//////////////////////////////////////////////////////////////////////// TITLE: GCN GRB OBSERVATION REPORT NUMBER: 3910 SUBJECT: GRB050904: Swift-BAT detection of a probable burst DATE: 05/09/04 03:07:21 GMT FROM: Scott Barthelmy at NASA/GSFC J. Cummings (GSFC/NRC), L. Angelini (GSFC), S. Barthelmy (GSFC), A. Cucchiara (PSU), N. Gehrels (GSFC), C. Gronwall (PSU), S.T. Holland (GSFC), V. Mangano (INAF-IASF), F. Marshall (GSFC), C. Pagani (PSU), D. Palmer (LANL) on behalf of the Swift team: At 01:51:44 UT, Swift-BAT triggered and located GRB050904 (trigger=153514). The spacecraft slewed immediately. The BAT on-board calculated location is RA,Dec 13.670d,+14.138d {00h 54m 41s,+14d 08' 17"} (J2000), with an uncertainty of 3 arcmin (radius, 90% containment, stat+sys). This was a 64-sec image trigger. The BAT light curve shows hints of emission, but it is not possible to separate source variations from background variations at this early stage in the analysis. Given that this is at high galactic latitude, we believe this is a burst rather than a hard x-ray transient. There is nothing in SIMBAD nor in the BAT Active Source list near this location. XRT slewed promptly to the target and observation started at 01:54:25 UT (T+161 sec) with XRT in auto state. XRT revealed an uncatalogued fading point source at RA (J2000): 00h 54m 50.4s Dec (J2000): +14d 05' 08.5" with an uncertainty of 6 arsec (radius), 3.9 arcmin from the BAT position. The UVOT began observing at 01:54:28 UT, 164 s after the BAT trigger. The UVOT image is 3 arcmin away from the XRT position, so it does not intersect the XRT or BAT error circle. We cannot tell whether there is an optical counterpart at this time. We are currently in the portion of the orbits where the spacecraft does not pass over the Malindi downlink station. Therefore, it will be 4 hours before we have access to the full data set for the refined analyses. //////////////////////////////////////////////////////////////////////// TITLE: GCN GRB OBSERVATION REPORT NUMBER: 3911 SUBJECT: GRB 050904: TAROT optical limits DATE: 05/09/04 07:23:23 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 050904 detected by SWIFT (trigger 153514) with the TAROT robotic telescope (D=25cm) located at the Calern observatory, France. First image was acquired 86s after the GCN trigger. The field had an elevation of 60 degrees above horizon and weather conditions were good. We detected no new source comparing our unfiltered images with the USNO-B catalog. From the first frame we give an early limit: Day : 2005-09-04 UT-start UT-end (sec since GRB) Exp(s) R-mag 01:53:10.33 - 01:54:08.33 86 - 101 15 >16.0 We co-added 13 first frames and no new source is detected: Day : 2005-09-04 UT-start UT-end (sec since GRB) Exp(s) R-mag 01:53:10.33 - 02:00:18.74 86 - 515 360 >18.5 Limiting magnitude was estimated with the nearby USNO-B1 stars. This message can be cited. //////////////////////////////////////////////////////////////////////// TITLE: GCN GRB OBSERVATION REPORT NUMBER: 3912 SUBJECT: GRB050904: P60 Observations DATE: 05/09/04 07:58:41 GMT FROM: Derek Fox at PSU Derek B. Fox (Penn State) and S. Bradley Cenko (Caltech) report on behalf of a larger collaboration: "We have imaged the BAT and XRT localization region for GRB050904 (Swift Trigger 153514; Cummings et al., GCN 3910) in a series of exposures with the Palomar Robotic 60-inch Telescope (P60). At the following mean epochs, and to the following limits in R- and i-band, we identify no new sources within the XRT localization region in our coadded images: Time (UT) Delta Limit (mag) =================================== 05:25 +3h33m R > 20.8 05:41 +3h49m i > 19.7 =================================== Our photometric calibration is performed against the USNO-B1.0 catalog R-band and I-band magnitudes for this field for our R- and i-filter images, respectively. Our observations of this field are continuing." //////////////////////////////////////////////////////////////////////// TITLE: GCN GRB OBSERVATION REPORT NUMBER: 3913 SUBJECT: GRB 050904: SOAR/PROMPT Observations DATE: 05/09/04 10:00:28 GMT FROM: Daniel E. Reichart at U.North Carolina