Migrating Dust Particles
... to the star, at different times. With a computer simulation we can see how long the disk survives to create and feed planets. In chapter 2 we will go through all properties of a protoplanetary disk. We start off with the Minimum Mass Solar Nebula in chapter 2.1, beginning with describing the column ...
... to the star, at different times. With a computer simulation we can see how long the disk survives to create and feed planets. In chapter 2 we will go through all properties of a protoplanetary disk. We start off with the Minimum Mass Solar Nebula in chapter 2.1, beginning with describing the column ...
Observation of Circumstellar Disks: Dust and Gas Components
... stars. They found that the observed inner disk sizes (rin ~ 0.1 AU) of T Tauri stars are consistent with the presence of an optically thin cavity for a NIR emission arising from silicate grains of sizes a ≥ 0.5–1 µm that are heated close to their temperature of sublimation. At NIR and optical wavele ...
... stars. They found that the observed inner disk sizes (rin ~ 0.1 AU) of T Tauri stars are consistent with the presence of an optically thin cavity for a NIR emission arising from silicate grains of sizes a ≥ 0.5–1 µm that are heated close to their temperature of sublimation. At NIR and optical wavele ...
Dust-free quasars in the early Universe
... six representative quasars from our sample in the four IRAC channels, the IRS PUI blue band (15.6 mm) and the MIPS 24 mm band. Typical on-source integration time of the Spitzer observations was 10230 min per source per band. The integration time for J000520006 at 15.6 and 24 mm was about four hours ...
... six representative quasars from our sample in the four IRAC channels, the IRS PUI blue band (15.6 mm) and the MIPS 24 mm band. Typical on-source integration time of the Spitzer observations was 10230 min per source per band. The integration time for J000520006 at 15.6 and 24 mm was about four hours ...
The stellar populations in the low-luminosity, early
... many luminous ETGs that have been the subject of stellar population analysis. Therefore, results for LLEs may be more susceptible to the well-known age–metallicity degeneracies that plague such analysis. It is for this reason that we wished to check our results for the most extreme LLEs, using new d ...
... many luminous ETGs that have been the subject of stellar population analysis. Therefore, results for LLEs may be more susceptible to the well-known age–metallicity degeneracies that plague such analysis. It is for this reason that we wished to check our results for the most extreme LLEs, using new d ...
Extraordinary Luminous Soft X-Ray Transient MAXI
... dwarf in a binary with a Be star, located near the Small Magellanic Cloud. An early turn-on of the super-soft X-ray source (SSS) phase (<0.44 days), the short SSS phase duration of about one month, and a 0.92 keV neon emission line found in the third MAXI scan, 1296 s after the first detection, sugg ...
... dwarf in a binary with a Be star, located near the Small Magellanic Cloud. An early turn-on of the super-soft X-ray source (SSS) phase (<0.44 days), the short SSS phase duration of about one month, and a 0.92 keV neon emission line found in the third MAXI scan, 1296 s after the first detection, sugg ...
Origin and Evolution of the Abundance Gradient along the Milky
... “inside-out” disk formation. In most classical chemical evolution models, it is generally assumed that the disk forms by gas infalling from the outer halo, and that the infall can be described by an exponential law, in which the infall time scale is always assumed to be radially dependent τ = τ (r), ...
... “inside-out” disk formation. In most classical chemical evolution models, it is generally assumed that the disk forms by gas infalling from the outer halo, and that the infall can be described by an exponential law, in which the infall time scale is always assumed to be radially dependent τ = τ (r), ...
The physics of neutron stars
... carries away results in a significant decrease in both the relativity were measured for the double pulsar. Any two orbit size and the orbital period. The measured decrease of them uniquely define masses of both pulsars MA and in the orbital period of the Hulse – Taylor pulsar is con- MB , while the ...
... carries away results in a significant decrease in both the relativity were measured for the double pulsar. Any two orbit size and the orbital period. The measured decrease of them uniquely define masses of both pulsars MA and in the orbital period of the Hulse – Taylor pulsar is con- MB , while the ...
Asymptotic Giant Branch stars viewed up-close and far-off
... Evolution of a 5 M⊙ star: The evolution of a 5 M⊙ star in the HR-diagram is shown in the right panel of Fig. 1.1. Due to the higher mass, and hence higher temperature, the nuclear burning in the core becomes highly sensitive to the temperature, leading to the development of a convective core. As hyd ...
... Evolution of a 5 M⊙ star: The evolution of a 5 M⊙ star in the HR-diagram is shown in the right panel of Fig. 1.1. Due to the higher mass, and hence higher temperature, the nuclear burning in the core becomes highly sensitive to the temperature, leading to the development of a convective core. As hyd ...
shock structures and momentum transfer in herbig
... profile that varies spatially across the object, it is easy to become overwhelmed by the sheer volume of information. In this section we will consider how to interpret spectra of HH objects and explore what these data tell us about conditions in the flows. A. Structure of Radiative Shocks The high r ...
