[AAVSO-HEN] Arto Oksanen discovers GRB afterglow

[arne]

Last night, October 10, 2007, the Swift gamma-ray burst satellite
announced the second burst of the day at 20:45:47 UT.
Swift is in the process of returning to normal operations,
and therefore only does automatic slewing to a source during
east-coast business hours.  This means that only the 3arcmin
radius gamma-ray localization was available for this burst.

Arto Oksanen, AAVSO Council member and long-time participant
in the High Energy Network, was using the Hankasalmi Observatory
robotic 40cm telescope, and was able to begin imaging within
17 minutes of the burst.  He immediately found a bright
unknown object in the error circle, and reported it to Matt
and myself.  The GCN alert from this report was sent out
about an hour after Arto's observations, and was the discovery
report for this afterglow.

Arto continued to observe, alternating between unfiltered,
V and Ic measures, until nearly 7 hours after the burst.  His
light curve is very good and perfectly adequate to determine
the decay rate of the afterglow.  This detection subsequently
triggered an 1800second Gemini North observation that determined
the redshift of the burst to be z=0.947.

This is the first amateur discovery of an optical afterglow since
Berto Monard accomplished the feat with GRB030725, over
four years ago.  We've put a link to the discovery GCN on the
AAVSO homepage.

Arto's discovery is well-deserved; he has monitored numerous
GRBs over the past few years.  It shows that perseverance works
in this field - many bursts are bright enough to be visible with
small telescopes, and conditions conspire against every observatory,
whether ground-based weather or space-based hardware failures.
Congratulations, Arto!
Arne