This file contains both GRBs: 051021A and 051021B //////////////////////////////////////////////////////////////////////// TITLE: GCN GRB OBSERVATION REPORT NUMBER: 4116 SUBJECT: GRB051021: A GRB Localized by HETE DATE: 05/10/21 15:14:48 GMT FROM: Carlo Graziani at U.Chicago A. Yoshida, 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, N. Ishikawa, A. Kobayashi, J. Kotoku, M. Maetou, M. Matsuoka, Y. Nakagawa, T. Sakamoto, R. Sato, T. Shimokawabe, Y. Shirasaki, S. Sugita, M. Suzuki, T. Tamagawa, and K. Tanaka, on behalf of the HETE WXM Team; N. Butler, G. Crew, 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 HETE FREGATE, WXM, and SXC instruments detected GRB 051021 (=H3947) at 13:21:57 UT (48117 SOD) on 21 October 2005. The WXM flight localization was first reported in a GCN Notice issued at 13:22:11 UT, which was 14s after the burst trigger. Ground analysis of the WXM data produced a refined WXM localization that was issued in a GCN Notice at 14:25:34 UT. This ground WXM localization can be expressed as a circle of 7.5 arcminutes radius (90% confidence), centered at R.A. = 01h 56m 24s ; Dec. = +09d 07' 05" (J2000). The SXC detected this event in its Y camera. Ground analysis of the SXC data therefore produced a 1-dimensional location. The intersection of this location with the WXM ground location was issued in a GCN Notice at 14:59:49 UT. This location can be expressed as a box with corners: R.A. = 01h 56m 01.92s ; Dec. = +09d 02' 02.4" R.A. = 01h 56m 54.00s ; Dec. = +09d 05' 16.4" R.A. = 01h 56m 54.72s ; Dec. = +09d 07' 22.8" R.A. = 01h 59m 57.12s ; Dec. = +09d 03' 46.8" (J2000). Further analysis is in progress. //////////////////////////////////////////////////////////////////////// TITLE: GCN GRB OBSERVATION REPORT NUMBER: 4118 SUBJECT: GRB051021.6: MASTER optical observation DATE: 05/10/21 16:14:23 GMT FROM: Vladimir Lipunov at Moscow State U/Krylov Obs V. Lipunov, V.Kornilov, D.Kuvshinov, N.Tyurina, A.Belinski, E.Gorbovskoy, A.Krylov, G.Borisov, A.Sankovich, V.Vladimirov Sternberg Astronomical Institute, Moscow Union 'Optic' MASTER robotic system (http://observ.pereplet.ru) responded to GRB051021.6 at 2002-10-21 15:39:37 under the bad weather conditions after sunset. An automated response took the first image at 01h 28min after the GRB time. The unfiltered image is calibrateds relative to USNO A2.0 (0.8 R + 0.2 B). The robot not find OT-candidate in error box. Our upper limit is about 14.0 m. The reduction is continuing. The JPG-image will be available at http://observ.pereplet.ru/images/GRB051021.6/1.jpg . This work is supported by RFFI 04-02-16411 grant. This message can be cited. //////////////////////////////////////////////////////////////////////// TITLE: GCN GRB OBSERVATION REPORT NUMBER: 4119 SUBJECT: GRB051021.63 DATE: 05/10/21 16:39:09 GMT FROM: Vladimir Lipunov at Moscow State U/Krylov Obs V. Lipunov, V.Kornilov, D.Kuvshinov, N.Tyurina, A.Belinski, E.Gorbovskoy, A.Krylov, G.Borisov, A.Sankovich, V.Vladimirov Sternberg Astronomical Institute, Moscow Union 'Optic' MASTER robotic system (http://observ.pereplet.ru) responded to GRB051021.63 (Swift triger 53550) at 2005-10-21 15:03:09.46 An automated response took the first image at 2005-10-21 16:14:29 UT, 01:11:19.54 after the GRB time The unfiltered image is calibrateds relative to USNO A2.0 (0.8 R + 0.2 B). The robot not find OT-candidate in error box. Our upper limit is about 16.3 m. The previouse circular number 4118 was about HETE Alert 3947. The reduction is continuing. The JPG-image will be available at http://observ.pereplet.ru/images/GRB051021.63/1.