//////////////////////////////////////////////////////////////////////// TITLE: GCN GRB OBSERVATION REPORT NUMBER: 3893 SUBJECT: GRB050827: Swift-BAT detection of a burst DATE: 05/08/27 19:26:32 GMT FROM: Scott Barthelmy at NASA/GSFC M. Capalbi (ASDC), S. Barthelmy (GSFC), J. Cummings (GSFC/NRC), N. Gehrels (GSFC), C. Markwardt (GSFC/UMD), D. Palmer (LANL), on behalf of the Swift-BAT team: At 18:57:15 UT, Swift-BAT triggered and located GRB050827 (trigger=152325). The spacecraft did not slew because of Moon constraint, and it will not be observable until ~13:00 UT 28/Aug/05 (T+18 hrs). The BAT on-board calculated location is RA,Dec 64.279d,+18.218d {04h 17m 07s,+18d 13' 03"} (J2000), with an uncertainty of 3 arcmin (radius, 90% containment, stat+sys). The BAT light curve shows multi-peaks with some pre-trigger emission starting at T-10 sec with a total duration of ~45 sec. The peak count rate was ~2500 counts/sec (15-350 keV), at ~2 seconds after the trigger. //////////////////////////////////////////////////////////////////////// TITLE: GCN GRB OBSERVATION REPORT NUMBER: 3894 SUBJECT: GRB 050827: Swift-BAT refined analysis DATE: 05/08/27 23:39:07 GMT FROM: Hans Krimm at NASA-GSFC T. Sakamoto (GSFC/NRC), L. Barbier (GSFC), S. Barthelmy (GSFC), J. Cummings (GSFC/NRC), E. Fenimore (LANL), N. Gehrels (GSFC), D. Hinshaw (GSFC-SPSYS), D. Hullinger (UMD), H. Krimm (GSFC/USRA), C. Markwardt (GSFC/UMD), K. McLean (LANL), D. Palmer (LANL), A. Parsons (GSFC), G. Sato (ISAS), J. Tueller (GSFC), on behalf of the Swift-BAT team: Using the full data set from T-300 to T+300 sec from the recent telemetry downlink, we report further analysis of Swift-BAT GRB 050827 (trigger #152325) (Capalbi, et al., GCN 3893). The refined BAT ground position is (RA,Dec) = 64.297,+18.217 {04h 17m 11s, +18d 13' 01"} [deg; J2000] +-1.3 arcmin, (90% containment). The partial coding was 61%. The mask-weighted light curve shows two peaks, with the first peak significantly larger than the second. The first peak is triangular in shape beginning at T-15 sec, rising to a maximum at T+0 and returning to background at T+9 sec. This peak shows a hint of spectral hardening as it progresses. There is a smaller second peak of duration ~3 sec, beginning at T+25 sec and a hint of a ~4-sec peak at T+31 sec. T90 (15-350 keV) is (49 +- 2) seconds (estimated error including systematics). The power law index of the time-averaged spectrum is 1.37 +- 0.10. The fluence in the 15-150 keV band is (2.11 +- 0.12) x 10^-6 erg/cm2. The 1-sec peak photon flux measured from T+2.5 sec in the 15-150 keV band is (1.78 +- 0.19) ph/cm2/sec. All the quoted errors are at the 90% confidence level. [GCN OPS NOTE(28aug05): The "05027: in the subject-line was changed to "050827".] //////////////////////////////////////////////////////////////////////// TITLE: GCN GRB OBSERVATION REPORT NUMBER: 3895 SUBJECT: GRB050827: RTT150 optical observations DATE: 05/08/28 02:47:40 GMT FROM: Irek Khamitov at TUG Z. Aslan, I. Khamitov (TUG), U. Kiziloglu (METU), E. Gogus (Sabanci Uni.), I. Bikmaev, A. Galeev, N. Sakhibullin (KSU/AST), R. Burenin, M. Pavlinsky, R. Sunyaev (IKI), report: We have observed the error box of Swift-BAT GRB 050827 (trigger #152325) (Capalbi, et al., GCN 3893; T. Sakamoto, et al., GCN 3894) with the Russian-Turkish 