Radiative hydrodynamics simulations of red supergiant stars. III
... gravity of Betelgeuse is poorly known, and this is not without consequences for the analysis that will be presented in Sect. 6.1 (see especially Fig. 18). For the computation of the intensity maps and spectra based on snapshots from the RHD simulations, we used the code OPTIM3D (see Paper I) which t ...
... gravity of Betelgeuse is poorly known, and this is not without consequences for the analysis that will be presented in Sect. 6.1 (see especially Fig. 18). For the computation of the intensity maps and spectra based on snapshots from the RHD simulations, we used the code OPTIM3D (see Paper I) which t ...
Characterizing the Cool KOIs III. KOI
... is necessary to estimate its luminosity and hence mass. In a previous paper (Muirhead et al. 2011b, hereafter Paper 1), we acquired a K-band spectrum of KOI 961 as part of a survey of low-mass KOIs. The spectrum confirmed that it is a dwarf and not a giant based on the shallowness of the CO absorpti ...
... is necessary to estimate its luminosity and hence mass. In a previous paper (Muirhead et al. 2011b, hereafter Paper 1), we acquired a K-band spectrum of KOI 961 as part of a survey of low-mass KOIs. The spectrum confirmed that it is a dwarf and not a giant based on the shallowness of the CO absorpti ...
space telescope imaging spectrograph survey of far
... The same consideration renders these features accessible in distant, unresolved stars. Furthermore, the UV coronal forbidden lines suffer much lower continuum absorption than coronal permitted lines, such as Mg x 625, that fall within the H i Lyman continuum (200–912 Å). This allows probes of loca ...
... The same consideration renders these features accessible in distant, unresolved stars. Furthermore, the UV coronal forbidden lines suffer much lower continuum absorption than coronal permitted lines, such as Mg x 625, that fall within the H i Lyman continuum (200–912 Å). This allows probes of loca ...
THE ORION NEBULA AND ITS ASSOCIATED POPULATION C. R. O
... because of the low temperature of θ 1 Ori C. Also, the Heo zone is quite narrow, but it did not provide a good match to observed line ratios outside of the central region. A more self consistent model was calculated by Baldwin et al. (1991) using the CLOUDY (Ferland et al. 1998) PI program, with whi ...
... because of the low temperature of θ 1 Ori C. Also, the Heo zone is quite narrow, but it did not provide a good match to observed line ratios outside of the central region. A more self consistent model was calculated by Baldwin et al. (1991) using the CLOUDY (Ferland et al. 1998) PI program, with whi ...
Differential rotation of main sequence F stars
... are prescribed by the boundary conditions and the stellar stratification, respectively, the only way for the system to adjust is by increasing the convection velocity, and hence shortening the turnover time. The values found are smaller than the 13.95 d of Kim & Demarque (1996), but the curve in Fig ...
... are prescribed by the boundary conditions and the stellar stratification, respectively, the only way for the system to adjust is by increasing the convection velocity, and hence shortening the turnover time. The values found are smaller than the 13.95 d of Kim & Demarque (1996), but the curve in Fig ...
Letter to the Editor - Max-Planck
... emission. In Cygnus X-1, strong reflection features indicate coronal emission in the X-ray band, but the jet emission may emerge in the gamma-ray band. The absence of reflection features in the spectra of the ultraluminous compact X-ray sources in nearby galaxies suggests that they are dominated by ...
... emission. In Cygnus X-1, strong reflection features indicate coronal emission in the X-ray band, but the jet emission may emerge in the gamma-ray band. The absence of reflection features in the spectra of the ultraluminous compact X-ray sources in nearby galaxies suggests that they are dominated by ...
Astronomy Astrophysics Kuiper belts around nearby stars &
... Feltzing (2000); Manoj et al. (2006); Thévenin & Idiart (1999). (c) Distances are from the Hipparcos Catalogue (Perryman et al. 1997) (d) From López-Santiago et al. (2006). Marked as T Tau-type in SIMBAD astronomical database. (e) Quadruple system composed of two spectroscopic binaries, Aa+b and Ba+ ...
... Feltzing (2000); Manoj et al. (2006); Thévenin & Idiart (1999). (c) Distances are from the Hipparcos Catalogue (Perryman et al. 1997) (d) From López-Santiago et al. (2006). Marked as T Tau-type in SIMBAD astronomical database. (e) Quadruple system composed of two spectroscopic binaries, Aa+b and Ba+ ...
