JET FORMATION FROM MASSIVE YOUNG STARS
... Observations indicate that outflows from massive young stars are more collimated during their early evolution compared to later stages. Our paper investigates various physical processes that impact the outflow dynamics, i.e., its acceleration and collimation. We perform axisymmetric magnetohydrodyna ...
... Observations indicate that outflows from massive young stars are more collimated during their early evolution compared to later stages. Our paper investigates various physical processes that impact the outflow dynamics, i.e., its acceleration and collimation. We perform axisymmetric magnetohydrodyna ...
INFRARED DUST BUBBLES: PROBING THE DETAILED
... zone where temperature sharply decreases and density rapidly increases (with radius); and a thin, dense shell of shocked H+ gas surrounded by a very thin shell of nonshocked H+ gas at about 104 K. The outer thin shell of 104 K H+ gas is the region classically thought to represent the photoionized H ...
... zone where temperature sharply decreases and density rapidly increases (with radius); and a thin, dense shell of shocked H+ gas surrounded by a very thin shell of nonshocked H+ gas at about 104 K. The outer thin shell of 104 K H+ gas is the region classically thought to represent the photoionized H ...
IGR J18483-0311: a new intermediate supergiant fast X
... In 2007 March 24, we performed optical photometry of IGR J18483−0311 in U, B, V, R, and I bands with the imager SUSI2 installed at ESO/NTT. We used the large field of view (5.′ 5×5.′5), and the plate scale was 0.′′ 16 per pixel. The exposure time was 60 s in all filters for each exposure. We also ob ...
... In 2007 March 24, we performed optical photometry of IGR J18483−0311 in U, B, V, R, and I bands with the imager SUSI2 installed at ESO/NTT. We used the large field of view (5.′ 5×5.′5), and the plate scale was 0.′′ 16 per pixel. The exposure time was 60 s in all filters for each exposure. We also ob ...
Magnetized massive stars as magnetar progenitors
... and envelope, we find a remnant compact object (i.e. neutron star) left behind at the centre with a radius of ∼106 cm and a mass range of ∼1−3 M . Moreover, we find that surface magnetic fields of such a type of compact objects can be ∼1014 –1015 G, consistent with those inferred for magnetars whic ...
... and envelope, we find a remnant compact object (i.e. neutron star) left behind at the centre with a radius of ∼106 cm and a mass range of ∼1−3 M . Moreover, we find that surface magnetic fields of such a type of compact objects can be ∼1014 –1015 G, consistent with those inferred for magnetars whic ...
Microlensing Events by Proxima Centauri in 2014 and 2016
... To refine the impact parameters and times of closest approach, we obtained Hubble Space Telescope (HST ) images of the field on 2012 October 1. Observations were taken with the UVIS channel of the Wide Field Camera 3 (WFC3) in the F475W, F555W, F606W, and F814W filters. Since the background stars ar ...
... To refine the impact parameters and times of closest approach, we obtained Hubble Space Telescope (HST ) images of the field on 2012 October 1. Observations were taken with the UVIS channel of the Wide Field Camera 3 (WFC3) in the F475W, F555W, F606W, and F814W filters. Since the background stars ar ...
Ultraluminous X-ray Sources in Andromeda Galaxy
... scale than the radiation pressure scale height. In these circumstances, a magnetohydrodynamical wave propagating in a direction perpendicular to the direction of the energy flow, causes variations in the density of the gas. Radiation ’leaks’ through the low density regions in these systems into the ...
... scale than the radiation pressure scale height. In these circumstances, a magnetohydrodynamical wave propagating in a direction perpendicular to the direction of the energy flow, causes variations in the density of the gas. Radiation ’leaks’ through the low density regions in these systems into the ...
Molecular Clouds and the Onset of Star Formation
... cloud cores. The clouds have been characterized as both clumpy and filamentary. The general properties on selected scales are listed in Table 2.1. In fact each type of structure exhibits a range of properties [335]. The clumpiness of a molecular cloud can be characterized by a so-called volume filli ...
... cloud cores. The clouds have been characterized as both clumpy and filamentary. The general properties on selected scales are listed in Table 2.1. In fact each type of structure exhibits a range of properties [335]. The clumpiness of a molecular cloud can be characterized by a so-called volume filli ...
An Optical Study of Young Stellar Clusters
... of the stars (temperatures, masses, ages). Specifically, the transformation of spectral types to effective temperatures is quite uncertain (Cohen & Kuhi, 1979; Luhman, 1999). Moreover, the modeling of the evolution of young stars, in terms of effective temperature and radius for a given stellar mass as ...
... of the stars (temperatures, masses, ages). Specifically, the transformation of spectral types to effective temperatures is quite uncertain (Cohen & Kuhi, 1979; Luhman, 1999). Moreover, the modeling of the evolution of young stars, in terms of effective temperature and radius for a given stellar mass as ...