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: 4120 SUBJECT: GRB 051021: Optical observations and candidate afterglow DATE: 05/10/21 16:59:15 GMT FROM: Derek Fox at PSU D.B. Fox (Penn State), with R. McNaught and B. Peterson (RSAA/ANU), report on behalf of a larger collaboration: "We have observed the HETE localization region for GRB051021 (Yoshida et al., GCN 4116) with the 40-inch telescope at Siding Spring Observatory, in a sequence of R-band exposures beginning at 13:48:48 UT (26m51s after the burst). Comparison of a coadded image with mean epoch 14:34:33 (1h12m post-burst) to the Digitized Sky Survey reveals the presence of a new R~18.5 mag source, at coordinates: R.A. 01:56:36.39, Dec +9:04:03.7 (J2000) with a coordinate uncertainty, relative to USNO-B1.0 catalog astrometry, of <0.5". Inspection of our individual images suggests fading of the source over the ~1 hour span of our observations. However, in the absence of a more sophisticated reduction of these data it is not possible to make a firm conclusion as to variability at this time. Moreover, the presence of a cosmetic defect at the source position in one image introduces significant uncertainty to our mean photometric estimate, above. We suggest that this source may be the optical afterglow of GRB051021." //////////////////////////////////////////////////////////////////////// TITLE: GCN GRB OBSERVATION REPORT NUMBER: 4121 SUBJECT: GRB 051021: ROTSE-III Confirmation of Optical Counterpart DATE: 05/10/21 17:37:42 GMT FROM: Heather Swan at U.of Michigan/ROTSE H. Swan (U Mich), T.A. McKay (U Mich), D.A. Smith (Guilford), B. Schaefer (Louisiana State), E.S. Rykoff (U Mich), F. Yuan (U Mich), report on behalf of the ROTSE collaboration: ROTSE-IIIa, located at Siding Spring Observatory, Australia, responded to GRB 051021 (HETE trigger 3947). The first image was at 13:22:28.4 UT, 31.8 s after the burst (6.6 s after the GCN notice time). The unfiltered images are calibrated relative to USNO A2.0. We confirm the presence of the source detected by Fox et. al. GCN # 4120. We observe the source to rise to 16.9 magnitude, at about 180 seconds, and then fade by half a magnitude over a period of 150 seconds. This source is not visible in DSS (second epoch), 2MASS or the MPChecker database. Continuing observations are in progress. > //////////////////////////////////////////////////////////////////////// TITLE: GCN GRB OBSERVATION REPORT NUMBER: 4122 SUBJECT: GRB 051021: Optical observations DATE: 05/10/21 18:04:54 GMT FROM: Sergei Guziy at IAA P. Tristram (Univ. of Canterbury, New Zealand),S. Guziy, A. de Ugarte Postigo, Shashi. B. Pandey, A. J. Castro-Tirado, M. Jelinek, J. Gorosabel (IAA-CSIC, Granada, Spain), and Ph. Yock (Univ. of Auckland, New Zealand) report: "We have observed the region centered around the HETE error box for GRB 051021 (Yoshida et al.2005, GCN 4116) with 0.6 m telescope at Mount John observatory (New Zealand), starting on October 21 ( 14:10 UT, 45 minutes after the GRB). We confirm the optical candidate reported by Fox et al. (GCN, 4120)." Further observations are in progress. This massage can be cited. //////////////////////////////////////////////////////////////////////// TITLE: GCN GRB OBSERVATION REPORT NUMBER: 4123 SUBJECT: GRB 051021 : optical afterglow observation at Lulin DATE: 05/10/21 19:19:48 GMT FROM: Kuiyun Huang at IANCU GRB 051021 : optical afterglow observation at Lulin H.H. Hsieh (IfAUH), M.S. Chang, K.Y. Huang, W.H. Ip (NCU), Y. Urata (RIKEN), Y. Qiu (BAO) on behalf of the East Asian collaboration report: The R-band observations of GRB 051021 (Yoshida et al., GCN 4116) were taken by Lulin 1-m telescope, Taiwan. The optical afterglow reported by Fox et al.