TITLE:   GCN CIRCULAR
NUMBER:  9162
SUBJECT: GRB 090418A: ROTSE-III Refined Analysis
DATE:    09/04/19 16:15:56 GMT
FROM:    Fang Yuan at ROTSE  <yuanfang@umich.edu>

F. Yuan (U Mich) report on behalf of the ROTSE collaboration:

ROTSE-IIIb, located at McDonald Observatory, Texas, responded to GRB  
090418A (Swift trigger 349510; Mangano et al, GCN 9149) 19.0 s after  
the burst, during the gamma-ray emission, and detected the optical  
counterpart (Yuan et al, GCN 9150). We took 10 5-sec, 10 20-sec and 26  
60-sec useful exposures before sunrise. Further analysis of single  
images revealed an initially rising lightcurve with two subsequent  
peaks at ~40s (~15.6 mag) and ~130s (~15.4 mag) before the OT dropped  
below our detection limit.