This file contains both GRBs 'A' and 'B'. //////////////////////////////////////////////////////////////////////// TITLE: GCN GRB OBSERVATION REPORT NUMBER: 5502 SUBJECT: GRB 060904: Swift detection of a bright burst DATE: 06/09/04 01:21:19 GMT FROM: Scott Barthelmy at NASA/GSFC D. Grupe (PSU), S. D. Barthelmy (GSFC), D. N. Burrows (PSU), M. M. Chester (PSU), N. Gehrels (NASA/GSFC), S. T. Holland (GSFC/USRA), S. D. Hunsberger (PSU), J. A. Kennea (PSU), H. A. Krimm (GSFC/USRA), C. B. Markwardt (GSFC/UMD), F. E. Marshall (NASA/GSFC), D. M. Palmer (LANL), M. Stamatikos (NASA/ORAU) and M. C. Stroh (PSU) report on behalf of the Swift Team: At 01:03:21 UT, the Swift Burst Alert Telescope (BAT) triggered and located GRB 060904 (trigger=227996). Swift slewed immediately to the burst. The BAT on-board calculated location is RA,Dec 237.743, +44.966 {15h 50m 58s, +44d 57' 57"} (J2000) with an uncertainty of 3 arcmin (radius, 90% containment, including systematic uncertainty). The BAT light curve shows 3 little peaks starting out and then a large peak at T+55 sec and a total burst duration of about 85 sec. The peak count rate was ~9000 counts/sec (15-350 keV), at ~55 sec after the trigger. The XRT began observing the field at 01:04:27 UT, 66 seconds after the BAT trigger. XRT found a bright, fading, uncatalogued X-ray source located at RA(J2000) = 15h 50m 54.9s, Dec(J2000) = +44d 59' 07.8", with an estimated uncertainty of 5.4 arcseconds (90% confidence radius). This location is 79 arcseconds from the BAT on-board position, within the BAT error circle. The initial flux in the 0.1s image was 2.7e-08 erg/cm2/s (0.2-10 keV). UVOT took a finding chart exposure of 100 seconds with the White (160-650 nm) filter starting 75 seconds after the BAT trigger. No afterglow candidate has been found in the initial data products. The 2.7'x2.7' sub-image covers 100% of the XRT error circle. The typical 3-sigma upper limit has been about 18.5 mag. The 8'x8' region for the list of sources generated on-board covers 100% of the XRT error circle. The list of sources is typically complete to about 18 mag. No correction has been made for the expected extinction corresponding to E(B-V) of 0.02. //////////////////////////////////////////////////////////////////////// TITLE: GCN GRB OBSERVATION REPORT NUMBER: 5503 SUBJECT: GRB060904 - SDSS Pre-Burst Observations DATE: 06/09/04 01:32:22 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 GRB060904 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/GRB060904 We supply FITS images in each of the 5 SDSS bands of a 8'x8' region centered on the GRB position (ra=237.743 (15:50:58.3), dec=44.9660 (44:57:57.6); Swift-BAT TRIGGER 227996), 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 GRB060904_sdss.calstar.dat, we report photometry and astrometry of 309 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 GRB060904_sdss.objects_flux.dat and GRB060904_sdss.objects_magnitudes.dat, we report photometry of 451 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 GRB060904_sdss.objects_flux.dat are in nanomaggies while the magnitudes listed in GRB060904_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=0.089 mag, A_g=0.065 mag, A_r = 0.047 mag, A_i=0.036 mag, and A_z=0.025 mag. The file GRB060904_sdss.spectro.dat contains a list of the 3 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/dr5. 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, 162, 38), when using the data or referring to the technical documentation. //////////////////////////////////////////////////////////////////////// TITLE: GCN GRB OBSERVATION REPORT NUMBER: 5504 SUBJECT: GRB 060904B: ROTSE-III Detection of Optical Counterpart DATE: 06/09/04 02:45:01 GMT FROM: Eli Rykoff at U of Michigan/ROTSE E.S. Rykoff (U Mich), W. Rujopakarn (U Mich), F. Yuan (U Mich), report on behalf of the ROTSE collaboration: ROTSE-IIIc, located at the H.E.S.S. site at Mt. Gamsberg, Namibia, responded to GRB 060904B (Swift trigger 228006). The first image was at 02:31:22.4 UT, 18.5 s after the burst (5.3 s after the GCN notice time). The unfiltered images are calibrated relative to USNO A2.0. We detect a 17.3 magnitude, brightening source with coordinates: 03:52:50.52 -00:43:30.85 (J2000) start UT mag mlim(of image) ---------------------------------- 02:31:22.4 17.3 18.1 A jpeg image is available at http://www.rotse.net/images/gsb228006_3c011-020_key.jpg Continuing observations are in progress. [GCN OPS NOTE(04sep06): Per author's request the 060904A was changed to B.] //////////////////////////////////////////////////////////////////////// TITLE: GCN GRB OBSERVATION REPORT NUMBER: 5505 SUBJECT: GRB 060904B: Swift detection of a burst with optical counterpart DATE: 06/09/04 02:51:23 GMT FROM: Scott Barthelmy at NASA/GSFC D. Grupe (PSU), S. D. Barthelmy (GSFC), M. M. Chester (PSU), J. R. Cummings (NASA/UMD), S. T. Holland (GSFC/USRA), S. D. Hunsberger (PSU), J. A. Kennea (PSU), H. A. Krimm (GSFC/USRA), C. B. Markwardt (GSFC/UMD), F. E. Marshall (NASA/GSFC), D. M. Palmer (LANL), M. Stamatikos (NASA/ORAU) and