(GCN 4120) was detected clearly in our R-band images. Compared with USNOB stars, the R band magnitude of afterglow is about 19.8 at 15.859 UT (~ 2.48 hrs after the burst). Further observations are on going. This message may be cited. //////////////////////////////////////////////////////////////////////// TITLE: GCN GRB OBSERVATION REPORT NUMBER: 4124 SUBJECT: GRB051021 (=H3947): Refined Analysis DATE: 05/10/21 20:57:21 GMT FROM: Carlo Graziani at U.Chicago J-F Olive, 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, N. Ishikawa, A. Kobayashi, J. Kotoku, M. Maetou, M. Matsuoka, Y. Nakagawa, T. Sakamoto, R. Sato, T. Shimokawabe, Y. Shirasaki, S. Sugita, M. Suzuki, T. Tamagawa, K. Tanaka, and A. Yoshida, on behalf of the HETE WXM Team; N. Butler, G. Crew, 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-P Dezalay, and K. Hurley, on behalf of the HETE FREGATE Team; report: We have analyzed the full FREGATE+WXM data for HETE trigger H3934 (GRB051021.56). The 30-400 keV light curve has two sharp peaks, separated by about 10 s, superposed on a gentler rise-and-fall. The burst had a T90 duration of 38s in the 7-40 keV band, and of 27s in the 30-400 keV band. Emission in the 2-25 keV band appears to continue for at least 90s post-trigger, mostly below 10 keV. The integrated spectrum is well-fit by a cutoff power-law function. The best-fit parameters are: alpha = -1.16 --- 90% confidence interval is [-1.25 -1.06] Epeak = 94.2 --- 90% confidence interval is [76.7 , 111.7] The 2-30 keV fluence is 3x10^-6 erg/cm2, while the 30-400 keV fluence is 6 x 10^-6 keV. Since the ratio S(2-30)/S(30-400) is 0.41, this event is classified as an X-Ray Rich GRB. The pseudo-redshift estimated for this burst is pz = 1.4. A light curve, a skymap, and spectral information for this event are provided at the following URL: http://space.mit.edu/HETE/Bursts/GRB051021 //////////////////////////////////////////////////////////////////////// TITLE: GCN GRB OBSERVATION REPORT NUMBER: 4125 SUBJECT: GRB051021: Swift XRT analysis DATE: 05/10/21 21:52:23 GMT FROM: Judith Racusin at PSU J. Racusin, J. Kennea, D. Morris, D. Fox, D. Burrows (PSU), N. Gehrels (GSFC) on behalf of the Swift XRT team: XRT began observing GRB051021 (Yoshida et al., GCN 4116) at 16:28:28 UT, approximately 3 hours after the HETE trigger. From the first 2 orbits of data, we detect an uncatlogued fading X-ray source at: RA(J2000): 01:56:36.4 Dec(J2000): +09:04:06.3 with an estimated uncertainty of 4 arcseconds (90% containment). This position is 4.3 arcminutes from the HETE position reported by Yoshida et al.(GCN 4116), and 2.7 arcseconds from the optical afterglow position reported by Fox et al.(GCN 4120). At the time of these observations using 4.7 ks of data, the measured flux was 2.7x10^-12 ergs/cm^2/s. Further observations are necessary to measure the lightcurve decay slope. //////////////////////////////////////////////////////////////////////// TITLE: GCN GRB OBSERVATION REPORT NUMBER: 4126 SUBJECT: GRB 051021B: Swift detection of a burst DATE: 05/10/22 00:21:30 GMT FROM: Scott Barthelmy at NASA/GSFC A. Retter (PSU), S. Barthelmy (GSFC), D. Burrows (PSU), M. Chester (PSU), N. Gehrels (GSFC), J. Kennea (PSU), F. Marshall (GSFC), D. Palmer (LANL), J. Racusin (PSU) on behalf of the Swift team: At 23:31:53 UT, Swift-BAT triggered and located GRB 051021B (trigger=160672). The BAT on-board calculated location is RA,Dec 126.037d,-45.519d {8h 24m 09s,-45d 31' 09"} (J2000), with an uncertainty of 3 arcmin (radius, 90% containment, stat+sys). The BAT light curve shows a single FRED-like peak with structure with a total duration of ~25 sec. There is some pre-trigger emission starting at T-8 sec. The peak count rate was ~1800 counts/sec (15-350 keV), at ~2 seconds after the trigger. The spacecraft slewed immediately and the XRT began observing at 23:33:14 UT (81 sec after the BAT trigger). The on-board centroiding algorithm was not able to determine a position, but the prompt lightcurve and spectrum strongly suggest that a fading source is present in the field of view. Further analysis will require ground-processed data. UVOT began observing 23:33:11 UT or 78 sec after the BAT trigger with a 200 sec V-band image. It is a crowded field with high, but uncertain extinction. No new sources are seen in either the small image or the list of sources produced in