ASTRONOMY AND ASTROPHYSICS Evolutionary models for solar
... 4.1. Open and globular cluster main sequences • 47 Tuc (Fig. 4) This globular cluster has been observed recently by Santiago et al. (1996) with the HST Wide Field and Planetary Camera-2 (WFPC2) in the F 606W and F 814W filters. Thanks to the courtesy of G. Gilmore and R. Elson, we are able to compar ...
... 4.1. Open and globular cluster main sequences • 47 Tuc (Fig. 4) This globular cluster has been observed recently by Santiago et al. (1996) with the HST Wide Field and Planetary Camera-2 (WFPC2) in the F 606W and F 814W filters. Thanks to the courtesy of G. Gilmore and R. Elson, we are able to compar ...
Massive z~1.3 evolved galaxies revealed
... two EROs is L ∼ 7L∗ . The brightest galaxies in the sample of Cimatti et al. (1999) have luminosities lower than L∗ while the candidate old galaxy Cl 0939+4713B revealed by Soifer et al. (1999) has a luminosity comparable to those of our targets if the possible magnification induced by the foregroun ...
... two EROs is L ∼ 7L∗ . The brightest galaxies in the sample of Cimatti et al. (1999) have luminosities lower than L∗ while the candidate old galaxy Cl 0939+4713B revealed by Soifer et al. (1999) has a luminosity comparable to those of our targets if the possible magnification induced by the foregroun ...
Applications of Photospheric Spot Temperature Models ... Stellar Angular Momentum Evolution
... T Tauri stars in the Trapezium region of the Orion Nebula Cluster. Our aim is to search for the relationship , if any, between spot temperatures and stellar rotation periods to better understand the relationship between accretion and angular momentum regulation in T Tauri stars. Current magnetic dis ...
... T Tauri stars in the Trapezium region of the Orion Nebula Cluster. Our aim is to search for the relationship , if any, between spot temperatures and stellar rotation periods to better understand the relationship between accretion and angular momentum regulation in T Tauri stars. Current magnetic dis ...
The Development of Constructed Response Astronomy Assessment
... the stars light is dispersed into a spectrum they are known as absorption lines. To an observer the color of a star is set by the wavelengths of light at which the star is most luminous. These dominant wavelengths are set by the stars thermal continuum emission. The absorption line processes are a ...
... the stars light is dispersed into a spectrum they are known as absorption lines. To an observer the color of a star is set by the wavelengths of light at which the star is most luminous. These dominant wavelengths are set by the stars thermal continuum emission. The absorption line processes are a ...
Masses, Radii, and Equation of State of Neutron Stars
... A number of other double neutron systems (DNSs) have since been discovered. The eleven systems for which mass constraints are known are listed in the top two groups in Table 1, together with the latest references. These systems are relatively rare, about 5% of the currently known population of binar ...
... A number of other double neutron systems (DNSs) have since been discovered. The eleven systems for which mass constraints are known are listed in the top two groups in Table 1, together with the latest references. These systems are relatively rare, about 5% of the currently known population of binar ...
observations and theory of star cluster formation
... Vogelaar and Wakker 1994). This power law structure includes both gas that is self-gravitating and gas that is non-self-gravitating, so the origin is not purely gravitational fragmentation. The most likely source is some combination of turbulence (see review in Falgarone and Phillips 1991), agglomer ...
... Vogelaar and Wakker 1994). This power law structure includes both gas that is self-gravitating and gas that is non-self-gravitating, so the origin is not purely gravitational fragmentation. The most likely source is some combination of turbulence (see review in Falgarone and Phillips 1991), agglomer ...
A propelling neutron star in the enigmatic Be-star γ Cassiopeia
... longer than the characteristic spin-down time at the propeller stage during the disc accretion on to the NS with the same magnetospheric ...
... longer than the characteristic spin-down time at the propeller stage during the disc accretion on to the NS with the same magnetospheric ...
The Tip of the Red Giant Branch and Distance of the Magellanic
... formed in the literature. We do not make any attempt to transform a magnitude, i.e. an integrated flux over the passband, into a flux density at a reference wavelength, in order to suppress one step which already makes an assumption on the spectral distribution of the source. We only use the integra ...
... formed in the literature. We do not make any attempt to transform a magnitude, i.e. an integrated flux over the passband, into a flux density at a reference wavelength, in order to suppress one step which already makes an assumption on the spectral distribution of the source. We only use the integra ...
Merging white dwarfs and thermonuclear supernovae
... the SN Ia rate. Furthermore, the expected range in mass matches that for which detonations yield sufficient 56 Ni. The questions are whether fusion is ignited, and whether this triggers a detonation. From simulations, the outcome of a white-dwarf merger depends strongly on whether the masses are sim ...
