A double detached shell around a post
... limit of 3.6 kpc for this interstellar cloud, which is also a lower limit of the distance to IRAS 17163. If the Galactic rotation model is applied to the component at 5.9 km s−1 , this would give a lower limit of 17.4+1.84 −1.33 kpc to the star. This, however, is incompatible with the inferred total ...
... limit of 3.6 kpc for this interstellar cloud, which is also a lower limit of the distance to IRAS 17163. If the Galactic rotation model is applied to the component at 5.9 km s−1 , this would give a lower limit of 17.4+1.84 −1.33 kpc to the star. This, however, is incompatible with the inferred total ...
Testing
... Molecular clouds form next, after gas cools enough to allow atoms to combine into molecules. ...
... Molecular clouds form next, after gas cools enough to allow atoms to combine into molecules. ...
Formation and Disruption of Cosmological Low Mass Objects
... luminous objects such as galaxies and QSOs. On the other hand, the reionization of the intergalactic medium and the presence of heavy elements at high-z suggest that there are other population of luminous objects, which precedes normal galaxies. Thus, theoretical approach to reveal the formation mec ...
... luminous objects such as galaxies and QSOs. On the other hand, the reionization of the intergalactic medium and the presence of heavy elements at high-z suggest that there are other population of luminous objects, which precedes normal galaxies. Thus, theoretical approach to reveal the formation mec ...
IMPLICATIONS OF EXTRASOLAR PLANETS FOR
... 1997), and 55 Cancri (Butler et al. 1997). The minimum masses of these objects are in the range of 0.47 to 6.6 MJ. Previous to these discoveries, a companion to the star HD 114762 with a minimum mass of 11 MJ had been reported by Latham et al. (1989); this object apparently lies near the borderline ...
... 1997), and 55 Cancri (Butler et al. 1997). The minimum masses of these objects are in the range of 0.47 to 6.6 MJ. Previous to these discoveries, a companion to the star HD 114762 with a minimum mass of 11 MJ had been reported by Latham et al. (1989); this object apparently lies near the borderline ...
The Recent Star Formation Histories of M81 Group Dwarf Irregular
... difference in the central wavelengths of two selected filters provides for a clearer separation between features in the CMD. While observing at very blue and red wavelengths (e.g., U or B and I) would provide for a greater color difference, it also makes the integration time to the same photometric ...
... difference in the central wavelengths of two selected filters provides for a clearer separation between features in the CMD. While observing at very blue and red wavelengths (e.g., U or B and I) would provide for a greater color difference, it also makes the integration time to the same photometric ...
Symbiotic Stars as Laboratories for the Study of
... Abstract Symbiotic binary stars typically consist of a white dwarf (WD) that accretes material from the wind of a companion red giant. Orbital periods for these binaries are on the order of years, and their relatively small optical outbursts tend to occur every few years to decades. In some symbioti ...
... Abstract Symbiotic binary stars typically consist of a white dwarf (WD) that accretes material from the wind of a companion red giant. Orbital periods for these binaries are on the order of years, and their relatively small optical outbursts tend to occur every few years to decades. In some symbioti ...
PPT - Chandra X
... 3. Fit the grouped spectrum (Chi-squared data-variance statistics, Levenberg-Marquardt optimization, kT1 [0.01-2] and kT2 [1-10] keV 4. If E(B-V) is unknown, fit again with kT, NH floating 5. Freeze kT and NH; fit for abundances 6. If two temperatures have not been found or the chi-squared statistic ...
... 3. Fit the grouped spectrum (Chi-squared data-variance statistics, Levenberg-Marquardt optimization, kT1 [0.01-2] and kT2 [1-10] keV 4. If E(B-V) is unknown, fit again with kT, NH floating 5. Freeze kT and NH; fit for abundances 6. If two temperatures have not been found or the chi-squared statistic ...
All About MACHO
... that we still don’t know what is the most common physical substance in the Universe. This mysterious “dark matter” completely dominates the gravity of all systems that have been measured; it controls the motion of the Sun through the Galaxy, the motion of galaxies in clusters of galaxies, and the fo ...
... that we still don’t know what is the most common physical substance in the Universe. This mysterious “dark matter” completely dominates the gravity of all systems that have been measured; it controls the motion of the Sun through the Galaxy, the motion of galaxies in clusters of galaxies, and the fo ...
ON THE ORIGIN OF THE SALPETER SLOPE FOR THE INITIAL
... characteristic value of mc ∼ 1 M , suggested to be linked to the Jeans mass (e.g., McKee & Ostriker 2007; Clarke 2009). Since we are interested only in the upper IMF, however, scale-free cloud fragmentation plausibly dominates in this regime. But we note that our model contrasts with those in which ...
