continuum emission and absorption and emission...

X-Ray Emission Mechanisms

Continuum emission !and !

absorption and emission lines

Elena Jiménez Bailón IA-UNAM

Ensenada, México

X-Ray Emission Mechanisms

1 Continuum emission

1.1 Thermal emission 1.2 Non-thermal emission

2 Emission Lines in X-rays

3 Absorption Lines in X-rays

outline

PART I

PART I

PART II

PART II

X-rays

Energy range: 0.1-100 Å 1x106 - 1x109 k 0.1-120 keV Highest emission: PKS 2126-150 z=3.7 Lx=5x1047 erg/s Lowest emission: Moon 7x1011 erg/s

VENUS IN X-Rays

Instruments to observe in X-rays

XMM-NEWTON CHANDRA SUZAKU

8

X-Ray EmissionContinuum emission

Fairall 31

X-Ray Emission

Black body emission --> temperatures > 106 k Material is almost completely ionised (no molecules or light atoms) Free-Free or Bremsstrahlung Free-bound or radiative recombination!

Cyclotron and Synchrotron emission Compton and Inverse Compton emission !

Continuum emission

bremsstrahlung

Radiative recombination

compton effectsynchrotron emission

NON THERMALTHERMAL

Continuum EmissionBlack body emission Free-Free or Bremsstrahlung Free-bound or radiative recombination!

NON THERMAL

THERMAL

Compton and Inverse Compton emission !Cyclotron and Synchrotron emission

The electrons are in Maxwell-Bolztman distribution: particles in thermodynamic equilibrium move freely without interacting one with each other, except for very brief collisions in which they exchange energy and momentum Temperatures > 106 k

The electrons distribution is a power law

The system has no temperature

X-Ray Emission

+ An ensemble of charge particles (ions) absorbing incident radiation

+ The absorbed radiation increase the “temperature” of the gas, which in turn radiates

+ The medium is optically thick + The radiation can be obtained through the

radiative transport equation.

Blackbody emission

Assume the perfect absorber: a container with a small hole: when a photon gets in it is difficult that the photon escapes. That’s what we call black body. The gas inside the container is in thermal equilibrium. Black-Body Radiation

If this container is heated, the walls emit photons filling the inside withradiation. Each photon is reabsorbed (the hole being negligible) - this isthermodynamic equilibrium - each physical process is balanced by theinverse. All populations described by Saha-Boltzmann statistics

A container that is completely closed exceptfor a very small hole in one wall. Any lightentering the hole has a very small probabilityof finding its way out again, and willeventually be absorbed by the walls or the gasinside the container: this is a perfect absorber

Of course there is a very small chance that the photon will find the hole again and getout - this probability is related the size of the hole relative to the area of the walls andtheir roughness and reflection coefficient. So it is not truly perfect, but can clearly bemade close enough that we cannot measure the difference. The container, or morespecifically the hole is called a BLACK BODY

THERMAL!

CONTINUUM

X-Ray EmissionBlackbody emission

Kirchhoff Law

A blackbody emission must follow the radiative transfer equation:

where I represents the intensity of the radiation and the j and a, are the emission and absorption coefficients. In thermal equilibrium, the intensity must be constant along the propagation path (or equivalent, along the optical depth (d!):

So, for a blackbody, the radiative transfer equation is:

Where B"(T) is the so-call Planck function and using the absorption and emission coefficients:

Kirchoff’s Lawmatter & radiation in thermal equilibrium:

in equilibrium the intensity must be spatially constant:

and hence:

i.e., if a material absorbs well at some wavelength it will also radiate well at thesame wavelength.

for thermal emission

i.e., source function & intensity are equal, and since

Kirchoff’s law holds for all thermal radiation, but not all thermal radiation isblackbody radiation. Thermal radiation only becomes blackbody radiation foroptically thick media. When this is not the case then andHowever since still holds,

only zero for BB-radiation



and hence:








and hence:








and hence:






Kirchoff Law

Optical Depth & Source FunctionThe RTE takes a particularly simple form if we replace path length, s byoptical depth, !"

