) . No effect on explosion. Note: If Δm ~101-2ev, resonance happens in the hot bubble region, energy deposition is greatly ...
... If we take values of oscillation parameters suggested by solar ν and atmospheric ν obs., no resonances occur in the core, but they occur in the mantle of SN (C+O shell, He shell) . No effect on explosion. Note: If Δm ~101-2ev, resonance happens in the hot bubble region, energy deposition is greatly ...
Searching for the Secrets of Massive Star Birth
... galactic interstellar medium (ISM). The first stars to form in the universe were massive. They were responsible for cosmic re-ionization and its initial chemical enrichment. Massive stars continue to power the “galactic ecology”, the cyclic conversion of the ISM into stars, the enrichment of the ISM ...
... galactic interstellar medium (ISM). The first stars to form in the universe were massive. They were responsible for cosmic re-ionization and its initial chemical enrichment. Massive stars continue to power the “galactic ecology”, the cyclic conversion of the ISM into stars, the enrichment of the ISM ...
Booklet - Centrum Astronomiczne im. M.Kopernika PAN
... The evolutionary state of Miras with changing pulsation period S. Uttenthaler, University of Vienna, Department of Astronomy, Austria We present an investigation of the evolutionary state of Mira variables with changing pulsation period. The changing periods have been speculated to be the consequenc ...
... The evolutionary state of Miras with changing pulsation period S. Uttenthaler, University of Vienna, Department of Astronomy, Austria We present an investigation of the evolutionary state of Mira variables with changing pulsation period. The changing periods have been speculated to be the consequenc ...
PLANETS AND INFRARED EXCESSES: PRELIMINARY RESULTS
... issue by searching for excess IR emission from known planetbearing stars. MIPS provides unprecedented sensitivity at midIR wavelengths and as such is an ideal instrument for searching for the dust emission from solar-type stars. While the focus of this paper is on observations of stars that are know ...
... issue by searching for excess IR emission from known planetbearing stars. MIPS provides unprecedented sensitivity at midIR wavelengths and as such is an ideal instrument for searching for the dust emission from solar-type stars. While the focus of this paper is on observations of stars that are know ...
Merging white dwarfs and thermonuclear supernovae
... Our alternative is that SN Ia result generally from mergers of carbon–oxygen white dwarfs, including those with sub-Chandrasekhar total mass [3]. Both theoretical [3] and empirical [24] rates are a factor 3 or so higher than near-Chandrasekhar rates, making them consistent with the SN Ia rate. Furth ...
... Our alternative is that SN Ia result generally from mergers of carbon–oxygen white dwarfs, including those with sub-Chandrasekhar total mass [3]. Both theoretical [3] and empirical [24] rates are a factor 3 or so higher than near-Chandrasekhar rates, making them consistent with the SN Ia rate. Furth ...
Binary Stars
... orbiting each other “connected’ by their mutual gravitational interaction. 50% of stars are binaries: ~100% O/B ~75% M Obs. biases ...
... orbiting each other “connected’ by their mutual gravitational interaction. 50% of stars are binaries: ~100% O/B ~75% M Obs. biases ...
Carbon, nitrogen and oxygen abundances in
... Fundamental parameters and the carbon, nitrogen and oxygen abundances are determined for 22 B-type stars with distances d ≤ 600 pc and slow rotation (v sin i ≤ 66 km s−1 ). The stars are selected according to their effective temperatures Teff and surface gravities log g, namely: Teff is between 15 3 ...
... Fundamental parameters and the carbon, nitrogen and oxygen abundances are determined for 22 B-type stars with distances d ≤ 600 pc and slow rotation (v sin i ≤ 66 km s−1 ). The stars are selected according to their effective temperatures Teff and surface gravities log g, namely: Teff is between 15 3 ...
Article PDF - IOPscience
... the instrument, we have always used a 692 nm filter with a width of 40 nm. However, in the second channel, we have used both an 880 nm with filter width of 50 nm and a 562 nm filter of width 40 nm. While the 562 nm filter gives superior resolution images (owing to its shorter wavelength), we find th ...
... the instrument, we have always used a 692 nm filter with a width of 40 nm. However, in the second channel, we have used both an 880 nm with filter width of 50 nm and a 562 nm filter of width 40 nm. While the 562 nm filter gives superior resolution images (owing to its shorter wavelength), we find th ...
Nucleosynthesis
Nucleosynthesis is the process that creates new atomic nuclei from pre-existing nucleons, primarily protons and neutrons. The first nuclei were formed about three minutes after the Big Bang, through the process called Big Bang nucleosynthesis. It was then that hydrogen and helium formed to become the content of the first stars, and this primeval process is responsible for the present hydrogen/helium ratio of the cosmos.With the formation of stars, heavier nuclei were created from hydrogen and helium by stellar nucleosynthesis, a process that continues today. Some of these elements, particularly those lighter than iron, continue to be delivered to the interstellar medium when low mass stars eject their outer envelope before they collapse to form white dwarfs. The remains of their ejected mass form the planetary nebulae observable throughout our galaxy.Supernova nucleosynthesis within exploding stars by fusing carbon and oxygen is responsible for the abundances of elements between magnesium (atomic number 12) and nickel (atomic number 28). Supernova nucleosynthesis is also thought to be responsible for the creation of rarer elements heavier than iron and nickel, in the last few seconds of a type II supernova event. The synthesis of these heavier elements absorbs energy (endothermic) as they are created, from the energy produced during the supernova explosion. Some of those elements are created from the absorption of multiple neutrons (the R process) in the period of a few seconds during the explosion. The elements formed in supernovas include the heaviest elements known, such as the long-lived elements uranium and thorium.Cosmic ray spallation, caused when cosmic rays impact the interstellar medium and fragment larger atomic species, is a significant source of the lighter nuclei, particularly 3He, 9Be and 10,11B, that are not created by stellar nucleosynthesis.In addition to the fusion processes responsible for the growing abundances of elements in the universe, a few minor natural processes continue to produce very small numbers of new nuclides on Earth. These nuclides contribute little to their abundances, but may account for the presence of specific new nuclei. These nuclides are produced via radiogenesis (decay) of long-lived, heavy, primordial radionuclides such as uranium and thorium. Cosmic ray bombardment of elements on Earth also contribute to the presence of rare, short-lived atomic species called cosmogenic nuclides.