The Herschel Orion Protostar Survey: Luminosity and Envelope
... Class II objects are post-protostellar, when the envelope has dissipated and only a circumstellar disk remains. (See Section 7.2.3 of Furlan et al. 2016 for a small number of exceptions to this distinction.) While Heiderman & Evans (2015) found that only half of their flat-spectrum sources, which we ...
... Class II objects are post-protostellar, when the envelope has dissipated and only a circumstellar disk remains. (See Section 7.2.3 of Furlan et al. 2016 for a small number of exceptions to this distinction.) While Heiderman & Evans (2015) found that only half of their flat-spectrum sources, which we ...
WSokolov-PROTVINO
... Gamma-ray bursts and their afterglows also allow us seeing the most distant explosions of massive stars at the end of their evolution. This is confirmed by observations of the "long" bursts, but, most probably, the "short" GRBs are also related to some very old compact objects formed in the course o ...
... Gamma-ray bursts and their afterglows also allow us seeing the most distant explosions of massive stars at the end of their evolution. This is confirmed by observations of the "long" bursts, but, most probably, the "short" GRBs are also related to some very old compact objects formed in the course o ...
critical angular momentum distributions in collapsars: quiescent
... 3.1. Linear Distributions of Specific Angular Momentum In Paper I, we considered simple, constant distributions of J (R) in order to gauge the effect of the absolute value of angular momentum and the general properties of the flow when compared to previous work, and provide a further guide. When J ( ...
... 3.1. Linear Distributions of Specific Angular Momentum In Paper I, we considered simple, constant distributions of J (R) in order to gauge the effect of the absolute value of angular momentum and the general properties of the flow when compared to previous work, and provide a further guide. When J ( ...
Star Captures by Quasar Accretion Disks: A Possible Explanation of
... & Tan 2003), and hence unstable to form stars? Why is the black hole mass tightly related to the velocity dispersion of the stellar system around it, when the physical scales of these components are so vastly different? Another possibility for the growth of black holes is by the direct capture of st ...
... & Tan 2003), and hence unstable to form stars? Why is the black hole mass tightly related to the velocity dispersion of the stellar system around it, when the physical scales of these components are so vastly different? Another possibility for the growth of black holes is by the direct capture of st ...
astro-ph/9505110 PDF
... Our results are shown in Figures 4 and 5 (Garnett et al. 1994, 1995). We nd that the C/O ratio increases monotonically as a function of O/H, from about 1/4 solar at the lowest metallicities up to solar values. At the same time, C/N also appears to increase with O/H in the irregular galaxies, but th ...
... Our results are shown in Figures 4 and 5 (Garnett et al. 1994, 1995). We nd that the C/O ratio increases monotonically as a function of O/H, from about 1/4 solar at the lowest metallicities up to solar values. At the same time, C/N also appears to increase with O/H in the irregular galaxies, but th ...
HD 24355 observed by the Kepler K2 mission: A rapidly oscillating
... There is an obvious difference between the roAp stars discovered with ground-based photometry, and those first detected by space-based observations: the amplitudes of the pulsations in the ground-based discoveries are generally in the range 0.5 − 10 mmag, whereas the Kepler observations did not dete ...
... There is an obvious difference between the roAp stars discovered with ground-based photometry, and those first detected by space-based observations: the amplitudes of the pulsations in the ground-based discoveries are generally in the range 0.5 − 10 mmag, whereas the Kepler observations did not dete ...
Observed Properties of Exoplanets
... To date, 7 planets are known that cross the disk of their star, 5 found photometrically by the dimming of the star.3), 9), 79) However, the two closest stars with transiting planets (HD 209458, HD 149026) were found first by the Doppler method.13), 34), 70) The fractional dimming of the star’s flux gi ...
... To date, 7 planets are known that cross the disk of their star, 5 found photometrically by the dimming of the star.3), 9), 79) However, the two closest stars with transiting planets (HD 209458, HD 149026) were found first by the Doppler method.13), 34), 70) The fractional dimming of the star’s flux gi ...
sBzKs
... very similar, clustering amplitudes ～10 times higher than generic galaxies in the same magnitude range. This suggests an evolutionary link between sBzKs at z～2 and EROs at z～1, with star formation on sBzKs quenching by z～1 thus producing passively evolving EROs. The clustering amplitude of pBzKs is ...
... very similar, clustering amplitudes ～10 times higher than generic galaxies in the same magnitude range. This suggests an evolutionary link between sBzKs at z～2 and EROs at z～1, with star formation on sBzKs quenching by z～1 thus producing passively evolving EROs. The clustering amplitude of pBzKs is ...
EBL - UCSC Physics - University of California, Santa Cruz
... with ground-based data, and the solid purple triangle is from a measurement by the Large Binocular Camera (Grazian et al. 2009). In the near-IR J, H and K bands, open violet points are the limits from Keenan et al. (2010). Open red triangles are from IRAC on Spitzer (Fazio et al. 2004), and the purp ...