In terms of pure absorption:

A medium is said to be optically thick, or opaque when !" integrated along atypical path through the medium > 1

When !" < 1 then the medium is said to be optically thin or transparent

Thus the formal solution of the RTE is:

Radiative Transfer Equation

Intensity is conserved along a ray

Unless there is emission or absorption

With emission coefficient, j! in W m-3 sr-1 Hz-1

and absorption coefficient, "! in m-1

The Equation of Radiative Transfer

THERMAL!

CONTINUUM


One of the consequences of the Kirchoff Law is that the intensity of the radiations at a given frequency only depends on the temperature. Therefore the blackbody emits light at all wavelengths with a certain efficiency for each temperature:

BB IntensityAn important property of of I! is that it is independent of the properties of theenclosure and depends only on TEMPERATURE.

B!(T) is called the PLANCK FUNCTION

Any object with a temperature above absolute zero emits light of all wavelengths withvarying degrees of efficiency; an ideal emitter is an object that absorbs all of thelight energy incident upon it and reradiates this energy with a characteristicspectrum. Because it reflects no light it is called a blackbody, and the radiation iscalled Blackbody radiation.

THERMAL!

CONTINUUM


22 Fundamentals of Radiatiw T m f e r

X (cm)

- c

L

w nl

c

I N

I N

u ( H z )

I l l l l l l l l i l l l l l l l l 106 104 102 1 10 2 10 4 10 6 10 8 10 10 i0-'2

h(cm)

Figrrre 1.11 Spctrutn of btackbody mdiation at Wrious tempemtams (taken from Kmus, J. D. 1% Radio Astronomy, McCmw-Hill Book Cavy)

so that

2hv3/c2 B'(T)= exp(hv/kT)- 1 '

(1.51)

Equation (1.51) expresses the Planck law.

unit frequency we have If we express the Planck law per unit wavelength interval instead of per

2hc2/~5 exp(hc/AkT)- 1 *

(1.52)


X (cm)

- c

L

w nl

c

I N

I N

u ( H z )


h(cm)


so that


(1.51)




(1.52)


X (cm)

- c

L

w nl

c

I N

I N

u ( H z )


h(cm)


so that


(1.51)




(1.52)

For higher temperatures the peak emission of the blackbody goes to higher energies (to the blue) The bolometric intensity of a blackbody is calculated integrating the intensity B, in all frequencies:

Assuming that the particles inside the blackbody are in thermal equilibrium and both photons and particles have the same temperature we can derive the blackbody emission using thermodynamical methods.

ergs s-1cm-2Hz-1steradian-1

ergs s-1cm-2steradian-1

THERMAL

CONTINUUM


The Stefan-Boltzmann lawSince temperature and volume are independent quantities for BB:

the soln of which:Integrated planck fn. Is defined by:

The emergent flux from an isotropically emittingsurface (BB) is ! x brightness

STEFAN-BOLTZMANN stefan-boltzmann constant

The bolometric intensity of a blackbody is calculated integrating the intensity B, in all frequencies, and so, the total energy radiated per unit of area and time across all wavelengths is:

THERMAL!

CONTINUUM

X-Ray EmissionBlackbody emission in astrophysics

All hot ˜106 k medium emits as a blackbody: stars, AGN emission, interstellar gas, intracluster gas…

RX1836.5-3754 in X-Rays

Neutron star Chandra Observation

Drake et al. 2002

THERMAL

CONTINUUM

X-Ray Emission

Free-free or bremsstrahlung emission

THERMAL!

CONTINUUM

The radiations is produce by an electron which is accelerated by an electrostatic field of charged particles: ions or nuclei of atoms

When a charge particle is accelerated it radiates (Lamor Law).

The value of the acceleration depends on distance, Z and velocity.