1.5-m telescope (Bakirlitepe, TUBITAK National Observatory, Turkey) using TFOSC in R band. We made 2*300s exposures at UT 23:27, August 27 (midtime), and 2*300s at UT 01:39, August 28, 2005. We found no fading source brighter than ~21.4. This message may be cited. //////////////////////////////////////////////////////////////////////// TITLE: GCN GRB OBSERVATION REPORT NUMBER: 3899 SUBJECT: GRB 050827: XRT possible afterglow detection DATE: 05/08/28 18:04:29 GMT FROM: Milvia Capalbi at ISAC/ASDC M. Capalbi (ASDC), V. Mangano (INAF-IASF), G. Tagliaferri (INAF-OAB), J. Kennea (PSU), N. Gehrels (GSFC), D. Hinshaw (GSFC-SPSYS), F. Marshall (GSFC) report on behalf of the Swift XRT team: We have analyzed the Swift XRT data from the first observation (2 orbits) of GRB 050827 (Capalbi, et al., GCN 3893). The spacecraft slewed to this burst after 17.8 hrs due to the Moon constraint. An uncatalogued, X-ray source was detected at the following position: RA(J2000) = 04h 17m 09.4s Dec(J2000) = +18 11 57.9 with an uncertainty of 8 arcseconds radius (90% containment). No other source is detected within the BAT error circle. This position is 69 arcsec from the refined BAT position given in GCN 3894 (Sakamoto et al.). This source has a count rate of (2.0+/-0.3)E-02 cts s^-1 that approximately corresponds to a flux of 1.0E-12 erg cm^-2 s^-1 (there are not enough counts for a spectral fit). The light curve however does not seem to decay, thus we need more data to confirm this source as the afterglow of GRB 050827. //////////////////////////////////////////////////////////////////////// TITLE: GCN GRB OBSERVATION REPORT NUMBER: 3900 SUBJECT: GRB 050827: Optical Limit DATE: 05/08/28 20:04:21 GMT FROM: Jules Halpern at Columbia U. J. P. Halpern (Columbia U.) reports on behalf of the MDM Observatory GRB follow-up team: "I observed the error box of GRB 050827 (Swift trigger #152325, GCN #3893) in the R band with the MDM 1.3m telescope for 50 minutes starting on Aug. 28 09:32 UT, or 14.6 hours after the burst. There is no optical object to a limiting magnitude R=23.5 within 16", or twice the error circle radius, of the XRT candidate afterglow reported by Capalbi et al. (GCN #3899). Even after correcting this limit for Galactic absorption A(R)=1.47 mag at its location (Schlegel et al. 1988), it would be unusual for a persistent X-ray source of flux 1.0E-12 erg cm^-2 s^-1 to have no optical counterpart. So this supports the identification of the X-ray source as the GRB afterglow." //////////////////////////////////////////////////////////////////////// TITLE: GCN GRB OBSERVATION REPORT NUMBER: 3901 SUBJECT: GRB050827: Swift/UVOT upper limits DATE: 05/08/29 02:25:11 GMT FROM: Alexander Blustin at MSSL-UCL A. J. Blustin (UCL-MSSL), M. Capalbi (ASDC), F. Marshall (GSFC), J. Nousek (PSU), N. Gehrels (GSFC) on behalf of the Swift UVOT team Swift/UVOT began observing the field of GRB050827 17.8 hours after the BAT trigger (Capalbi, et al., GCN 3893); previous to that, the target was unobservable due to a moon constraint. No new source with respect to the DSS image is detected in the XRT error circle (Capalbi, et al., GCN 3899) down to the following upper limits in the six filters: Filter T-range (hrs) Exp (s) 3sig_limit V 20.9-24.3 1800 20.1 B 19.5-26.2 2444 21.0 U 19.3-25.9 