A Decade of Radial-Velocity Discoveries in the
... the volume-limited CORALIE sample (including stellar binaries), for the same mlim , we count 9/1650 = 0.5% occurrence of Hot Jupiters and overall, that 63/1650 = 3.8% of stars have planets within 4 AU. As binaries with separations closer than 2 to 6 00. are usually eliminated from planet-search prog ...
... the volume-limited CORALIE sample (including stellar binaries), for the same mlim , we count 9/1650 = 0.5% occurrence of Hot Jupiters and overall, that 63/1650 = 3.8% of stars have planets within 4 AU. As binaries with separations closer than 2 to 6 00. are usually eliminated from planet-search prog ...
stellar rotation in m35: mass–period relations, spin
... He specifically proposed that coeval stars fall along two “rotational sequences” in the color versus rotation period plane. From an analysis of these sequences and their dependences on stellar age, Barnes (2003) proposed a framework for connecting internal and external magnetohydrodynamic processes ...
... He specifically proposed that coeval stars fall along two “rotational sequences” in the color versus rotation period plane. From an analysis of these sequences and their dependences on stellar age, Barnes (2003) proposed a framework for connecting internal and external magnetohydrodynamic processes ...
the reality of the wolf 630 moving group - TigerPrints
... Stars in the solar neighborhood (i.e. within 500 pc of the Sun) have been actively studied for over a century. The eventual goal of these studies is to piece together the dynamic and chemical evolution of the Galactic disk. To this end, one of the principle approaches for probing the disk has been t ...
... Stars in the solar neighborhood (i.e. within 500 pc of the Sun) have been actively studied for over a century. The eventual goal of these studies is to piece together the dynamic and chemical evolution of the Galactic disk. To this end, one of the principle approaches for probing the disk has been t ...
Evolution and colors of helium-core white dwarf stars with high
... white dwarfs offers the possibility of constraining globular cluster dynamics and evolution (Moehler & Bono 2008). The possible detection of single low-mass white dwarfs in NGC 6791, one of the oldest (> ∼8 Gyr) and most metal-rich ([Fe/H] ≈ +0.4) open clusters in our Galaxy (Origlia et al. 2006), ha ...
... white dwarfs offers the possibility of constraining globular cluster dynamics and evolution (Moehler & Bono 2008). The possible detection of single low-mass white dwarfs in NGC 6791, one of the oldest (> ∼8 Gyr) and most metal-rich ([Fe/H] ≈ +0.4) open clusters in our Galaxy (Origlia et al. 2006), ha ...
Galactic Evolution - Harvard-Smithsonian Center for Astrophysics
... stars typically do today. How much more is unknown, but if Pop-III stars really did exist, they must have contained hundreds of solar masses. No such colossal stars are seen today, the most massive star ever definitively “weighed” being ~76 M. (Repeated claims of discoveries for stars >100 M have ...
... stars typically do today. How much more is unknown, but if Pop-III stars really did exist, they must have contained hundreds of solar masses. No such colossal stars are seen today, the most massive star ever definitively “weighed” being ~76 M. (Repeated claims of discoveries for stars >100 M have ...
CENTRAL STARS OF PLANETARY NEBULAE IN THE LARGE
... of the PN itself. This obstruction is removed for the PNe of the LMC, all of which lie at essentially the same distance, allowing the physical parameters to be scaled to absolute values. In addition, the lower metallicity of the LMC relative to the Milky Way allows the role of metallicity in low/int ...
... of the PN itself. This obstruction is removed for the PNe of the LMC, all of which lie at essentially the same distance, allowing the physical parameters to be scaled to absolute values. In addition, the lower metallicity of the LMC relative to the Milky Way allows the role of metallicity in low/int ...
Carbon-enhanced metal-poor stars: a window on AGB
... in the predictions of the element-to-element ratios. In our models CEMP-s stars are typically formed in wide systems with periods above 10,000 days, while most of the observed CEMP-s stars are found in relatively close orbits with periods below 5,000 days. This evidence suggests that either the samp ...
... in the predictions of the element-to-element ratios. In our models CEMP-s stars are typically formed in wide systems with periods above 10,000 days, while most of the observed CEMP-s stars are found in relatively close orbits with periods below 5,000 days. This evidence suggests that either the samp ...
Period-Luminosity Relations for delta Scuti Stars
... at visible bands: the amplitude of the variables is smaller, with which the mean magnitudes have lower dispersion; the interstellar extinction is lower (AK /AV ∼ 1/10); and the infrared luminosities are less sensitive to temperature changes (instability strip is narrower), so PL relations are tighte ...
... at visible bands: the amplitude of the variables is smaller, with which the mean magnitudes have lower dispersion; the interstellar extinction is lower (AK /AV ∼ 1/10); and the infrared luminosities are less sensitive to temperature changes (instability strip is narrower), so PL relations are tighte ...
" Galaxy," Defined
... models based on more extreme assumptions than previously considered identify regions of parameter space where binaries could impact Segue 1-like velocity dispersion systems (McConnachie & Côté 2010). Tidally unbound and MW foreground stars can also contaminate spectroscopic samples of a MW compani ...