Considering also the density of media: ne and ni

The ionised medium is assume to be in local thermal equilibrium (LTE), with a temperature T and therefore following a Maxwell-Boltzman distribution!

This form of continuum emission is very common in X-ray as the gas which emits in X-rays is composed by a wide range of ionised especies.

X-Ray Emission


THERMAL!

CONTINUUM

The Coma Cluster

Total Mass 1015 Msol

1000 galaxies

Emits as bremsstrahlung + emission lines

X-Ray Emission


THERMAL!

CONTINUUM

The gas inside the clusters of Galaxies emits in X-rays via free-free emission:

+ The effective temperature can reach !8 keV (108 k)

+ The density of the gas is very low ne˜104m-3 and therefore is optically thin

X-Ray Emission

Describes the capture of an unbound electrons into a bound level i (into an ion)

The radiated photon has an energy higher than Ei

The emission is proportional to NeN(Z,i+1)Ei-3

In general it is very very weak but gives us an !excellent diagnostic if it can be measure. Could be relevant in Clusters of galaxies, binary systems, AGN…

Radiative recombination or Free-Bound Emission

THERMAL!

CONTINUUM

X-Ray Emission

Electrons moving in the presence of a magnetic field experience a Lorentz force, therefore accelerate and radiate (Lamor Law again)

As the force must be perpendicular to the magnetic field B, the movement of the electron is helicoidal, a combination of:

+ circular motion around the magnetic field with a frequency which depends on the magnetic field wB=qB/#mec

+ uniform motion along the magnetic field (this movement is not accelerated so no radiation is produce)

There are two regimes for this radiation:

+ v<<c non-relativistic velocities cyclotron emission!

+ v˜c relativistic velocities synchrotron emission

Radiation by electrons in a magnetic Field NON-THERMAL!

CONTINUUM

X-Ray Emission

Non-relativistic electrons moving in a magnetic field emit cyclotron radiation The frequency of the circular movement for the non-relativistic approach can be simplify to:

wC=eB/m

In a line of sight perpendicular to the magnetic field B, the acceleration of the electron has a sinusoidal pattern. Therefore, the radiation is polarised at this frequency, with a dipole radiation pattern: two lobes.

The intensity of the radiation depends on square of the acceleration, and this on the velocity and B. In this regime, only in strong magnetic fields the intensity of the radiation is detectable. Also, as the frequency depends also of B, for B=1010-12 G, wC falls in hard X-rays 10-30 keV.

Cyclotron Radiation NON-THERMAL!

CONTINUUM

X-Ray Emission

In hard X-ray neutron star binaries and some isolated, magnetic fields can reach these values. Her X1: In this binary system, the accreting protons are radiating in the presence of a strong magnetic field B˜1012 G

1E 1207.4-5209: In this isolated neutron star, the residuals found in the XMM-Newton spectrum fitted with a thermal emission (blackbody) at 0.7, 1.4, 2.1 (2.8) keV can be explained as cyclotron scattering features.

Cyclotron Radiation NON-THERMAL

CONTINUUM

1E 1207.4-5209 (Bignami et al. 2003)

X-Ray Emission

Relativistic electrons moving in a magnetic field emit synchrotron radiation

wB=2#2qB/me (observer frame)

When v˜c, the relativistic beaming makes the cyclotronic bipolar radiation to be concentrated in a narrow angle in the direction of the movement of the e-.

Synchrotron Radiation NON-THERMAL!

CONTINUUM

X-Ray EmissionSynchrotron Radiation NON-THERMAL

CONTINUUM

X-Ray Emission

The power radiated by an electron with energy E is:

As the processes which produce relativistic electrons in astronomy normally lead to a power law, E-$, and the synchrotron radiation results from the superposition of individual electron spectra, then the radiation spectrum is also a power-law with index b=($-1)/2

Synchrotron Radiation NON-THERMAL!

