TITLE: GCN GRB OBSERVATION REPORT NUMBER: 1324 SUBJECT: GRB011212: Optical Observations DATE: 02/04/03 17:11:02 GMT FROM: George Ricker at MIT GRB011212: Optical Observations A. Dullighan, G. Monnelly, G. Ricker, R. Vanderspek, N. Morgan (MIT); and D. Tholen (U.Hawaii) write: We have observed the error box of the HETE GRB011212 (GCN #1194) with the Baade 6.5m telescope at Magellan on 2001 December 14.17 UT (Epoch 1) and December 15.17 UT (Epoch 2) using the MagIC CCD detector. Twelve 360s R-band exposures were used to mosaic the entire HETE and RXTE/ASM joint error box on each night. Both nights had a seeing of 0.7" with a limiting magnitude of 24.5, except for the last half of the second night when the seeing decreased slowly to 1.3", with a limiting magnitude of 24.0 on the last frame. Third epoch observations were made with the University of Hawaii 2.2m telescope on Mauna Kea on 2002 February 16.33 and 17.38 UT. Three frames were used to mosaic the error box each with three 600s VR-band exposures under conditions of 1.3" seeing, giving a limiting magnitude of 24.5 after summing. Aperture photometry was performed on all objects detected in the Epoch 1 images and then again at the same positions in the later epochs. The absolute magnitude of each source was calculated using a nearby USNO catalog star: for each source, the same calibration star was used in all epochs, and the quoted error in the magnitude does not include the uncertainty in the magnitude of the calibration star. Comparison with Epoch 3 is complicated by the fact that it is in VR-band, whereas Epochs 1 and 2 are in R-band. Four sources were determined to have faded between both Epochs 1 and 2 and between Epochs 1 and 3. Their positions and magnitudes are listed below. Sources 2, 3, and 4 faded to near the detection limit in Epoch 2, and to below the detection limit in Epoch 3. The observed fading and upper limits are consistent with a temporal power law decay index between -1 and -2, except for source 1 in Epoch 3, but this flattening of the decay could be due to an underlying galaxy. grb event: 2001 December 12.1695 UT Epoch 1: 2001 December 14.17 2.0 days after Epoch 2: 2001 December 15.17 3.0 days Epoch 3: 2002 February 16.33 66.2 days 2002 February 17.38 67.2 days Fading Sources RA Dec Epoch 1 m(R) Epoch 2 m(R) Epoch 3 m(VR) 1 4:59:58.1 +32:02:57 23.14 +/- 0.12 23.89 +/- 0.22 24.08 +/-0.24 2 4:59:59.4 +32:03:43 23.80 +/- 0.18 24.65 +/- 0.39 > 24.5 3 4:59:59.0 +32:09:04 23.75 +/- 0.18 24.80 +/- 0.48 > 24.5 4 4:59:39.5 +32:08:34 23.38 +/- 0.12 24.41 +/- 0.38 > 24.5 Finder charts have been prepared of the four sources from the Epoch 1 observations at http://space.mit.edu/HETE/Bursts/GRB011212. The charts contain the source, marked by crosshairs, a bright star (B) from the USNO catalogue, and a constant star (C) of comparible magnitude to the source. The charts have a width and height of 33 arcseconds in RA and Dec. North is up and East is to the left. Source# m(R) Star B m(R) Star C m(R) 1 23.14 +/- 0.12 18.8(USNO) 23.65 +/- 0.15 2 23.80 +/- 0.18 16.9(USNO) 23.59 +/- 0.15 3 23.75 +/- 0.18 14.4(USNO) 23.48 +/- 0.14 4 23.38 +/- 0.12 16.8(USNO) 23.11 +/- 0.09 This message may be cited.