J. Haislip, D. Reichart, E. Cypriano, S. Pizzaro, A. LaCluyze, J. Rhoads, E. Figueredo report on behalf of the UNC team of the FUN GRB Collaboration. We imaged the XRT localization of GRB 050904 (Cummings et al., GCN 3910) with 4.1m SOAR at CTIO beginning about three hours after the burst. We detect a relatively bright (J ~ 17.5 mag) and fading source within the XRT error circle: RA: 00 54 51.3 DEC 14 05 09.7 There is no source at this location in POSS2 or SDSS. Near-simultaneous imaging with PROMPT reveals no source to about the POSS2 detection limit. This suggests that the afterglow is either very extinguished or at high redshift. //////////////////////////////////////////////////////////////////////// TITLE: GCN GRB OBSERVATION REPORT NUMBER: 3914 SUBJECT: GRB 050904: Possible High-Redshift GRB DATE: 05/09/04 12:04:56 GMT FROM: Daniel E. Reichart at U.North Carolina J. Haislip, D. Reichart, E. Cypriano, S. Pizzaro, A. LaCluyze, J. Rhoads, E. Figueredo report on behalf of the UNC team of the FUN GRB Collaboration. With SOAR, we have continued to image the NIR afterglow (Haislip et al., GCN 3913) of GRB 050904 (Cummings et al., GCN 3910) in JHK. Between 3.0 and 7.4 hours after the burst, we measure the temporal index to be -1.20. At 7.4 hours after the burst, we measure J - K = 1.2 mag, corresponding to a spectral index of -0.35. Scaling the i and R limits of Fox et al. (GCN 3912) to 3.0 hours after the burst, we measure i - J > 1.85 mag and R - J > 3.05 mag, corresponding to spectral indexes of <-1.90 and <-3.35, respectively. This is too steep to be explained by even heavy extinction. If interpretted as dropout, this corresponds to 5.3 < z < 9.0 (calculated using filter centers). Further NIR and especially z observations are strongly encouraged. //////////////////////////////////////////////////////////////////////// TITLE: GCN GRB OBSERVATION REPORT NUMBER: 3915 SUBJECT: GRB 050904: Environmental Constraints DATE: 05/09/04 14:36:07 GMT FROM: Daniel E. Reichart at U.North Carolina D. Reichart reports on behalf of the UNC team of the FUN GRB Collaboration. We have computed preliminary error bars on the temporal and spectral indexes of Haislip et al. (GCN 3914). The temporal index is -1.20 +/- 0.17 and the spectral index is -0.35 +/- 0.33. This disfavors the ISM-RED and WIND-RED cases at the 2.2 sigma confidence level, the ISM-BLUE case at the 1.3 sigma confidence level, and the WIND-BLUE case only at the 0.3 sigma confidence level (e.g., Sari, Piran & Narayan 1998; Chevalier & Li 2000). If the WIND-BLUE case is borne out by further observations, this suggests an electron-energy distribution index of p = 1.9 +/- 0.2, as well as a massive-star origin. If the NIR afterglow is strongly extinguished, and the intrinsic spectrum is even shallower than -0.35, or even positive, then none of the standard cases hold. This also suggests that the afterglow is probably not strongly extinguished, and supports the conclusion of Haislip et al. (GCN 3914) that the sharp spectral break between the J and i bands is likely due to dropout. Furthermore, given that the K to J spectral index is so shallow, and the J to i spectral index is so steep, the redshift range is probably narrower than that implied by the J and i filter centers (5.3 < z < 9.0), and is probably between 6 and 8. Careful modeling will better constrain this, but z, Z and/or Y observations, preferably contemporaneous with addition NIR observations would be most useful. //////////////////////////////////////////////////////////////////////// TITLE: GCN GRB OBSERVATION REPORT NUMBER: 3916 SUBJECT: GRB050904: Optical Observations DATE: 05/09/04 16:19:06 GMT FROM: Aaron Price at AAVSO Dr. D.T. Durig (Cordell-Lorenz Observatory, University of the South), Dennis Hohman (Stone Edge Observatory) and Aaron Price report on behalf of the AAVSO International High Energy Network on observations of the field of GRB050409 (GCN 3910; Cummings et al.). Durig does not detect any afterglow with SNR>3 on unfiltered images centered at 08:30:59 UT. However, sources do exist with an SNR=3 at locations near that reported in GCN #3913 (Haislip et al.). Locations and magnitude: 