CONTINUUM

X-Ray EmissionSynchrotron Radiation

!"#$%&'"()* +,#$*-*./)#()*0102%"3%.%-'*24$"% 567685677

9:;:+"#$4)#4$*0<=04>0!?@Tanto la existencia de un disco grueso cerca del SMBH como lapresencia de campos magnéticos están siendo investigados comoposibles causantes de la existencia de jets en los AGN. Los jetsestarían alineados con el eje de rotación del disco y el disco gruesoharía de embudo para material que sería expulsado a velocidadesrelativistas, ayudados y siguiendo la trayectoria impuesta por loscampos magnéticos.

El hecho de que en muchos AGN solo se observa un jet se sueleexplicar con efectos de orientación, ya que si el jet está ligeramentealineado con la visual existen efectos de “relativistic beaming” quehace que el jet apuntando hacia el observador aparezca mucho másbrillante que el otro.Los jets son globalmente neutros, asíque deben estar formados porelectrones/positrones (menosmasivos y más fáciles de acelerar) oelectrones/iones.

NASA

The jets emit synchrotron radiation due to the relativistic velocity por electron-positron pairs and the magnetic field close to the AGN

!"#$%&'"()* +,#$*-*./)#()*0102%"3%.%-'*24$"% 567685677

9:;:+"#$4)#4$*0<=04>0!?@Cuando el material es expulsado en la forma de un jet, su energía esen su mayor parte cinética. Este jet encuentra material del IGM y sefrena, excitando nubes de gas y polvo y produciendo ondas dechoque. Este proceso es muy complicado (debe tener en cuentatambién turbulencias, interacción del campo magnético con elmaterial del IGM, etc…).

Los jets emiten radiación sincrotrón, que debe desacelerar laspartículas. Típicamente las partículas deberían frenarse por completo(haber radiado toda su energía) antes de 10000 yr, por lo que nopuede haber jets muy largos. Pero estos se observan, así que debenexistir mecanismos de aceleración (choques, campos magnéticosperturbados, presión de radiación,…).

MPIfR

MPIfR

NON-THERMAL!

CONTINUUM

X-Ray EmissionSynchrotron Radiation

The radiation de-accelerates particles. Typically the particles would completely de-accelerate after 10 thousand years but we observe very long jets.

Possible mechanisms of acceleration are magnetic fields, radiation pressure and shocks.

NON-THERMAL!

CONTINUUM

M87

X-Ray Emission

Crab Nebula

SNR Filamentary emission due to H and O lines Radio to X-rays emission dominated by synchrotron Central pulsar or neutron star Radio emission is a power law and polarised

Synchrotron Radiation NON-THERMAL

CONTINUUM

Crab Nebula in X-ray, optical, IR and Radio

X-Ray Emission

When a free electron and a photon scatter and the exchange energy. Can be:

+ Direct Compton effect: low energy photon ends with lower energy (when electrons are cooler than photons)

+ Inverse Compton effect: low energy photon ends with higher energy (when electrons are cooler than photons)

Compton effect NON-THERMAL!

CONTINUUM

X-Ray EmissionCompton effect

With at least UV photons boosted by hot electrons can reach X-rays

NON-THERMAL

CONTINUUM


The corona in AGN

The simplest model postulates an accretion disk with two phases, an inner hotter one and an exterior cooler.

The photons from the exterior phase interact with the inner region electrons.

Photons are upper scattered and emitted in X-rays, as a power law.

Cut-off energy producing the Compton Hump!

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9:;:+"#$4)#4$*0<=04>0!?@En una región más externa, hasta 105rs (1pc para 108 Mb) habría undisco fino soportado por presión del gas. Esta parte del disco es cadavez más ancha según nos alejamos del SMBH. Como la parte internaes ancha, el disco caliente puede irradiar el disco más externo.

Finalmente la parte más externa se rompería en nubes de gasindividuales (que podrían ir cayendo a zonas más internas al chocarentre ellas).