M. C. Stroh (PSU) report on behalf of the Swift Team: At 02:31:03 UT, the Swift Burst Alert Telescope (BAT) triggered and located GRB 060904B (trigger=228006). Swift slewed immediately to the burst. The BAT on-board calculated location is RA,Dec 58.213, -0.720 {03h 52m 51s, -00d 43' 11"} (J2000) with an uncertainty of 3 arcmin (radius, 90% containment, including systematic uncertainty). The BAT light curve shows an initial 5-sec wide peak at T+1 sec followed by an ~30-sec wide weaker peak at T+150 sec. The total duration is about 180 sec. The peak count rate was ~3000 counts/sec (15-350 keV), at ~1 sec after the trigger. The XRT began observing the field at 02:32:12 UT, 69 seconds after the BAT trigger. XRT found a variable, uncatalogued X-ray source located at RA(J2000) = 03h 52m 50.0s, Dec(J2000) = -00d 43' 32.8", with an estimated uncertainty of 6.5 arcseconds (90% confidence radius). This location is 26 arcseconds from the BAT on-board position, within the BAT error circle. The initial flux in the 2.5s image was 4.3e-10 erg/cm2/s (0.2-10 keV). The source shows a rapid increase in count rate indicating a bright flare that is possibly correlated with the second bright peak in the BAT. UVOT took a finding chart exposure of 246 seconds with the V filter starting 70 seconds after the BAT trigger. There is a candidate afterglow in the rapidly available 2.7'x2.7' sub-image at (RA,DEC) (J2000) of (58.2106,-0.7253) or (03h52m50.54s,-00o43'31.1") with a 1-sigma error radius of about 0.7 arc sec. This position is 7.7 arc sec. from the center of the XRT error circle. The estimated magnitude is 18.6 with a 1-sigma error of about 0.5 mag. No correction has been made for the expected extinction of about 0.6 magnitudes. //////////////////////////////////////////////////////////////////////// TITLE: GCN GRB OBSERVATION REPORT NUMBER: 5506 SUBJECT: GRB 060904: TAROT optical observations DATE: 06/09/04 02:51:49 GMT FROM: Alain Klotz at CESR-CNRS Klotz, A. (CESR-OMP), Boer M. (OHP), Atteia J.L. (LATT-OMP) report: We imaged the field of GRB 060904 detected by SWIFT (trigger 227996) with the TAROT robotic telescope (D=25cm) located at the Calern observatory, France. First image was acquired 26.8s after the GRB trigger (9.4s after the notice). The field elevation decreased from 10 degrees above horizon and weather conditions were excellents. First image was acquired during the prompt phase. Date of trigger : t0 = 2006-09-04T01:03:21.600 First image is 60.0 exposure trailed. No OT is visible in the XRT error box (Grupe et al. GCNC 5502) t0+26.8s to t0+86.8s : R > 16.0 Second image is 30.0 exposure. No OT is visible: t0+93.7s to t0+123.7s : R > 17.3 We co-added a series of exposures. No OT is visible: t0+93.7s to t0+376.2s : R > 19.5 Magnitudes were estimated with the nearby USNO-B1 stars and are not corrected for galactic dust extinction. N.B. Galactic coordinates are lon= 71.6566 lat=+50.2105 and the galactic extinction in R band is 0.0 magnitudes estimated from D. Schlegel et al. 1998ApJ...500..525S. This message may be cited. //////////////////////////////////////////////////////////////////////// TITLE: GCN GRB OBSERVATION REPORT NUMBER: 5507 SUBJECT: GRB060904B - SDSS Pre-Burst Observations DATE: 06/09/04 02:59:39 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 GRB060904B 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/GRB060904B We supply FITS images in each of the 5 SDSS bands of a 8'x8' region centered on the GRB position (ra=58.2130 (03:52:51.1), dec=-0.720000 (-00:43:12.0); Swift-BAT TRIGGER 228006), 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 GRB060904B_sdss.calstar.dat, we report photometry and astrometry of 299 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 GRB060904B_sdss.objects_flux.dat and GRB060904B_sdss.objects_magnitudes.dat, we report photometry of 1078 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 GRB060904B_sdss.objects_flux.dat are in nanomaggies while the magnitudes listed in GRB060904B_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=0.899 mag, A_g=0.661 mag, A_r = 0.480 mag, A_i=0.364 mag, and A_z=0.258 mag. The file GRB060904B_sdss.spectro.dat contains a list of the 18 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/dr5. 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, 162, 38), when using the data or referring to the technical documentation. //////////////////////////////////////////////////////////////////////// TITLE: GCN GRB OBSERVATION REPORT NUMBER: 5508 SUBJECT: GRB 060904B: TAROT optical counterpart observations DATE: 06/09/04 03:35:01 GMT FROM: Alain Klotz at CESR-CNRS Klotz, A. (CESR-OMP), Boer M. (OHP), Atteia J.L. (LATT-OMP) report: We imaged the field of GRB 060904B detected by SWIFT (trigger 228006) with the TAROT robotic telescope (D=25cm) located at the Calern observatory, France. First image was acquired 23.1s after the GRB trigger (10.4s after the notice). The field elevation increased from 37 degrees above horizon and weather conditions were excellents. Images were taken during the prompt phase. Date