//////////////////////////////////////////////////////////////////////// TITLE: GCN GRB OBSERVATION REPORT NUMBER: 3865 SUBJECT: GRB 050824 optical candidate DATE: 05/08/25 00:12:45 GMT FROM: Javier Gorosabel at LAEFF-INTA, Madrid J. Gorosabel, V. Casanova, R. Garrido, A.J. Castro-Tirado, M. Jelinek, de Ugarte Postigo, (IAA-CSIC), report: We have carried out R-band observations starting at 23:49 UT (~37 min after the GRB) with the 1.5m OSN telescope. A visual comparison reveals an object placed at: RA(J2000) = 00:48:56.1 DEC(J2000)= 22:36:32 not present on the DSS. A finding chart will be shortly available at http://www.dsri.dk/~jgu/grb050824/FCs/osn.R.gif The object has a magnitude of R~18. Further observations would be required to confirm whether the object is fading." //////////////////////////////////////////////////////////////////////// TITLE: GCN GRB OBSERVATION REPORT NUMBER: 3866 SUBJECT: GRB050824: Swift-BAT detection of a burst DATE: 05/08/25 00:31:30 GMT FROM: Scott Barthelmy at NASA/GSFC S. Campana (INAF-OAB), S. Barthelmy (GSFC), D. Burrows (PSU), J. Cummings (GSFC/NRC), N. Gehrels (GSFC), S. Hunsberger (PSU), M. Ivanushkina (PSU), F. Marshall (GSFC), D. Palmer (LANL), G. Tagliaferri (INAF-OAB), on behalf of the Swift team: At 23:12:16 UT, Swift-BAT triggered and located GRB050824 (trigger=151905). This was a 64-sec image trigger. The spacecraft did not automatically slew due to proximity to the moon (25 degrees). Hence there will be no immediate results from XRT or UVOT. However, a TOO is being planned for this target. The BAT on-board calculated location is RA,Dec 12.237d,+22.592d {00h 48m 57s,+22d 35' 31"} (J2000), with an uncertainty of 3 arcmin (radius, 90% containment, stat+sys). The BAT light curve shows a broad peak from T+30 to T+70 sec. The emission is present only in the 15-50 keV band. The peak count rate was ~500 counts/sec (15-50 keV) at ~40 seconds after the trigger. At this early stage of the analysis we think this is likely a GRB, as there is no known gamma-ray source at this location in the SIMBAD database and the galactic latitude is -40 degrees. //////////////////////////////////////////////////////////////////////// TITLE: GCN GRB OBSERVATION REPORT NUMBER: 3867 SUBJECT: GRB 050824: ROTSE-III Optical Limits DATE: 05/08/25 01:58:31 GMT FROM: Brad Schaefer at LSU B. E. Schaefer (Louisiana State), Fang Yuan (U Mich), and K. Alatalo (Berkeley) report on behalf of the ROTSE collaboration: ROTSE-IIIc, located at the H.E.S.S. site at Mt. Gamsberg, Namibia, responded to GRB 050824 (Swift trigger 151905), producing images beginning 7.1 s after the GCN notice time. An automated response took the first image at 23:22:02.1 UT, 585.8 s after the burst, under good conditions although with the gibbous Moon only 25 degrees away. We took 10 5-sec, 10 20-sec and 130 60-sec eposures. These unfiltered images are calibrated relative to USNO A2.0 (R). ROTSE-IIId, located at the Turkish National Observatory at Bakirlitepe, Turkey, also responded, producing images beginning 5.8 s after the GCN notice time. An automated response took the first image at 23:22:00.8 UT, 584.5 s after the burst, under good conditions (but again, with the gibbous Moon nearby). We took 10 5-sec, 10 20-sec and 80 60-sec eposures. These unfiltered images are also calibrated relative to USNO A2.0 (R). Comparison to the DSS (second epoch) reveals no new sources within the 3-sigma error circle, for both single images and coadding into