00 54 51.38 14 04 48.9 20.0 mag 00 54 50.42 14 05 30.6 20.1 mag 00 54 51.55 14 05 28.8 20.2 mag Full details, including a link to the FITS image is available at the bottom of this notice. Also, Hohman observed the field with an Rc filter centered on 06:18 UT and does not report any afterglow to Rc=18.6. Details on his observation are also below. The AAVSO thanks the Curry Foundataion for their continued support of the AVSO International High Energy Network. Report filed on Sun Sep 4 07:54:36 2005: Name: Dr. D. T. Durig email: ddurig@sewanee.edu Observer: D. T. Durig, A. P. Long, A. L. Yacko, J. L. Rouquette, J. C. Heiss Site: Cotrdell-Lorenz Observatory Location: Sewanee, Tenn, USA LatitudeLongitude: 35 12 N 85 55 W Elevation: 600m Scope: SCT 0.30 m ScopeFocalRatio: f/5.9 1760 mm CCDVendor: SBIG STL-1001E CCDDetector: KAF-1001E CCDSize: 1024x1024 CCDPixelScale: 2.8 CCDFOV: 48x48 full, 12x12 quater shown Object: GRB050904 ObsDate: 2005 Sept 4 ObsMidPointTime: 08 30 59 UT TimePerFrame: 300 sec NumberOfFrames: 37 Filters: CR Processing: dark, flat, register, add, 1/4 frame crop Seeing: ~6 LimitingMag: approx. 20.5 Sky: clear but windy afterglowmag: NA afterglowerr: NA compstars: 850 USNO B1.0 in Full Frame Report: Total exposure 185 minutes (37x300 sec= 11,100 sec ). I see no afterglow at the reported position(s) above my detection limit but there appears to be three very dim diffuse sources nearby at 00 54 51.38 14 04 48.9 20.0 mag 00 54 50.42 14 05 30.6 20.1 mag 00 54 51.55 14 05 28.8 20.2 mag All three are near my limiting mag with sigma equal to 3. In the noise I measure 00 54 49.69 14 05 08.5 21.9 mag but with sigma equal to 1.5 and below my detection limit of 20.5 mag. A FITS image has been uploaded to ftp://ftp.aavso.org/grb/Dr.D.T.Durig_GRB050904_2453617.99625_.fits -------------------- Report filed on Sun Sep 4 03:36:21 2005: Name: Dennis Hohman email: dennishohman@adelphia.net Observer: Dennis Hohman HDF Site: Stone Edge Observatory Location: Orchard Park, NY USA LatitudeLongitude: -78 45, 42 46 Elevation: 290M Scope: C8 200mm ScopeFocalRatio: 1200 CCDVendor: ST7XME CCDDetector: KAF402E CCDSize: CCDPixelScale: 1.55 CCDFOV: 19x13 Object: GRB050904 ObsDate: 09/04/05 ObsMidPointTime: 06:18 TimePerFrame: 240 sec NumberOfFrames: 8 Filters: R Processing: Darks,Flats, bias, coadd Seeing: 4 LimitingMag: 18.6 Sky: mostly clear with occasional patchy clouds afterglowmag: afterglowerr: compstars: Report: Full error circle covered. No new object observed to a limiting magnitude of 18.6 based USNO A2.0 catalog comments: A FITS image has been uploaded to ftp://ftp.aavso.org/grb/DennisHohman_GRB050904_2453617.81691_.fits //////////////////////////////////////////////////////////////////////// TITLE: GCN GRB OBSERVATION REPORT NUMBER: 3917 SUBJECT: GRB 050904: TAROT optical measurements DATE: 05/09/04 22:18:42 GMT FROM: Alain Klotz at CESR-CNRS Klotz, A. (CESR-OMP), Boer M. (OHP), Atteia J.L. (LATT-OMP) report: We did not explore the location of the Haislip et al. (GCNC 3913) source candidate in the first analyzis reported in GCNC 3911. This source is detected in three composited images taken by TAROT in the 8 first minutes after GRB. Magnitudes are calculated using the R USNO-B magnitudes of three nearby stars. [sec after GRB] start end magnitude 86 144 R>18.1 +/- 0.3 (no detected) 150 253 R=18.5 +/- 0.3 312 370 R=18.7 +/- 0.3 376 479 R=19.1 +/- 0.4 Corresponding images can be seen at: http://www.cesr.fr/~klotz/grb050904 After 8 minutes, the CCD camera cooler failed. Then, images are very noisy. We will try to obtain corresponding dark frames in the next days to reprocess images after t_GRB+8 min. This message can be cited. //////////////////////////////////////////////////////////////////////// TITLE: GCN GRB OBSERVATION REPORT NUMBER: 3918 SUBJECT: GRB 050904: BAT refined analysis of partial data set DATE: 05/09/05 02:46:12 GMT FROM: Jay R. Cummings at NASA/GSFC/Swift D. Palmer (LANL), L. Barbier (GSFC), S. Barthelmy (GSFC), J. Cannizzo (GSFC-UMBC), J. Cummings (GSFC/NRC), D. Hullinger (GSFC/UMD), E. Fenimore (LANL), N. Gehrels (GSFC), H. Krimm (GSFC/USRA), C. Markwardt (GSFC/UMD), A. Parsons (GSFC), T. Sakamoto (GSFC/NRC), G. Sato (ISAS), M. Tashiro (Saitama U.), J. Tueller (GSFC) on behalf of the Swift-BAT team: Using only a small amount of the full data set from recent telemetry downlinks, we report further analysis of Swift-BAT Trigger #153514 (Cummings, et al., GCN 3910). Due to a large backlog in data downlinking, we have only the data from T-40 to T+120 sec. We do not expect the full data set for at least another 2 days, so we are issuing this partial report. The ground-analysis position is RA,Dec 13.722,14.081 {0h54m53s, 14d04'52"} (J2000) with an uncertainty of 2.6 arcmin (radius, 90%, stat+sys). This is 3.9 arcmin from the onboard position and 0.54 arcmin from the IR afterglow position reported by Haislip et al. in GCN Circ. 3913. This is a long burst with T90 greater than 120 sec. The burst started at T+0 sec with continued emission past T+120 sec (where the downlinked data stops). //////////////////////////////////////////////////////////////////////// TITLE: GCN GRB OBSERVATION REPORT NUMBER: 3919 SUBJECT: GRB 050904: SOAR YJ and PROMPT Ic Observations DATE: 05/09/05 07:04:32 GMT FROM: Daniel E. Reichart at U.North Carolina J. Haislip, M. Nysewander, D. Reichart, E. Cypriano, D. Maturana, S. Pizarro, C. MacLeod, J. Kirschbrown, E. Figueredo report on behalf of the UNC team of the FUN GRB Collaboration. We continued observations of the afterglow (Haislip et al., GCN 3913) of GRB 050904 (Cummings et al., GCN 3910) with SOAR and PROMPT at CTIO in YJ and Ic, respectively, beginning 26.4 hours after the burst. We detect the afterglow in J and refine the fading rate to be -1.00 +/- 0.12. We also detect the afterglow in Y, which suggests that the redshift is at the lower end of the redshift ranges of Haislip et al. (GCN 3914) and Reichart (GCN 3915). Furthermore, a redshift of 6 (+/- 1) appears to be consistent with the relatively faint, unfiltered optical detections of Klotz et al. (GCN 3917) from only minutes after the burst: Extrapolation of our J-band light curve back to this time suggests that the afterglow was probably relatively bright (J ~ 13 mag) redward of the Ly-alpha forest. Integration of the light across a broad optical spectral response curve would then result in significantly fainter magnitudes for such redshifts. //////////////////////////////////////////////////////////////////////// TITLE: GCN GRB OBSERVATION REPORT NUMBER: 3920 SUBJECT: GRB 050904: early Swift XRT analysis results DATE: 05/09/05 10:55:21 GMT FROM: Teresa Mineo at INAF T. Mineo(INAF-IASF), V. Mangano(INAF-IASF), V. La Parola(INAF-IASF), G. Cusumano (INAF-IASF), L. Angelini (GSFC), J. Cummings (GSFC/NRC), D. N. Burrows (PSU), F. Marshall (GSFC), P. Boyd (GSFC-UMBC) report on behalf of the Swift XRT team: We have analyzed the Swift XRT data from the first observation of GRB 050904 (Cummings et al. 2005, GCN 3910) consisting of four orbits (about 20 ks). The refined coordinates of the X-ray afterglow are: RA(J2000) = 0h 54m 50.6s Dec(J2000) = +14d 05' 04.5" with an estimated uncertainty is of 6 arcseconds radius (90% containment). This position is 37 arcsec from the revised BAT position given in GCN 3918 (Palmer et al. 2005), 4.5 arcseconds from the XRT position determined on board and 11 arcseconds from the SOAR position (Haislip et al., GCN 3913). The 0.2-10 keV light curve, that starts in Windowed Timing (WT) mode 169 seconds after the BAT trigger (T0), shows a fading behaviour. Moreover two flares are clearly detected in the first orbit: the first at T0+466 s in WT data and the second at at T0+1240 s in Photon Counting (PC) mode data. The light curve decay index, obtained excluding the flare time intervals, is -2.08+/-0.03. The remaining three orbits show irregular rate variations likely due to other flares. A preliminary spectral fit to WT and PC data of the first orbit, excluding the flare time intervals, shows an evidence of spectral evolution from hard to soft: Time interval(s) Photon Index NHx10^20(cm^-2) Flux(erg cm^-2 s^-1) T0+170-370 1.33+/-0.04 15+/-1 1.8x10^-9 T0+580-1760 1.70+/-0.08 5.6+/-1.0 4.6x10^-11 The Galactic absorption in the GRB direction is 5x10^20 cm^-2. I.A.S.F. INAF