TITLE: GCN CIRCULAR NUMBER: 11080 SUBJECT: GRB 100807A: P200 Infrared Observations DATE: 10/08/11 15:01:54 GMT FROM: S. Bradley Cenko at Caltech R. Chary and J. Davies (Caltech) report: We have imaged the field of GRB 100807A (Grupe et al., GCN 11067) with the WIRC instrument on the Palomar 200 inch telescope in the J and H bands beginning at 9:47 UT on 7 August (~ 35 mins after the Swift trigger). The fading transient reported in Cenko et al. (GCN 11073) is clearly detected. Using 2MASS stars for relative photometry, we measure the following photometry for the object: UT (mid-point) t_burst (min) Filter Magnitude --------------------------------------------------------------- 09:55 41 J 19.76 +/- 0.1 10:10 56 H 19.05 +/- 0.1 12:16 183 J 21.10 +/- 0.2 The red colors of the source compared to the optical photometry can be attributed to the A_V=2.5 mag of Galactic extinction in this region. A nearby object 3" to the SE is also quite red with H=18.75+/-0.1 and J-H=1.5 mag and could potentially be the host galaxy. All magnitudes are in the Vega system.