2699 21.1 UVW1 18.1-25.7 2939 20.6 UVM2 17.8-24.6 2531 20.7 UVW2 20.6-24.1 1800 20.8 Where T_range is the time range in hours post-trigger over which 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 magnitudes are based on preliminary zero-points, measured in orbit, and will require refinement with further calibration. //////////////////////////////////////////////////////////////////////// TITLE: GCN GRB OBSERVATION REPORT NUMBER: 3902 SUBJECT: GRB 050827: P200 NIR Observations DATE: 05/08/29 07:06:07 GMT FROM: S. Bradley Cenko at Caltech Dae-Sik Moon and S. Bradley Cenko (Caltech) report on behalf of a larger collaboration: We have imaged the error circle of GRB 050827 (Capalbi et al., GCN 3893) with the Wide-Field Infrared Camera mounted on the Palomar 200-inch Hale Telescope. We find no sources within the possible XRT error circle (Capalbi et al., GCN 3899) at the following limits: Mean Epoch (UT) Time Since Burst Filter Limit -------------------------------------------------------------------------- 28 August 09:40 14.7 hours J > 21 28 Auguts 10:50 15.9 hours Ks > 20 //////////////////////////////////////////////////////////////////////// TITLE: GCN GRB OBSERVATION REPORT NUMBER: 3903 SUBJECT: GRB 050827 : OSN 1.5m optical observations DATE: 05/08/29 17:52:41 GMT FROM: Sergei Guziy at IAA S. Guziy, J. Gorosabel, A.J. Castro-Tirado, V. Casanova, A. de Ugarte Postigo, M. Jelinek, (IAA-CSIC) report: "We have acquired R and I-band images of the GRB 050827 XRT error box (Capalbi et al. GCN Circ. 3899) with the OSN 1.5m telescope. We detect two objects consistent with the 8" radius XRT error circle. The coordinates of the two objects are: Source 1: RA(J2000) = 04:17:08.9 DEC(J2000)= +18:11:57.0 Source 2: RA(J2000) = 04:17:09.6 DEC(J2000)= +18:12:02.0 with a conservative astrometric error of 1.5". Based on the USNO catalog we estimate magnitudes of R=23.7 ± 0.37 and R=23.4 ± 0.26 for S1 and S2, respectively. A finding chart can be found at: http://www.dsri.dk/~jgu/grb050827/FCs/osn.R.gif Further observations are encouraged to check the reliability/variability of the two optical sources. We thank Julius Halpern for making us available his 1.3m MDM telescope images." This message can be cited. //////////////////////////////////////////////////////////////////////// TITLE: GCN GRB OBSERVATION REPORT NUMBER: 3906 SUBJECT: GRB 050827: Swift XRT preliminary analysis results DATE: 05/09/01 08:29:17 GMT FROM: Milvia Capalbi at ISAC/ASDC M. Capalbi (ASDC), G. Tagliaferri (INAF-OAB), P. Romano (INAF-OAB), P. Boyd (GSFC-UMBC), W. Voges (MPE), D. N. Burrows (PSU) and N. Gehrels (GSFC) report on behalf of the Swift XRT team: We have analyzed 62 ks of Swift XRT data of GRB 050827 (Capalbi et al., GCN 3893) collected up to August 30, 2005 at 21:16:58 UT. The XRT 0.3-10 keV light curve shows a temporal decay with a power law index of -1.2 +/- 0.2 (90% confidence level), thus confirming that the source suggested in the previous circular (Capalbi et al., GCN 3899) is the X-ray afterglow of GRB 050827. A spectral fit to the data in the 0.3-10 keV band, gives a power law photon index of 1.9 +/- 0.2 (90% confidence level) with an absorption column density of 4.0 (-1.0, +1.5)E21 cm^-2 (90% confidence level), slightly in excess of the Galactic value(1.95E21cm^-2).