the on-board processing. The limiting magnitude in the small image is about 19th mag. The on-board list of sources covers the entire BAT error region and is typically complete to about 17th mag. Further analysis will be delayed due the lack of telemetry downlink passes for several hours. //////////////////////////////////////////////////////////////////////// TITLE: GCN GRB OBSERVATION REPORT NUMBER: 4127 SUBJECT: GRB 051021: SOAR NIR Observations DATE: 05/10/22 03:54:03 GMT FROM: Josh Haislip at U.North Carolina J. Haislip, M. Nysewander, E. Cypriano, D. Reichart, M. Bayliss report on behalf of the UNC Team of the FUN GRB Collaboration: The SOAR-4.1m Telescope at CTIO began imaging the afterglow of the HETE GRB 051021 (Yoshida et al., GCN 4116; Fox et al., GCN 4120) at 01:38:51 UT, 12.3 hours after the burst in YJHKs. We detect the afterglow at a magnitude of J = 17.16 +- 0.06 based on three 2MASS stars at a mean time of 01:47:19.2 UT, 12.4 hours after the GRB. //////////////////////////////////////////////////////////////////////// TITLE: GCN GRB OBSERVATION REPORT NUMBER: 4128 SUBJECT: GRB051021B: Swift XRT Position DATE: 05/10/22 08:03:04 GMT FROM: Judith Racusin at PSU J. Racusin, D. Morris, C. Pagani, D. Burrows, A. Retter (PSU), N. Gehrels (GSFC) on behalf of the Swift XRT team: The Swift XRT began observing GRB 051021B (trigger #160672, Retter et al., GCN 4126) at 23:33:14 UT, but was unable to obtain an on-board centroid. Analysis of the first 2 orbits of the ground data reveal a previously uncatalogued, fading X-ray source at the following coordinates: RA(J2000) = 08 24 11.8 Dec(J2000) = -45 32 30.8 We estimate an uncertainty of 4 arcseconds (90% containment), including corrections for the XRT boresight offset. This position lies 88 arcseconds from the BAT position reported in GCN 4126. //////////////////////////////////////////////////////////////////////// TITLE: GCN GRB OBSERVATION REPORT NUMBER: 4129 SUBJECT: GRB 051021,optical observation DATE: 05/10/22 09:08:20 GMT FROM: Eri Sonoda at U of Miyazaki/Japan E.Sonoda,S.Maeno,Y.Tokunaga, M.Yamauchi (University of Miyazaki) "We have observed the field covering the SXC error box of GRB051021(HETE trigger 3947; trigger time 13:21:5 UT ) with the unfiltered CCD camera on the 30-cm telescope at University of Miyazaki.The observation was started 13:22:30 UT on Oct.21. We have compared our image with the USNO A2.0 catalog . Preliminary analysis shows there is no new source brighter than 14.3 mag. at the position reported by D.B.Fox et al.(GCN4120). " //////////////////////////////////////////////////////////////////////// TITLE: GCN GRB OBSERVATION REPORT NUMBER: 4135 SUBJECT: GRB 051021B: Refined analysis of the Swift-BAT burst DATE: 05/10/22 15:52:56 GMT FROM: Scott Barthelmy at NASA/GSFC S. Barthelmy (GSFC), L. Barbier (GSFC), P. Boyd (GSFC-UMBC), J. Cummings (GSFC/NRC), E. Fenimore (LANL), N. Gehrels (GSFC), D. Hullinger (GSFC/UMD), H. Krimm (GSFC/USRA), C. Markwardt (GSFC/UMD), D. Palmer (LANL), A. Parsons (GSFC), T. Sakamoto (GSFC/NRC), G. Sato (ISAS), J. Tueller (GSFC), W. Voges (MPE) 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 051021B (trigger #160672) (Retter, et al., GCN 4126). The ground-analysis position is RA,Dec 126.059,-45.537 {8h 24m 14.2s,-45d 32' 13.0"} (J2000) with an uncertainty of 1.3 arcmin (radius, 90%, stat+sys). T90 is 47 +- 3 sec. The partial coding fraction is 88 %. The lightcurve has single FRED peak starting at T-6 sec (FWHM of ~12 sec) with the decay extending out to greater than T+20 sec. There is a second, smaller peak at ~T+20. Fitting a simple power law over the full interval from T-5.5 to T+51.5 sec, the photon index is 1.52 +/- 0.14 with a fluence of 9.1 +/- 0.8 X 10^-7 erg/cm^2. The peak flux in a 1-sec wide window starting at T-2.5 sec is 0.63 +/- 0.13 ph/cm^2/sec. All values are in the 15-150 keV band at the 90% confidence