Mailing System Outgoing mail is certified Virus Free. Checked by McAfee anti-virus system //////////////////////////////////////////////////////////////////////// TITLE: GCN GRB OBSERVATION REPORT NUMBER: 3921 SUBJECT: GRB 050904: NIR object inside the XRT error box DATE: 05/09/05 11:38:11 GMT FROM: Paolo D'Avanzo at INAF-OAB P. D'Avanzo (INAF/OAB), L. A. Antonelli (INAF/OAR), S. Covino (INAF/OAB), D. Malesani (SISSA), G. Tagliaferri, G. Chincarini (INAF/OAB) on behalf of the MISTICI collaboration report: We observed the field of GRB 050904 (Cummings et al., GCN 3910), in the J band with the 3.6m TNG telescope (equipped with NICS) and with the ESO VLT-UT1 (equipped with ISAAC). We don't detect the NIR source at the position indicated by Haislip et al. (R.A. 00:54:51.3, Dec. 14:05:09.7, GCN 3913, 3919) and by Klotz et al. (GCN 3917) to a limit J > 22 (5sigma). We also note that this position is ~ 6 arcsec out from the XRT error box (Mineo et al., GCN 3920) and ~ 11" away from its center. We detect however a single fading source inside the XRT error box, which is likely the NIR counterpart of GRB 050904. Its coordinates are: R.A.(J2000) = 00:54:50.8 Dec.(J2000) = +14:05:10.0 The detected source faded by 0.30 +/- 0.15 mag between the two epochs (24.7 and 26 h after the burst, respectively). That source has a J magnitude which is consistent with the one expected from the source proposed by Haislip et al. with a decay slope of t^-1, A finding chart is available at the following URL: http://www.sissa.it/~malesani/GRB/050904/GRB050904_finder.jpg We thank the TNG and ESO staff, in particular Marco Pedani, Poshak Gandhi and Nancy Ageorges for carefully performing our observations and quickly providing the data. This message can be cited. //////////////////////////////////////////////////////////////////////// TITLE: GCN GRB OBSERVATION REPORT NUMBER: 3922 SUBJECT: GRB 050904: Afterglow Astrometry DATE: 05/09/05 17:25:07 GMT FROM: Daniel E. Reichart at U.North Carolina M. Nysewander, D. Reichart, J. Haislip report on behalf of the UNC GRB team of the FUN GRB Collaboration: Using a single 348 sec coadd from last night's SOAR data (Haislip et al., GCN 3919) and 7 USNO stars, we measure the coordinates of the afterglow to be: RA: 00:54:50.794 DEC: +14:05:09.42 with uncertainties of 1.6" in RA and 2.3" in DEC. This is consistent with the astrometry of D'Avanzo et al. (GCN 3921) and the refined coordinates of the X-ray afterglow (Mineo et al.; GCN 3920). DR apologizes for the crudeness of our initial astrometry. //////////////////////////////////////////////////////////////////////// TITLE: GCN GRB OBSERVATION REPORT NUMBER: 3923 SUBJECT: GRB 050904: Swift/UVOT observations DATE: 05/09/05 17:50:27 GMT FROM: Antonino Cucchiara at PSU A. Cucchiara (PSU), J. Cummings (GSFC), S. Holland (GSFC), C. Gronwall (PSU), A. Blustin (MSSL), F. Marshall (GCFS), A. Smale (NASA HQ), L. Cominsky (Sonoma State U.), N. Gehrels (GSFC) on behalf of the Swift UVOT team Swift/UVOT began observing the field of GRB050904 at 01:54:25 UT, 164 s after the BAT trigger (Cummings, et al., GCN 3910) in all the six filters. In the first 100 s V-band image (T+ 214 s), no new source is detected with respect to the DSS down to a 3 sigma upper limit of 18.9 mag in the XRT error circle (GCN 3910). At T+90 min after the trigger, in a single 900 s V-band image the upper limit was 20.1. The instrument continued to collect data during all the other orbits detecting no new source down to the following upper limits: Filter Start_Time(UT) Stop_Time(UT) Exp(s) 3sig_limit V 01:54 16:20 4887 20.9 B 01:56 18:12 4773 21.9 U 01:56 17:57 4686 21.6 UVW1 01:56 16:49 4292 21.1 UVM2 01:56 16:35 4684 21.4 UVW2 01:57 18:26 4331 21.4 Where Start_Time and Stop_Time are the time range over wich the summed images were accumulated and Exp is the total exposure time (in seconds) of the summed image. The magnitude upper limits are not corrected for extinction. These non-detections are consistent with a high redshift GRB, as reported by J. Haislip, et al. (GCN 3914 and 3919). These magnitudes are based on preliminary zero-points, measured in orbit, and will require refinement