!"#$%&'"()* +,#$*-*./)#()*0102%"3%.%-'*24$"% 567685677

9:5:;*"-%"0%<"=$>*)(%?*.="0@=0.%"0!AB

Gilli(2007)

Risaliti & Elvis (2004)

NON-THERMAL!

CONTINUUM


The corona in X-ray binaries

X-ray binaries often also emit a power-law spectrum of hard X-rays and even gamma-rays.

Its origin is Compton scattering of softer X-rays and ultraviolett radiation in a tenuous corona of very hot electrons, which may be located on top of (and below) the accretion disk, or in the innermost portions of the accretion flow.

NON-THERMAL!

CONTINUUM

X-Ray Emission Mechanisms II

!Emission and Absorption features

Elena Jiménez Bailón IA-UNAM

Ensenada, México

X-Ray EmissionContinuum Emission

NON-THERMAL

CONTINUUM

Thermal Equilibrium Electron in magnetic fields

Photon-electron up-scattering

Electrons in electric field

Isolated neutron starsX-ray binaries

Supernovae & SNRStellar corona X-ray binariesAGN Clusters of Galaxies

Synchrotron: GRB, Blazars, jets ICE: X-ray binaries, AGN, SN

X-Ray EmissionAbsorption and Emission lines

Bound-bound radiation An electron moves to a lower atomic energy level emitting a photon

Fluorescence

Charge interchange

An ion interacts with an neutral atom exchanging electrons

Absorption features

bound-bound radiation

charge interchange

EMISSION

ABSORPTION

EMISSION

EMISSION

X-Ray EmissionEmission lines

Bound-bound radiation

An electron moves to a lower atomic energy level emitting a photon

The process is the following:

1. Excitation of atoms by: 1. Thermal collision 2. Radiative excitation

2. Radiative de-excitation

The most common of line emission is from collisionally but also from photoionisation


Excitation and Ionisation

When two atoms collide and some of the energy of the collision is transferred to the electron, bumping it to a higher level



When two atoms collide and some of the energy of the collision is transferred to the electron, escaping from the atom converting it to an ion



When a photon with high energy is absorbed by an atom dissociating it into an ion and an electron

Also photoexcitation !!!



An atom emits spontaneously one of its electrons. It can occur when the electrons in outer-shells are excited or when one or more inner-shell electrons are missing (AUGER EFFECT)


Deexcitation

When a deexcitation occurs a photon is emitted.


Recombination

An electron and an ion combine to form an atom emitting a photon

X-Ray Emission

Emission lines

Gabriel & Jordan 1969

Ly series transitions n>=2 —> n=1


Bound-bound radiation

Ly series transition of H-like ionsRatio of line intensities: Energy resolution

a=e2/hc Lines are bright Abundance and gas velocity determination Not good for density and temperature estimation

Ne X @ 107 K

Foster el al. 2012


Binary System Procyon

He series transitions

n=2 —> n=1


He-like series transition

Sensitive to temperature and density

Foster et al. 2012

It was firstly wide use in solar plasma Now in collosionally (stellar corona) and photo ionised (X-ray binaries, AGN)


More complex ions…

Virtually impossible!


In summary…


How do we identify emission lines?

By matching the observed line with the expected line (theoretical or laboratory determination)

Problems:

Unless the analysis is done line by line taking into account wavelength errors is a nightmare Not all wavelengths are known

Accuracy of 1% not always enough:

v/c=Dl/l —> v=0.01c= 1000km/s

Use APEC instead of MEKAL if you need accuracy



ATOMDB Chianti SPEX


Grating spectrum of the Seyfert 2 galaxy NGC1068

Collisional plasma H-like and He-like transitions of carbon to silicon Fe L-shell emission lines narrow RRC hints of photoexcitacion

+ Study of the Chemistry of clusters

+ 70% ends as colapse stars + 30% as SNR, mainly SN Ia

Werner et al. 2007 de Plaa et al. 2006

Galaxy clusters

37

Origin Of Elements In Galaxy Clusters Origin Of Elements In Galaxy Clusters

• Abundances – 30% of the supernovae in these clusters

were exploding white dwarfs (Type Ia’)– 70% were collapsing stars at the end of

their lives (core collapse)