of trigger : t0 = 2006-09-04T02:31:04.224 First image is a 60.0s exposure trailed from t0+23.1s to t0+83.1s. The OT noticed by Rykoff et al. (GCNC5504) is visible as a short flash of magnitude R=15.8 during few seconds near t0+50s. Second image is 30.0s exposure. OT is marginally detected at R~18.5. In the following images the OT becomes brighter. A first visual inspection seems to show that the peak of brightness (R~17) was reached near t0+~400s. The OT was still well detected on individual images at t0+40min (R~17.7). OT position (+/- 2 arcsec): RA(J2000.0) = 03h 52m 50.62s DEC(J2000.0) -00d 43' 29.4" Magnitudes were estimated with the nearby USNO-B1 stars and are not corrected for galactic dust extinction. N.B. Galactic coordinates are lon=189.4387 lat=-39.1315 and the galactic extinction in R band is 0.1 magnitudes estimated from D. Schlegel et al. 1998ApJ...500..525S. This message may be cited. //////////////////////////////////////////////////////////////////////// TITLE: GCN GRB OBSERVATION REPORT NUMBER: 5509 SUBJECT: GRB 060904B BOOTES-IR and 1.5m OSN observations DATE: 06/09/04 04:28:18 GMT FROM: Antonio Deugarte at IAA-CSIC A. de Ugarte Postigo, F. Aceituno, A.J. Castro-Tirado (IAA-CSIC Granada), P. Kubanek (ASU AV CR ndrejov & ISDC Versoix) on behalf of a larger collaboration report: "The 0.6m BOOTES-IR and 1.5m telescope, located at IAA-CSIC Observatorio de Sierra Nevada in Granada (Spain), observed the SWIFT error box for GRB 060904B (Grupe et al. GCN 5505) starting at 02:38:30 UT observing in I & R-bands. We clearly detect the optical counterpart reported by Rykoff et al. (GCN 5504), at coordinates J2000 (+/-0.5"): 03:52:50.54 -00:43:30.5 >From 02:38:30 to 02:48:35 UT the object has declined in 0.66 +/- 0.17 magnitudes. This message is quotable." [GCN OPS NOTE(04sep06): Per author's request, the 'B' was added.] //////////////////////////////////////////////////////////////////////// TITLE: GCN GRB OBSERVATION REPORT NUMBER: 5510 SUBJECT: GRB060904B: Watcher observations DATE: 06/09/04 05:05:41 GMT FROM: Petr Kubanek at AIO A. de Ugarte Postigo (IAA-CSIC Granada), J.French (UCD Dublin) and P.Kubanek (AsU AV CR Ondrejov & ISDC Versoix) reports on behalf of the Watcher collaboration: The 0.4m Watcher telescope, located at Boyden Observatory, South Africa, observed the SWIFT error box for GRB 060904B (Grupe et al. GCN 5505) starting at 02:32:05 UT observing in R, V, I bands + unfiltered. We detect the optical counterpart at coordinates reported by Rykoff et al. (GCN 5504), with peak brightness unfiltered 17.1+/-0.3 at 02:39:30 UT, consistent with Tarot peak detection (Klotz et al. GCN 5508). This message is quotable. //////////////////////////////////////////////////////////////////////// TITLE: GCN GRB OBSERVATION REPORT NUMBER: 5511 SUBJECT: GRB 060904B: Optical observations at Crni Vrh DATE: 06/09/04 05:40:46 GMT FROM: Jure Skvarc at OCV J. Skvarc on behalf of PIKA observing program at Crni vrh Observatory reports: We observed optical counterpart of GRB060904B (Swift trigger 228006) using 60 cm robotic telescope at Crni Vrh Observatory, Slovenia. A variable object was detected at ra=03:52:50.52, dec=-0:43:30.9. The coordinates are derived using UCAC-2 catalog. 1-sigma accuracy of these coordinates is about 0.2 arcseconds. Alternating exposures using R and B filters were taken, starting 45 s after the trigger was received. The following table contains start of exposure (2006-09-04 UT), exposure duration in seconds and magnitude: R filter: 2:32:02 90 18.21 2:37:32 90 17.01 2:43:03 90 17.11 2:48:33 90 17.79 2:54:03 90 18.19 2:59:37 90 17.66 3:08:27 180 17.78 3:13:23 180 17.79 3:17:50 180 17.99 B filter: 02:34:02 180 18.32 02:39:32 180 17.51 02:45:03 180 18.56 02:50:33 180 18.81 The magnitudes are derived using comparison stars from the USNO A2 catalog. Estimated 1-sigma statistical uncertainty is 0.02 for R and 0.04 for B filter. //////////////////////////////////////////////////////////////////////// TITLE: GCN GRB OBSERVATION REPORT NUMBER: 5512 SUBJECT: GRB 060904A: P60 Observations DATE: 06/09/04 07:40:17 GMT FROM: S. Bradley Cenko at Caltech S. B. Cenko and A. Rau (Caltech) report on behalf of a larger collaboration: We have imaged the error circle of GRB 060904a (Grupe et al; GCN 5502) with the automated Palomar 60-inch telescope. Observations began at 4:57 UT 4 September (3.9 hours after the burst) and consisted of 12 x 180 s images in the Kron R and Sloan i' and z' filters. We find no sources inside the XRT error circle, to a limiting magnitude of R > 22.0 (estimated by comparison with several USNO-B objects in the field). //////////////////////////////////////////////////////////////////////// TITLE: GCN GRB OBSERVATION REPORT NUMBER: 5513 SUBJECT: GRB 060904B: VLT redshift DATE: 06/09/04 09:33:08 GMT FROM: Daniele Malesani at SISSA-ISAS,Trieste,Italy D. Fugazza, P. D'Avanzo (INAF/OABr), D. Malesani (SISSA), G. Tagliaferri (INAF/OABr), G. Chincarini (Univ. Milano-Bicocca), L. Stella (INAF-OAR), J.P.U. Fynbo (DARK/NBI), C. Lidman, H. Sana (ESO), report