with further calibration. This message can be cited. //////////////////////////////////////////////////////////////////////// TITLE: GCN GRB OBSERVATION REPORT NUMBER: 3924 SUBJECT: GRB 050904: photometric redshift DATE: 05/09/05 18:55:57 GMT FROM: Daniele Malesani at SISSA-ISAS,Trieste,Italy L.A. Antonelli, A. Grazian (INAF/OAR), P. D'Avanzo (INAF/OABr), V. Testa (INAF/OAR), S. Covino, G. Tagliaferri, G. Chincarini (INAF/OABr), A. Fernandez-Soto (Univ. Valencia), D. Malesani (SISSA), F. Fiore and L. Stella (INAF/OAR) report on behalf of the MISTICI collaboration: "We observed the field of GRB 050904 (Cummings et al., GCN 3910; Mineo et al., GCN 3920) with the ESO VLT-UT1, in the J, H, and K bands (with ISAAC) and in the I band (with FORS2). The afterglow (Haislip et al., GCN 3913; D'Avanzo et al., GCN 3921) is detected in all filters, including the I band. We derive for this source a photometric redshift z = 6.10 (+0.37, -0.12; 90% confidence) by adopting a chi square minimization technique (Fontana et al., 2000, AJ, 120, 2206). This is in agreement with the result of Haislip et al. (GCN 3919). This message can be cited." //////////////////////////////////////////////////////////////////////// TITLE: GCN GRB OBSERVATION REPORT NUMBER: 3925 SUBJECT: GRB 050904: More SOAR DATE: 05/09/06 09:06:47 GMT FROM: Daniel E. Reichart at U.North Carolina C. MacLeod, J. Kirschbrown, D. Reichart, E. Cypriano, P. Ugarte, A. Alvarez, E. Figueredo report on behalf of the UNC team of the FUN GRB Collaboration. We continued observations of the afterglow (Haislip et al., GCN 3913) of GRB 050904 (Cummings et al., GCN 3910) with 4.1m SOAR at CTIO in J, beginning 52.9 hours after the burst. The afterglow is no longer detected: J > 21.6 (2 sigma). This implies that temporal index has steepened from -1.0 +/- 0.1 (Haislip et al., GCN 3919) to <-2.3 over the past day, which suggests that we are now past the jet-break time. //////////////////////////////////////////////////////////////////////// TITLE: GCN GRB OBSERVATION REPORT NUMBER: 3928 SUBJECT: GRB 050904: Did SWIFT/XRT see the prompt GRB emission ? DATE: 05/09/06 14:27:48 GMT FROM: Jean-Luc Atteia at Lab d Astrophys.,OMP,Toulouse J-L. Atteia (LAT-OMP) communicates: The high redshift of GRB 050904 suggests a possible interpretation of the XRT observations reported in GCNC 3920 (T. Mineo et al.) as the *prompt emission* of the burst. - The maximum effective area of SWIFT/XRT (2 keV) corresponds to a restframe energy of ~14 keV for a source at redshift z=6.1. - The time of the first XRT flare is 466/(7.1) ~ 66 sec in the restframe. - The spectral index of -1.33 is suggestive of the spectral index of the prompt emission below the the break energy (Epeak). All these numbers are compatible with an interpretation of the early SWIFT/XRT observations in terms of GRB prompt emission. In view of this possibility, further information on the duration of GRB 050904, would be of great interest. //////////////////////////////////////////////////////////////////////// TITLE: GCN GRB OBSERVATION REPORT NUMBER: 3929 SUBJECT: GRB 050904: BOOTES early R-band observation DATE: 05/09/06 15:34:03 GMT FROM: Alberto Castro-Tirado at Inst.de Astro. de Andalucia M. Jelinek, A.J. Castro-Tirado, A. de Ugarte Postigo (IAA-CSIC Granada), P. Kubanek (ASU AV CR Ondrejov), S. Vitek (CVUT Praha), J. Gorosabel and S. Guziy (IAA-CSIC), R. Hudec (ASU AV CR), J.M. Castro Ceron (DARK NBI Kobenhavn), P. Pata and M. Bernas (CVUT), report: The BOOTES-1B 30 cm robotic telescope in Southern Spain, has followed-up the high-redshift GRB 050904 (Cummings et al. GCN 3910, Haislip et al. 3913, 3914, Reichart et al. 3915, Antonelli et al. GCN 3924) starting 124s after the onset of the burst. The upper limits derived from our R-band filter measurements during the time interval 124s -1100s after the event, together with the values reported by TAROT (Klotz et al. GCN 3917) are consistent with an early decay index of alpha = -1.2 (i.e. in agreement with the value reported at a later epoch in the J-band by Haislip et al. GCN 3914). This message can be quoted. [GCN OPS NOTE(06sep05): Per author's request: "NBI" --> "DARK