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Topic: Eddington luminosity

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	Eddington limit - Wikipedia, the free encyclopedia
		In physics, the Eddington Limit is a natural limit to the luminosity that can be radiated by spherically symmetric accretion onto a compact object, like a fl hole.
		If luminosity exceeds the Eddington limit, there would be so much radiation pressure that the surrounding gas is pushed outward rather than inward.
		Without gas to provide energy, the luminosity naturally decreases to the Eddington limit where gas is pushed inward again.
	en.wikipedia.org /wiki/Eddington_limit (139 words)

	Research Summary (Site not responding. Last check: 2007-10-13)
		Another agreement is between the average luminosity properties of novae which can be used to predict a mass loss and the observed ejected mass of novae, as a function of WD mass.
		The development of a complete 3D simulation of a super Eddington atmosphere has began in order to quantitatively show that atmospheres indeed become inhomogeneous and the wind that is generated by them agrees with the theory developed for the wind.
		The possibility of integrating the wind theory and the theory of super Eddington atmospheres with the simulations of thermonuclear runaways in Novae is being discussed with several nova experts.
	www.cita.utoronto.ca /~shaviv/research/Eddington_Winds.html (666 words)

	Sir Arthur Eddington (Site not responding. Last check: 2007-10-13)
		Eddington severely criticized the work of Chandrasekhar although his own ideas were outdated and incorrect.
		Eddington can be called the "Father of Modern Theoretical Astrophysics." He published several books that helped to expand these areas including "Mathematical Theory of Relativity" which Einstein referred to as the best publication in this area.
		Eddington was one of the earliest creators of the concept of relativity.
	www.usd.edu /phys/courses/phys300/gallery/clark/edd.html (624 words)

	Astrophysics and Mysticism: the life of Arthur Stanley Eddington
		Arthur Stanley Eddington was born on 28 Dec 1882 in Kendal, on the edge of the Lake District.
		Eddington thought he had a proof that the inverse of the fine structure constant (the dimensionless constant formed from the values h, c and e, that governs the strength of radiative interactions in atoms) is precisely 137.
		Eddington identifies three types of knowledge: (1) structural, with the approximate meaning of mathematical, but in Eddington's thinking the structure appears to be almost identified with Group theory, (2) direct awareness (approximately sensation) and (3) sympathetic understanding, which he argues is essential because a remembered sensation is sympathetic understanding of a past sensation.
	silas.psfc.mit.edu /eddington (4942 words)

	Friedrich Meyer (Site not responding. Last check: 2007-10-13)
		Abstract: Ultraluminous X-ray sources (ULXs) with observed luminosities of $10^{39.5}$ to $10^{41}$erg/s and spectra fitted by multi-temperature fl body radiation of temperatures 1-2 keV are thought to be fl holes accreting mass from a late O type stellar companion at high rate.
		In order not to exceed the Eddington limit the accreting fl holes would have to be of intermediate mass, 50-100 $M_\odot$, while the observed disk temperatures are too high for such fl hole masses (Makishima et al.
		In a non-linear version such radiation driven inhomogeneities can allow the escaping flux to exceed the Eddington limit and were suggested as resolution of the ULX problem (Begelman 2000, 2002).
	www.mpa-garching.mpg.de /~bh-grow/Program/Posters/FriedrichMeyer.html (231 words)

	[No title] (Site not responding. Last check: 2007-10-13)
		The Eddington luminosity corresponding to this mass is L
		By contrast the X-ray luminosity of the nucleus of NGC 4258 between 2 - 10 keV is (4 ± 1) × 10
		We show that the properties of the AGN in NGC 4258 can be explained by an accretion flow in the form of a very hot, optically-thin plasma which advects most of the viscously generated thermal energy into the central fl hole and radiates only a small fraction of the energy.
	cfa-www.harvard.edu /ep/preprint/janfeb96/4251.html (278 words)

