Hard X-ray source sizesHard X-ray source sizes

Eduard Kontar and Natasha Jeffrey

Department of Physics and AstronomyUniversity of Glasgow, UK

Genoa RHESSI workshop , September, 2009

Primary and Compton scattered flux

Id Iu

Observer

Flaring region

Observed Flux = Direct + Scattered

Downward emitted X-ray photons can be either

a) Compton scattered X-rays into observer direction

ora) Photoelectrically

absorbed

Reflected flux

Reflected flux can be ~40-45 % of the total flux even for an isotropic source!

Reflected flux

Observed fluxPrimary

Source sizes

How does X-ray albedo affect the source sizes?

h, s

ourc

e h

eig

ht

X-ray source size

a) Source (r) ~ exp(-r2/(2Size2))

Radial distance from the source centre

b) Photon spectrum is power-law

Primary source:

Isotropic source of photons

Isotropic distribution

Primary Gaussian source Reflected flux

Total observed flux

Source sizes

“Beamed” distribution

“Pan-cake” distribution

Note that total Flux downwards = total Flux upwards!

Source sizes

Size =0.5hSize =2h

Size =0.2h Size =5h

Source sizes: can we detect albedo ?

Size =5h Size =0.2h

Source sizes and Compton back-scattering

X-ray back-scattering need to be taken into account when X-ray source sizes are discussed

X-ray back-scattering component is probably better seen for sources height > source size

X-ray source sizes are sensitive to angular distribution of electrons(additional method to detect angular distribution of electrons? )