NBI", added "Haislip et al. 3913, 3914, Reichart et al. 3915,", "our R-band meaurements" --> "our R-band filter measurements", "the value later reported" --> "the value reported at a later epoch".] [GCN OPS NOTE(21oct05): Per author's request: in the Subject line "detection" is changed to "observation", and in the body "Our R-band filter measurements" is changed to "The upper limits derived from our R-band filter measurements".] //////////////////////////////////////////////////////////////////////// TITLE: GCN GRB OBSERVATION REPORT NUMBER: 3930 SUBJECT: GRB 050904: more VLT NIR observations DATE: 05/09/06 18:28:44 GMT FROM: Gianpiero Tagliaferri at OAB-INAF P. D'Avanzo (INAF/OABr), L.A. Antonelli(INAF/OAR), S. Covino (INAF/OABr), A. Grazian, V. Testa (INAF/OAR), D. Malesani (SISSA), D. Fugazza, G. Tagliaferri (INAF/OABr), G. Chincarini (INAF/OAB & UNIMIB), L. Stella (INAF/OAR), and A. Fernandez-Soto (Univ. Valencia) report on behalf of the MISTICI collaboration: We continued monitoring the afterglow (Haislip et al., GCN 3913; D'Avanzo et al., GCN 3921) of GRB 050904 (Cummings et al., GCN 3910; Mineo et al., GCN 3920) with the ESO VLT-UT1 (equipped with ISAAC). Observations were performed in the J, H, and K bands, at about 50, 51 and 51.5 hours after the burst. We still detect the afterglow in all filters. The measured magnitudes are consistent with an unbroken decay with slope ~1 from 3 to ~50 hr after the GRB. We thank the ESO staff, in particular Nancy Ageorges for carefully performing our observations and quickly providing the data. More observations are planned. This message can be cited. //////////////////////////////////////////////////////////////////////// TITLE: GCN GRB OBSERVATION REPORT NUMBER: 3932 SUBJECT: GRB 050904: Keck I-band Imaging DATE: 05/09/06 18:58:03 GMT FROM: Josh Bloom at UC Berleley D. Perley, J. S. Bloom, M. Cooper (UCB), J. Newman (LBL), P. Guhatakurta (UCSC), J. X. Prochaska (UCO Lick) and H.-W. Chen (MIT/U Chicago) report on behalf of a larger group: "We observed the field of GRB 050904 (GCN 3910) using the DEIMOS imager on the Keck II during the early morning twilight of 05 Sept 2005 UT. The afterglow candidate reported by Haislip et al. (GCN 3913, 3922) is well-detected in the first 300-second I-band exposure, taken at UTC=14:50 (~37.0 hours after the burst). Calibrating against three nearby stars in SDSS, we measure a preliminary magnitude for the afterglow of i~=22.9 +/- 0.6. This uncertainty is dominated by the photometric calibration which we expect to improve with further processing." This message may be cited. //////////////////////////////////////////////////////////////////////// TITLE: GCN GRB OBSERVATION REPORT NUMBER: 3937 SUBJECT: GRB 050904: Subaru Optical Spectroscopy DATE: 05/09/07 16:38:55 GMT FROM: Nobuyuki Kawai at Tokyo Tech N. Kawai (Tokyo Tech), T. Yamada (NAOJ), G. Kosugi, T. Hattori, and K. Aoki (Subaru/NAOJ) report on behalf of Subaru GRB team: "We observed the field of GRB 050904 (GCN 3910) with Faint Object Camera And Spectrograph on the Subaru 8.2m telescope atop Mauna Kea on the night of September 6, approximately 3.5 days after the burst. We obtained spectra of the afterglow candidate (Haislip et al. GCN 3913, 3922, D'Avanzo et al. GCN 3921). Based on the absorption features we measure the redshift to be z=6.29 +- 0.01, confirming the photometoric redshift reported earlier (Haislip et al. GCN 3914, 3919, Antonelli et al. GCN 3924)." This message may be cited. //////////////////////////////////////////////////////////////////////// TITLE: GCN GRB OBSERVATION REPORT NUMBER: 3938 SUBJECT: GRB 050904 BAT refined analysis of complete data set DATE: 05/09/07 18:55:04 GMT FROM: Jay R. Cummings at NASA/GSFC/Swift T. Sakamoto (GSFC/NRC), L. Barbier (GSFC), S. Barthelmy (GSFC), J. Cummings (GSFC/NRC), D. Hullinger (GSFC/UMD), E. Fenimore (LANL), N. Gehrels (GSFC), H. Krimm (GSFC/USRA), C. Markwardt (GSFC/UMD), D. Palmer (LANL), A. Parsons (GSFC), G. Sato (ISAS), J. Tueller (GSFC) on behalf of the Swift-BAT team: We now have the complete BAT data for GRB 050904 (Cummings et al., GCN circ. 3910 and Palmer et al. GCN circ. 3918). This was