level. //////////////////////////////////////////////////////////////////////// TITLE: GCN GRB OBSERVATION REPORT NUMBER: 4136 SUBJECT: GRB051021: Swift/UVOT Upper Limits DATE: 05/10/22 17:01:06 GMT FROM: Peter Brown at PSU P. J. Brown (PSU), D. Fox (PSU), M. Trippico (GSFC-SSAI), J. Nousek (PSU), & N. Gehrels (GSFC) on behalf of the Swift/UVOT team report: The Swift-UVOT began observing the field of GRB 051021 (HETE Trigger H3947; Yoshida et al. GCN 4116) at 2005-10-21 16:28:27, about 3 hours after the burst. No source is detected at the position of the optical counterpart found by Fox, McNaught, & Peterson (GCN 4120) in any of our 6 filters down to the following 3-sigma upper limits: Filter T_range(hours) Exp(sec) 3sigUL V 3.36-8.34 1988 20.2 B 5.30-6.71 1304 21.1 U 5.04-5.29 900 20.5 W1 4.79-5.04 900 20.8 M2 3.61-3.80 900 20.9 W2 3.11-6.96 1800 21.7 Where T_range is time post-trigger. //////////////////////////////////////////////////////////////////////// TITLE: GCN GRB OBSERVATION REPORT NUMBER: 4138 SUBJECT: GRB 051021: MDM Upper Limit DATE: 05/10/22 18:37:45 GMT FROM: Jules Halpern at Columbia U. J. Eastman, D. L. Depoy (Ohio State U.), A. P. Crotts, & D. J. Beirne (Columbia U.) observed the afterglow (Fox et al., GCN 4120) of HETE GRB 051021 (Yoshida et al., GCN 4116; Olive et al., GCN 4124) in the R band using the MDM 1.3m, and in SDSS r using the MDM 2.4m. On Oct. 22 04:45 UT, 15.4 hours after the burst, they report a 5-sigma upper limit of R > 23.0. Compared with the Lulin measurement of R=19.8 at 2.5 hours (Hsieh et al., GCN 4123), this indicates a mean temporal decay index steeper than -1.6, possibly a jet break. In combination with the bright near-IR detection by Haislip et al. (GCN 4127), J=17.16 at 12.4 hours, and if the decay index between 12.4 and 15.4 hours is not steeper than -3.5, the implied R-J color is greater than 5, which requires a high redshift. //////////////////////////////////////////////////////////////////////// TITLE: GCN GRB OBSERVATION REPORT NUMBER: 4140 SUBJECT: GRB 051021: P200 Ks Observations DATE: 05/10/22 21:41:37 GMT FROM: S. Bradley Cenko at Caltech S. Bradley Cenko, Chris Conselice, Kevin Bundy, (Caltech), Derek B. Fox (Penn State), and Edo Berger (Carnegie), report on behalf of the Caltech-NRAO-Carnegie GRB collaboration: "We have imaged the field of GRB 051021 (Yoshida et al., GCN 4116) with the Wide Field Infrared Camera mounted on the Palomar 200" Hale Telescope. Our images consisted of 9 x 120 s exposures taken in the Ks filter at a mean epoch of approximately 22 October 5:24 UT (~ 16 hours after the burst). We find at best a marginal (< 3-sigma) detection at the location of the OT (Fox et al., GCN 4120). Our 3-sigma limiting magnitude, calculated with respect to several 2mass stars in the field, is approximately Ks > 19.0. We note that under the standard afterglow model, our result is inconsistent with the J-band detection reported by Haislip et. al (GCN 4127), and therefore calls into question the interpreration of GRB 051021 as a high redshift event." //////////////////////////////////////////////////////////////////////// TITLE: GCN GRB OBSERVATION REPORT NUMBER: 4142 SUBJECT: GRB 051021, SMARTS optical/IR observations DATE: 05/10/23 01:56:24 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 051021 (GCN 4116, Yoshida et al.) with a mid-exposure time of 2005-10-22 02:53 UT, which is ~13.5 hours post-burst. Total summed exposure times amounted to 36 minutes in I and 30 minutes in J. At the position of the reported afterglow (GCN 4120, Fox et al.), an object is marginally detected in our I-band images. The preliminary magnitude of this object is determined to be I = 22.0 +/- 0.4, in comparison with several nearby USNO B1.0 stars. The afterglow candidate is not, however, detected in the J-band. Using several 2MASS comparison stars, the limiting magnitude of this image is