Dosimetry intercomparison using a 35-keV x-ray synchrotron ...
What is X-ray Astronomy?What is X-ray Astronomy? • Energy range ≈ 0.1 - 500 keV (“soft”,...
Transcript of What is X-ray Astronomy?What is X-ray Astronomy? • Energy range ≈ 0.1 - 500 keV (“soft”,...
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What is X-ray Astronomy?• Energy range ≈ 0.1 - 500 keV (“soft”, “hard”)
• Flux: F = 3 x 10-12 ergs/cm2/s over 0.2-10 keV• Luminosity: L = 4D2F = 4 x 1037 ergs/s• Flux density: 2 x 10-4 ph/cm2/s/keV at 1 keV
• Thermal emission: - blackbody - bremsstrahlung - emission/absorption lines (inner electrons)
• Non-thermal emission - synchrotron - inverse Compton
Energy (keV)
Ph
oton
s/cm
2 /s/
keV
Glen Mackie / Sarah Bank / Jörn Wilms
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Magnetic field
by synchrotron radiation (by )
Radiation field
• Bremsstrahlung • emission
e
Matter
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X-ray observations
Complex X-ray spectra: Power-law component with
Γ=1-2 (hot corona + Compton scattering)
Black-body component at soft energies (<1keV; accretion disk)
• Also variability, high/low states, absorption etc…
X-ray Astronomy Summer School, Athens 2006
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Black-Hole vs. Neutron-Star Binaries
Black Holes: Accreted matter disappears beyond the event horizon without a trace.
Neutron Stars: Accreted matter produces an X-ray flash as it impacts on the
neutron star surface.
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DISKSurface
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Ron RemillardRon RemillardKavli Center for Astrophysics and Space ResearchKavli Center for Astrophysics and Space Research
Massachusetts Institute of TechnologyMassachusetts Institute of Technology
http://xte.mit.edu/~rr/rr_8.971.ppthttp://xte.mit.edu/~rr/rr_8.971.ppt
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X-ray States of BHBsX-ray States of BHBs
• Thermal State:
inner accretion disk
Energy spectra Power density spectra
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14
Accretion Disk StructureThe accretion disk (AD) can be
considered as rings or annuli of blackbody emission.
R
blackbody flux
)(4 RT
Model: multi-temperature (multicolor)
disk used to describe thermal
component in x-ray spectra total disk luminosity in steady
state
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X-Ray States: Luminosity
Very High State (VHS) strong ultra-soft (US) component and unbroken power-law (PL)
component; strong QPOs at ~ 10Hz
High/Soft State (HS) US dominates; very weak PL component; high luminosity; MCD
Intermediate State US and steeper PL at high energies
Low/Hard State (LH) no US component; hard power-law PDS (power density
spectrum); ~ 1.7 (2-20keV); low luminosity; radio emission
Quiescent State truncated disk; ADAF down to the ISCO
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X-Ray States: Luminosity“Unified MCD and ADAF model”
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http://arxiv.org/pdf/astro-ph/0506731
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Solar Corona
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Figure 6: Suggested geometries for an accretion disk and Comptonizing corona for predominantly spectrally hard states. The top figure is referred to as a ``slab'' or ``sandwich'' geometry; however, it tends to predict spectra softer than observed. The remaining three show ``photon starved geometries'' wherein the corona is less effectively cooled by soft photons from the disk. The middle two geometries are often referred to as ``sphere+disk geometries'', while the bottom geometry is often referred to as a ``patchy corona'' or ``pill box'' model Chris Reynolds 2003-03-24
http://www.astronomy.ohio-state.edu/~dhw/A825/notes5.pdf