(meteorobs) Bolide size question

[Leo S.]

Hello all,

The recent Slovenian bolide, and its report on spaceweather.com has 
brought up a couple of questions which I'm curious to find out the 
answers to. Perhaps someone on this list could help me answer these 
questions?

Firstly, on spaceweather.com it says that: "The July 25th fireball falls 
into the category of superbolides--exploding meteors of magnitude -17 or 
brighter. They are, essentially, small asteroids measuring a few to 10 
meters in diameter and massing a few hundred metric tons"

Is it just me or does "a few to 10 meters in diameter" seem a little bit 
of an exaggeration, even for an event of this magnitude? My 
understanding of the subject would be that a -20 mag. could quite easily 
be caused by a meteoroid of less that 1m diameter (with dense stony or 
iron meteoroids), but perhaps I am mistaken! Would anyone here be 
willing to speculate on the the size of this superbolide?

Secondly, assuming a stony or iron composition, and an entry angle of 45 
degrees for sake of argument, what would be the approximate cut-off 
point in terms of diameter for meteoroids to retain cosmic velocity all 
the way down to the ground?

Best regards,
Leo