	[No title]
		In the optical thin case the scattered luminosity is proportional to the mass of the illuminated scattering material.
		The correspondence between the observed scattered flux and the luminosity of the GC is therefore not one to one anymore.
		The dotted line marks the Galactic luminosity produced by X-ray binaries.} \label{flares} \end{figure} \subsection{Fluorescent iron K$_{\alpha}$-line luminosity} Scattering of X-rays produced by a powerful AGN is accompanied by X-ray photo absorption by heavy elements and emission in the narrow fluorescent K$_{\alpha}$-lines.
	www.aoc.nrao.edu /~gcnews/gcnews/Vol.14/conrad@MPA-Garching.MPG.DE_0108294.txt (10422 words)

	[No title]
		Draw a Hertzsprung-Russell diagram, with labelled Luminosity and Temperature axes, and on this draw a main sequence (with some stellar masses labelled), describe the main features of the post-main sequence evolution of stars of different masses, and their final states 10^{10} years after birth.
		Derive the Eddington luminosity, and discuss at least three different astronomical circumstances where it is important.
		What is their peak luminosity (optical band; V band magnitude will do).
	www.astro.caltech.edu /~srk/Option/Sample-Questions.html (1809 words)

	Photospheric radius expansion X-ray bursts as standard candles (Site not responding. Last check: 2007-10-13)
		We examined the maximum bolometric peak luminosities during type I X-ray bursts from the persistent or transient luminous X-ray sources in globular clusters.
		This empirical critical luminosity is consistent with the Eddington luminosity limit for hydrogen poor material.
		Since the critical luminosity is more or less always reached during photospheric radius expansion X-ray bursts (except for one source), such bursts may be regarded as empirical standard candles.
	www.edpsciences.org /articles/aa/abs/2003/08/aah3715/aah3715.html (249 words)

	Eddington Luminosity (Site not responding. Last check: 2007-10-13)
		The classical Eddington luminosity is the theoretical maximum luminosity for a star of a given mass.
		At this luminosity, the outward force due to radiation pressure exactly equals the inward pull due to gravity; particles in the outer layers are no longer bound.
		For the classical Eddington luminosity, the opacity is taken to be entirely due to free electron scattering in a fully ionized gas.
	www.pha.jhu.edu /~ericpeng/seminar/node4.html (274 words)

	The Astrophysics Spectator: Energetics of Keplerian Accretion Disks
		Multiplying this by the thickness of the ring dR and replacing the particle mass with the rate at which mass flows through the disk, dM/dt, and we have the rate at which potential and orbital kinetic energy is convert into thermal energy in a ring of thickness dR.
		For a neutron star, we see that accretion at close to the Eddington limit produces a disk with a surface temperature at its inner edge of over 1 keV, which places its radiation in the soft x-ray band.
		Dropping the luminosity by a factor of 100, which is a very common accretion luminosity in neutron star close binary systems, and we see that the surface temperature drops to 0.5 keV.
	www.astrophysicsspectator.com /background/survey/galactic/DisksAccretionKeplerianEnergetics.html (857 words)

	[No title]
		Within the frame of this model, the fraction of the luminosity emitted in hard X-rays strongly decreases with an increase of the luminosity to the Eddington luminosity ratio.
		The distribution of infrared luminosities, temperatures, opacities and sizes of the emitting dust component are derived from the analysis of the observed infrared spectra of the four selected objects.
		Taken with the bolometric luminosity, this implies that the bulk of the X-rays in PDS 456 are emitted within a few Schwarzschild radii of the central super-massive fl hole.
	www.xray.mpe.mpg.de /~bol/abstracts.txt (6101 words)

	[No title] (Site not responding. Last check: 2007-10-13)
		From the distances to the supernova remnants and the observed burst fluxes, the luminosity of a typical burst from a SGR is $\sim 10^{41}-10^{42}$ erg s$^{-1}$; the March 5, 1979 event from SGR 0526--66 had an inferred peak luminosity of $\sim 5\times 10^{44}$ erg/s.
		These luminosities are orders of magnitude larger than the Eddington luminosity $L_E\sim 2\times 10^{38}$ erg/s for a neutron star.
		Although most of the luminosity emerges in the perpendicular mode, the fraction $\sim (\omega/\omega_c)$ that scatters into the parallel mode dominates the radiation force.
	www.astro.umd.edu /~miller/paper9.html (332 words)