Sersic 159-03 2A 0335+096

N. Werner, et al. ,

2006, A&A 446, 475;

J. de Plaa, et al.

2006, A&A 452, 397

& 2007, A&A 465,

345

37

Origin Of Elements In Galaxy Clusters Origin Of Elements In Galaxy Clusters

• Abundances – 30% of the supernovae in these clusters

were exploding white dwarfs (Type Ia’)– 70% were collapsing stars at the end of

their lives (core collapse)

Sersic 159-03 2A 0335+096

N. Werner, et al. ,

2006, A&A 446, 475;

J. de Plaa, et al.

2006, A&A 452, 397

& 2007, A&A 465,

345

X-Ray Emission

X-Ray Emission

Fluorescence

Absorption of an incident photon which excites an atom and follow by the transfer of an outer shell electron down to the vacant level, emitting a photon with an E equal to the difference of the two levels.

Emission lines

X-Ray EmissionAbsorption and Emission lines

Fluorescence

Absorption of an incident photon which excites an atom and follow by the transfer of an outer shell electron down to the vacant level, emitting a photon with an E equal to the difference of the two levels.

There are only certain ways in which the electron drops to a lower energy level:

K-alpha —> from L shell to K shell K-beta —> from M shell to K shell M-alpha —> from M shell to L shell

X-Ray Emission

Fluorescence emission lines in the Moon

Emission lines

X-Ray Emission

Iron line in AGN

Emission lines

The fluorescence emission is in general weak, but the intensity yield with Z4, so it is appreciable for high-Z elements


The iron Ka fluorescence emission line

La línea de Fe¿Dónde y cómo se origina?

0.5 1 1.5

Line profile

Gravitational redshiftGeneral relativity

Transverse Doppler shift

Beaming

Special relativity

Newtonian

� � � " � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � �� ff� � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � �� ! � ! �

El hecho de que este originándose en un disco que está girando hace que se generen dos picos de emisión, corridos uno al azul otro al rojo.

La relatividad especial, que debe aplicarse debido al hecho de que el material se esta moviendo a grandes velocidades, hace que el pico azul sufra un aumento frente al pico rojo.

La relatividad general hace que el perfil de la línea se ensanche y se corra hacia el rojo, por el llamado efecto Doppler transversal (el material que se mueve a gran velocidad se retarda) y corrimiento al rojo gravitacional (el material cerca del influjo de un intenso potencial gravitatorio se retrasa).

La línea de Fe¿Dónde y cómo se origina?

El ángulo de inclinación con el que vemos el disco tiene el efecto

de mover el pico azul mayores energías según aumenta el ángulo.

31

!"#$%&'()*&*+(,,(#)&-"#+&("#)&./ $)%&0&,1*''&

2"$),(2(#),&()&21*&$32(4*&5$'$67&89&:;:;/<=>

• )$""#?&'()*&@*7-*"2&8&

Î A"#$%&'()*,&-"#+&("#)&./ $)%&0&,1*''&

31$"$32*"(B*%&A7C

– line ration (photons) 1:20– 1.3 – 400 rg– emissivity index 4– a > 0.98

Î D"*EF*)37/%*G*)%*)2&'$5,&A*2?**)&

21*&:HI/8/J*K&$)%&8/</J*4&A$)%

Î Negative lag for f> 6 x 10-4 HzÎ Power law changes before refection

• LHMH&D$A($)N&O::=N&P$2F"*&<>=N&><:

1H 0707-495

AGN and X-ray binaries Narrow 200 keV in BLR, NLR or inner disk Broad due to relativistic effects