on behalf of the MISTICI collaboration. We observed the optical counterpart of GRB 060904B (Grupe et al., GCN 5505; Rykoff et al., GCN 5504). Spectroscopy was performed with VLT + FORS1, with mean time Sep 4.318 UT (5.15 hr after the burst). Several absorption features were clearly identified, among which FeII 2586, FeII 2600, Mg II 2795,2803, Mg I 2852, Ca H&K 3933,3968. The inferred redshift is z = 0.703. We acknowledge excellent support from the ESO staff. This message can be cited. //////////////////////////////////////////////////////////////////////// TITLE: GCN GRB OBSERVATION REPORT NUMBER: 5514 SUBJECT: GRB 060904A: Suzaku-XIS and -HXD observation plan DATE: 06/09/04 10:33:57 GMT FROM: Makoto Tashiro at Saitama U/Swift Kazuhisa Mitsuda on behalf of Suzaku team We have just started to observe GRB 060904A (GCN 5502: D. Grupe et al.) at location (RA, Dec)={15h 50m 58s, +44d 57' 57"} (J2000) with the Suzaku narrow field instruments (the XIS and HXD). The observation has started at 10:30 UT, on 4 September (UT), and continue until 05:04 of 5 September, 2006 (UT). We encourage further follow-up observations with other wavelengths. //////////////////////////////////////////////////////////////////////// TITLE: GCN GRB OBSERVATION REPORT NUMBER: 5515 SUBJECT: GRB 060904A: Swift-XRT refined analysis DATE: 06/09/04 10:50:28 GMT FROM: Dirk Grupe at PSU/Swift-XRT D. Grupe (PSU) reports on behalf of the Swift/XRT team We have analyzed the first orbit with a total observing time of 2.06 ks of Swift XRT data of GRB 060904A (Grupe et al., GCN 5502). The X-ray light curve displays the end of a giant flare with a flattening of the light curve at 200s after the burst. The initial decay slope is 3.8+/-0.2 followed by 1.3+/-0.2. Spectral fits to the Windowed Timing mode data during the flare phase suggest a significant absorption column density in excess of the Galactic value (1.41e20 cm**-2). The spectrum can be fitted by a single power law with a photon index Gamma=1.93+/-0.04 and an absorption column density NH=1.7+/-0.1e21. Due to the detection of GRB 060904B (Grupe et al., GCN 5505) about about 1.5 hours after the trigger of GRB 060904A, only one orbit has been observed on GRB 060904A and the data were only taken in Windowed Timing mode. Therefore no photon counting mode data exist currently and no improved position can be given yet. This circular is an official product of the Swift XRT Team. //////////////////////////////////////////////////////////////////////// TITLE: GCN GRB OBSERVATION REPORT NUMBER: 5516 SUBJECT: GRB 060904A: Refined analysis of the Swift-BAT burst DATE: 06/09/04 12:33:22 GMT FROM: Scott Barthelmy at NASA/GSFC H. Krimm (GSFC/USRA), L. Barbier (GSFC), S. D. Barthelmy (GSFC), J. Cummings (GSFC/UMD), E. Fenimore (LANL), N. Gehrels (GSFC), D. Grupe (PSU), D. Hullinger (BYU-Idaho), C. Markwardt (GSFC/UMD), D. Palmer (LANL), A. Parsons (GSFC), T. Sakamoto (GSFC/ORAU), G. Sato (GSFC/ISAS), M. Stamatikos (GSFC/ORAU), J. Tueller (GSFC) on behalf of the Swift-BAT team: Using the data set from T-110 to T+843 sec from recent telemetry downlinks, we report further analysis of BAT GRB 060904 (trigger #227996) (Grupe, et al., GCN Circ. 5502). The BAT ground-calculated position is (RA,Dec) = 237.730, 44.984 deg {15h 50m 55.3s, 44d 59' 3.7"} (J2000) +- 1.5 arcmin, (radius, sys+stat, 90% containment). The partial coding was 94%. The mask-weighted lightcurve shows the emission starting at a very low level at ~T-70 sec, then increasing slightly at ~T-7 sec for the trigger with several small peaks until the main peak. The main emission peak starts at T+45, peaking at T+56, and ending at ~T+125 sec. T90 (15-350 keV) is 80 +- 2 sec (estimated error including systematics). Note that the spacecraft slewed to the field of view containing the burst approximately 110 seconds before the trigger, so there is no BAT data before this time. The time-averaged spectrum from T-23.9 to T+108.7 is best fit by a simple power-law model. The power law index of the time-averaged spectrum is 1.52 +- 0.04. The fluence in the 15-150 keV band is 7.9 +- 0.2 x 10^-6 erg/cm2. The 1-sec peak photon flux measured from T+55.34 sec in the 15-150 keV band is 4.9 +- 0.2 ph/cm2/sec. All the quoted errors are at the 90% confidence level. //////////////////////////////////////////////////////////////////////// TITLE: GCN GRB OBSERVATION REPORT NUMBER: 5517 SUBJECT: GRB 060904B: Swift-XRT refined analysis DATE: 06/09/04 12:56:25 GMT FROM: Dirk Grupe at PSU/Swift-XRT D. Grupe (PSU), O. Godet (U Leicester), and S. Barthelmy (GSFC) report on behalf of the Swift/XRT team We have analyzed the first 3 orbits with a total observing time of 5.3 ks of Swift XRT data of GRB 060904B (Grupe et al., GCN 5505), with 4.9 ks in photon counting mode (pc) and 427s in Windowed Timing mode (WT). The Photon Counting mode image provides a refined XRT position: RA(J2000) = 03h 52m 50.26s, Dec(J2000) = -00d 43' 32.5" with an error of 3.6" (90% confidence). This position is 3.9" away from the preliminary XRT position reported in GCN 5505. After