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GCN Circular 2648

Subject
CXO observation of GRB 040812
Date
2004-08-18T15:27:41Z (20 years ago)
From
Peter Woods at UAH/MSFC <peter.woods@msfc.nasa.gov>
S. Patel (USRA/NSSTC), C. Kouveliotou (NASA/MSFC,NSSTC), S. Mereghetti,
D. Gotz (IASF-Milano), N. Lund, J. Chenevez (Danish Space Research
Institute), P. Ubertini (IASF-Rome), E. van den Heuvel (University of
Amsterdam), K. Hurley (UCB), report on behalf of a larger Integral team:

We observed with Chandra/ACIS-S the error box of the Integral GRB 040812
(Gotz et al. 2004, GCN 2640Loading...
 
 ). The observation started at 2004-08-17
7:08:22 UT, approximately 5 days after the trigger, and lasted for 10
ks. We find 4 sources above SNR=2.6 within a 2' radius (90% c.l.) 
centered at the refined Integral/IBIS location (RA=246.50, DEC=-44.70). 

     No.       RA         Dec      Counts*      SNR
      1  16 26 0.47 -44 41  22.6	  9         2.8
      2  16 26 2.25 -44 43  49.4	 57         6.9
      3  16 26 6.48 -44 43  20.8	 10         2.9
      4  16 26 8.44 -44 41  25.2	 33         5.0

*0.5-8.0 keV band

Within the Jem-X error region centered at RA=16:25:55.0, Dec=-44:42:40
(1.7' preliminary error radius) which is consistent with the IBIS
location, we detect no source above SNR=2.6.  Our source detection
method found 3 sources above SNR=1.7 in this region as given below.
These sources become more significant when we increase the search 
energy band to 0.1-10 keV.

       No.       RA         Dec      Counts*  SNR
       5   16 25 54.65 -44 42  49.4    6      1.9
       6   16 25 58.73 -44 41  47.0    4      1.9
       7   16 26  1.21 -44 42  46.6    4      1.9

*0.5-8.0 keV band

All coordinates are given in J2000.

None of these sources exhibits significant variability within the 10ks 
observation. No X-ray source was found at the position of the radio
source reported by Soderberg et al (2004, GCN 2643Loading...
 
 ).  At this point we
cannot identify any of these sources as the counterpart of GRB040812,
and we strongly encourage searches for optical variability.  Another 
planned 10 ks Chandra DDT observation may reveal the GRB counterpart.

We are grateful to the Chandra Science Data Center for processing the 
data rapidly and in particular to Harvey Tananbaum and Andrea Prestwich
for approving this DDT observation.