High energy Astrophysics

Mat Page

Mullard Space Science Lab, UCL

Revision lecture

Revision lecture:

• This lecture:• Quick race through the course!

• Intended to inspire you to look back through your notes!

1: What is high energy astrophysics?

• “High energy” because:– Photons emitted above 100 eV (X-ray

sources)– Large energy density in photon field or

magnetic field, (eg X-ray binaries, pulsars)– Large amount of energy stored in

gravitational field (eg Black holes)

• Unusually high concentrations of energy

X-rays from stellar photospheres?• Take the Sun.

T=5800K

XUIVR

X-ray, -ray and radio skies

2: The whole range of X-ray sources

3: emission mechanisms

4+5: accreting X-ray binaries

accretion efficiency

• How much energy can we get from accretion compared to fusion?

• Energy released per unit mass of material accreted = GM/R

• Energy equivalent per unit rest mass = c2

• So we can consider the ‘efficiency’ of accretion to be GM/(Rc2)

• For a white dwarf this is ~ 1.5 x 10-4

• Fusion of hydrogen converts 0.007 of rest mass to energy so we could say this has an efficiency of 0.7%

6: radio galaxies

e.g. Faranoff-Riley 1 galaxy

shell-like filled in

Cas A Crab

7: supernova remnants

8: AGN

9: The X-ray background

Coma cluster

10: Masses of hot gas

11: Gamma-ray bursts

Burst lightcurves

12: Cosmic rays

13: Gravitational waves

14: The Galactic centre

15: The future!