the start of the XRT observation in pc mode, a giant flare started at 86s after the trigger and lasted to 490s after the trigger. This flare has a total 0.3-10.0 keV flux of 2.2e-9 ergs/s/cm2 and a fluence of 8.8e-7 ergs/cm2. The underlying afterglow decay slope is 1.11+/-0.25. The predicted flux 24h after the burst is 3e-13 ergs/cm2/s. Spectral fits to the Windowed Timing mode data during the flare suggest a significant absorption column density in excess of the Galactic value (1.21e21 cm**-2). The spectrum can be fitted by a single power law with a photon index Gamma=2.16+/-0.04 and an absorption column density NH=4.09+/-0.13 e21. Using the redshift z=0.703 as reported by Fugazza et al. (GCN 5513) the intrinsic absorption column density is NH,intr=7.6+/-0.4 e21 cm-2. The spectrum of the pc mode data agrees within the errors with this result. This circular is an official product of the Swift XRT Team. //////////////////////////////////////////////////////////////////////// TITLE: GCN GRB OBSERVATION REPORT NUMBER: 5518 SUBJECT: Konus-Wind observation of GRB 060904A DATE: 06/09/04 13:36:59 GMT FROM: Valentin Pal'shin at Ioffe Inst S. Golenetskii, R.Aptekar, E. Mazets, V. Pal'shin, D. Frederiks, and T. Cline on behalf of the Konus-Wind team report: The most intense part of the long GRB 060904A (Swift-BAT trigger #227996; Grupe et al., GCN 5502; Krimm et al., GCN 5516) triggered Konus-Wind at T0=3853.821 s UT (01:04:13.821). As observed by Konus-Wind the burst emission started at T-T0 ~-56 s, peaked at T-T0 ~0 s, and ended at T-T0 ~26 s, so the total burst duration is ~80 s. The burst fluence is 1.59(-0.21, +0.40)x10^-5 erg/cm2, and the 256-ms peak flux measured from T0-0.128 s 1.38(-0.33, +0.46)x10^-6 erg/cm2/s (both in the 20 keV - 2 MeV energy range). The spectrum of the main pulse (from T0 to T0+16.64 s) is well fitted (in the 20 keV - 2 MeV range) by GRBM (Band) model for which: the low-energy photon index is alpha = -1.00(-0.17, +0.23), the high energy photon index beta = -2.57(-1.00, 0.37), the break energy E0 = 163 (-54, +65) keV (chi2 = 40/61 dof). The peak energy Ep = 163 +/- 31 keV. All the quoted errors are at the 90% confidence level. //////////////////////////////////////////////////////////////////////// TITLE: GCN GRB OBSERVATION REPORT NUMBER: 5519 SUBJECT: GRB060904b: Optical observations with Swift/UVOT DATE: 06/09/04 14:50:10 GMT FROM: Samantha Oates at MSSL S. R. Oates (UCL-MSSL), D. Grupe (PSU) on behalf of the Swift UVOT team The Swift Ultra-Violet/Optical Telescope (UVOT) began observations of GRB060904b at 02:32:14 UT, ~71 seconds after the initial Swift BAT trigger (Grupe et al, GCN 5505). An optical counterpart was detected with the V filter at a position RA(J2000)= (03h,52m,50.54s, -00o43'31.1'') to within 0.5''. An optical afterglow was detected in V, B, U, UVW1, UVM2 and UVW2 filters. The photometery results are given for the 6 filters below: Filter Tstart Tstop Magnitudes and UL --------------------------------------------- V 71 316 18.64 +/- 0.33 4732 4931 19.16 +/- 0.36 5960 6100 18.25 3 sigma UL B 4322 4521 18.98 +/- 0.15 5550 5749 19.56 +/- 0.28 U 4117 4316 18.32 +/- 0.19 5346 5545 18.65 +/- 0.23 UVW1 3913 4112 18.78 +/- 0.31 5141 5340 19.11 +/- 0.36 UVM2 3708 3907 18.88 +/- 0.36 4936 5135 19.66 +/- 0.55 UVW2 4528 4727 18.96 +/- 0.33 5756 5955 19.32 +/- 0.41 --------------------------------------------- The values quoted above are not corrected for the expected Galactic extinction of E_{B-V}=0.173. //////////////////////////////////////////////////////////////////////// TITLE: GCN GRB OBSERVATION REPORT NUMBER: 5520 SUBJECT: GRB 060904B: Swift-BAT refined analysis DATE: 06/09/04 15:45:45 GMT FROM: Scott Barthelmy at NASA/GSFC C. Markwardt (GSFC/UMD), L. Barbier (GSFC), S. D. Barthelmy (GSFC), J. Cummings (GSFC/UMD), E. Fenimore (LANL), N. Gehrels (GSFC), D. Grupe (PSU), D. Hullinger (BYU-Idaho), H. Krimm (GSFC/USRA), D. Palmer (LANL), A. Parsons (GSFC), T. Sakamoto (GSFC/ORAU), G. Sato (GSFC/ISAS), M. Stamatikos (GSFC/ORAU), J. Tueller (GSFC) on behalf of the Swift-BAT team: Using the data set from T-239 to T+807 sec from recent telemetry downlinks, we report further analysis of BAT GRB 060904B (trigger #228006) (Grupe, et al., GCN Circ. 5505). The BAT ground-calculated position is RA,Dec = 58.218, -0.729 deg {3h 52m 52.3s, 0d 43' 45.0"} (J2000) +- 0.9 arcmin, (radius, sys+stat, 90% containment). The partial coding was 50%. The mask-weighted lightcurve shows the burst starting at ~T-2 sec with a FRED peak shape (halfwidth ~9 sec) with a return to background level at ~T+50 sec. Then a second, weaker peak starts at ~T+120 sec, peaks at ~T+155 sec and is done by ~T+220 sec. T90 (15-350 keV) is 192 +- 5 sec (estimated error including systematics). The time-averaged spectrum from T-0.9 to T+212.8 is best fit by a simple power-law model. The power law index of the time-averaged spectrum is 1.70 +- 0.14. The fluence in the 15-150 keV band is 1.7 +- 0.2 x 10^-6 erg/cm2. The 1-sec peak photon flux measured from T+1.16 sec in the 15-150 keV band is 