... characteristic value of mc ∼ 1 M , suggested to be linked to the Jeans mass (e.g., McKee & Ostriker 2007; Clarke 2009). Since we are interested only in the upper IMF, however, scale-free cloud fragmentation plausibly dominates in this regime. But we note that our model contrasts with those in which ...
View - ESA
... are many and generally incomplete in several respects, making it necessary to merge information of differing quality, scope and accuracy. It must be realized, however, that stellar catalogues are a difficult business, since they have to extract information from the original observation records, publ ...
... are many and generally incomplete in several respects, making it necessary to merge information of differing quality, scope and accuracy. It must be realized, however, that stellar catalogues are a difficult business, since they have to extract information from the original observation records, publ ...
A variation of the fraction of stars that form in
... few times 103 M ), incompleteness for older sources (i.e. older than ∼300 Myr) and to avoid the centre of the galaxy where the extinction is highly variable, causing a highly spatially dependent completeness limit. A total of 429 objects (out of the 992) passed our criteria. The majority of the clu ...
... few times 103 M ), incompleteness for older sources (i.e. older than ∼300 Myr) and to avoid the centre of the galaxy where the extinction is highly variable, causing a highly spatially dependent completeness limit. A total of 429 objects (out of the 992) passed our criteria. The majority of the clu ...
Discovery of Eclipsing Binary with the Longest Known Period
... J0953+3353 can not be self-luminous. As in case of ε Aur, we are dealing with a dust disk that absorbs the light of the central star(s) resulting in the gray eclipse. Also, no significant pulsations in maximum light are present in the historical light curve of J0953+3353 which also tells in favor of ...
... J0953+3353 can not be self-luminous. As in case of ε Aur, we are dealing with a dust disk that absorbs the light of the central star(s) resulting in the gray eclipse. Also, no significant pulsations in maximum light are present in the historical light curve of J0953+3353 which also tells in favor of ...
Five New Extrasolar Planets
... added 120 M dwarfs, located within 10 pc and having declination north of –30 deg, all listed in Wright et al. (2004). For the late–type K and M dwarfs, we restricted our selection to stars brighter than V=11. Two years ago, we added an additional 100 young FGK stars with ages of 50–500 Myr from the ...
... added 120 M dwarfs, located within 10 pc and having declination north of –30 deg, all listed in Wright et al. (2004). For the late–type K and M dwarfs, we restricted our selection to stars brighter than V=11. Two years ago, we added an additional 100 young FGK stars with ages of 50–500 Myr from the ...
WASP-86b and WASP-102b: super-dense versus bloated planets
... and a radius of 1.3RJ it is another example of an extremely low density planet (ρpl = 0.068ρJ). However its host star is a G0 and its orbital period is ∼ 4 d implying that WASP-127b does not receive the same amount of flux as the two examples mentioned above. To assess the inflation status of a syst ...
... and a radius of 1.3RJ it is another example of an extremely low density planet (ρpl = 0.068ρJ). However its host star is a G0 and its orbital period is ∼ 4 d implying that WASP-127b does not receive the same amount of flux as the two examples mentioned above. To assess the inflation status of a syst ...
An atlas of 2.4 to 4.1 mu m ISO/SWS spectra of early - UvA-DARE
... becomes too high to observe the embedded stars. The IR emission of the warm dust cocoon covering the newly formed massive stars in UCHii regions peaks typically at about 100 µm. At wavelengths longwards of 5–10 µm, the thermal emission of the dust dominates the photospheric flux, and can be as much ...
... becomes too high to observe the embedded stars. The IR emission of the warm dust cocoon covering the newly formed massive stars in UCHii regions peaks typically at about 100 µm. At wavelengths longwards of 5–10 µm, the thermal emission of the dust dominates the photospheric flux, and can be as much ...
STELLAR SPECTRA A. Basic Line Formation
... objective prisms. Annie Cannon classifies over 200 000 spectrograms and fine-tunes the Harvard spectral classification sequence O – B – A – F – G – K – M. This is a purely morphological division on the basis of spectral line appearances; – Hertzsprung (1908) and Russell (1913) independently plot a d ...
... objective prisms. Annie Cannon classifies over 200 000 spectrograms and fine-tunes the Harvard spectral classification sequence O – B – A – F – G – K – M. This is a purely morphological division on the basis of spectral line appearances; – Hertzsprung (1908) and Russell (1913) independently plot a d ...