a very long, bright burst. The light curve shows 3 main peaks. There are 15-second long peaks at ~T+28 sec and ~T+56 sec, and the main peak was from ~T+80 sec to ~T+220 sec, along with weaker peaks. Emission in the BAT energy range continues to almost T+500 sec with a weak peak at ~T+470 sec. T90 was 225 +/- 10 sec (estimated error including systematics, 15-350 keV). Fitting a simple power law from T+17 sec to T+226 sec, the photon index is 1.34 +/- 0.06. The fluence is 5.4 +/- 0.2 x 10^6 ergs/cm^2. The 1-second peak flux from T+27.5 sec is 0.8 +- 0.2 photons/cm^2/sec. All errors are 90% confidence, energy range 15-150 keV. Haislip et al. (GNC circ. 3914, 3919) reported a Ly-alpha break for this burst corresponding to a redshift of 5.3 to 9.0. Antonelli et al. (GCN circ. 3924) calculate a redshift of 6.1. Kawai et al. (GCN circ. 3937) report a spectrographic redshift of 6.29. With the above fluence at this redshift (6.29), the isotropic energy equivalent is 3.8 x 10^53 ergs in the range 109 - 1094 keV in the GRB rest frame. //////////////////////////////////////////////////////////////////////// TITLE: GCN GRB OBSERVATION REPORT NUMBER: 3939 SUBJECT: GRB050904: CrAO optical observations DATE: 05/09/07 21:38:18 GMT FROM: Vasilij Rumjantsev at CrAO V.Rumyantsev (CrAO), V.Biryukov (SAI, MSU), A.Pozanenko (IKI), M. Ibrahimov (MAO) on behalf of larger GRB follow up collaboration report: We observed the BAT and XRT error boxes of GRB050904 (Swift # 153514; Cummings et al., GCN 3910) with 2.6m Shain telescope (CrAO) on September 4 between (UT) 20:39 - 21:31 in R-band filter. The OT (Haislip et al., GCN 3913, D'Avanzo et al. GCN 3921) is not detected in our combine image. Preliminary estimation of the limiting value of the combined image based on USNO-A2.0 catalog is following Mean time Exposure Filter Magnitude (UT) s 21:04 24x120 R 23.5 Combined image can be found in http://grb.rssi.ru/GRB050904. This message may be cited. //////////////////////////////////////////////////////////////////////// TITLE: GCN GRB OBSERVATION REPORT NUMBER: 5300 SUBJECT: Host galaxy of GRB050904: 250 GHz upper limit with MAMBO at the IRAM 30m DATE: 06/07/12 13:31:17 GMT FROM: Fabian Walter at MPIA F. Walter (MPIA Heidelberg), C. Carilli (NRAO), F. Bertoldi (AIfA Bonn), A. Weiss (MPIfR Bonn) report: We observed the host galaxy of GRB 050904 (GCN 3910) at redshift z=6.29 (GCN 3937), RA 00:54:50.83, Dec +14:05:10 (J2000), with the Max-Planck-Millimeter Bolometer (MAMBO-2) array at the IRAM 30-m telescope on 27 February 2006 and 03 March 2006, and obtained a non-detection of S_nu(250 GHz,1.20mm) = -0.76 +/- 0.45 mJy (1 sigma error), i.e. a 3 sigma upper flux density limit of 1.35 mJy. The MAMBO-2 bolometer detectors cover 210-290 GHz (half power). The host galaxy of GRB 050904 is well within our 10.7 arcsec FWHM beam. This message may be cited. //////////////////////////////////////////////////////////////////////// TITLE: GCN CIRCULAR NUMBER: 6018 SUBJECT: GRB 050904: Second Epoch of HST/NICMOS Observations DATE: 07/01/17 19:41:48 GMT FROM: Edo Berger at Carnegie Obs E. Berger (Carnegie Observatories) reports on behalf of a large collaboration: "We re-observed the position of GRB 050904 (z=6.295) with NICMOS on the Hubble Space Telescope on 2006 July 22 UT. A total of 6 orbits (15360 sec) were obtained with the F160W (H-band) filter. Previous observations of the burst with NICMOS on 2005 Sep 27 UT revealed a source with F160W(AB)=26.1+/-0.2 mag (Berger et al. astro-ph/0603689), which was interpreted as a combination of afterglow and host galaxy light. The new observations reveal no source at the position of the burst to a 3-sigma limit of F160W(AB)=27.2 mag. This result indicates that the host galaxy is fainter than about 0.05 microJy, and that the light contribution from the afterglow to the source detected in the Sep 2005 observations was >60%, confirming the proposed jet break at t~3 days (Tagliaferri et al. 2005; Haislip et al. 2006). A complete analysis of the new NICMOS observations, and their implications for the afterglow and host galaxy properties, will be made available in a revised version of astro-ph/0603689."