2.5 +- 0.2 ph/cm2/sec. All the quoted errors are at the 90% confidence level. //////////////////////////////////////////////////////////////////////// TITLE: GCN GRB OBSERVATION REPORT NUMBER: 5521 SUBJECT: GRB 060904A: pseudo-z from spectral parameters of the prompt emission DATE: 06/09/04 16:07:09 GMT FROM: Alexandre Pelangeon at LATT,OMP,Toulouse A. Pelangeon & J-L. Atteia (LATT-OMP) report: We have used the spectral parameters of GRB 060904A provided by Golenetskii et al. (GCNC 5518) to compute the spectral pseudo-redshift** of this burst detected by SWIFT-BAT (trigger #227996: Grupe et al., GCNC 5502; Krimm et al., GCN 5516). We find a pseudo-redshift pz= 1.84 ± 0.85 We thank V. Pal'shin for providing the fluence of this GRB during the main pulse (from T0 to T0+16.64 s, KONUS time). ** cf. http://www.ast.obs-mip.fr/grb/pz //////////////////////////////////////////////////////////////////////// TITLE: GCN GRB OBSERVATION REPORT NUMBER: 5522 SUBJECT: GRB 060904A: Subaru NIR observation DATE: 06/09/04 16:14:48 GMT FROM: Nobuyuki Kawai at Tokyo Tech K. Aoki, I. Tanaka (Subaru Telescope, NAOJ) and N. Kawai (Tokyo Tech) report on behalf of the Subaru GRB team: "We began observing the field of GRB 060904A (Grupe et al., GCN 5502) with MOIRCS on the 8.2m Subaru Telescope at ~6 UT (5 hours after the burst). In the stacked image of the 18 x 120 sec exposure (mid time UT 6:24) in Ks band, we detected an object with 20.2 mag in the XRT error circle, though the object may be extended. In the the J band image of 21 x 120 sec exposure (mid time UT 7:13), we did not detect an object brighter than 21.0 mag in the XRT error circle. The magnitudes were estimated based on the 2 MASS objects in the field." //////////////////////////////////////////////////////////////////////// TITLE: GCN GRB OBSERVATION REPORT NUMBER: 5523 SUBJECT: GRB060904A: Swift/UVOT optical observations DATE: 06/09/04 19:26:56 GMT FROM: Samantha Oates at MSSL S.R. Oates (UCL-MSSL), D. Grupe (PSU) report on behalf of the Swift/UVOT team: The Swift/UVOT began observing the field of GRB 060904A at 01:04:36 on 2006-09-04, 75 s after the BAT trigger (Grupe et al., GCN 5502). No new source was detected within the XRT error circle in coadded images in any filter down to the following 3-sigma magnitude upper limits: Filter Tstart Tstop Exposure 3-sigma UL ------------------------------------------------- V 55 1888 1680 20.11 B 658 1984 97 19.85 U 634 1959 117 19.49 UVW1 610 1936 117 19.91 UVM2 586 1911 117 19.95 UVW2 687 2014 128 20.55 White 75 1997 352.2 21.69 ------------------------------------------------ These upper limits are not corrected for Galactic extinction E(B-V) = 0.018. //////////////////////////////////////////////////////////////////////// TITLE: GCN GRB OBSERVATION REPORT NUMBER: 5524 SUBJECT: GRB 060904B: RTT150 optical observations DATE: 06/09/04 19:32:33 GMT FROM: Alexander Mescheryakov at IKI RAN A. Mescheryakov, R. Burenin, M. Pavlinsky, R. Sunyaev (IKI), I. Khamitov, Z. Aslan (TUG), U. Kiziloglu (METU), E. Gogus (Sabanci Uni.), I. Bikmaev, N. Sakhibullin (KSU/AST) report: We observed the optical counterpart of GRB 060904B (Grupe et al., GCN 5505; Rykoff et al., GCN 5504; D. Fugazza et al., GCN 5513) with Russian-Turkish 1.5-m telescope (RTT150, Bakirlitepe, TUBITAK National Observatory, Turkey). The observations were started at 02:39:35 UT, i.e. 8.21 min after the trigger and were ended approximately 20 min later due to sunrize. We made series of 30 s exposures in R and also few exposures in B and V. We estimate the following magnitudes for the OT: UT t-t0 Rc err --------------------------------------------------------- 2:39:50 8:46 16.75 0.02 41:00 9:58 16.86 0.03 42:09 11:05 16.99 0.03 43:19 12:15 17.05 0.04 44:29 13:05 17.22 0.05 45:39 14:35 17.34 0.06 47:58 16:54 17.48 0.09 49:07 18:03 17.50 0.09 50:17 19:13 17.64 0.10 The magnitudes are derived using comparison stars from the USNO-B1 catalog. This message can be cited. //////////////////////////////////////////////////////////////////////// TITLE: GCN GRB OBSERVATION REPORT NUMBER: 5525 SUBJECT: GRB 060904b: SMARTS optical/IR afterglow observations DATE: 06/09/05 04:47:23 GMT FROM: Bethany Cobb at Yale U B. E. Cobb and C. D. Bailyn (Yale), part of the larger SMARTS consortium, report: Using the ANDICAM instrument on the 1.3m telescope at CTIO, we obtained optical/IR imaging of the error region of GRB 060904b (GCN 5505, Grupe et al.) with a mid-exposure time of 2006-09-04 06:28 UT (~4 hrs post-burst ) and again at 2006-09-04 08:28 UT (~6 hrs post-burst). For each set of observations, total summed exposure times amounted to 15 minutes in I and V and 12 minutes in J and K. (Imaging was carried out in a symmetrical manner so that the mid-exposure time is the same for all final combined images in a given set of observations.) The afterglow of GRB 060904b (GRB 5505, Grupe et al.) is detected in each combined image. filter magnitude at change in magnitude 4hrs post-burst between 4 and 6hrs post-burst -------------------------------------------------------- V - 0.56 +/- 0.06 I 19.04 +/- 0.03 0.63 +/- 0.04 J 17.84 +/- 0.08 0.29 +/- 0.10 K 15.99 +/- 0.06 0.46 +/- 0.07 Unfortunately, imaging was done under non-photometric conditions so no Landolt or Persson standard stars are available with which to determine the offset between instrumental and apparent magnitude. Therefore, the above values are determined using "on-chip" standards with USNO-B1.0 stars in the optical and 2MASS stars in the IR. The errors on the photometric calibration are ~0.3 in I and ~0.1 in J and K; these errors are in addition to the statistical errors listed above. No USNO-B1.0 V-band values are available to calibrate our V-band observations, so we can only report the change in magnitude between epochs. These values have not been corrected for galactic extinction. The average optical decay rate (afterglow flux proportional to t^-alpha) between 4 and 6 hours post-burst is alpha ~ 1.4, and the average IR decay rate is alpha ~ 0.9. After correcting for a galactic extinction of E(B-V) = 0.173, the spectral index of the afterglow at 4 hrs post burst is found to be beta ~ -1.3 (flux proportional to wavelength^-beta). //////////////////////////////////////////////////////////////////////// TITLE: GCN GRB OBSERVATION REPORT NUMBER: 5526 SUBJECT: GRB060904b, optical observations DATE: 06/09/05 14:41:54 GMT FROM: Adalberto Piccioni at Astronomy, Bologna U. G. Greco (Bologna University), F. Terra (Second University of Roma "Tor Vergata"), C. Bartolini, A. Guarnieri, A. Piccioni (Bologna University), D. Nanni (INAF/OAR and Second University of Rome "Tor Vergata"), S. Bernabei (Bologna Observatory), S. Sclavi(University of Rome "La Sapienza") and G. Pizzichini (INAF/IASF Bologna) report: On Sept. 5 we observed the field of GRB 060904b (Grupe et. al., GCN 5165) with the 152 cm Cassini Telescope located in Loiano, equipped with BFOSC (seeing 1".5). The photometry is based on the SDSS stars (J035252.20 -004344.1, J035249.70 -004345.8 , also quoted in GCN 5507 by Cool et al.) and the trasformation derived from Lupton (2005). For the OT detected by Klotz et al. (GCN 5508) we find the following magnitudes: ..Mean..UT .......Filter........Exptime (s).......magnitude Sept...5.111........Rc............900............21.75+/-0.11 Sept...5.123........Rc............900............21.74+/-0.12 Sept...5.145........Rc............900............21.8 +/-0.2 One of our images is available in a public directory from where it can be retrieved by sftp by using: hostname: ermione.bo.astro.it username: publicGRB password: GRB_bo directory: GRB060904b //////////////////////////////////////////////////////////////////////// TITLE: GCN GRB OBSERVATION REPORT NUMBER: 5527 SUBJECT: GRB 060904A Milagro GeV/TeV Observations DATE: 06/09/05 17:57:46 GMT FROM: Pablo Saz Parkinson at UCSC/Milagro Pablo Saz Parkinson (UC Santa Cruz) on behalf of the Milagro collaboration reports: We have searched Milagro data for emission at GeV/TeV energies from the bright GRB 060904A detected by Swift (GCN Circ 5502, D. Rupe et al.), during the main period of emission lasting 80s (GCN Circ 5516, H. Krimm et al.). No evidence for prompt GeV/TeV emission was found. A preliminary analysis, assuming a differential photon spectral index of -2.4, gives an upper limit on E^2dN/dE at 99% confidence of: E^2dN/dE at 2 TeV < 2.9 * 10^(-7) erg cm^(-2) (No EBL absorption) TeV photons are attenuated by pair production with infrared photons in intergalactic space. We calculate an upper limit assuming a redshift of 0.5 using the extragalactic infrared background light (EBL) absorption model of Primack et al. 2005 (AIP Conf. Proc. 745, p. 23). We find 99% confidence level upper limits on E^2dN/dE of: E^2dN/dE at 200 GeV < 5.5 * 10^(-5) erg cm^(-2) (Primack et al. EBL model) The energies quoted represent the approximate median energy of the events that would be detected assuming a power law spectrum with differential index -2.4 convolved with the absorption model. These upper limits are preliminary and will be refined with further analysis. //////////////////////////////////////////////////////////////////////// TITLE: GCN GRB OBSERVATION REPORT NUMBER: 5541 SUBJECT: GRB060904b optical detections (delayed report due to internet outage) DATE: 06/09/07 02:58:40 GMT FROM: Gottfried Kanbach at MPE N.Prymak, G. Kanbach, H. Steinle, A. Stefanescu, S. Duscha, F. Schrey, M. Muehlegger (MPE Garching) of the OPTIMA-Burst Team report on optical observations of GRB060904b (BAT trigger Nr. : 228006; Circ.Nr. 5505, Grupe et al.): OPTIMA-Burst at the 1.3m Skinakas Observatory, of the University of Crete, Greece, observed the Swift/UVOT 0.5"-errorcircle of GRB060904b (GCN Circ. 5519, Oats et al.) on 2006 Sept. 04. Relative photometry to several close-by USNO catalog stars (referenced by their R magnitude) was performed for the detected optical transient in our unfiltered images of 25 second exposure each. Results are listed: 2006/Sept/04 post-BAT start time(UT) time(s) R magnitude 02:39:25 502 16.90+-0.12 02:41:56 653 17.09+-0.16 02:44:00 777 17.24+-0.19 