TITLE: GCN CIRCULAR NUMBER: 2269 SUBJECT: GRB030528(=H2724): Observations with the Chandra X-ray Observatory DATE: 03/06/04 14:56:11 GMT FROM: George Ricker at MIT GRB030528(=H2724): Observations with the Chandra X-ray Observatory N. Butler, A. Dullighan, P. Ford, G. Ricker, R. Vanderspek (MIT); K. Hurley , G. Jernigan (U.C.- Berkeley); and D. Lamb (U.Chicago) on behalf of the Chandra GRB ToO Team and the HETE Science Team write: On 3 June, the Chandra Observatory targeted the field of GRB030528, which was localized by the HETE satellite (Atteia et al, GCN2256). The 25 ksec observation spanned the interval 12:22-20:08 UT, 5.97 - 6.29 days after the burst. The revised SXC error region from Villasenor et al. (GCN2261) was completely contained within the field-of-view of the Chandra ACIS-S3 chip (see planning comments in Ricker et al. GCN2264). Within the revised SXC error region, we detected four sources in the 0.5-8 keV band: # Chandra Name RA DEC dR(s) dD(") Cts 1 CXOU J170400.3-223710 17 4 0.31 -22 37 9.99 0.053 0.91 39 4 CXOU J170348.4-223826 17 3 48.39 -22 38 25.93 0.054 0.92 30 9 CXOU J170400.1-223548 17 4 0.11 -22 35 48.10 0.053 0.92 11 10 CXOU J170354.0-223654 17 3 53.95 -22 36 53.67 0.054 0.93 9 The # column refers to the source's relative ranking (in terms of total counts) among all the sources detected in the entire ACIS-S3 field-of-view. For completeness, we tabulate below seven additional sources that are within the ACIS-S3 field-of-view but are outside the revised SXC error region: # Chandra Name RA DEC dR(s) dD(") Cts 2 CXOU J170358.7-224237 17 3 58.67 -22 42 36.67 0.063 0.94 31 3 CXOU J170355.7-223503 17 3 55.73 -22 35 2.66 0.053 0.92 23 5 CXOU J170342.8-223548 17 3 42.81 -22 35 48.19 0.053 0.92 24 8 CXOU J170403.9-223543 17 4 3.87 -22 35 43.30 0.053 0.92 13 14 CXOU J170341.4-223646 17 3 41.44 -22 36 46.07 0.053 0.95 6 15 CXOU J170411.2-224032 17 4 11.24 -22 40 32.01 0.055 0.96 11 17 CXOU J170345.8-224133 17 3 45.81 -22 41 32.71 0.060 1.00 10 The astrometry was calibrated using six stars with detectable X-ray emission from the list generated by A. Henden (GCN2267) that lay within the ACIS-S3 field-of-view. In the above 2 tables, dR, the uncertainty in RA, and dD, the uncertainty in DEC, were established by summing the following in quadrature for each coordinate: the X-ray centroiding error, the correlation error between the X-ray and optical positions, and the error estimates from the reference stars. We gratefully acknowledge the timely assistance of the personnel at the Chandra Science Center in the acquisition and preliminary processing of these data. This message may be cited.