The University of Sydney Page
... Because the core is degenerate, when helium ignites and produces more energy, the temperature of the core rises but the core does not expand. This means that the rate of energy production keeps going up, which keeps increasing the temperature, in a runaway process. In a few hours the temperature ju ...
... Because the core is degenerate, when helium ignites and produces more energy, the temperature of the core rises but the core does not expand. This means that the rate of energy production keeps going up, which keeps increasing the temperature, in a runaway process. In a few hours the temperature ju ...
Debris disks: dynamics of small particles in
... NB in diffraction limit FWHM ≈ λ/D so that disks of radius r (AU) can be resolved on a telescope D (m) in diameter at wavelength λ (μm) out to dlim = 10rD/λ pc e.g., 100AU disks can be resolved to 18pc with JCMT 50AU disks to 270pc with Gemini/VLT (more like 100pc with stellar flux) ...
... NB in diffraction limit FWHM ≈ λ/D so that disks of radius r (AU) can be resolved on a telescope D (m) in diameter at wavelength λ (μm) out to dlim = 10rD/λ pc e.g., 100AU disks can be resolved to 18pc with JCMT 50AU disks to 270pc with Gemini/VLT (more like 100pc with stellar flux) ...
Formation and Evolution of Binary Millisecond Pulsars with Helium
... interacting binaries. Of particular interest are the millisecond or ‘recycled’ pulsars. The majority of these pulsars are found in binary systems and this affirms the hypothesis that the short rotational periods are caused by the accretion of matter from a companion that had previously overfilled it ...
... interacting binaries. Of particular interest are the millisecond or ‘recycled’ pulsars. The majority of these pulsars are found in binary systems and this affirms the hypothesis that the short rotational periods are caused by the accretion of matter from a companion that had previously overfilled it ...
The thin disk
... Cumulative ranked sum test: straight segments show age intervals over which the velocity dispersion remains constant. Abrupt changes of slope show appearance of discrete component Freeman 1991 ...
... Cumulative ranked sum test: straight segments show age intervals over which the velocity dispersion remains constant. Abrupt changes of slope show appearance of discrete component Freeman 1991 ...
Wind-Blown Bubbles around Evolved Stars
... between the initial fully adiabatic stage to the stage where the swept-up interstellar medium cools radiatively (Falle, 1975). Subsequent numerical studies in two dimensions show that instabilities develop during the evolution of windblown bubbles, where the nature of the instability present depends ...
... between the initial fully adiabatic stage to the stage where the swept-up interstellar medium cools radiatively (Falle, 1975). Subsequent numerical studies in two dimensions show that instabilities develop during the evolution of windblown bubbles, where the nature of the instability present depends ...
AST1100 Lecture Notes
... high that a quantum mechanical effect sets in: there is no more space in the core for more electrons. Quantum physics sets an upper limit on the number of electrons within a certain volume with a certain momentum. This is called electron degeneracy. The core has become electron degenerate. In the n ...
... high that a quantum mechanical effect sets in: there is no more space in the core for more electrons. Quantum physics sets an upper limit on the number of electrons within a certain volume with a certain momentum. This is called electron degeneracy. The core has become electron degenerate. In the n ...
The Components of a Spiral Galaxy
... • Conventional theoretical 'wisdom' : disks form at the center of dark matter halos as a consequence of angular momentum conservation during the dissipational collapse of gas (Fall & Efstathiou 1980) , spheroids result predominantly from merger events" • Thus morphology is a transient feature of t ...
... • Conventional theoretical 'wisdom' : disks form at the center of dark matter halos as a consequence of angular momentum conservation during the dissipational collapse of gas (Fall & Efstathiou 1980) , spheroids result predominantly from merger events" • Thus morphology is a transient feature of t ...
PDF document
... At the position of the GRB in the difference images, our photometric analysis gives R606,AB >28.25 (2 upper limit) and H160,AB = 25.73±0.20. In both cases, we fitted a model point-spread function (psf) and estimated the errors from the variance of the flux at a large number of locations chosen to ha ...
... At the position of the GRB in the difference images, our photometric analysis gives R606,AB >28.25 (2 upper limit) and H160,AB = 25.73±0.20. In both cases, we fitted a model point-spread function (psf) and estimated the errors from the variance of the flux at a large number of locations chosen to ha ...
xrayecc
... This transfer leads to variations in the orbital parameters, including the eccentricity, orbital period and separation. In some binary systems, the accreting component is degenerate, that is a neutron star, or black hole. The infalling matter thus loses a large amount of gravitational energy as it f ...