... profile that varies spatially across the object, it is easy to become overwhelmed by the sheer volume of information. In this section we will consider how to interpret spectra of HH objects and explore what these data tell us about conditions in the flows. A. Structure of Radiative Shocks The high r ...
The importance of episodic accretion for low
... (2009b) include radiative feedback due to the conversion of gravitational energy to thermal energy only down to the sink radius, i.e. 0.5 AU; thus, Bate (2009b) simulations only account for a small fraction (∼ 2%) of the total radiative feedback from young protostars and represent a lower limit on t ...
... (2009b) include radiative feedback due to the conversion of gravitational energy to thermal energy only down to the sink radius, i.e. 0.5 AU; thus, Bate (2009b) simulations only account for a small fraction (∼ 2%) of the total radiative feedback from young protostars and represent a lower limit on t ...
Dust in Protoplanetary Disks: Properties and Evolution
... grown to centimeter size by the time the central star becomes optically visible. However, one should remember that this technique is limited today by the sensitivity and resolution of existing millimeter interferometers. For example, studies of the radial dependence of the dust properties are still ...
... grown to centimeter size by the time the central star becomes optically visible. However, one should remember that this technique is limited today by the sensitivity and resolution of existing millimeter interferometers. For example, studies of the radial dependence of the dust properties are still ...
Star formation rates from young-star counts and the structure of the
... occur. A similar conclusion is reached by Heiderman et al. (2010) who study the SFR versus gas within those clouds using YSOs. The typical spatial scale over which they compare these quantities is from a few tenths of a parsec to a few parsec. Their data show a very sharp decrease in SFR below ...
... occur. A similar conclusion is reached by Heiderman et al. (2010) who study the SFR versus gas within those clouds using YSOs. The typical spatial scale over which they compare these quantities is from a few tenths of a parsec to a few parsec. Their data show a very sharp decrease in SFR below ...
Galactic Stellar and Substellar Initial Mass Function Invited Review Gilles Chabrier
... ABSTRACT. We review recent determinations of the present-day mass function (PDMF) and initial mass function (IMF) in various components of the Galaxy—disk, spheroid, young, and globular clusters—and in conditions characteristic of early star formation. As a general feature, the IMF is found to depen ...
... ABSTRACT. We review recent determinations of the present-day mass function (PDMF) and initial mass function (IMF) in various components of the Galaxy—disk, spheroid, young, and globular clusters—and in conditions characteristic of early star formation. As a general feature, the IMF is found to depen ...
The Kuiper Belt Explored by Serendipitous Stellar Occultations
... R* is the radius of the star projected at the distance of the occulting object. Note that if the star’s apparent size is known, the occultation profile provides some information on the object’s size without any hypothesis about its albedo. The angular sizes of the stars depend on their spectral and ...
... R* is the radius of the star projected at the distance of the occulting object. Note that if the star’s apparent size is known, the occultation profile provides some information on the object’s size without any hypothesis about its albedo. The angular sizes of the stars depend on their spectral and ...
Andrea Santangelo
... • How the energy of the line is related to the luminosity ? Do we observe a change of regime ...
... • How the energy of the line is related to the luminosity ? Do we observe a change of regime ...
ongoing massive star formation in the bulge of m511 hjglm lamers,2
... F814W in 1995. We will refer to these Ðlters as the UV, U, B, V , R, and I Ðlters. The observations in the UV, U, and B Ðlters were split into four, three, and two exposures of 500, 400, and 700 s respectively, while a single exposure of 600 s was taken with the remaining Ðlters. The data were proce ...
... F814W in 1995. We will refer to these Ðlters as the UV, U, B, V , R, and I Ðlters. The observations in the UV, U, and B Ðlters were split into four, three, and two exposures of 500, 400, and 700 s respectively, while a single exposure of 600 s was taken with the remaining Ðlters. The data were proce ...
CORONAL EVOLUTION OF THE SUN IN TIME: HIGH
... 1030 ergs s1 for a solar-mass star; Maggio et al. 1987; Güdel et al. 1997a]. Even the magnetic cycle of the Sun induces an X-ray luminosity variation over 1 order of magnitude (Micela & Marino 2003). Such systematic cyclic or semicyclic variations in turn limit the accuracy with which we can attri ...
... 1030 ergs s1 for a solar-mass star; Maggio et al. 1987; Güdel et al. 1997a]. Even the magnetic cycle of the Sun induces an X-ray luminosity variation over 1 order of magnitude (Micela & Marino 2003). Such systematic cyclic or semicyclic variations in turn limit the accuracy with which we can attri ...
Maximum Mass Restraint of Neutron Stars
... star are influenced at high levels. A solid conclusion is not possible however, until more high level magnetic fields can be observed. In most cases particular temperature, pressure, and quantum state requirements must be met for significant changes in the EOS to take place. Even if just the outer l ...