... the SN Ia rate. Furthermore, the expected range in mass matches that for which detonations yield sufficient 56 Ni. The questions are whether fusion is ignited, and whether this triggers a detonation. From simulations, the outcome of a white-dwarf merger depends strongly on whether the masses are sim ...
xrayecc
... star. In larger mass systems, a second mechanism tends to dominate. This is wind driven transfer. Giant stars can lose material from their outer layers, which forms a wind. The companion moves through this wind, and so will accrete matter as it orbits. In this case, the shape of the orbit is importa ...
... star. In larger mass systems, a second mechanism tends to dominate. This is wind driven transfer. Giant stars can lose material from their outer layers, which forms a wind. The companion moves through this wind, and so will accrete matter as it orbits. In this case, the shape of the orbit is importa ...
GAIA A Stereoscopic Census of our Galaxy - Cosmos
... – unbiased sky sampling (magnitude, colour, resolution) – all-sky catalogue at Gaia resolution (0.1 arcsec) to G~20 mag does not ...
... – unbiased sky sampling (magnitude, colour, resolution) – all-sky catalogue at Gaia resolution (0.1 arcsec) to G~20 mag does not ...
KIC 8462852 Faded Throughout the Kepler Mission
... rotated by 90◦ every three months, there are generally three consecutive FFIs with all stars located on the same pixels. A star then cycles through four different detectors over the course of a year, returning to its original position and repeating the cycle a year later. Because there are ∼ 13 obse ...
... rotated by 90◦ every three months, there are generally three consecutive FFIs with all stars located on the same pixels. A star then cycles through four different detectors over the course of a year, returning to its original position and repeating the cycle a year later. Because there are ∼ 13 obse ...
Formation of low-mass helium white dwarfs
... and low magnetic fields. These neutron stars are believed to be the end-product of binary evolution, in which an old neutron star accretes matter and angular momentum from a close stellar companion for an extended period of time, while being observable as an X-ray binary. During this evolutionary ph ...
... and low magnetic fields. These neutron stars are believed to be the end-product of binary evolution, in which an old neutron star accretes matter and angular momentum from a close stellar companion for an extended period of time, while being observable as an X-ray binary. During this evolutionary ph ...
Post Common Envelope Binaries from SDSS. I: 101 white dwarf
... We present a detailed analysis of 101 white dwarf-main sequence binaries (WDMS) from the Sloan Digital Sky Survey (SDSS) for which multiple SDSS spectra are available. We detect significant radial velocity variations in 18 WDMS, identifying them as post common envelope binaries (PCEBs) or strong PCE ...
... We present a detailed analysis of 101 white dwarf-main sequence binaries (WDMS) from the Sloan Digital Sky Survey (SDSS) for which multiple SDSS spectra are available. We detect significant radial velocity variations in 18 WDMS, identifying them as post common envelope binaries (PCEBs) or strong PCE ...
A DEBRIS disk around the planet hosting M
... addition, there are a few candidate disks with excesses above photospheric level (e.g. Smith et al. 2006; Lestrade et al. 2006; Plavchan et al. 2009). Finally, in the cluster NGC 2547 (∼40 Myr old and ∼433 pc), deep Spitzer MIPS observations have revealed 11 M-stars with 24 μm excesses above photosp ...
... addition, there are a few candidate disks with excesses above photospheric level (e.g. Smith et al. 2006; Lestrade et al. 2006; Plavchan et al. 2009). Finally, in the cluster NGC 2547 (∼40 Myr old and ∼433 pc), deep Spitzer MIPS observations have revealed 11 M-stars with 24 μm excesses above photosp ...
Heating and Cooling of Neutron Star Crusts
... stars cooling into quiescence. Transient neutron stars are a class of objects which are observed to go through accretion outburst periods followed by long quiescent intervals. These sources offer unique opportunities to probe the interior physics of neutron stars. In order to interpret these observa ...
... stars cooling into quiescence. Transient neutron stars are a class of objects which are observed to go through accretion outburst periods followed by long quiescent intervals. These sources offer unique opportunities to probe the interior physics of neutron stars. In order to interpret these observa ...
Foretellings of Ragnar\" ok: World-engulfing Asymptotic Giants and
... frequency components. f ′ and cF are order-unity parameters, and γF an exponent determining the nature of the frequency dependence. Analytical and numerical work suggests ...
... frequency components. f ′ and cF are order-unity parameters, and γF an exponent determining the nature of the frequency dependence. Analytical and numerical work suggests ...
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.