Five New Giant Exoplanets from the California
... We could not carry out an LTE analysis of Gl 179 because its cool temperature resides outside the lowest temperature for which our continuous and molecular opacities are accurate. The luminosity of each star is determined from the apparent V-band magnitude, the bolometric correction, and the paralla ...
... We could not carry out an LTE analysis of Gl 179 because its cool temperature resides outside the lowest temperature for which our continuous and molecular opacities are accurate. The luminosity of each star is determined from the apparent V-band magnitude, the bolometric correction, and the paralla ...
Summary of IAU GA SpS5-I. Obscured and distant clusters
... (1996). It is the youngest and also the most compact of the three clusters. The current census of the massive star population includes 13 Wolf–Rayet stars and more than 100 OB stars. All Wolf–Rayet stars are late–type WNh stars. There is no WC or red supergiant. The quantitative analysis of their fu ...
... (1996). It is the youngest and also the most compact of the three clusters. The current census of the massive star population includes 13 Wolf–Rayet stars and more than 100 OB stars. All Wolf–Rayet stars are late–type WNh stars. There is no WC or red supergiant. The quantitative analysis of their fu ...
Population synthesis for double white dwarfs-II. Semi
... 1979). The matter that cannot be accreted is lost from the system, taking along some angular momentum. The binary system may remain stable even though it loses extra angular momentum. However heating of the transferred material, may cause it to expand and form a common envelope in which the two whit ...
... 1979). The matter that cannot be accreted is lost from the system, taking along some angular momentum. The binary system may remain stable even though it loses extra angular momentum. However heating of the transferred material, may cause it to expand and form a common envelope in which the two whit ...
Another cluster of red supergiants close to RSGC1
... are due to spectral variability. For instance, two of the three supergiants falling close to the position of the giants are known spectral type variables (RW Cep and AX Sgr), and have not been used for the fit. The two giants falling along the location of the supergiants have luminosity class II. Mo ...
... are due to spectral variability. For instance, two of the three supergiants falling close to the position of the giants are known spectral type variables (RW Cep and AX Sgr), and have not been used for the fit. The two giants falling along the location of the supergiants have luminosity class II. Mo ...
Age patterns in a sample of spiral galaxies
... nebular recombination lines [15]. UV emission is mainly dominated by O-B type stars, with lifetimes . 108 yr [13, 15]. In contrast, the Hα line is strong only in the presence of the most massive, hot O stars (masses > 10 M , ages < 20 Myr) that have enough energy to ionize the surrounding hydrogen. ...
... nebular recombination lines [15]. UV emission is mainly dominated by O-B type stars, with lifetimes . 108 yr [13, 15]. In contrast, the Hα line is strong only in the presence of the most massive, hot O stars (masses > 10 M , ages < 20 Myr) that have enough energy to ionize the surrounding hydrogen. ...
Search for giant planets in M67 III: excess of Hot Jupiters in dense
... Hot Jupiters (HJs) are defined as giant planets (M p > 0.3MJup ) in short period orbits (P < 10 days). They show an occurance rate of ∼1.2% around Sun-like field stars (Wright et al. 2012; Mayor et al. 2011). These close-in giant planets are highly unlikely to have formed in situ and it is believed ...
... Hot Jupiters (HJs) are defined as giant planets (M p > 0.3MJup ) in short period orbits (P < 10 days). They show an occurance rate of ∼1.2% around Sun-like field stars (Wright et al. 2012; Mayor et al. 2011). These close-in giant planets are highly unlikely to have formed in situ and it is believed ...
the challenge of wide-field transit surveys: the case of
... Nearly all of the more than 130 known extrasolar planets have been discovered by means of radial velocity observations. Such observations provide no information on the planet’s size, and, because of the unknown orbital inclination, only a lower limit on the mass of the planet can be established. One ...
... Nearly all of the more than 130 known extrasolar planets have been discovered by means of radial velocity observations. Such observations provide no information on the planet’s size, and, because of the unknown orbital inclination, only a lower limit on the mass of the planet can be established. One ...
Young Stellar Objects in the Orion B Cloud
... SWIRE (Spitzer Wide-area Infrared Extragalactic) catalogue and select an area the same in size as our target area and then place this sample of extragalactic objects behind the Orion B Molecular Cloud. In practice this means applying extinction to the extragalactic objects according to our extinctio ...
