High Energy Astrophysics h energy astrophysics typically deals with x-rays a er energy radiation. It also deals with high energy rinos and other particles such as protons, electron gh energy radiation is produced by objects at high atures and/or relativistic particles. 1 ev = 10,000 K, 1 kev = 10 7 K • • • usually requires compact objects such as white dwa ron stars or blackholes with deep gravitational pot V esp =(2GM/R) 1/2 approaching c Or R not much greater than the Schwarzschild radiu GM/c 2 (2.95 km for a solar mass object).
High Energy Astrophysics. •. •. •. High energy astrophysics typically deals with x-rays and higher energy radiation. It also deals with high energy neutrinos and other particles such as protons, electrons, - PowerPoint PPT Presentation
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High Energy Astrophysics
High energy astrophysics typically deals with x-rays and higher energy radiation. It also deals with high energy
neutrinos and other particles such as protons, electrons, positrons etc.
High energy radiation is produced by objects at high temperatures and/or relativistic particles.
1 ev = 10,000 K, 1 kev = 107 K
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This usually requires compact objects such as white dwarfs, neutron stars or blackholes with deep gravitational potential.
Vesp=(2GM/R)1/2 approaching c
Or R not much greater than the Schwarzschild radius: 2 GM/c2 (2.95 km for a solar mass object).
X-ray astronomy: 0.1 to 100 kev
Gamma-ray astronomy: >100 kev.
E=h \nu = k T ==> x-rays probe 106 -- 109 K and gamma-rays > 109 K
Eddington Luminosity: 1.3x1038 erg/s for 1 Mo.
Optically thick blackbody radiation in x-rayrequires a compact object!
(derive the Eddington limit)
T as a function of object mass, radius (in units of Schwarzschild radius) and Luminosity (in units of Eddington luminosity), is given by:
T ~ 7 kev (L/L_Edd)^{1/4} (R/R_s)^{-1/2} (M/M_sun)^{-1/4}
Brief Property and History of Compact Objects
White dwarfs: R~10,000 km, Vesc~0.02 c, density~ 106 g/cc
(Nuclear reaction is more efficient source of energythan the PE release of in-falling gas on WDs).
1. 1914: Adams-- Sirius B has M~ 1Mo, T~ 8000 K, R~10,000km2. 1925: Adams confirmed M & R by measuring gravitational
redshift -- z ~ GM/(R c2)=0.0003.
3. 1926: F-D statistics discovered. Fowler applied it to model WDs.
4. 1930: Chandrasekhar: WD model including relativity; mass limit.