sets of 10. Individual images have limiting magnitudes ranging from 15.4-17.0; we set the following specific limits. ROTSE start UT end UT t_exp(s) mlim t_start-tGRB(s) Coadd? -------------------------------------------------------------------------- III-c 23:22:02.1 23:23:27.1 85 17.3 585.8 Y III-c 23:23:27.7 23:28:21.7 294 18.2 671.4 Y III-d 23:22:00.8 23:24:20.8 140 17.4 584.5 Y III-d 23:24:21.5 23:29:20.5 299 17.9 725.2 Y In particular, we do not see the new source described by Gorosabel et al. (GCN 3865), with this source being near or below our detection threshold. //////////////////////////////////////////////////////////////////////// TITLE: GCN GRB OBSERVATION REPORT NUMBER: 3869 SUBJECT: GRB050824: MASTER observation OT DATE: 05/08/25 02:29:00 GMT FROM: Vladimir Lipunov at Moscow State U/Krylov Obs Corrected subject to GCN3868. V. Lipunov, V.Kornilov, N.Tyurina, A.Belinski, E.Gorbovskoy, D.Kuvshinov, A.Krylov, G.Borisov, V.Vladimirov, Krushinski V. Sternberg Astronomical Institute, Moscow Union "Optic" MASTER (http://observ.pereplet.ru) responded to GRB 050824 (Swift trigger 151905). The first image was 764 sec after SWIFT GRB050824 detection under the not very good weather condition (Moon light). We see OT J. Gorosabel (GCN 3865) with m = 17.5 (unfiltered close to R, exp. 45 sec) on 2-3 sigma level. On summ of 9 images from 19.5 up to 28.5 minut after GRB Time (23 12 16.00 UT) m= 18.0 on 5 sigma. UT After GRB time m 23 25 00 764s 17.9 23 31 44 19.5min - 28.5 min 18.3 23 31 44 19.5min - 37.75 min 18.8 The JPG-image of the summ will be available at http://observ.pereplet.ru/images/GRB050824/1.jpg . The reduction is continuing. This work is supported by RFFI 04-02-16411 grant. This message can be cited. Mailto: lipunov@sai.msu.ru //////////////////////////////////////////////////////////////////////// TITLE: GCN GRB OBSERVATION REPORT NUMBER: 3870 SUBJECT: GRB050824: MASTER:OT decay DATE: 05/08/25 03:05:59 GMT FROM: Vladimir Lipunov at Moscow State U/Krylov Obs V. Lipunov, V.Kornilov, A.Krylov, N.Tyurina, A.Belinski, E.Gorbovskoy, D.Kuvshinov, G.Borisov, V.Vladimirov, G.Antipov, Krushinski V. Sternberg Astronomical Institute, Moscow Union "Optic" MASTER (http://observ.pereplet.ru) responded to GRB 050824 (Swift trigger 151905) (see GCN3869). The first image was 764 sec after SWIFT GRB050824 detection under the not very good weather condition (Moon light). We see OT-candidate proposed by J. Gorosabel (GCN 3865) with m = 17.9 (unfiltered, close to R, exp. 45 sec) on 2-3 sigma level. Our m = 0.89R + 0.11B (R & B from USNO A). UT (start) After GRB time m 23 25 00 764s 17.9 45 sec 23 31 44 19.5min - 28.5 min 18.3 summ of 9 images 23 42 07 29.8min - 36.7 min 19.4 summ of 7 images The calibration will be continued. The JPG-image of the summ will be available at http://observ.pereplet.ru/images/GRB050824/1.jpg . This work is supported by RFFI 04-02-16411 grant. This message can be cited. Mailto: lipunov@sai.msu.ru //////////////////////////////////////////////////////////////////////// TITLE: GCN GRB OBSERVATION REPORT NUMBER: 3871 SUBJECT: GRB 050824: BAT refined analysis of a soft weak burst DATE: 05/08/25 04:40:32 GMT FROM: Jay R. Cummings at NASA/GSFC/Swift H. Krimm (GSFC/USRA), L. Barbier (GSFC), S. Barthelmy (GSFC), J. Cummings (GSFC/NRC), K. Gendreau (GSFC), D. Hullinger (GSFC/UMD), E. Fenimore (LANL), N. Gehrels (GSFC), C. Markwardt (GSFC/UMD), P. Meszaros (PSU), D. Palmer (LANL), A. Parsons (GSFC), T. Sakamoto (GSFC/NRC), G. Sato (ISAS), J. Tueller (GSFC) on behalf of the Swift-BAT team: Using the full data set from the recent telemetry downlink, we report further analysis of Swift-BAT GRB 050824 (trigger #151905) (Campana, et al., GCN 3866). The ground-analysis position is RA,Dec 12.256 +22.618 (J2000) with an uncertainty of 3 arcmin (radius, 90%, stat+sys). This is 1.9 arcmin from the onboard position and 1.4 arcmin from the optical candidate reported by Gorosabel et al. in GCN Circ. 3865. The light curve shows a single peak with slow rise and slow decay. T90 is 25 +- 5 seconds. Fitting a simple power law over the interval from T+38 to T+64 sec, the photon index is 2.7 +/- 0.4 with a fluence of 2.3 +/- 0.5 x 10^-7 erg/cm^2 in the 15-150 keV band (90% c.l). The peak flux in a 1-second wide window starting at T+53 sec is 0.5 +/- 0.2 ph/cm^2/sec (15-150 keV). The original GCN Notices were delayed in transmission to the ground by 500 sec due to the burst happening during a telemetry downlink session when the TDRSS real-time messages are held in a buffer until the end of the downlink. //////////////////////////////////////////////////////////////////////// TITLE: GCN GRB OBSERVATION REPORT NUMBER: 3872 SUBJECT: GRB 050824: XRT refined analysis and possible afterglow detection DATE: 05/08/25 05:28:52 GMT FROM: Sergio Campana at INAF-OAB S. Campana (INAF-OAB), V. Mangano (INAF-IASF Palermo), G. Chincarini (INAF-OAB & Uni. Bicocca), G. Tagliaferri (INAF-OAB), D.N. Burrows (PSU), L. Cominsky (Sonoma State U.) and J. Norris (GSFC) report on behalf of the Swift XRT team: We have analyzed the Swift XRT data from the first orbit observation of GRB 050824 (Campana et al., GCN3866). The new refined coordinates are: RA(J2000) = 0h48m56.05s Dec(J2000) = +22:36:28.5 This position is 59 arcseconds from the BAT position given in GCN3866 (and 83 arcsec from the refined BAT position, Krimm et al. GCN3871) and 3.4 arcsec from the suggested optical counterpart (Gorosabel et al., GCN3865). We estimated an uncertainty of 6.8 arcseconds radius (90% confidence level, throughout the circular). A second fainter X-ray source is located 2.5 arcmin from the suggested afterglow position (and further away from the BAT refined position). The 0.5-10 keV light curve XRT started 2005-08-25 UT00:53:45, 6089 seconds after the BAT trigger, following an uploaded TOO since Swift did not automatically slewed on source (due to the Moon constraint). At the moment we have data from one Swift orbit. During the first orbit we accumulated 1346 seconds of good data. The afterglow candidate is detected with a count rate of (4.1+/-1.1)x10^-2 counts/second (55 total counts). We found no indication of count rate decay. The number of counts is too low to perform a full spectral analysis. Fixing the column density to the Galactic value (3.6x10^20 cm-2) a preliminary spectral fit to the PC data gives a spectral power law photon index of 2.6+/-0.6 in the 0.5-10 keV band. The average unabsorbed 0.5-10 keV flux is about (1.2+/-0.7)E-12 erg cm-2 s-1. //////////////////////////////////////////////////////////////////////// TITLE: GCN GRB OBSERVATION REPORT NUMBER: 3874 SUBJECT: GRB 050824: Spectroscopic redshift from the VLT DATE: 05/08/25 12:40:03 GMT FROM: Johan U. Fynbo at U.Copenhagen GRB 050824: Spectroscopic redshift from the VLT J. P. U. Fynbo, B. L. Jensen, J. Sollerman, J. Hjorth, D. Watson, K. Pedersen, P. Jakobsson, J. M. Castro Cerón (DARK Cosmology Centre/Niels