... models based on more extreme assumptions than previously considered identify regions of parameter space where binaries could impact Segue 1-like velocity dispersion systems (McConnachie & Côté 2010). Tidally unbound and MW foreground stars can also contaminate spectroscopic samples of a MW compani ...
The First Galaxies: Assembly under Radiative Feedback from the
... in the IGM impedes the accretion of gas onto these low-mass halos, an effect known as Jeans-filtering (e.g., Shapiro et al. 1994; Gnedin & Hui 1998; Okamoto et al. 2008). In contrast, star formation inside the first dwarf galaxies should be more robust to this negative radiative feedback as their de ...
... in the IGM impedes the accretion of gas onto these low-mass halos, an effect known as Jeans-filtering (e.g., Shapiro et al. 1994; Gnedin & Hui 1998; Okamoto et al. 2008). In contrast, star formation inside the first dwarf galaxies should be more robust to this negative radiative feedback as their de ...
m82 as a galaxy: morphology and stellar content of the disk and halo
... et al. 2008, SSCs). The energy liberated from massive stars in these clusters is released as galactic superwinds, which are traced by the Hα and X-ray emitting gas as cone-shaped structures along the minor axis of the galaxy up to distances as far as 10 kpc above the galactic plane (Lehnert, Heckman ...
... et al. 2008, SSCs). The energy liberated from massive stars in these clusters is released as galactic superwinds, which are traced by the Hα and X-ray emitting gas as cone-shaped structures along the minor axis of the galaxy up to distances as far as 10 kpc above the galactic plane (Lehnert, Heckman ...
The spin-up of contracting red supergiants
... surface relative to the total angular momentum of the envelope. An envelope structure which holds most of the mass close to its bottom favors high angular momentum loss rates, since this decreases hr2 ienv . In red supergiants, on the other hand, hr2 ienv is rather high, since those stars store a la ...
... surface relative to the total angular momentum of the envelope. An envelope structure which holds most of the mass close to its bottom favors high angular momentum loss rates, since this decreases hr2 ienv . In red supergiants, on the other hand, hr2 ienv is rather high, since those stars store a la ...
400 YEARS OF STELLAR ROTATION - DFTE
... In 1609 the news reached Venice that a certain Flemish optician had built a special spyglass through which it was possible to see distant objects closer with a magnification of about 4 times. Galileo (or some friends of him) was able just on empirical basis to quickly push the magnification first to ...
... In 1609 the news reached Venice that a certain Flemish optician had built a special spyglass through which it was possible to see distant objects closer with a magnification of about 4 times. Galileo (or some friends of him) was able just on empirical basis to quickly push the magnification first to ...
Physical Properties of Wolf-Rayet Stars
... Typically, WR stars have masses of 10–25 M , and are descended from O-type stars. They spend ∼10% of their ∼5-Myr lifetime as WR stars (Meynet & Maeder 2005). At Solar metallicity the minimum initial mass for a star to become a WR star is ∼25 M . This corresponds closely to the Humphreys & Davidso ...
... Typically, WR stars have masses of 10–25 M , and are descended from O-type stars. They spend ∼10% of their ∼5-Myr lifetime as WR stars (Meynet & Maeder 2005). At Solar metallicity the minimum initial mass for a star to become a WR star is ∼25 M . This corresponds closely to the Humphreys & Davidso ...
Chapter 4 On the possibility of a helium white dwarf donor in the
... Second, it has an X-ray luminosity which is low for an active LMXB, namely less than or equal to 1% of the Eddington limit for a canonical (1.4 M⊙ , 10 km radius) neutron star (Jonker et al. 2001). Third, 2S 0918–549 appears to have an unusually high Ne/O abundance ratio, a characteristic which it s ...
... Second, it has an X-ray luminosity which is low for an active LMXB, namely less than or equal to 1% of the Eddington limit for a canonical (1.4 M⊙ , 10 km radius) neutron star (Jonker et al. 2001). Third, 2S 0918–549 appears to have an unusually high Ne/O abundance ratio, a characteristic which it s ...
shock structures and momentum transfer in herbig
... Species such as O III are followed by O II and finally O I in well-defined cooling zones behind the shock (Raymond 1979; Fig. 1). These cooling zones are nowhere near ionization equilibrium, so, to predict emission line fluxes and ionization fractions accurately, one must construct a numerical code ...
... Species such as O III are followed by O II and finally O I in well-defined cooling zones behind the shock (Raymond 1979; Fig. 1). These cooling zones are nowhere near ionization equilibrium, so, to predict emission line fluxes and ionization fractions accurately, one must construct a numerical code ...
Statistical Properties of Exoplanets - INAF
... During the past decade, our understanding of planetary formation had to integrate several new peculiar characteristics. With the number of detected planets regularly increasing, we must continuously reexamine the statistical properties of the derived orbital elements and stellar-host characteristics ...
... During the past decade, our understanding of planetary formation had to integrate several new peculiar characteristics. With the number of detected planets regularly increasing, we must continuously reexamine the statistical properties of the derived orbital elements and stellar-host characteristics ...