... SWIRE (Spitzer Wide-area Infrared Extragalactic) catalogue and select an area the same in size as our target area and then place this sample of extragalactic objects behind the Orion B Molecular Cloud. In practice this means applying extinction to the extragalactic objects according to our extinctio ...
Metallicity distribution for planet
... (FGK-type dwarfs) tend to be more metal-rich compared to field stars without gas giant planets. Johnson et al. (2010) indicated that there is planet-metallicity relation: positive metallicity-planet occurrence relation for M-dwarf host stars, however it is lower compared to solar-mass stars. Buchhav ...
... (FGK-type dwarfs) tend to be more metal-rich compared to field stars without gas giant planets. Johnson et al. (2010) indicated that there is planet-metallicity relation: positive metallicity-planet occurrence relation for M-dwarf host stars, however it is lower compared to solar-mass stars. Buchhav ...
Interacting Binary Star System Activity
... and others that take much longer periods of time like years. Astronomers study variable stars and interacting binary star systems for many reasons, to learn more about stellar evolution or to discover the mysteries associated with finding dark matter and dark energy. Eclipsing binary stars are a ric ...
... and others that take much longer periods of time like years. Astronomers study variable stars and interacting binary star systems for many reasons, to learn more about stellar evolution or to discover the mysteries associated with finding dark matter and dark energy. Eclipsing binary stars are a ric ...
Stellar Dynamics
... medium) flows into the centre of the cluster, falling into the gravitational potential well. As a result this gas gets heated up and emits copious amount of X-rays through which it can be observed. Near the centre of rich clusters the gas becomes dense and its cooling time is estimated to be shorter ...
... medium) flows into the centre of the cluster, falling into the gravitational potential well. As a result this gas gets heated up and emits copious amount of X-rays through which it can be observed. Near the centre of rich clusters the gas becomes dense and its cooling time is estimated to be shorter ...
3 The lives of galaxies
... Dark Matter halos. For a typical spiral galaxy, 90% of its mass is dark matter. The luminous matter is more concentrated than the total gravitating matter. In the central parts, including the radius in the Milky Way where the Sun resides, dark matter is present but negligible. Most of the dark matte ...
... Dark Matter halos. For a typical spiral galaxy, 90% of its mass is dark matter. The luminous matter is more concentrated than the total gravitating matter. In the central parts, including the radius in the Milky Way where the Sun resides, dark matter is present but negligible. Most of the dark matte ...
The evolution of Red Supergiants to supernova in the LMC cluster
... be small compared to the age of the cluster. Hence, we can assume that all stars currently in the RSG phase had the same initial mass to within a few tenths of a solar mass. Since the stars’ masses are so similar, they will all follow almost the same path across the H-R diagram. Differences in lumin ...
... be small compared to the age of the cluster. Hence, we can assume that all stars currently in the RSG phase had the same initial mass to within a few tenths of a solar mass. Since the stars’ masses are so similar, they will all follow almost the same path across the H-R diagram. Differences in lumin ...
The Dark Age of the Universe
... Tvir ⬵ 2000 K and mass ⬃106 MJ; at lower temperatures, the rotational transitions of H2 do not provide sufficient cooling for the gas to dissipate its energy. The slow cooling in these first objects leads to the formation of a central core with a mass of 100 to 1000 MJ of gas cooled to ⬃200 K, and t ...
... Tvir ⬵ 2000 K and mass ⬃106 MJ; at lower temperatures, the rotational transitions of H2 do not provide sufficient cooling for the gas to dissipate its energy. The slow cooling in these first objects leads to the formation of a central core with a mass of 100 to 1000 MJ of gas cooled to ⬃200 K, and t ...
Data Reduction pipeline for MOST Guide Stars and Application to
... A further issue is that if the stray light is extremely high or if the targets have been observed only during orbital phases of maximum stray light (for example switch targets), the decorrelation method significantly increases the time domain point-to-point scatter. For those targets, the decorrelati ...
... A further issue is that if the stray light is extremely high or if the targets have been observed only during orbital phases of maximum stray light (for example switch targets), the decorrelation method significantly increases the time domain point-to-point scatter. For those targets, the decorrelati ...
On the role of the WNH phase in the evolution of very massive stars
... hydrogen in WN stars is not limited to late types, rendering “WNL” an inappropriate designation as it refers mainly to WN7/WN8 (Moffat & Seggewiss 1979). The shorthand “WNH” would encompass both early- and late-type WN stars with hydrogen. Second, the designation “WNH” is also useful to emphasize th ...