determined to be J > 19.9 +/- 0.1. There is an object near to the position of the afterglow candidate (at RA = 1:56:35.6, Dec = 9:04:26.2) that is measured in our image to have a magnitude of J = 17.2 +/- 0.1. This object is below the detection limits of 2MASS, so it is not detected in the 2MASS images (though it is present in the USNO B1.0 survey). Possibly, this is the object reported by Haislip et al. (GRB 4127). Therefore, in agreement with Cenko et al. (GCN 4140), there is not yet clear evidence to suggest that this is a high redshift event. //////////////////////////////////////////////////////////////////////// TITLE: GCN GRB OBSERVATION REPORT NUMBER: 4144 SUBJECT: GRB 051021: Correction DATE: 05/10/23 03:52:56 GMT FROM: Daniel E. Reichart at U.North Carolina D. Reichart reports on behalf of the UNC team of the FUN GRB Collaboration: Cobb & Bailyn (GCN 4142) are correct. The correct J magnitude at 12.3 hours after the burst is 20.3 +/- 0.2 mag. Using 4.1m SOAR, we observed the afterglow in BVRIYJHKs. We will report on the SFD in a forthcoming GCN. //////////////////////////////////////////////////////////////////////// TITLE: GCN GRB OBSERVATION REPORT NUMBER: 4146 SUBJECT: GRB051021b: Magellan IR Imaging DATE: 05/10/23 05:45:47 GMT FROM: Josh Bloom at UC Berkeley D. L. Kaplan (MIT), H-W. Chen (Chicago), J. S. Bloom (UCB), J. X. Prochaska (UCO LIck) report on behalf of a large collaboration: "We obtained deep K-band imaging of the field of GRB 051021b (GCN 4135) with PANIC on the Magellan Baade Telescope starting at 08:42:56 October 22, 2005 UTC. We identify 4 sources within the XRT error circle (GCN 4128): 08:24:11.803 -45:32:30.79 J2000 08:24:11.598 -45:32:31.93 J2000 08:24:11.622 -45:32:33.70 J2000 08:24:11.724 -45:32:34.20 J2000 The 1 sigma uncertainty relative to 2MASS is 300 mas. As all of these sources are significantly fainter than the 2MASS detection limit we cannot identify an obvious afterglow candidate." This message may be cited. //////////////////////////////////////////////////////////////////////// TITLE: GCN GRB OBSERVATION REPORT NUMBER: 4147 SUBJECT: GRB 051021: PROMPT RcIc Observations DATE: 05/10/23 06:53:44 GMT FROM: Melissa Nysewander at UNC,Chapel Hill M. Nysewander, C. Macleod, D. Reichart, A. Crain, A. Foster report on behalf of the UNC team of the FUN GRB Collaboration: Under the control of Skynet, PROMPT observed the localization of GRB 051021 (Yoshida et al., GCN 4116; Fox et al., GCN 4120) beginning 12.9 hours after the burst, in Rc and Ic simultaneously. We do not detect the afterglow of the burst. In two 90 x 60 sec integrations of mean epoch 14.2 hours after the burst, we measure 3-sigma limiting magnitudes of Rc = 20.7 and Ic = 20.4 based on 5 USNO-B1.0 stars. PROMPT is still being built and commissioned. //////////////////////////////////////////////////////////////////////// TITLE: GCN GRB OBSERVATION REPORT NUMBER: 4151 SUBJECT: GRB051021A: Swift XRT refined analysis DATE: 05/10/23 18:34:01 GMT FROM: Judith Racusin at PSU J. Racusin, D. Fox, D. Burrows (PSU), N. Gehrels (GSFC) on behalf of the Swift XRT team: We have analyzed the first four orbits of data after XRT began observing the field of GRB051021A (Yoshida et al., GCN 4116) at 16:28:28 UT. The refined XRT coordinates are: RA(J2000): 01 56 36.5 Dec(J2000): +09 04 6.1 with an estimated uncertainty of 4 arcseconds (90% containment), including corrections for the XRT boresight offset. This position is 1 arcsecond from the position we quoted in Racusin et al. (GCN 4125), and 2.9 arcseconds from the optical afterglow candidate reported by Fox et al. (GCN 4120). The XRT light curve shows a steady decline with a power-law fit decay index of 1.06+/-0.16. The Photon Counting mode spectra can be fit with an absorbed power-law with a photon index of 2.17+/-0.18 and a column density of 1.4+/-0.5 E21 cm-2 which is in excess of the Galactic