... with ground-based data, and the solid purple triangle is from a measurement by the Large Binocular Camera (Grazian et al. 2009). In the near-IR J, H and K bands, open violet points are the limits from Keenan et al. (2010). Open red triangles are from IRAC on Spitzer (Fazio et al. 2004), and the purp ...
Measuring Reddening with SDSS Stellar Spectra and Recalibrating
... measured. Accordingly, we exclude from this analysis stars targeted to have unusual colors and very red stars with dereddened g − r > 1 mag. Likewise, we exclude any white dwarf targets. Finally, we exclude any objects with stellar parameters marked as unreliable by the SSPP (according the parameter ...
... measured. Accordingly, we exclude from this analysis stars targeted to have unusual colors and very red stars with dereddened g − r > 1 mag. Likewise, we exclude any white dwarf targets. Finally, we exclude any objects with stellar parameters marked as unreliable by the SSPP (according the parameter ...
L95 IRON-RICH EJECTA IN THE SUPERNOVA
... in each radial shell. The mean charge state of each species in the fit is calculated using the values quoted above for kT and ne t. For example, the mean number of electrons per ion is 11.8 for Si and 18.2 for Fe. The main uncertainty in converting EMs to Fe and Si density and mass estimates is not ...
... in each radial shell. The mean charge state of each species in the fit is calculated using the values quoted above for kT and ne t. For example, the mean number of electrons per ion is 11.8 for Si and 18.2 for Fe. The main uncertainty in converting EMs to Fe and Si density and mass estimates is not ...
Hewitt/Lyons/Suchocki/Yeh, Conceptual Integrated Science
... We measure the Sun’s luminosity as LSun. If we were on a spaceship twice as far away from the Sun, its apparent brightness would appear A. B. C. D. ...
... We measure the Sun’s luminosity as LSun. If we were on a spaceship twice as far away from the Sun, its apparent brightness would appear A. B. C. D. ...
Star Cluster Trivia!
... Why are open clusters young but globular clusters are old? Star clusters tend to disperse, or evaporate, over time Open clusters are more loosely bound than globulars - Lose stars more easily, in shorter amount of time - Don’t survive more than a few billion years. Globular clusters - more massive, ...
... Why are open clusters young but globular clusters are old? Star clusters tend to disperse, or evaporate, over time Open clusters are more loosely bound than globulars - Lose stars more easily, in shorter amount of time - Don’t survive more than a few billion years. Globular clusters - more massive, ...
Gas giants in hot water: inhibiting giant planet
... evolution is in fact dominated by the irradiation from the cluster as a whole, and not from the host star, for semi-major axes larger than a few au. This keeps the discs essentially isothermal and hot as a function of radius, affecting their structure and their potential to form planets via gravitat ...
... evolution is in fact dominated by the irradiation from the cluster as a whole, and not from the host star, for semi-major axes larger than a few au. This keeps the discs essentially isothermal and hot as a function of radius, affecting their structure and their potential to form planets via gravitat ...
Galactic Molecular Clouds and Their Place in the
... DMCs contain comparable, by number density, amounts of both atomic and molecular Hydrogen, though Table 1.2 further defines these charateristics. Its close to unity extinction means that background radiation can easily traverse the areas which these clouds occupy, allowing us to detect the absorptio ...
... DMCs contain comparable, by number density, amounts of both atomic and molecular Hydrogen, though Table 1.2 further defines these charateristics. Its close to unity extinction means that background radiation can easily traverse the areas which these clouds occupy, allowing us to detect the absorptio ...
The dual nature of the Milky Way stellar halo
... be stripped from accreted DM satellites, hosting dwarf galaxies, during their orbits before the final merger. Minor mergers are the most probable sources for these kind of stars, firstly because they do not destroy the galactic disk and can thus happen in all evolutionary phases of the life of a disk ...
... be stripped from accreted DM satellites, hosting dwarf galaxies, during their orbits before the final merger. Minor mergers are the most probable sources for these kind of stars, firstly because they do not destroy the galactic disk and can thus happen in all evolutionary phases of the life of a disk ...
William Herschel`s Wonderful Decade, 1781-1790
... late 1780s Saturn’s ring was edge-on to Earth, something that happens every fifteen years or so, and then it may be possible to see moons of Saturn that are normally lost in the glare of the ring. In the summer of 1787, Herschel examined the planet with his twenty-foot, but it was then in a region w ...
... late 1780s Saturn’s ring was edge-on to Earth, something that happens every fifteen years or so, and then it may be possible to see moons of Saturn that are normally lost in the glare of the ring. In the summer of 1787, Herschel examined the planet with his twenty-foot, but it was then in a region w ...
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.