... hydrogen in WN stars is not limited to late types, rendering “WNL” an inappropriate designation as it refers mainly to WN7/WN8 (Moffat & Seggewiss 1979). The shorthand “WNH” would encompass both early- and late-type WN stars with hydrogen. Second, the designation “WNH” is also useful to emphasize th ...
The effect of starspots on the radii of low-mass
... Fig. 1 compares the evolutionary tracks and radius as a function of time predicted by the BCAH98 model (for [M/H] = 0, Y = 0.275 and Lmix = HP ) with the results of the polytropic model for parameter values A = −132, B = 14 and n = 1.73 (corresponding to a = 0.35 and b = 16 in equation 2). The const ...
... Fig. 1 compares the evolutionary tracks and radius as a function of time predicted by the BCAH98 model (for [M/H] = 0, Y = 0.275 and Lmix = HP ) with the results of the polytropic model for parameter values A = −132, B = 14 and n = 1.73 (corresponding to a = 0.35 and b = 16 in equation 2). The const ...
Present classification: Suggested
... variable stars, though quite an expert in traditional ones and the person responsible for collecting ideas for the new classification systems to be approved by the IAU. Classification begins as soon as people notice variable stars. Old chronicles: “a guest star” (Nova, Supernova, comet), then “Stell ...
... variable stars, though quite an expert in traditional ones and the person responsible for collecting ideas for the new classification systems to be approved by the IAU. Classification begins as soon as people notice variable stars. Old chronicles: “a guest star” (Nova, Supernova, comet), then “Stell ...
HS0702+ 6043: A star showing both short-period p
... From the uncontaminated optical spectrum of HS 0702+6043, we can easily exclude a potential F- or G-type main sequence companion. Because the star is relatively faint, 2MASS photometry is only accurate enough to require that any hypothetical companion must be later than K-type. At the supposed 1 h o ...
... From the uncontaminated optical spectrum of HS 0702+6043, we can easily exclude a potential F- or G-type main sequence companion. Because the star is relatively faint, 2MASS photometry is only accurate enough to require that any hypothetical companion must be later than K-type. At the supposed 1 h o ...
Fundamentals of Atmospheric Chemistry and Astrochemistry
... chemistry of the universe. Instead, all of the information we have comes from passive observations. The data from telescopes arrives in the form of spectroscopic signatures recorded in various portions of the electromagnetic spectrum (UV‐vis, infrared, microwave etc) for different ...
... chemistry of the universe. Instead, all of the information we have comes from passive observations. The data from telescopes arrives in the form of spectroscopic signatures recorded in various portions of the electromagnetic spectrum (UV‐vis, infrared, microwave etc) for different ...
Toward $ ab\, initio $ extremely metal poor stars
... star particle. This replacement capped the gas density around the maximum, where the star particle was inserted, at a ceiling computed consistent with mass conservation. We ray-traced ionizing radiation from the star particle to compute the dynamical expansion of the HII region over the star’s lifet ...
... star particle. This replacement capped the gas density around the maximum, where the star particle was inserted, at a ceiling computed consistent with mass conservation. We ray-traced ionizing radiation from the star particle to compute the dynamical expansion of the HII region over the star’s lifet ...
Understanding LMXBs in Elliptical Galaxies
... Short & old (10Gyr ago) star formation episode does NOT lead to similar LMXB formation pattern LMXB formation rate: very high at ~500Myr but continues at lower levels for 10Gyr to present Short-lived LMXBs (e.g., persistent ultra-compacts) follow the LMXB formation rate pattern and NOT the star form ...
... Short & old (10Gyr ago) star formation episode does NOT lead to similar LMXB formation pattern LMXB formation rate: very high at ~500Myr but continues at lower levels for 10Gyr to present Short-lived LMXBs (e.g., persistent ultra-compacts) follow the LMXB formation rate pattern and NOT the star form ...
The incidence of stellar mergers and mass gainers among massive
... exceeds 104 L⊙ . A binary system containing two mainsequence stars is counted only once. The simulations started with 70% binaries and 30% single stars at birth. For the case of continuous star formation we find that the contribution of pre interaction binaries is reduced from 70% at birth to 50% in ...
... exceeds 104 L⊙ . A binary system containing two mainsequence stars is counted only once. The simulations started with 70% binaries and 30% single stars at birth. For the case of continuous star formation we find that the contribution of pre interaction binaries is reduced from 70% at birth to 50% in ...
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.