02:45:52 889 17.36+-0.17 02:47:47 1004 17.44+-0.14 02:48:56 1073 17.58+-0.14 02:55:29 1466 17.70+-0.22 02:56:01 1505 17.75+-0.20 02:58:52 1669 17.94+-0.18 03:00:14 1751 17.79+-0.21 03:01:05 1802 17.89+-0.14 Sorry for the delay, we didn't have Internet connection from Sept 2.5 to 6.7. //////////////////////////////////////////////////////////////////////// TITLE: GCN GRB OBSERVATION REPORT NUMBER: 5543 SUBJECT: GRB 060904A: Suzaku/WAM observation of the prompt emission DATE: 06/09/08 04:47:19 GMT FROM: Makoto Tashiro at Saitama U/Swift M. Tashiro, K. Abe, K. Onda, Y. Sato, M. Suzuki, Y. Urata (Saitama U.), M. Ohno, T. Takahashi, T. Asano, T. Uehara, Y. Fukazawa (Hiroshima U.), K. Yamaoka, S. Sugita (Aoyama Gakuin U.), T. Enoto, R. Miyawaki, K. Kokubun, K. Makishima (Univ. of Tokyo), K. Nakazawa, T. Takahashi (ISAS/JAXA), M. Suzuki, Y. Terada, T. Tamagawa (RIKEN), S. Hong (Nihon U.), on behalf of the Suzaku WAM team report: The bright, long burst, GRB 060904A (Swift-BAT trigger #227996; D. Grupe et al., GCN 5502; Krimm et al., GCN 5516), triggered the Suzaku Wideband All-sky Monitor (WAM) which covers an energy range of 50 keV - 5 MeV at 01:04:09.040 (UT). The three little peaks and following large peak (GCN 5502) are clearly seen in the light curve observed with the WAM. The T90 duration was ~79 seconds. The fluence in 100 - 1000 keV was 8.66(-4.19 +0.39)x10-6 erg/cm2, while the 1-s peak flux was 2.07(-1.12 +0.09) photons/cm2/s in the same energy range. Preliminary result shows that the time-averaged spectrum is well described with a single power-law model with the energy index of 1.16 (-0.18 0.20). All the quoted errors are at statistical 90% confidence level, in which systematic errors are not included. //////////////////////////////////////////////////////////////////////// TITLE: GCN GRB OBSERVATION REPORT NUMBER: 5547 SUBJECT: GRB 060904A : Optical limit DATE: 06/09/08 11:53:10 GMT FROM: Yuji Urata at Saitama U H. Mito, T. Soyano, (Tokyo Univ.) and Y. Urata (Saitama Univ.) on behalf of EAFON report: "We have observed the position of X-ray afterglow using Kiso 1.05m Schmited telescope. The observation was started at 10:20 UT September 4, 2006. The combined image from 20 frames taken with 300 sec exposure shows no optical afterglow associated with the X-ray afterglow position brighter than 22.4 (R) mag. ------------------------------------------- Start time Exposure Limit(SN=3) 10:20 300 sec x 20 frame > 22.4 ------------------------------------------- This message may be cited." //////////////////////////////////////////////////////////////////////// TITLE: GCN GRB OBSERVATION REPORT NUMBER: 5548 SUBJECT: GRB 060904B: Kiso Optical observation DATE: 06/09/08 11:55:05 GMT FROM: Yuji Urata at Saitama U T. Soyano, H. Mito (Tokyo Univ), and Y. Urata (Saitama Univ) on behalf of EAFON report: " We have made R-band follow-up observation of GRB 060904B afterglow (Grup et al.; Rykoff et al; Fugazza et al.) using Kiso 1.05m Schmidt telescope. The observation was started at 15:27 UT September 4, 2006 and lasted till 19:30. The preliminary analysis shows the optical afterglow with 21.4+/-0.2 mag at 15.72 hours after the burst. Further analysis is in progress. This message may be sited." //////////////////////////////////////////////////////////////////////// TITLE: GCN GRB OBSERVATION REPORT NUMBER: 5549 SUBJECT: GRB 060904B : CFHT/WIRCam NIR afterglow observations DATE: 06/09/08 11:56:31 GMT FROM: Yuji Urata at Saitama U K.Y. Huang, W.H. Ip, Y.S. Lee (NCU) and Y. Urata (Saitama Univ.) on behalf of EAFON report: "The NIR afterglow observations of GRB 060904B (Grup et al.; Rykoff et al; Fugazza et al.) with CFHT/WICam started from 9.40 hours after the GRB occurred. Our J and Ks images show the magnitude of the afterglow are J~ 19 at 10.8 hours and Ks~ 17 at 9.4 hours (compare with 2MASS stars). Refer to the SMART observations (Cobb et al., GCN 5515), our J band result indicates the decay rate (Flux ~ t^alpha) may change form ~- 0.65 to ~ -1.37. However, we do not find the decay rate change from our Ks band results. We would like to thank CFHT/WIRCam staff, especially A. Loic and P. Martin for their assistance. This message may be cited." //////////////////////////////////////////////////////////////////////// TITLE: GCN CIRCULAR NUMBER: 5741 SUBJECT: GRB060904b: optical observations DATE: 06/10/20 20:42:14 GMT FROM: Alexei Pozanenko at IKI, Moscow I. Asfandyarov, M. Ibrahimov (MAO), A. Pozanenko (IKI), on behalf of larger GRB follow up collaboration report: We observed the error box of GRB060904b (Grupe et al., GCN 5505) with 1.5 m telescope of Maidanak Astronomical Observatory (MAO) on September 4 and 5. A set of R images were taken under good weaher conditions. The afterglow (Rykoff et al., GCN 5504; Grupe et al., GCN 5505) is clearly detected in combined images of each epochs. A photometry of the afterglow based on USNO A2.0 is following: Mid time (UT), Exposure (s), R_ mag., Seeing Sep. 04.999 4x360 21.63 +/-0.18 1.4" Sep. 05.993 4x300 22.40 +/-0.30 1.1" The message may be cited