//////////////////////////////////////////////////////////////////////// TITLE: GCN GRB OBSERVATION REPORT NUMBER: 4904 SUBJECT: GRB 060323: Swift detection of a burst with a possible optical afterglow DATE: 06/03/23 15:11:36 GMT FROM: Scott Barthelmy at NASA/GSFC L. Vetere (ASDC), S.D. Barthelmy (GSFC), A.P. Beardmore (U Leicester), D.N. Burrows (PSU), M.M. Chester (PSU), N. Gehrels (NASA/GSFC), S.T. Holland (GSFC/USRA), J.A. Kennea (PSU), V. Mangano (INAF-IASFPA), F.E. Marshall (NASA/GSFC), P.T. O'Brien (U Leicester), K.L. Page (U Leicester), D.M. Palmer (LANL), M. Perri (ASDC), P. Romano (INAF-OAB) and P. Roming (PSU) report on behalf of the Swift Team: At 14:32:36 UT, the Swift Burst Alert Telescope (BAT) triggered and located GRB 060323 (trigger=202505). Swift slewed immediately to the burst. The BAT on-board calculated location is RA,Dec 174.409,+49.975 {11h 37m 38s,+49d 58' 30"} (J2000) with an uncertainty of 3 arcmin (radius, 90% containment, including systematic uncertainty). The burst starts at T-8 sec and lasts at least until T+20 sec. The peak count rate is ~1000 cnts/sec at T+3 sec. XRT began observing the field at about 14:38:00 UT, however due to the instrument being in Manual state, it did not attempt to centroid on the field until 14:44:59 UT, 744 seconds after the BAT trigger, when it switched back to Auto state. The XRT on-board centroid algorithm did not find a source in the image and no prompt position is available. Downlinked short (~5s exposure combined) images of the field with XRT do not show any obvious point source. We are waiting for downlinked data to detect and determine a position for the source. UVOT took a finding chart exposure of nominal 100 seconds with the White filter starting 295 seconds after the BAT trigger. A possible new source is apparent in the list of sources generated onboard. The estimated magnitude is 20.9 (white), with an uncertainty of +/- 1 mag, and located at 11:37:44.91, +50:00:33.5, with an estimated uncertainty of +/- 1 arcsec. The 8'x8' region for the list of sources generated on-board covers 100% of the BAT error circle. No correction has been made for extinction. We are currently in the gap of telemetry downlinks. We will not get the full data set on this burst until ~22:00 UT. //////////////////////////////////////////////////////////////////////// TITLE: GCN GRB OBSERVATION REPORT NUMBER: 4905 SUBJECT: GRB060323 - SDSS Pre-Burst Observations DATE: 06/03/23 15:37:42 GMT FROM: Richard J. Cool at U.of AZ/Steward Obs Richard J. Cool (Arizona), Daniel J. Eisenstein (Arizona), David W. Hogg (NYU), Michael R. Blanton (NYU), David J. Schlegel (LBNL), J. Brinkmann (APO), Donald Q. Lamb (Chicago), Donald P. Schneider (PSU), and Daniel E. Vanden Berk (PSU) report: The Sloan Digital Sky Survey (SDSS) imaged the field of burst GRB060323 prior to the burst. As these data should be useful as a pre-burst comparison and for calibrating photometry, we are supplying the images and photometry measurements for this GRB field to the community. Data from the SDSS, including 5 FITS images, 3 JPGS, and 3 files of photometry and astrometry, are being placed at http://mizar.as.arizona.edu/~grb/public/GRB060323 We supply FITS images in each of the 5 SDSS bands of a 8'x8' region centered on the GRB position (ra=174.409 (11:37:38.2), dec=49.9750 (49:58:30.0); Swift-BAT TRIGGER 202505), as well as 3 gri color-composite JPGs (with different stretches). The units in the FITS images are nanomaggies per pixel. A pixel is 0.396 arcsec on a side. A