	Hertzsprung-Russell Diagram
		When colour index or, equivalently, temperature, is plotted against absolute luminosity, stellar properties are displayed in two dimensions and any natural clustering of their properties becomes easy to observe.
		A spectroscopic definition of the main sequence, which restricts the term to luminosity class V (dwarfs); stars belonging to other luminosity classes are not considered to be on the main sequence.
		Stellar clusters are invaluable in the study of stellar evolution because, approximately, all of their members are at the same distance, allowing direct and immediate observation of their relative brightness, and because they are assumed to be all of the same approximate age.
	www.peripatus.gen.nz /Astronomy/HerRusDia.html (2389 words)

	Disk luminosity and accretion rates (Site not responding. Last check: 2007-10-13)
		This is the luminosity at which the radiative momentum flux from a spherically symmetric source is balanced by the gravitational force from a central object.
		Generally, however, most source luminosities tend to be below their Eddington value, with the more powerful x-ray sources coming within an order of magnitude or so.
		The latter may itself be radiated in a boundary layer on the surface of the central star, but if a fl hole is the accretor, the energy may be permanently lost.
	astron.berkeley.edu /~jrg/ay202/node116.html (529 words)

	Brightest possible quasar - Bad Astronomy and Universe Today Forum
		Some Blazars have a large blazar multifrequency variability and you must also think about a jet component of the quasar, I think a study has shown that the disc luminosity is often 1 to 20 times related to the jet power.
		As you noted, a logical possible limit is the Eddington Luminosity limit.
		Taking these into account, the maximum expected quasar luminosity could be as high as 10^49 ergs/s or 3e15 L_sun in round numbers.
	www.bautforum.com /showthread.php?p=355331#post355331 (697 words)

	SUN
		The physical parameters deduced directly from observations are luminosity and surface temperature, and indirectly the size of a star.
		This is the period during which its luminosity is derived from the conversion of hydrogen to helium.
		The Eddington luminosity was derived for pure ionized hydrogen.
	www.columbia.edu /~ah297/unesa/astrophysics/astro-chapter5.html (6199 words)

	[No title]
		The maximum luminosity that a body could emit without driving away surrounding material.
		The ring or near ring into which the image of a distant quasar is distorted if the quasar lies directly behind a galaxy or cluster of galaxies producing a gravitational lens.
		A luminosity function is often expressed as the number of objects per unit volume of space that are brighter than a given absolute magnitude or luminosity.
	highered.mcgraw-hill.com /sites/0072482621/student_view0/chapter24/glossary.html (472 words)

	ASTR 304 - 2003W - Week 1
		At this limit the inward gravitational force on a piece of material is balanced by the outgoing radiation pressure.
		Although this limiting luminosity, the Eddington luminosity, can be evaded in various ways, it can provide a useful (if not truly firm) estimate of the minimum mass of a particular source of radiation.
		Equate the outgoing force due to radiation on the pair with the inward force of gravity on the pair.
	www.physics.ubc.ca /~heyl/ASTR304_2003W/week1.html (645 words)

	Implications for GRS 1915+105 (Site not responding. Last check: 2007-10-13)
		If diskoseismic g-modes are responsible for the observed 67 Hz periodicity, then the fl hole mass can range from 10.6 times the mass of the Sun for a non-rotating fl hole to 36.3 times the mass of the Sun for a maximally rotating fl hole.
		Such a large mass might not be unreasonable, given that the maximum observed luminosity for this system reached the Eddington luminosity for a 48 solar mass fl hole.
		(The Eddington luminosity is the maximum luminosity before radiation pressure outward becomes stronger than the pull of gravity inward.
	rocinante.colorado.edu /~mnowak/DISKO/imp19.html (165 words)

	The Role of Accretion (Site not responding. Last check: 2007-10-13)
		The sub-Eddington (and possibly, advective) nature of the accretion will ensure that such sources are of relatively low luminosity, and of low radio power, and such objects might be identifiable with the FR I radio sources as is indeed postulated in the unified models of radio sources (Urry and Padovani 1995).
		This accretion rate is well above the Eddington accretion rate for any reasonable value of BH mass, and will increase rapidly as dynamical friction slows the relative velocities of cloud and BH.
		Although equation(1) suggests that the radius of attraction can become very large for small values of the relative velocity, in practice it is limited by the tidal radius, or radius of influence of the BH.
	www.atnf.csiro.au /pasa/14_3/dopita/paper/node2.html (1838 words)