... star are influenced at high levels. A solid conclusion is not possible however, until more high level magnetic fields can be observed. In most cases particular temperature, pressure, and quantum state requirements must be met for significant changes in the EOS to take place. Even if just the outer l ...
Black hole tidal problem in the Fermi normal coordinates
... where r denotes the orbital separation and µcrit is a constant ≈ 10–20 which depends on r/M , R/M , spin of the black hole, and equations of state (see Sec. V). If the condition (1) is satisfied outside a minimum orbital radius (e.g., r = 6GM/c2 for a star in a circular orbit around a Schwarzschild ...
... where r denotes the orbital separation and µcrit is a constant ≈ 10–20 which depends on r/M , R/M , spin of the black hole, and equations of state (see Sec. V). If the condition (1) is satisfied outside a minimum orbital radius (e.g., r = 6GM/c2 for a star in a circular orbit around a Schwarzschild ...
H 2 O, OH, SiO, NH 3 and CH 3 OH
... Prestellar cores start off with similar masses. Their location within the molecular cloud determines the final mass of the star. High mass stars are formed in the cluster centres where the gas reservoir is denser. ...
... Prestellar cores start off with similar masses. Their location within the molecular cloud determines the final mass of the star. High mass stars are formed in the cluster centres where the gas reservoir is denser. ...
Computation of the off-axis effective area of the New Hard X
... able to effectively focus X-rays beyond the present limit of 10 keV. This will be made possible not only by the increase of the size of the optics, but also by the adoption of shallow incidence angles and multilayer coatings to extend the reflected bandwidth to hard X-rays. The sensitivity of these ...
... able to effectively focus X-rays beyond the present limit of 10 keV. This will be made possible not only by the increase of the size of the optics, but also by the adoption of shallow incidence angles and multilayer coatings to extend the reflected bandwidth to hard X-rays. The sensitivity of these ...
Radio-loud ROSAT sources near the North Ecliptic Pole
... RASS catalog will take years, special attention has been paid to the regions of the ecliptic poles which have unusually long exposures. As the ROSAT satellite carried out scans on great circles along ecliptic latitudes, the two ecliptic poles were observed for half a year once per orbit for up to 32 ...
... RASS catalog will take years, special attention has been paid to the regions of the ecliptic poles which have unusually long exposures. As the ROSAT satellite carried out scans on great circles along ecliptic latitudes, the two ecliptic poles were observed for half a year once per orbit for up to 32 ...
Optical hydrogen absorption consistent with a thin bow shock
... appear as the absorption of stellar flux when in truth it is merely variation in the amount emitted by the star. For our case, stellar variability due to time-dependent Balmer line emission from active regions can mimic the spectral line absorption: if the star is more active during the times when t ...
... appear as the absorption of stellar flux when in truth it is merely variation in the amount emitted by the star. For our case, stellar variability due to time-dependent Balmer line emission from active regions can mimic the spectral line absorption: if the star is more active during the times when t ...
Cygnus X-1
Cygnus X-1 (abbreviated Cyg X-1) is a well-known galactic X-ray source, thought to be a black hole, in the constellation Cygnus. It was discovered in 1964 during a rocket flight and is one of the strongest X-ray sources seen from Earth, producing a peak X-ray flux density of 6977229999999999999♠2.3×10−23 Wm−2 Hz−1 (7003230000000000000♠2.3×103 Jansky). Cygnus X-1 was the first X-ray source widely accepted to be a black hole and it remains among the most studied astronomical objects in its class. The compact object is now estimated to have a mass about 14.8 times the mass of the Sun and has been shown to be too small to be any known kind of normal star, or other likely object besides a black hole. If so, the radius of its event horizon is about 7004440000000000000♠44 km.Cygnus X-1 belongs to a high-mass X-ray binary system about 7019574266339685654♠6070 ly from the Sun that includes a blue supergiant variable star designated HDE 226868 which it orbits at about 0.2 AU, or 20% of the distance from the Earth to the Sun. A stellar wind from the star provides material for an accretion disk around the X-ray source. Matter in the inner disk is heated to millions of degrees, generating the observed X-rays. A pair of jets, arranged perpendicular to the disk, are carrying part of the energy of the infalling material away into interstellar space.This system may belong to a stellar association called Cygnus OB3, which would mean that Cygnus X-1 is about five million years old and formed from a progenitor star that had more than 7001400000000000000♠40 solar masses. The majority of the star's mass was shed, most likely as a stellar wind. If this star had then exploded as a supernova, the resulting force would most likely have ejected the remnant from the system. Hence the star may have instead collapsed directly into a black hole.Cygnus X-1 was the subject of a friendly scientific wager between physicists Stephen Hawking and Kip Thorne in 1975, with Hawking betting that it was not a black hole. He conceded the bet in 1990 after observational data had strengthened the case that there was indeed a black hole in the system. This hypothesis has not been confirmed due to a lack of direct observation but has generally been accepted from indirect evidence.