column density of 0.56E21 cm-2 in this direction. The observed 0.2-10 keV flux is 2.02E-12 ergs cm-2 s-1, corresponding to an unabsorbed flux of 2.28E-12 ergs cm-2 s-1. //////////////////////////////////////////////////////////////////////// TITLE: GCN GRB OBSERVATION REPORT NUMBER: 4159 SUBJECT: GRB051021a: optical observations DATE: 05/10/24 13:59:34 GMT FROM: Vasilij Rumjantsev at CrAO V.Rumyantsev (CrAO), V.Biryukov (SAI, MSU), and A.Pozanenko (IKI) on behalf of larger GRB follow up collaboration report: We observed the SXC error box of HETE-2 GRB051021a (Yoshida et al., GCN4116) with 0.6 m telescope (Crimean laboratory of SAI) equipped with FLI IMG-1001E camera. The series of 60 sec R-band exposures were taken between October 21, 21:19:01 and October 22, 00:23:24. We clearly detect the optical afterglow (Fox et al. GCN4120, Swan et al. GCN4120) on stacked image. Coordinates of the source are RA=01 56 36.37 Dec=+09 04 03.27 (J2000) with uncertainty of 0.5 arcsec. Preliminary photometry of the stacked image is following: Mid time (UT) Exposure R Oct. 21 22:51 146x60 21.9 +/-0.2 Photometry and astrometry of the source are based on USNO-A2.0. Stacked image can be found in http://grb.rssi.ru/GRB051021a/. Taken R-band magnitudes (GCNs 4120, 4123) and upper limit reported in GCN4138 (Eastman et al.) our results is compatible within statistical error with single power-law decay light curve alpha ~ -1.6. Also extrapolating backward J-band (Reichart et al., GCN 4144) observations to our epoch (Oct. 21 22:51) we found R-J ~ 1.0 which do not imply a high redshift source. This message may be cited. //////////////////////////////////////////////////////////////////////// TITLE: GCN GRB OBSERVATION REPORT NUMBER: 4160 SUBJECT: GRB051021B: Swift XRT refined analysis DATE: 05/10/24 23:02:36 GMT FROM: Judith Racusin at PSU J. Racusin, C. Pagani, D. Morris, A. Retter, D. Burrows (PSU), N. Gehrels (GSFC) on behalf of the Swift XRT team: We have analyzed the first 13 orbits of data from GRB051021B (Retter et al., GCN 4126). XRT observations began in Window Timing mode 87 seconds after the BAT trigger and continued for 32 seconds before switching to Photon Counting mode. The XRT light curve shows an initial decline with a decay slope of 1.9+/-0.1 , followed by a break at ~T+2500s to a shallower decay slope of 0.6+/-0.1. A preliminary spectral fit using an absorbed power-law to the Photon Counting mode data yields a photon index of 1.64+/-0.12 in the 0.85-10 keV band, fixing nH to the Galactic value of 7.7E21 cm-2. The observed 0.85-10 keV flux for the Photon Counting mode data in the first orbit is 7.3E-12 ergs cm-2 s-1 corresponding to an unabsorbed flux of 9.0E-12 ergs cm-2 s-1. //////////////////////////////////////////////////////////////////////// TITLE: GCN GRB OBSERVATION REPORT NUMBER: 4166 SUBJECT: GRB 051021, Optical Observations DATE: 05/10/26 14:33:54 GMT FROM: Kuntal Mishra at ARIES,Nainital,India Kuntal Misra (ARIES, Nainital) and Atish P. Kamble (Raman Research Institute, Bangalore) on behalf of a larger Indian GRB collaboration We observed the field of GRB 051021 (HETE trigger 3947) using the 104 cm reflector telescope at ARIES, Nainital. We do not find any new source upto a limiting magnitude of 21 in our combined (exposure 3*300 sec) R band images on October 22.675 UT with respect to five nearby USNO-A2.0 stars. This message may be cited. //////////////////////////////////////////////////////////////////////// TITLE: GCN GRB OBSERVATION REPORT NUMBER: 4167 SUBJECT: GRB051021B: Swift/UVOT Upper limits DATE: 05/10/26 20:33:52 GMT FROM: Peter Brown at PSU P. J. Brown (PSU), A. Retter (PSU), F. Marshall (GSFC), A. Smale (NASA HQ), N. Gehrels (GSFC) on behalf of the Swift/UVOT team report: Swift-UVOT observed the field of GRB 051021B (BAT Trigger=160672; Retter et al. GCN 4126) starting at 2005-10-21 23:33:11, 78 seconds after