[AAVSO-HEN] GRB 090902B: ROTSE-III Detection of Optical Afterglow

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TITLE:   GCN CIRCULAR
NUMBER:  9878
SUBJECT: GRB 090902B: ROTSE-III Detection of Optical Afterglow
DATE:    09/09/03 20:40:17 GMT
FROM:    Shashi Bhushan Pandey at ROTSE  <shaship at umich.edu>

S. B. Pandey, W. Zheng, F. Yuan and C. Akerlof (U Mich), report on behalf
of the
ROTSE collaboration:

ROTSE-IIIa, located at the Siding Spring Observatory Australia, responded ~
283 sec after the GBM trigger 273582310 (Bissaldi E. & Connaughton V. GCNC
9866). The Set of images starting ~ 1.4 hours after the trigger covered the
GRB 090902B location. The OT (Perley et al. GCNC 9870, Kennea & Stratta
GCNC 9868) was detected at 15.9+-0.2 mag in the sum of 30x60 sec exposures.

The images taken by ROTSE-IIIc (located naer the H.E.S.S. site at Mt.
Gamsberg, Namibia) around 6.6 hours after the burst marginally detect the
OT, indicating a decay of ~ 2 magnitudes. The unfiltered images were
calibrated relative to USNO B1.0. Further analysis is in progress.