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GCN Circular 1312

SN 2002ap - peak brightness date (SN/GRB?)
2002-03-28T10:57:54Z (22 years ago)
Eran Ofek at Tel Aviv U. <>
A. Gal-Yam, E. O. Ofek, O. Shemmer

Using the Wise Observatory 1m telescope we have obtained UBVRI
photometry of SN 2002ap during February 2002. Using our most conservative 
estimate for the date of the $B-$band peak, 
Feb. $7.1_{-1.3}^{+7.6}$ days, and assuming that the lag between a
hypothetical GRB (that might have been associated with this SN) and the time
of $B-$band maximum is similar to that measured for SN 1998bw (14.3 days,
Galama et al. 1998), we would expect the GRB trigger to have occurred around
Jan. $23.8_{-1.3}^{+7.6}$ days. 
However, if we use instead our estimated $U-$band peak date, 
Feb. $4.7_{-1.9}^{+1.1}$ days, which is best constrained by our photometry, 
along with the appropriate $U-$band time lag from Galama et al. 1998 
(13.7 days), the resulting GRB trigger time is Jan. $22.0_{-1.9}^{+1.1}$ 
days. Hurley et al. (GCN 1252) found no candidate GRB that might be 
associated with SN 2002ap in an intensive search of gamma-ray data from 
the IPN, starting Jan. 21. Our results suggest that 
the GRB trigger may have occurred outside the time frame searched. 
If the GRB-peak magnitude time lag for SN 2002ap was just one day longer
than the lag measured for SN 1998bw, the trigger is likely to have been
missed by Hurley et al. We conclude that in order to detect, or set a secure
upper limit to the fluence of a GRB associated with SN 2002ap, a search similar
to the one reported by Hurley et al. should be extended to include data
taken several days prior to January 21.   

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