the burst. No source was detected within the XRT error circle (Racusin et al GCN 4128) during the first 200 second image (Tmid=178 seconds after the burst) down to a 3 sigma limiting magnitude of V=19. Using summed images, we also did not detect a source in any of our 6 filters down to the following 3-sigma magnitude upper limits: Filter T_range(sec) Exp(sec) 3sigUL V 78-19380 1779 19.9 B 444-17793 1634 21.1 U 390-13591 961 19.9 W1 336-12417 1199 19.5 M2 282-12005 1199 19.6 W2 553-18702 1940 20.0 White 498-926 100 19.5 Where T_range is time post-trigger. We note that this position is near the galactic plane, so the extinction and background in this line of sight are high. //////////////////////////////////////////////////////////////////////// TITLE: GCN GRB OBSERVATION REPORT NUMBER: 4180 SUBJECT: GRB 051021A: RTT150 optical observations DATE: 05/10/30 06:41:30 GMT FROM: Rodion Burenin at IKI, Moscow R. Burenin, D. Denisenko, M. Pavlinsky, R. Sunyaev (IKI), I. Khamitov, Z. Aslan (TUG), U. Kiziloglu (METU), E. Gogus (Sabanci Uni.), I. Bikmaev, N. Sakhibullin (KSU/AST) report: The optical transient associated with GRB 051021A (Yoshida et al., GCN 4116; Fox et al., GCN 4120) was observed with Russian-Turkish 1.5-m telescope (RTT150, Bakyrlytepe, TUBITAK National Observatory, Turkey) in BVR filter set, starting at Oct. 21, 18:15 UT, 4.88 hours after the burst. Compared to USNOB, the magnitudes are about: t-t0,h 5.34 R=21.1 9.95 R=21.8 5.70 V=22.2 10.18 V=22.6 In B the object was detected only marginally. This message may be cited. //////////////////////////////////////////////////////////////////////// TITLE: GCN GRB OBSERVATION REPORT NUMBER: 4184 SUBJECT: Recent GRB UBVRcIc field photometry DATE: 05/10/31 16:31:02 GMT FROM: Arne A. Henden at AAVSO A. Henden (AAVSO/USNO) reports on behalf of the USNO GRB Team: We have acquired UBVRcIc all-sky photometry for 23x23arcmin fields centered on the coordinates of recent GRB localizations with the USNOFS 1.0-m telescope on 1 or 2 photometric nights. We are using a new CCD, and so place an additional zeropoint error of about 0.03mag that should be added in quadrature to the errors reported in the files listed below. Stars brighter than V=13.0 are saturated and should be used with care. We have placed the photometric data on our anonymous ftp site: ftp://ftp.nofs.navy.mil/pub/outgoing/aah/grb/grb050505.dat ftp://ftp.nofs.navy.mil/pub/outgoing/aah/grb/grb051021.dat ftp://ftp.nofs.navy.mil/pub/outgoing/aah/grb/grb051022.dat ftp://ftp.nofs.navy.mil/pub/outgoing/aah/grb/grb051028.dat Since these bursts had identified optical afterglows, we may improve the photometric calibration on subsequent observing runs. As always, you should check the dates on the .dat file prior to final publication to get the latest photometry. There is a README file on the ftp directory to give you information about the procedures used to calibrate these fields. //////////////////////////////////////////////////////////////////////// TITLE: GCN GRB OBSERVATION REPORT NUMBER: 4294 SUBJECT: GRB 051021 Optical Observations DATE: 05/11/20 05:37:23 GMT FROM: T.P. Prabhu at Indian Astro. Obs. D.K. Sahu, G. Pandey, P. Bama and N.K. Chakradhari (Indian Institute of Astrophysics, Bangalore,India) communicate on behalf of a larger Indian collaboration: We observed the error box of the HETE trigger 3947 in Bessell R and I filters with the 2-m Himalayan Chandra Telescope, Hanle, India, between 20:25 UT and 21:00 UT, 2005 October 21 (about 7 hours after the burst). We could clearly detect the OT of GRB 051021 reported by Fox et al. (GCN 4120) with effective exposures of 600s (2x300s) in R and 900s (3x300s) in I band. The preliminary magnitudes for the OT, estimated using the calibration provided by Henden (GCN 4184) are as follows: Filter Mean Mid-UT Magnitude R 20:43 21.51+/-0.15 I 20.43 20.93+/-0.10 This message may be cited.