nanomaggie is a flux-density unit equal to 10^-9 of a magnitude 0 source or, to the extent that SDSS is an AB system, 3.631e-6 Jy. The FITS images have WCS astrometric information. In the file GRB060323_sdss.calstar.dat, we report photometry and astrometry of 179 bright stars (r<20.5) within 15' of the burst location. The magnitudes presented in this file are asinh magnitudes as are standard in the SDSS (Lupton 1999, AJ, 118, 1406). Beware that some of these stars are not well-detected in the u-band; use the errors and object flags to monitor data quality. In the files GRB060323_sdss.objects_flux.dat and GRB060323_sdss.objects_magnitudes.dat, we report photometry of 1183 objects detected within 6' of the GRB position. We have removed saturated objects and objects with model magnitudes fainter than 23.0 in the r-band. The fluxes listed in GRB060323_sdss.objects_flux.dat are in nanomaggies while the magnitudes listed in GRB060323_sdss.objects_magnitudes.dat are asinh magnitudes. All quantities reported are standard SDSS photometry, meaning that they are very close to AB zeropoints and magnitudes are quoted in asinh magnitudes. Photometric zeropoints are known to about 2% rms. None of the photometry is corrected for dust extinction. The Schlegel, Finkbeiner, and Davis (1998) predictions for this region are A_U=0.083 mag, A_g=0.061 mag, A_r = 0.044 mag, A_i=0.034 mag, and A_z=0.024 mag. The file GRB060323_sdss.spectro.dat contains a list of the 4 objects with SDSS spectroscopy within 6 arcminutes of the GRB position. In addition to the redshift and 1-sigma error for each object, this file also lists the object spectroscopic classification. SDSS astrometry is generally better than 0.1 arcsecond per coordinate. Users requiring high precision astrometry should take note that the SDSS astrometric system can differ from other systems such as those used in other notices; we have not checked the offsets in this region. More detailed information pertaining to our SDSS GRB releases can be found in our initial data release paper (Cool et al. 2006, astro-ph/0601218). See the SDSS DR4 documentation for more details: http://www.sdss.org/dr4. These data have been reduced using a slightly different pipeline than that used for SDSS public data releases. We cannot guarantee that the values here will exactly match those in the data release in which these data are included. In particular, we expect the photometric calibrations to differ by of order 0.01 mag. This note may be cited, but please also cite the SDSS data release paper, Adelman-McCarthy et al. (2006, ApJS, in press, astro-ph/0507711), when using the data or referring to the technical documentation. //////////////////////////////////////////////////////////////////////// TITLE: GCN GRB OBSERVATION REPORT NUMBER: 4906 SUBJECT: GRB060323, optical observation DATE: 06/03/23 16:22:12 GMT FROM: Eri Sonoda at U of Miyazaki/Japan E.Sonoda, S.Maeno, M.Yamauchi (University of Miyazaki) "We have observed the field covering the error circle of GRB060323 (GCN 4904) with the unfiltered CCD camera on the 30-cm telescope at University of Miyazaki. The observation was started 14:34:16 UT on Mar. 23. After co-adding a set of 15 images (14:34:16 - 14:51:25 UT) of 30 sec exposures, we have compared with the USNO A2.0 catalog. Preliminary analysis shows there is no new source brighter than 15.2 mag." [GCN OPS NOTE(24nov06): The Subject was changed from "GRB0600323" to "GRB060323".] //////////////////////////////////////////////////////////////////////// TITLE: GCN GRB OBSERVATION REPORT NUMBER: 4908 SUBJECT: GRB 060323: Swift/XRT position DATE: 06/03/23 22:21:54 GMT FROM: Jamie A. Kennea at PSU/Swift-XRT J. A. Kennea, J. L. Racusin, D. N. Burrows (PSU), L. Vetere and M. Perri (ASDC) report on behalf of the Swift/XRT team: We have performed a preliminary analysis of downlinked data from GRB 060323 (Vetere et al, GCN 4904). We find a previously uncatalogued source at the following coordinates: RA(J2000): 11:37:45.4 Dec(J2000): +49:59:05.5 with an estimated uncertainty of 3.9 arcseconds radius (90% containment). We note that this position lies 78 arcseconds from the BAT position reported in GCN 4904 and 88 arcseconds from the proposed UVOT afterglow candidate, which would rule out that object as the GRB afterglow. //////////////////////////////////////////////////////////////////////// TITLE: GCN GRB OBSERVATION REPORT NUMBER: 4909 SUBJECT: GRB 060323: BVRI observations at Tautenburg, aftreglow candidate DATE: 06/03/23 23:17:25 GMT FROM: Alexander Kann at TLS Tautenburg D. A. Kann, B. Stecklum (TLS Tautenburg) report: The field of GRB 060323 (Vetere et al., GCN 4904) was observed with the 1.34m Tautenburg Schmidt telescope under excellent conditions in BVRcIc. The observation log is the following: Midtime Exp Filter lim. Mag 0.1948 6 * 600 s Ic 21.8 0.2227 1 * 600 s Rc 22.5 0.2309 1 * 600 s V 22.5 0.2385 1 * 600 s B 22.5 Limiting magnitudes were derived via comparison with SDSS pre-burst observations (Cool et al., GCN 4905). For the star at RA= 174.38742 (11:37:32.98) Dec = +50.02251 (+50:01:21.04) I derive via the transformation equations of Lupton (2005) and the SDSS photometry: B = 19.187 V = 18.848 Rc = 18.654 Ic = 18.002 with typical erros of 0.03 mags. Aperature photometry instrumental magnitudes are then compared with the magnitudes of sources near the detection limit. The limiting magnitudes may be improved with further analysis. There is no source detected at the position of the possible UVOT afterglow (Vetere et al., GCN 4904). At the position of the X-ray afterglow (Kennea et al., GCN 4908), we detect a faint source (Rc ~ 21) at RA= 11:37:44.56 Dec = +49:58:59.8 that is not visible in the SDSS (limiting mag ~ r = 23). We suggest this source as the possible afterglow of GRB 060323. This message may be cited. //////////////////////////////////////////////////////////////////////// TITLE: GCN GRB OBSERVATION REPORT NUMBER: 4910 SUBJECT: GRB 060323: Swift XRT refined analysis DATE: 06/03/24 00:49:32 GMT FROM: Matteo Perri at ISAC/ASDC L. Vetere, M. Perri (ASDC), J.A. Kennea, D.N. Burrows (PSU) report on behalf of the Swift/XRT team: We have analysed the first five orbits of Swift XRT data on the BAT GRB 060323 (Vetere, et al., GCN 4904). The XRT began observing in Windowed Timing mode at 14:35:20 UT on 2006-03-23, 164 s after the BAT trigger. In the 0.3-10 keV energy band the afterglow shows a flat light curve from T+164s up to about T+800s, then it fades with a decay index of 1.2+/-0.1 up to T+20ks. The X-ray spectrum covering the time period from T+164s to T+614s is well fit by an absorbed power-law with a photon index of 1.9+/-0.3 and a column density consistent with the Galactic value in the direction of the source (1.54e20 cm**-2). The unabsorbed 0.3-10 keV flux for this spectrum is 7.5e-12 erg/cm**2/s. Assuming the X-ray emission continues to decline at the same rate, we predict a 0.3-10 keV XRT count rate of 0.002 count/s at T+24hr, which corresponds to an unabsorbed 0.3-10 keV flux of 1.1e-13 erg/cm**2/s. This circular is