TITLE:   GCN GRB OBSERVATION REPORT
NUMBER:  3990
SUBJECT: GRB 050915a: IR Transient
DATE:    05/09/16 14:52:12 GMT
FROM:    Josh Bloom at UC Berleley  <jbloom@astron.berkeley.edu>

J. S. Bloom (UC Berkeley) reports:

"Further imaging of the field of GRB 050915a (GCNs 3977, 3979, 3983)  
with the PAIRITEL 1.3m began at  2005-09-16 10:58:38 UTC. We confirm  
that the source present in the first epoch (GCN 3984) has faded and  
is thus the likely IR afterglow of GRB 050915a. In particular, the  
mean H-band magnitude of the source during the first epoch was  
H=18.25 +/- 0.16. The source was undetected in the second epoch, with  
an approximate 3-sigma detection threshold of H(upper limit)=18.55 mag.

An improved astrometric solution was obtained for the imaging on  
2005-09-15 UTC, yielding a J2000 position of the IRT of:

    RA    =  05:26:44.804
    DEC = -28:00:59.27

The 1 sigma uncertainties relative to the 2MASS catalog are 0.18" and  
0.09" in RA and DEC, respectively. This position is 3.2" from the  
revised XRT position reported by Grupe et al. (GCN 3983).

We encourage deep z band and NIR imaging."

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