[ RadSafe ] the magnetar eruption

[A Karam]

OK - I dug up some information on the magnetar we've been discussing.  The integrated energy output was about 10^46 ergs and the distance was about 15 kilo-parsecs.  One parsec is about 3.26 light years, or about 3.086x10^18 cm.  
 
Quick calculation - the energy flux at the top of the earth's atmosphere from the magnetar flare was about 0.4 ergs per square cm, integrated over the entire event (assuming a total energy of 10^46 ergs).  1 rad is equal to the absorption of 100 ergs per gram of absorber, so this would give a maximum dose of about 4 mrad (40 microGy) to someone above the atmosphere.  So it's not dangerous (even to astronauts), but still pretty impressive from such a great distance.
 
Some other comparisons - a really big solar flare has an energy of about 10^36 ergs (about 1000 times that of a normal flare), a supernova has an energy of about 10^50 - 10^51 ergs, and a gamma ray burst is up to 10^54 ergs (if memory serves me correctly).  Incidentally, I once calculated that a gamma ray burst in the Andromeda Galaxy would produce a measureable dose at the Earth.
 
Andy