an official product of the Swift XRT Team. //////////////////////////////////////////////////////////////////////// TITLE: GCN GRB OBSERVATION REPORT NUMBER: 4911 SUBJECT: GRB 060323: optical observations at TNG DATE: 06/03/24 01:41:34 GMT FROM: Daniele Malesani at SISSA-ISAS,Trieste,Italy S. Covino (INAF/OABr), D. Malesani (SISSA), L.A. Antonelli (INAF/OAR), D. Fugazza (INAF/OABr), V. Lorenzi, G. Tessicini (INAF/TNG), report on behalf of a larger collaboration: We observed the field of GRB 060323 (Vetere et al., GCN 4904) with the Italian 3.6m TNG telescope. Observations were acquired in the V and R filters (10 min exposure). The mean time of the R-band exposure was Mar 23.9738 UT (8.8 hr after the GRB). We clearly detect the object reported by Kann & Stecklum (GCN 4909). Its magnitude, using as a reference the star quoted in GCN 4909 (R=18.65), is R=22.6. Thus, the object seems to have faded. We note however that this candidate lies 9.6" off the center of the XRT error box (Kennea et al., GCN 4908), which has a quoted error radius of 3.9". We retrieved the g-, r-, and i-band frames from the publicly available SDSS survey (Cool et al., GCN 4905). Coadding the three frames, the afterglow candidate is clearly visible, thus casting some doubt on its nature. Inspection of the XRT error circle, moreover, reveals a faint, pointlike source at the coordinates (J2000): alpha = 11:37:45.25 delta = +49:59:07.3 Its magnitude is R~23.1 (referenced to the same comparison star). It is also barely visible in the V-band images. We thus consider also this object as a plausible afterglow candidate. Further observations are encouraged. We thank the TNG staff for their valuable support. This message can be cited. [GCN OPS NOTE(27mar06): Per author's request, Lorenzi and Tessicini were added to the author list.] //////////////////////////////////////////////////////////////////////// TITLE: GCN GRB OBSERVATION REPORT NUMBER: 4912 SUBJECT: GRB 060323: Refined analysis of the Swift-BAT burst DATE: 06/03/24 01:44:03 GMT FROM: Scott Barthelmy at NASA/GSFC A. Parsons (GSFC), L. Barbier (GSFC), S. Barthelmy (GSFC), J. Cummings (GSFC/NRC), E. Fenimore (LANL), N. Gehrels (GSFC), D. Hullinger (BYU-Idaho), H. Krimm (GSFC/USRA), C. Markwardt (GSFC/UMD), D. Palmer (LANL), T. Sakamoto (GSFC/NRC), G. Sato (ISAS), J. Tueller (GSFC), L. Vetere (ASDC) on behalf of the Swift-BAT team: Using the data set from T-239 to T+824 sec from recent telemetry downlinks, we report further analysis of BAT GRB 060323 (trigger #202505) (Vetere, et al., GCN 4904). The BAT ground-calculated position is RA,Dec = 174.412,+50.003 deg {11h 37m 38.9s, 50d 0' 9.2"} (J2000) +- 1.3 arcmin, (radius, sys+stat, 90% containment). The partial coding was 80%. The mask-weighted lightcurve shows multiple overlapping peaks starting at T-5 sec and ending about T+25 sec. Because the s/c executed a pre-planned slew spanning T+85 to T+215 sec, we do not have lightcurve data covering this interval. There is no apparent emission between T+220 and T+824 sec. T90 (15-350 keV) is 18 +- 2 sec (estimated error including systematics). The time-averaged spectrum from T-5.1 to T+14.7 is best fit by a simple power-law model. The power law index of the time-averaged spectrum is 1.53 +- 0.17. The fluence in the 15-150 keV band is 5.7 +- 0.6 x 10^-07 erg/cm2. The 1-sec peak photon flux measured from T+2.59 sec in the 15-150 keV band is 0.8 +- 0.1 ph/cm2/sec. All the quoted errors are at the 90% confidence level. //////////////////////////////////////////////////////////////////////// TITLE: GCN GRB OBSERVATION REPORT NUMBER: 4913 SUBJECT: GRB 060323: Tautenburg OT candidate retraction DATE: 06/03/24 03:57:00 GMT FROM: Alexander Kann at TLS Tautenburg D. A. Kann (TLS Tautenburg), S. Covino (INAF/OABr) and D. Malesani (SISSA) report: We concur that the candidate afterglow of GRB 060323 reported by Kann & Stecklum (GCN 4909) is faintly visible in the SDSS. The astrometry reported by Kann & Stecklum (with errors of 0."7) is correct, but the object was misidentified. The afterglow candidate reported by Covino et al. (GCN 4911) is visible on the TLS Ic and Rc image and possibly on the V band image. Photometry of the OT candidate by Covino et al. using the comparison star given by Kann & Stecklum shows marginal evidence for fading, but the low S/N makes it difficult to assess this with certainty. Assuming the magnitude of 23.1 at 0.37 days after the GRB to be correct, this is one of the faintest afterglows ever discovered. The extinction along the line of sight is negligible (E(B-V)=0.015, Schlegel et al., 1998) and there are no indications of excess hydrogen column density in the X-ray afterglow (Vetere et al., GCN 4910). This seems to exclude a large extinction within the GRB host galaxy. The afterglow is fainter at this epoch than all afterglows in the sample of Kann, Klose & Zeh (ApJ, in press, astro-ph/0512575), and also fainter than other faint OTs not in the sample. Another explanation for the faintness may be that this is a high-redshift event, even though the BAT analysis (Parsons et al., GCN 4912) shows no signs of extended low-level emission often seen in high-redshift events (e.g., GRB 050904). We highly encourage NIR observations of the Covino et al. afterglow candidate to determine the colors and look for a possible Lyman dropout. Spectroscopy is also encouraged, but very large facilities will be needed. This message may be cited. //////////////////////////////////////////////////////////////////////// TITLE: GCN GRB OBSERVATION REPORT NUMBER: 4914 SUBJECT: GRB 060323: Optical Observations DATE: 06/03/24 07:39:46 GMT FROM: Kuntal Mishra at ARIES,Nainital,India Kuntal Misra (ARIES, Nainital) on behalf of a larger Indian GRB collaboration We observed the field of GRB 060323 (trigger=202505, GCN 4904) using the 1-m Sampurnanad Telescope at ARIES, Nainital in R band . We do not detect any possible afterglow candidate at the position mentioned by Kann et al. (GCN 4909) in our co-added image (6*300s) 3.6 hours after the burst. //////////////////////////////////////////////////////////////////////// TITLE: GCN GRB OBSERVATION REPORT NUMBER: 4915 SUBJECT: GRB060323: NOT observations DATE: 06/03/24 15:04:56 GMT FROM: Brian Lindgren Jensen at U.of Copenhagen Brian Lindgren Jensen, Jens Hjorth, Johan Fynbo (Dark Cosmology Centre) and Hugo Schwarz (CTIO) report: "We have obtained R band observations of GRB 060323 (Vetere et al., GCN 4904) with the 2.56-m Nordic Optical Telescope and StanCam at La Palma. Observations started at UT 23.95 (8.2hr after the burst) and cover the position of the Swift XRT source (Kennea et al., GCN 4909). Inside the XRT error circle we clearly detect the source reported by Covino et al. (GCN 4911) at a position of: RA = 11:37:45.21 Dec = +49:59:07.3 Additionally, we clearly detect the source reported by Kann et al. (GCN 4909). In our combined image it appears extended. A finding chart of the field of the XRT error-circle can be found at: http://www.astro.ku.dk/~brian_j/grb/grb060323.606/ " //////////////////////////////////////////////////////////////////////// TITLE: GCN GRB OBSERVATION REPORT NUMBER: 4916 SUBJECT: GRB 060323: optical afterglow confirmed DATE: 06/03/24 16:03:11 GMT FROM: Daniele Malesani at SISSA-ISAS,Trieste,Italy S. Covino (INAF/OABr), L.A. Antonelli (INAF/OAR), D. Fugazza, P. D'Avanzo (INAF/ OABr), and D. Malesani (SISSA), report on behalf of a larger collaboration: We observed again the field of GRB 060323 (Vetere et al., GCN 4904; Parsons et al., GCN 4912) with the Italian 3.6m TNG telescope. Observations were acquired in the V and R filters (20 min exposure). The mean time of the R-band exposure was Mar 24.239 UT (15.2 hr after the GRB). The candidate afterglow inside the XRT error circle (Kennea et al., GCN 4908) reported by Covino et al. (GCN 4911; see also Kann et al., GCN 4913; Jensen et al., GCN 4915) is no longer visibile. The two datasets have comparable image quality. We therefore confirm this is the optical afterglow of GRB 060323. We thank the TNG staff for their excellent support. This message can be cited. //////////////////////////////////////////////////////////////////////// TITLE: GCN GRB OBSERVATION REPORT NUMBER: 4917 SUBJECT: GRB 060323: Swift/UVOT Observations DATE: 06/03/24 20:56:10 GMT FROM: Frank Marshall at GSFC F. Marshall (GSFC/NASA) and L. Vetere (ASDC) on behalf of the Swift/UVOT team The Swift/UVOT began taking data on the field of GRB 060323 at 14:37:30 UT on 2006-03-23, approximately 294s after the BAT trigger (Vetere et al., GCN 4904). There are marginal detections at the position of the optical afterglow (Covino et al. GCN 4911; Jensen et al. GCN 4915; Covino et al. GCN 4916) in the White, V, and B filters. The table below provides the results for the initial finding chart exposure using the White filter and for summed exposures. The UVOT on-board detection of a weak source suggested as a possible afterglow by Vetere et al. is not confirmed in ground analysis of the complete finding chart image. Filter T_range(s) Exp(s) 3-sigma UL Possible Detection Mag sigma White 294-393 100 20.0 21.1 1.8 White 486-17446 2171 21.9 V 525-22318 2012 20.6 21.6 2.1 B 473-16535 1308 21.3 22.1 2.6 U 449-6313 453 21.2 UVW1 425-23955 1163 21.3 These magnitudes are uncorrected for the expected Galactic extinction corresponding to E(B-V) = 0.015. //////////////////////////////////////////////////////////////////////// TITLE: GCN GRB OBSERVATION REPORT NUMBER: 4918 SUBJECT: GRB060323: P60 Observations DATE: 06/03/24 23:15:32 GMT FROM: S. Bradley Cenko at Caltech S. B. Cenko, E. O. Ofek, A. M. Soderberg (Caltech), and D. B. Fox (Penn State) report on behalf of a larger collaboration: We have imaged the field of GRB060323 (Vetere et al.; GCN 4904) with the automated Palomar 60-inch telescope. Observations were taken in both the i' (mean epoch March 24.22 UT) and z' (mean epoch March 24.28 UT) filters, approximately 15.5 hours after the burst. Inside the XRT error circle (Kennea et al.; GCN 4908), we do not find any sources. The limiting magnitude of our coadded images is approximatly i' > 21.5, z' > 20.5, calibrated with respect to the SDSS pre-burst data provided by Cool et al. (GCN 4905). In particular, we note we do not detect the optical afterglow (Covino et al.; GCNs 4911, 4916) to the above limits. //////////////////////////////////////////////////////////////////////// TITLE: GCN GRB OBSERVATION REPORT NUMBER: 4921 SUBJECT: GRB060323: NOT optical observations DATE: 06/03/25 16:07:07 GMT FROM: Brian Lindgren Jensen at U.of Copenhagen Brian Lindgren