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GCN Circular 9246

GRB 090424: THO optical observations
2009-04-25T05:35:50Z (15 years ago)
Veli-Pekka Hentunen at Taurus Hill Obs,A95 <>
Markku Nissinen (Taurus Hill Observatory) and Veli-Pekka Hentunen (Taurus
Hill Observatory) report:

We used 0.35m C14 XLT telescope with SBIG ST-8XME CCD at Taurus Hill Observatory
(Varkaus, Finland) for follow-up observations of GRB090424. The observations 
were started on April 24, at 19:59 UTC (5.8 hours after the burst) and stopped
on April 24, at 23:11 UTC. Sixteen unfiltered 600 seconds images were taken. 
We detected clear optical afterglow object at the position of RA 12h 38m 05s.12 and DEC 
+16o 50' 15".2 with respect to POSSII F/USNO-B1.0 which is in good correlation 
with enhanced Swift XRT-UVOT position. Upper limit for the observations is >20.4 mag.
Quoted upper limit has been derived using POSSII F and USNO-B1.0 field stars 
as reference.

Filter     Tmid(s)      Exp(s)     Mag (CR) USNO-B1.0
u         20:14:23      600      19.55+/-0.37
u         20:37:30      600      19.95+/-0.38
u         21:32:48      600      20.15+/-0.34

A jpeg preview of the observation showing the position of the afterglow is 
available at this URL:
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