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GCN Circular 2271

GRB 030528: tentative NIR counterpart
2003-06-05T15:21:43Z (20 years ago)
Jochen Greiner at MPI <>
J. Greiner, A. Rau (both MPE Garching) and S. Klose 
(Thueringer Landessternwarte Tautenburg) report for the GRACE collaboration:

We have observed the original, 2 arcmin radius error box of GRB 030528 
(=H2724) (Atteia et al, GCN 2256) with the near-infrared camera SOFI 
at the NTT (La Silla, ESO) on three epochs as given below:

   Date (Start UT)   Filters   Exposure time   Seeing    
  2003-05-29 04:58    JHKs      15 min each     0.6"
  2003-05-30 04:54    JHKs      20 min each     1.0"
  2003-06-01 04:07     Ks       60 min          0.7"

The Chandra sources #1 and #10 (Butler et al., GCN 2269) are within
our field of view, the other two Chandra sources from within the 
shifted GRB location (Villasenor et al, GCN 2261) are outside our 
images. Comparing the Ks band images of the first and third epoch 
reveals a counterpart for each of the two Chandra sources. One of 
these two sources, i.e. #1 = CXOU J170400.3-223710 shows a fading 
by about 0.9 mag. The other of these two Chandra sources, 
#10 = CXOU J170354.0-223654 is about 4 magnitudes brighter in Ks, and
constant to within 0.1 mag (provisional photometric calibration was 
done against the 2MASS catalog, taken from the NASA/ IPAC Infrared 
Science Archive).

We therefore propose Chandra source #1 = CXOU J170400.3-223710 and 
its near-infrared counterpart as the tentative afterglow of GRB 030528.
K band images of two epochs for this source will be displayed at

Since we are missing two of the Chandra sources due to the shift of the
GRB location, only a second Chandra observation can (dis)prove this
tentative counterpart. We note, that the proposed counterpart is
the brightest X-ray source in the previous Chandra image, so a second
Chandra observation of the same exposure time can already be decisive.
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