Jensen, Jens Hjorth, Johan Fynbo (Dark Cosmology Centre) and Hugo Schwarz (CTIO) report: "We have, further to Jensen et al. (GCN 4915), obtained R band observations of GRB 060323 (Vetere et al., GCN 4904) with the 2.56-m Nordic Optical Telescope and StanCam at La Palma. Observations started at UT 24.95 (32hr after the burst) and cover the position of the Swift XRT source (Kennea et al., GCN 4909). The afterglow candidate (Covino et al., GCN 4911) is not visible in our combined image to an approximate upper limit of R~24. We hence confirm the conclusion of Covino et al. (GCN 4916) that the optical afterglow has been correctly identified. Finding charts of the field of the XRT error-circle can be found at: http://www.astro.ku.dk/~brian_j/grb/grb060323.606/ " //////////////////////////////////////////////////////////////////////// TITLE: GCN GRB OBSERVATION REPORT NUMBER: 4926 SUBJECT: GRB060323: optical limit DATE: 06/03/27 12:02:53 GMT FROM: Alexei Pozanenko at IKI, Moscow G. Kornienko (UAPhO), A.Pozanenko (IKI), V.Rumyantsev (CrAO), on behalf of larger GRB follow up collaboration report: We have observed the error box of the Swift GRB060323 (Vetere et al., GCN 4904) with 0.4m telescope of Ussuriysk Astrophysical Observatory (UAPhO) in R-band between Mar. 23 (UT) 15:00 - 15:51. We do not detect the optical afterglow (Covino et al., GCNs 4911, 4916), and upper limits of combined images calibrated against of USNO-A2.0 (R) are following: Mid time, Exposure, Limiting mag. (UT) (s) Mar.23.629 5x60 ~16.0 Mar.23.642 20x60 ~17.0 //////////////////////////////////////////////////////////////////////// TITLE: GCN GRB OBSERVATION REPORT NUMBER: 4930 SUBJECT: GRB 060323: Early optical observation at Xinglong DATE: 06/03/27 19:30:23 GMT FROM: W.K. Zheng at NAOC W.K. Zheng, M.Zhai, Y.L. Qiu, J.Y. Wei, J.Y. Hu and J.S. Deng, report on behalf of the Xinglong GRB follow-up team: We have imaged the field of GRB 060323A with the 0.8m telescope at Xinglong Observatory.The first image was taken at 14:41:05 UT, approximately 540s after the BAT trigger.Preliminary analyses reveal a clear object at the position reported in GCN 4911. The unfiltered brightness reached a peak of about 18.2 mag about 640s after the trigger and showed a steady decay between about 710s and 3300s. R-band magnitudes from USNO A2.0 were used to calibrate our observations. We imaged the field again at Mar 25 12:15:54 UT,about 2 days after the burst. No obvious source was detected at the same position up to a 3-sigma limit of about 20.2 mag. Further analysis is under progress. This message may be cited. //////////////////////////////////////////////////////////////////////// TITLE: GCN GRB OBSERVATION REPORT NUMBER: 4931 SUBJECT: GRB 060323 : WIDGET simultaneous optical observations DATE: 06/03/27 19:50:09 GMT FROM: Toru Tamagawa at RIKEN K. Abe, K. Onda, M. Tashiro (Saitama-U), T. Tamagawa, Y. Urata (RIKEN), H. Azuma, M. Kuwahara (RIKEN/TUS), F. Usui (ISAS/JAXA) on behalf of the WIDGET collaboration report: "We have observed the error box of the Swift GRB 060323 (Vetere et al., GCN 4904) with a very wide-field camera, WIDGET, located at Akeno, Japan. WIDGET is continuously monitored the region with repeat of unfiltered 5 seconds exposures between 750 seconds before and 82 seconds after the burst trigger. We have not found any optical emission at the Swift XRT source position (Kennea et al., GCN 4909). The 1-sigma limiting magnitude of each frame derived by the Tycho 2 catalog was around V=12.0 magnitude." This message may be cited.