Lesson 4: Stellar Explosions and Neutron Stars
... • You are carbon based – this is where you come from! Carbon burning • Major reaction: 12C + 4He → 16O + γ • Minor reaction: 12C + 12C → 24Mg + γ • For a 20-solar mass star, this continues for about 1 thousand years. • This is where the oxygen that you breathe comes from. Oxygen burning • Major reac ...
... • You are carbon based – this is where you come from! Carbon burning • Major reaction: 12C + 4He → 16O + γ • Minor reaction: 12C + 12C → 24Mg + γ • For a 20-solar mass star, this continues for about 1 thousand years. • This is where the oxygen that you breathe comes from. Oxygen burning • Major reac ...
The Primeval Populations of the Ultra
... Because the UFD metallicity distribution extends much lower than that of any globular cluster, the age determination must rely upon theoretical isochrones (see §3.2), but a comparison to M92 is still instructive. In our analysis, the largest uncertainties are the distances of the UFDs relative to th ...
... Because the UFD metallicity distribution extends much lower than that of any globular cluster, the age determination must rely upon theoretical isochrones (see §3.2), but a comparison to M92 is still instructive. In our analysis, the largest uncertainties are the distances of the UFDs relative to th ...
Cooling neutron stars: Theory and observations
... Ordinary cooling isolates neutron stars of age 1 kyr—1 Myr • There is one basic phenomenological cooling concept (but many physical realizations) • Main cooling regulator: neutrino luminosity function • Warmest observed stars are low-massive; their neutrino luminosity seems to be <= 1/30 of modified ...
... Ordinary cooling isolates neutron stars of age 1 kyr—1 Myr • There is one basic phenomenological cooling concept (but many physical realizations) • Main cooling regulator: neutrino luminosity function • Warmest observed stars are low-massive; their neutrino luminosity seems to be <= 1/30 of modified ...
Understanding Mass-Loss and the Late Evolution of Intermediate
... 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 unsurpassed in providing large field-of-view images with very high dynamical range (crucial for detecting faint ...
... 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 unsurpassed in providing large field-of-view images with very high dynamical range (crucial for detecting faint ...
Large scale kinematics and dynamical modelling of the Milky Way
... known in detail at small scales, but the large scale kinematics beyond 1 pc remain uncertain. For example, the rotation is not yet well determined, although a rotation law can provide insights on the processes that play a role in the formation of the nuclear star cluster. Calculations of the Galacti ...
... known in detail at small scales, but the large scale kinematics beyond 1 pc remain uncertain. For example, the rotation is not yet well determined, although a rotation law can provide insights on the processes that play a role in the formation of the nuclear star cluster. Calculations of the Galacti ...
The Orbital Period Distribution of Wide Binary Millisecond Pulsars
... focus on the BMSPs forming through the He N and He T channels. The orbital period distribution of BMSPs forming through channels He N and He T show a peak at long and short orbital periods, respectively. We tentatively identify these two subpopulations of BMSPs with the systems comprising the long- ...
... focus on the BMSPs forming through the He N and He T channels. The orbital period distribution of BMSPs forming through channels He N and He T show a peak at long and short orbital periods, respectively. We tentatively identify these two subpopulations of BMSPs with the systems comprising the long- ...
Galaxies (Professor Powerpoint)
... Mergers can transform two spirals into an elliptical galaxy. Some astronomers think that galaxies are always born as spirals, and they can become ellipticals only via mergers. ...
... Mergers can transform two spirals into an elliptical galaxy. Some astronomers think that galaxies are always born as spirals, and they can become ellipticals only via mergers. ...
First axion bounds from a pulsating helium
... particles to dark matter is dependent on their mass (or coupling constant). However, the models do not provide information about the value of the axion mass, and therefore it has to be inferred from observations. In particular, stars can be employed to place constraints on the mass of the axion [8, ...
... particles to dark matter is dependent on their mass (or coupling constant). However, the models do not provide information about the value of the axion mass, and therefore it has to be inferred from observations. In particular, stars can be employed to place constraints on the mass of the axion [8, ...
A PCA approach to stellar effective temperatures⋆
... resolution spectroscopic analyses in the literature. When multiple values are available from different sources, the library catalog adopts a weighted average, giving preference to data with smaller errors. The goal is to end up with a homogeneous set of values for all parameters. Quality flags (Q) ar ...
... resolution spectroscopic analyses in the literature. When multiple values are available from different sources, the library catalog adopts a weighted average, giving preference to data with smaller errors. The goal is to end up with a homogeneous set of values for all parameters. Quality flags (Q) ar ...
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.