	[49.16] X-ray Luminosity Function of LMXB in Early Type Galaxies (Site not responding. Last check: 2007-10-13)
		We have derived bias-corrected X-ray luminosity functions (XLFs) of sources detected in a uniformly selected sample of 14 E and S0 galaxies observed with Chandra ACIS-S3.
		The break luminosity is 4.8 +- 1.2 x 1038 ergs s-1, consistent with the Eddington luminosity of the theoretical maximum mass of a neutron star (3 Mo) or of He-enriched neutron star binaries.
		We confirm that the total X-ray luminosity of LMXBs is correlated with the optical and the near-IR luminosities, but in both cases the scatter exceeds that expected from measurement errors.
	www.aas.org /publications/baas/v36n2/aas204/111.htm (353 words)

	Possible Mechanisms
		The classical Eddington limit, where opacity is due to electron scattering only, has already been explained to depict an LBV's tenuous hold on its outer layers.
		For a star that is already near the Eddington limit, this increase in opacity could cause radiation pressure to overwhelm gravity.
		For models incorporating the modified Eddington luminosity,, a star is only in a stable state if: -- the luminosity of the star is below the modified Eddington luminosity; and -- the star is in a local minimum of opacity with respect to effective temperature, i.e.
	www.pha.jhu.edu /~ericpeng/seminar/node8.html (476 words)

	How are black holes and active galactic nuclei connected?
		This is as bright as all the stars in the rest of the galaxy combined.
		These NLRGs are divided further by their morphology, depending on the luminosity of then nucleus and the appearance of jets.
		is the luminosity of the object in units of
	www.astro.queensu.ca /~macmilla/research/projects/bh/node3.html (681 words)

	Hayashida (Site not responding. Last check: 2007-10-13)
		Black Hole (BH) Mass and luminosity are the key parameters of AGNs.
		In this paper, we apply the method to the various classes of AGNs observed with ASCA to see their systematic difference on the luminosity vs mass plane.
		Location on the luminosity mass plane is important not only for the current sate of the AGNs but also for the evolution of the AGNs.
	www.astropa.unipa.it /EVENTS/XRAY2000/X-ray_Astronomy/Hayashida.htm (316 words)

	Unified AGN Model (Site not responding. Last check: 2007-10-13)
		Although there is not yet direct proof of the existence of SMB, energetic arguments as to how can so much energy be generated in such a small volume, rule out dense clusters of stars and other scenarios put forward.
		A qualitative description was put forward by Eddington, who defined a characteristic luminosity (now known as the Eddington luminosity) of a source as being the maximum luminosity of source being fuelled by spherical accretion onto a central object.
		From the precept that the inward gravitational force acting on a gas must balance or exceed the outward radiation pressure, the Eddington limit is defined thus,
	www.astro.soton.ac.uk /~ns/thesis/node19.html (393 words)

	Spectral transition for ULXs (Site not responding. Last check: 2007-10-13)
		We suggest that the high luminosities are truly super-Eddington, but that the source of energy is not accretion, but magnetic extraction of energy from a rapidly rotating spinning fl hole.
		The dissipation of this energy fills the corona above the disk with moderately relativistic particles, part of which impinge on the accretion disk underneath and provide its super-Eddington luminosity.
		We discuss requirements and derive order of magnitude estimates for magnetic field strength, particle density, relativistic gamma-factor and surface density of the disk.
	www.mpa-garching.mpg.de /Binary/emm1380_abstract.html (146 words)

	ASTR 304 - 2003W - Answers for Week 5
		For a neutron star the material is stuck on the surface.
		If the surface luminosity increases faster with temperature than the helium burning rate, then the layer is stable.
		Type-I bursts typically recur on a timescale of hours at one-tenth of the Eddington accretion rate.
	www.physics.ubc.ca /~heyl/ASTR304_2003W/answer5.html (658 words)

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