... This transfer leads to variations in the orbital parameters, including the eccentricity, orbital period and separation. In some binary systems, the accreting component is degenerate, that is a neutron star, or black hole. The infalling matter thus loses a large amount of gravitational energy as it f ...
APS Apr 2008 - User Web Pages
... rates, rather than increasing, as expected theoretically • Such bursts are often much fainter than might be expected (given the wait time and inferred accretion rate), suggesting an “energy leak” • A (possibly) related issue is that “normal” thermonuclear bursts don’t produce enough carbon to power ...
... rates, rather than increasing, as expected theoretically • Such bursts are often much fainter than might be expected (given the wait time and inferred accretion rate), suggesting an “energy leak” • A (possibly) related issue is that “normal” thermonuclear bursts don’t produce enough carbon to power ...
The Astrophysical Origins of the Short
... 3. Concordant production of 26Al, 41Ca requires Fe,Mg silicate mantle to surround Ca,Al-rich core, but real minerals do not separate this way (e.g., Simon et al. 2002) 4. Production of 26Al or 41Ca at meteoritic levels will overproduce 10Be, using best-case scenario [Gounelle et al. (2001)] and new ...
... 3. Concordant production of 26Al, 41Ca requires Fe,Mg silicate mantle to surround Ca,Al-rich core, but real minerals do not separate this way (e.g., Simon et al. 2002) 4. Production of 26Al or 41Ca at meteoritic levels will overproduce 10Be, using best-case scenario [Gounelle et al. (2001)] and new ...
Daly2014
... The normalization and slope of the relationship between beam power and black hole mass provide indications of which model(s) may accurately describe outflows from AGN (Daly & Sprinkle 2014). A low normalization indicates that energy and angular momentum extraction from the accretion disk, as in the ...
... The normalization and slope of the relationship between beam power and black hole mass provide indications of which model(s) may accurately describe outflows from AGN (Daly & Sprinkle 2014). A low normalization indicates that energy and angular momentum extraction from the accretion disk, as in the ...
Bayesian mass and age estimates for transiting exoplanet host stars⋆
... Most of the stars currently known to host exoplanets do not have accurately measured trigonometrical parallaxes. For these stars we set log(L /L ) = 0±5 so that this parameter has a negligible influence on the results. For stars with measured parallaxes the observed luminosity is L = 4πd2 f⊕ wher ...
... Most of the stars currently known to host exoplanets do not have accurately measured trigonometrical parallaxes. For these stars we set log(L /L ) = 0±5 so that this parameter has a negligible influence on the results. For stars with measured parallaxes the observed luminosity is L = 4πd2 f⊕ wher ...
Stellar Evolution Task
... You will have noticed that some horizontal branch stars seemed to be above the normal region favoured by the others. These special stars are variable stars. Maybe you can spot them in the image of an old stellar cluster. These special stars are used to determine distance in our Galaxy. ...
... You will have noticed that some horizontal branch stars seemed to be above the normal region favoured by the others. These special stars are variable stars. Maybe you can spot them in the image of an old stellar cluster. These special stars are used to determine distance in our Galaxy. ...
l~ JHd 111
... dwarf. This dise and espeeially its "hot spot"-Le. the plaee where the gas stream from the red eomponent falls onto the dise-are the most prominent light sources of the entire system. This model resembles that of the X-ray binaries, but the masses and dimensions of dwarf novae are mueh smaller, abou ...
... dwarf. This dise and espeeially its "hot spot"-Le. the plaee where the gas stream from the red eomponent falls onto the dise-are the most prominent light sources of the entire system. This model resembles that of the X-ray binaries, but the masses and dimensions of dwarf novae are mueh smaller, abou ...
Collapse of rapidly rotating massive stellar core to a black hole
... Shock occurs at the disk Outcome: low density region, high temperature thick disk ...
... Shock occurs at the disk Outcome: low density region, high temperature thick disk ...
Gravitational Radiation:
... Comparison with observed waveforms: Tests of general relativity in high dynamical, nonlinear, strong-gravity regime. “Ultimate tests” ...
... Comparison with observed waveforms: Tests of general relativity in high dynamical, nonlinear, strong-gravity regime. “Ultimate tests” ...
The Formation of Systems with Tightly
... for radial gravitational acceleration gr , gas pressure p, gas density ρ, and disk radius r. For a monotonically decreasing pressure, vφ will always be less than the Keplerian orbital speed vK . The result is that a solid, which does not have pressure support and moves at vK , will orbit with a head ...
... for radial gravitational acceleration gr , gas pressure p, gas density ρ, and disk radius r. For a monotonically decreasing pressure, vφ will always be less than the Keplerian orbital speed vK . The result is that a solid, which does not have pressure support and moves at vK , will orbit with a head ...
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.