Bohr Institute), Javier Gorosabel (IAA-CSIC) report: "Using FORS2 on the ESO Very Large Telescope (VLT) we have obtained spectra of the afterglow of GRB 050824 (GCN 3865, 3866) on 2005, Aug 25.4 UT. We detect [OII], [OIII], H-beta, and [NeIII] in emission and MgII in absorption, corresponding to a redshift of z=0.83. We acknowledge excellent support from the Paranal staff, especially Emmanuel Jehin." //////////////////////////////////////////////////////////////////////// TITLE: GCN GRB OBSERVATION REPORT NUMBER: 3875 SUBJECT: GRB050824: Radio Observations DATE: 05/08/25 15:58:41 GMT FROM: Patrick B. Cameron at Caltech P. B. Cameron (Caltech) and D. A. Frail (NRAO) report on behalf of a larger collaboration: "We have undertaken VLA observations at a frequency of 8.46 GHz toward GRB 050824 (GCN 3866) on August 25.32 UT. No radio afterglow is detected. At the position of the optical afterglow (GCN 3865) the point-source limit is 44 +/- 50 microJy. No further observations are planned. The National Radio Astronomy Observatory is a facility of the National Science Foundation operated under cooperative agreement by Associated Universities, Inc." //////////////////////////////////////////////////////////////////////// TITLE: GCN GRB OBSERVATION REPORT NUMBER: 3876 SUBJECT: GRB050824, I-band imaging DATE: 05/08/25 16:13:00 GMT FROM: Arne A. Henden at AAVSO D. Hohman (Stone Edge Observatory, NY) reports on behalf of the AAVSO International High Energy Network on optical observations of the Swift burst GRB050824 (Campana et al., GCN3866). Images taken with a 20cm SCT and Ic filter with midpoint time of 050825 0530UT (6.3hrs after the burst) do not show any object at the candidate afterglow location by Gorosabel et al. (GCN3865) down to the DSS-2 N-plate limit (about I=18). The full report is given below. The AAVSO thanks the Curry Foundation for support of the AAVSO International High Energy Network. --------------------------- Report filed on Thu Aug 25 08:37:34 2005: Name: Dennis Hohman email: dhohman@txrx.com Observer: HDF Site: Stone Edge Observatory Location: Orchard Park, NY LatitudeLongitude: Elevation: 275 meters Scope: SCT 20 cm ScopeFocalRatio: F5.9 CCDVendor: ST7XME CCDDetector: KAF402E CCDSize: 752x512 CCDPixelScale: 1.5 CCDFOV: 13x19 arc min Object: 050824 ObsDate: 08/25/05 ObsMidPointTime: 05:30 TimePerFrame: 240 sec NumberOfFrames: 13 Filters: I Processing: Flats/Darks/coadd Seeing: 4 - 4.5 LimitingMag: Sky: Clear afterglowmag: afterglowerr: compstars: Report: Full error circle covered. No new object to the limit of the POSS2/UKSTU IR plate. comments: A FITS image has been uploaded to ftp://ftp.aavso.org/grb/DennisHohman_050824_2453608.02609_.fits //////////////////////////////////////////////////////////////////////// TITLE: GCN GRB OBSERVATION REPORT NUMBER: 3877 SUBJECT: GRB050824: decay of the XRT light curve and updated X-ray spectrum DATE: 05/08/25 17:27:22 GMT FROM: Sergio Campana at INAF-OAB S. Campana (INAF-OAB), A. Moretti (INAF-OAB), V. Mangano (INAF-IASF Palermo), D.N. Burrows (PSU), report: We have analyzed 13 ks of Swift XRT data of GRB 050824 (Campana et al., GCN3866). The 0.2-10 keV light curve XRT (started 6089 seconds after the BAT trigger) now shows an indication of a temporal decay with a power law index of -0.4+/-0.2 (90% confidence level). The power law fit is better than a constant fit at a 3.3 sigma level (F-test). This indicates that the source suggested in the previous XRT circular (Campana et al., GCN3872) is the X-ray afterglow of GRB050824. The 307 photons in the 0.3-10 keV evergy band were also used for spectral analysis. We fixed the column density to the Galactic value (3.6x10^20 cm-2) and added a free local absorption at z=0.83 (Fynbo et al., GCN3874) plus a power law. We found an accepetable model (chi2_red=1.01) with a NH_loc=(1.7+/-1.3)x10^21 cm-2 and a power law photon index of 2.0+/-0.2 (90% confidence level). [GCN OPS NOTE(25aug05): Per author's request, "...afterglow of GRB050724" was changed to "...afterglow of GRB050824".] //////////////////////////////////////////////////////////////////////// TITLE: GCN GRB OBSERVATION REPORT NUMBER: 3878 SUBJECT: GRB050824: Swift/UVOT detection of fading afterglow DATE: 05/08/25 17:41:46 GMT FROM: Patricia Schady at MSSL/Swift The Swift Ultra-Violet/Optical Telescope (UVOT) observations began at 00:53:49 UT, 1.8 hrs after the BAT trigger. UVOT detects a fading source at a position consistent with that reported by Gorosabel et al. (GCN 3865) in 5 of its 6 filters. The magnitudes or 3-sigma upper limit in the first exposure taken in each filter are as follows: Filter Mid Time (hrs) Exp (s) Mag/3-sig UL V 1.8 109 20.02+/-0.39 B 5.1 305 20.88+/-0.36 U 3.6 217 19.55+/-0.32 W1 9.5 205 19.85+/-0.33 M2 11.7 121 19.34+/-0.36 W2 12.3 1457 > 20.79 The afterglow has faded below 2-sigma above background 11hrs after the burst trigger in all filters apart from the V and U, where it is still detected at the 2.3-sigma and >3-sigma level, respectively. The magnitudes have not been corrected for extinction. These magnitudes are based on preliminary zero-points, measured in orbit, and will require refinement with further calibration. //////////////////////////////////////////////////////////////////////// TITLE: GCN GRB OBSERVATION REPORT NUMBER: 3880 SUBJECT: GRB050824: CORRECTION to UVOT observing times DATE: 05/08/25 19:00:58 GMT FROM: Patricia Schady at MSSL/Swift P. Schady (MSSL/PSU), R. Fink (GSFC), M. Ivanushkina (PSU), S. Holland (GSFC/USRA), K. McGowen (MSSL), N. Gehrels (GSFC) on behalf of the Swift UVOT team CORRECTION: The mid time and exposure durations previously reported for observations made by Swift/UVOT of GRB050824 are incorrect (Schady et al. GCN 3878). The correct times are given below. The Swift Ultra-Violet/Optical Telescope (UVOT) observations began at 00:53:49 UT, 1.8 hrs after the BAT trigger. UVOT detects a fading source at a position consistent with that reported by Gorosabel et al. (GCN 3865) in 5 of its 6 filters. The magnitudes or 3-sigma upper limit in the first exposure taken in each filter are as follows: Filter Mid Time (hrs) Exp (s) Mag/3-sig UL V 1.8 900 20.02+/-0.39 B 5.1 900 20.88+/-0.36 U 3.6 545 19.55+/-0.32 W1 3.4 900 19.85+/-0.33 M2 2.1 532 19.34+/-0.36 W2 7.8 1457 > 20.79 The afterglow has faded below 2-sigma above background 11hrs after the burst trigger in all filters apart from the V and U, where it is still detected at the 2.3-sigma and >3-sigma level, respectively. The magnitudes have not been corrected for extinction. The reddening in this direction is E_{B-V} = 0.04mag. These magnitudes are based on preliminary zero-points, measured in orbit, and will require refinement with further calibration. //////////////////////////////////////////////////////////////////////// TITLE: GCN GRB OBSERVATION REPORT NUMBER: 3883 SUBJECT: GRB050824: MASTER final analysis of the OT observations DATE: 05/08/25 20:26:17 GMT FROM: Vladimir Lipunov at Moscow State U/Krylov Obs V. Lipunov, V.Kornilov, A.Krylov, N.Tyurina, A.Belinski, E.Gorbovskoy, D.Kuvshinov, G.Borisov, V.Vladimirov, G.Antipov, Krushinski V. Sternberg Astronomical Institute, Moscow Union "Optic" MASTER (http://observ.pereplet.ru) responded to GRB 050824 (Swift trigger 151905) (see GCN3869). The first image was 764 sec after SWIFT GRB050824 detection under the Moon light. We see OT-candidate proposed by J. Gorosabel (GCN 3865). Our m = 0.89R + 0.11B (R & B from USNO A2). We made new reduction and confirm previous our OT-decay result (GCN3870): New reduction give next results about OT: UT After GRB m error expotime mean time 23 25 00 788s >17.8 45 s 23 25 00 - 23 47 55 24.0 min 18.6 +-0.3 15x30 s 23 49 00 - 00 09 35 47.0 min 19.4 +-0.3 15x30 s The JPG-images available at http://observ.pereplet.ru/images/GRB050824/1.jpg . This work is supported by RFFI 04-02-16411 grant. This message can be cited. Mailto: lipunov@sai.msu.ru //////////////////////////////////////////////////////////////////////// TITLE: GCN GRB OBSERVATION REPORT NUMBER: 3886 SUBJECT: GRB050824: First 2 hours of power low optical decay? DATE: 05/08/26 17:27:26 GMT FROM: Vladimir Lipunov at Moscow State U/Krylov Obs V. Lipunov, V.Kornilov, N.Tyurina, A.Belinski, E.Gorbovskoy, D.Kuvshinov Sternberg Astronomical Institute, Moscow Union "Optic" We have analysed all photometric points obtained during first 2 hours (see picture http://observ.pereplet.ru/images/GRB050824/2.jpg ) from ROTSE (GCN Circ 3867), MASTER (GCN Circ 3883), J. Gorosabel et al. (GCN Circ 3865) and Swift UVOT(GCN Circ 3880) in similar colors . The upper limits of ROTSE and MASTER for 500-750 sec (GRB time) are in agreement. Both instrumental systems are more or less similar. There is some contradiction with J. Gorosabel et al. (GCN 3865) and MASTER data (GCN Circ 3880) for 24 - 47 minutes. But there is no error bar in J. Gorosabel et al.(GCN 3865). The SWIFT UVOT V-band is most closed to MASTER in color sense. If we include only 2 MASTER points and Swift UVOT V-point we can obtain next power low: m = 2.1(+-0.2) log (t) + 19.5 , t in hours. This corresponds to usual flux power law F ~ t^-0.9 However there is strong contradiction with ROTSE (11 min) uper limit and J. Gorosabel et al. (GCN 3865) point. JPG-images are available at http://observ.pereplet.ru/images/GRB050824/2.jpg . This work is supported by RFFI 04-02-16411 grant. This message can be cited. Mailto: lipunov@sai.msu.ru //////////////////////////////////////////////////////////////////////// TITLE: GCN GRB OBSERVATION REPORT NUMBER: 3890 SUBJECT: GRB050824, HETE-2 Observation DATE: 05/08/27 04:40:15 GMT FROM: Carlo Graziani at U.Chicago G. Crew, G. Ricker, J-L. Atteia, N. Kawai, D. Lamb, and S. Woosley, on behalf of the HETE Science Team; M. Arimoto, T. Donaghy, E. Fenimore, M. Galassi, C. Graziani, J. Kotoku, M. Maetou, M. Matsuoka, Y. Nakagawa, T. Sakamoto, R. Sato, Y. Shirasaki, M. Suzuki, T. Tamagawa, K. Tanaka, Y. Yamamoto, and A. Yoshida, on behalf of the HETE WXM Team; N. Butler, J. Doty, G. Prigozhin, R. Vanderspek, J. Villasenor, J. G. Jernigan, A. Levine, G. Azzibrouck, J. Braga, R. Manchanda, and G. Pizzichini, on behalf of the HETE Operations and HETE Optical-SXC Teams; M. Boer, J-F Olive, J-P Dezalay, and K. Hurley, on behalf of the HETE FREGATE Team; report: The FREGATE instrument onboard HETE also detected the Swift burst GRB 050824 (Campana, et al., GCN 3866) as an untriggered