Relativistic Iron Line

Resultados

+ 10% of AGN present broad Fe line

+ In a flux limited sample: 36% of AGN present broad Fe line

+ All detections are produce for L< 1044 erg/s

+ No difference for Sy and QSO

+ Mean inclination is 28±5 deg

+ No spin determination

12 Guainazzi et al.: The ultimate driver of relativistic effects in AGN

0.01

0.1

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/s/k

eV

NGC4507

105−4−2

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Mrk348

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NGC4388

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Markarian6

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NGC2110

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10−3

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NGC5252

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NGC7172

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0241+622

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NGC5506

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NGC4151

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0.01

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NVSSJ173728−290802

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0.01

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NGC526A

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MCG−5−23−16

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Fig. 9. Spectra (upper panels) and residuals in units of standard deviations (lower panels) when the best-fit models asin Tab. 3 are applied to the GREDOS sample.

X-Ray Emission

Núcleos Galácticos Activos

NGC3516: Apart form the 6.4 keV line, a 6.1 keV line is detected varying its energy within the observation from 5.7 to 6.5 keV. A “hot spot” co-rotating in the disk at a distance from 3.5 to 8 rg Iwasawa et al. 2005

Elusive Fe lines

34

Flux And Energy Modulation Of Iron Flux And Energy Modulation Of Iron

Emission In NGC 3516Emission In NGC 3516

• K. Iwasawa, G. Miniutti, A.C. Fabian, 2004, MNRAS 355, 1073

“Co-rotating” flare at a (3.5-8) rSch

• Mass of the BH: (1-5) × 107Mo

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Flux And Energy Modulation Of Iron Flux And Energy Modulation Of Iron

Emission In NGC 3516Emission In NGC 3516

• K. Iwasawa, G. Miniutti, A.C. Fabian, 2004, MNRAS 355, 1073

“Co-rotating” flare at a (3.5-8) rSch

• Mass of the BH: (1-5) × 107Mo

X-Ray Emission

Charge interchange

An ion interacts with an neutral atom (H or He) picking up an electron in a excited state. The electron decays and emits a photon.

We need neutral atoms coexisting with ions (an X-ray gas)

The solar wind has plenty of highly ionised carbon and oxygen. The neutral atoms of Hydrogen are in the solar system (a comet) !

C/1999 S4 charge exchange from solar wind

Emission lines

X-Ray Emission

Absorption features

Absorption of a photon of a certain energy that excites or ionised the atom

Close related to photoionisation

It is used to calculate abundance, density, and velocity

Probability of an absorption process

RRC

X-Ray Emission

Absorption lines

LMC X3 (Wang et al 2005; Yao et al. 2008 & 2009)

The high resolution spectrographs allow to study the absorption lines in K and L band of several elements. The more abundant are Oxygen and Neon Diagnosis of abundance, temperature, gas velocity…

Detected in AGN, interestella gas…

Mrk 421

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•!One line (e.g., OVII K!) ! velocity centroid and EW ! constraints on the column density, assuming b and T •!Two lines of different ionization states (OVII and OVIII K!) ! T •!Two lines of the same state (K! and K") ! b •!Lines from different species ! abundance fa •!Joint-fit of absorption and emission data --> pathlength and density •!Multiple sightlines --> differential hot gas properties

Spectroscopic diagnostics

X-Ray Emission

Absorption features

X-Ray EmissionUTA (Unresolved Transition Array)

X-Ray EmissionContinuum Emission

NON-THERMAL

CONTINUUM

Thermal Equilibrium Electron in magnetic fields

Photon-electron up-scattering

Electrons in electric field

Isolated neutron starsX-ray binaries

Supernovae & SNRStellar corona X-ray binariesAGN Clusters of Galaxies

Synchrotron: GRB, Blazars, jets ICE: X-ray binaries, AGN, SN

X-Ray Emission

Emission and Absorption features

Emission lines —> Information of temperature, abundance, density of medium, velocity Collisional Photoionased Fluorescence

Absorption Features —> Information about abundance, density, velocity

continuum emission and absorption and emission...

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