Galaxies
... IRREGULARS The final galaxy class identified by Hubble—irregular galaxies—named in this way because their visual appearance does not allow us to place them into any of the other categories just discussed. Irregulars tend to be rich in interstellar matter and young, blue stars, but they lack any regu ...
... IRREGULARS The final galaxy class identified by Hubble—irregular galaxies—named in this way because their visual appearance does not allow us to place them into any of the other categories just discussed. Irregulars tend to be rich in interstellar matter and young, blue stars, but they lack any regu ...
A search for the cause of cyclical wind variability in O stars
... Ritter Astrophysical Research Center, The University of Toledo, Toledo, OH 43606, USA ...
... Ritter Astrophysical Research Center, The University of Toledo, Toledo, OH 43606, USA ...
black holes can play a constructive role as well
... prime example of recent jet-induced star-formation, which is probably still ongoing (Mould et al. 2000; Rejkuba et al. 2004). On the other hand, no such HI cloud is observed in the vicinity of the inner filament. Despite the lack of cold gas and distributed stellar populations, the inner filament ap ...
... prime example of recent jet-induced star-formation, which is probably still ongoing (Mould et al. 2000; Rejkuba et al. 2004). On the other hand, no such HI cloud is observed in the vicinity of the inner filament. Despite the lack of cold gas and distributed stellar populations, the inner filament ap ...
Measuring Reddening with SDSS Stellar Spectra and Recalibrating
... The eighth data release of the SDSS has spectra for about 500,000 stars (Aihara et al. 2011). The SEGUE Stellar Parameter Pipeline (Lee et al. 2008a, SSPP) has uniformly processed these spectra to measure the temperature, metallicity, and gravity of each of these stars using a variety of methods, in ...
... The eighth data release of the SDSS has spectra for about 500,000 stars (Aihara et al. 2011). The SEGUE Stellar Parameter Pipeline (Lee et al. 2008a, SSPP) has uniformly processed these spectra to measure the temperature, metallicity, and gravity of each of these stars using a variety of methods, in ...
AN ULTRA-DEEP NEAR-INFRARED SPECTRUM OF
... quiescent galaxies beyond z = 2, it implies that quenching of star formation is extremely efficient and also indicates that low luminosity active galactic nuclei (AGNs) could be common in these objects. Nuclear emission is a potential concern for the size measurement. However, we show that the AGN c ...
... quiescent galaxies beyond z = 2, it implies that quenching of star formation is extremely efficient and also indicates that low luminosity active galactic nuclei (AGNs) could be common in these objects. Nuclear emission is a potential concern for the size measurement. However, we show that the AGN c ...
Stars, neutral hydrogen and ionised gas in early
... of the 2MASS objects, 2MASX J13090029–5153544, contains detectable atomic gas at the same velocity of IC 4200: this is an Sc galaxy 6.8 arcmin (110 kpc) northwest of IC 4200 and is the closest object to our target. In addition, our H i image shows two more sources at ∼3900 km/s. These are 15 and 17 ...
... of the 2MASS objects, 2MASX J13090029–5153544, contains detectable atomic gas at the same velocity of IC 4200: this is an Sc galaxy 6.8 arcmin (110 kpc) northwest of IC 4200 and is the closest object to our target. In addition, our H i image shows two more sources at ∼3900 km/s. These are 15 and 17 ...
Planetary nebula
A planetary nebula, often abbreviated as PN or plural PNe, is a kind of emission nebula consisting of an expanding glowing shell of ionized gas ejected from old red giant stars late in their lives. The word ""nebula"" is Latin for mist or cloud and the term ""planetary nebula"" is a misnomer that originated in the 1780s with astronomer William Herschel because when viewed through his telescope, these objects appeared to him to resemble the rounded shapes of planets. Herschel's name for these objects was popularly adopted and has not been changed. They are a relatively short-lived phenomenon, lasting a few tens of thousands of years, compared to a typical stellar lifetime of several billion years.A mechanism for formation of most planetary nebulae is thought to be the following: at the end of the star's life, during the red giant phase, the outer layers of the star are expelled by strong stellar winds. Eventually, after most of the red giant's atmosphere is dissipated, the exposed hot, luminous core emits ultraviolet radiation to ionize the ejected outer layers of the star. Absorbed ultraviolet light energises the shell of nebulous gas around the central star, appearing as a bright coloured planetary nebula at several discrete visible wavelengths.Planetary nebulae may play a crucial role in the chemical evolution of the Milky Way, returning material to the interstellar medium from stars where elements, the products of nucleosynthesis (such as carbon, nitrogen, oxygen and neon), have been created. Planetary nebulae are also observed in more distant galaxies, yielding useful information about their chemical abundances.In recent years, Hubble Space Telescope images have revealed many planetary nebulae to have extremely complex and varied morphologies. About one-fifth are roughly spherical, but the majority are not spherically symmetric. The mechanisms which produce such a wide variety of shapes and features are not yet well understood, but binary central stars, stellar winds and magnetic fields may play a role.