event (U11648) with a significance of 6 sigma. The direction to the burst source was about 50 degrees from the instrument boresight, placing it outside the WXM and SXC fields-of-view. We have analyzed the spectrum of the event. A power-law (PL) fit to the full FREGATE energy range (6-400 keV) yields a best-fit power-law index of 2.35 +0.88/-0.48 (90% CL), consistent with the PL index reported by the Swift BAT team (Krimm et al., GCN 3871). Assuming the best-fit PL index, the value of the fluence ratio S(2-30)/S(30-400) is 2.7. GRB 050824 is thus an X-Ray Flash. A PL fit restricted to photons with energy above 20 keV yields a best-fit PL index of 3.29 +2.50/-1.36 (90% CL). This steepening of the PL index suggests that the spectrum is representable by a Band model with a value of E_peak near or below the low end of the FREGATE energy range, so that the PL fit to the full energy range represents an average of the contributions from the high- and low-energy parts of the Band model. Because of the low S/N of the event, a PL times exponential fit and a Band-function fit are not statistically preferred over the simple PL model. Nonetheless, in order to constrain E_peak, we have performed a "constrained-Band model" analysis of the spectrum (see Sakamoto et al., ApJ 602, 875), and find E_peak < 12.7 keV (90% CL). FREGATE light curve data and plots will be available soon at the following URL: http://space.mit.edu/HETE/Bursts/U11648. //////////////////////////////////////////////////////////////////////// TITLE: GCN GRB OBSERVATION REPORT NUMBER: 3897 SUBJECT: GRB050824: Maidanak optical limits DATE: 05/08/28 10:13:25 GMT FROM: Alexei Pozanenko at IKI, Moscow D. Sharapov, G. Abdullaeva, M. Ibrahimov (MAO), A.Pozanenko (IKI), V.Rumyantsev (CrAO) on behalf of larger GRB follow up collaboration report: We observed the field of OT (GCNs 3865, 3868, 3880) of GRB050824 (GCN 3866) with 1.5m telescope of Maidanak Astronomical Observatory. A set of R images were taken between (UT) 21:27 - 22:01, on August 25. We do not detect the OT in a stacked image. Based on USNO A2.0 nearby stars we estimate limiting magnitude (3 sigma) of the stacked image (6x300 s) as R ~ 22.0. Detailed calibration of the stacked image is underway. This message may be cited. //////////////////////////////////////////////////////////////////////// TITLE: GCN GRB OBSERVATION REPORT NUMBER: 3907 SUBJECT: GRB 050824: MDM Observations DATE: 05/09/02 18:31:11 GMT FROM: Jules Halpern at Columbia U. J. P. Halpern (Columbia U.) and N. Mirabal (U. Michigan) report on behalf of the MDM Observatory GRB follow-up team: "We observed the Swift GRB 050824 afterglow (Gorosabel et al., GCN #3865) in the R band on five consecutive nights using the MDM 1.3m telescope. Photometry was established using two Landolt standard-star fields on one photometric night. From 5.6 to 12.6 hours, the decay is consistent with a power law of index -0.55+/-0.05, which extrapolates well to the MASTER photometry at 24 and 47 minutes (Lipunov et al., GCN #3883). This decay index is similar to that seen in the Swift XRT light curve, -0.4+/-0.2 (Campana et al., CGN #3877), immediately preceding the MDM observations. An unobserved inflection in the optical light curve then occurs, and from 1.3 to 4.4 days the decay index is -0.43+/-0.04. Our final measured point is R=22.18+/-0.06 on Aug. 29.32. Images and light curves are posted at http://www.astro.columbia.edu/~jules/grb/050824/ This message may be cited."