//////////////////////////////////////////////////////////////////////// TITLE: GCN CIRCULAR NUMBER: 10283 SUBJECT: GRB 091221: Swift detection of a burst DATE: 09/12/21 21:17:35 GMT FROM: David Palmer at LANL H. A. Krimm (CRESST/GSFC/USRA), D. N. Burrows (PSU), P.A. Curran (MSSL-UCL), A. de Ugarte Postigo (INAF-OAB), N. Gehrels (NASA/GSFC), D. Grupe (PSU), C. Guidorzi (U Ferrara), S. T. Holland (CRESST/USRA/GSFC), E. A. Hoversten (PSU), N. P. M. Kuin (MSSL), J. Mao (INAF-OAB), R. Margutti (Univ Bicocca&OAB), C. B. Markwardt (CRESST/GSFC/UMD), F. E. Marshall (NASA/GSFC), P. T. O'Brien (U Leicester), D. M. Palmer (LANL), J. L. Racusin (NASA/GSFC), P. Romano (INAF-IASFPA), B. Sbarufatti (INAF-IASFPA), M. H. Siegel (PSU), M. C. Stroh (PSU), E. Troja (NASA/GSFC/ORAU) and T. N. Ukwatta (GSFC/GWU) report on behalf of the Swift Team: At 20:52:52 UT, the Swift Burst Alert Telescope (BAT) triggered and located GRB 091221 (trigger=380311). Swift slewed immediately to the burst. The BAT on-board calculated location is RA, Dec 55.754, +23.212 which is RA(J2000) = 03h 43m 01s Dec(J2000) = +23d 12' 42" with an uncertainty of 3 arcmin (radius, 90% containment, including systematic uncertainty). The BAT light curve shows a peak from T+0 to T+15 seconds with a second, larger peak from T+15 to T+40. There is some complexity in the light curve from A0535+262 (currently in outburst at ~5 Crabs of flux) in the Field Of View, but the GRB peaks are distinguishable from the softer A0535+262 emission. The peak count rate was 3500 counts/sec at ~30 sec after the trigger. The XRT began observing the field at 20:54:04.7 UT, 72.4 seconds after the BAT trigger. Using promptly downlinked data we find a bright, fading, uncatalogued X-ray source located at RA, Dec 55.79831, 23.24030 which is equivalent to: RA(J2000) = 03h 43m 11.59s Dec(J2000) = +23d 14' 25.1" with an uncertainty of 4.2 arcseconds (radius, 90% containment). This position may be improved as more data are received; the latest position is available at http://www.swift.ac.uk/sper. This position is 170 arcseconds from the BAT position. A power-law fit to a spectrum formed from promptly downlinked event data gives a column density consistent with the Galactic value of 1.09e+21 cm^-2 (Kalberla et al. 2005). The initial flux in the 2.5 s image was 1.47e-09 erg cm^-2 s^-1 (0.2-10 keV). UVOT took a finding chart exposure of 150 seconds with the White filter starting 79 seconds after the BAT trigger. No credible afterglow candidate has been found in the initial data products. The 2.7'x2.7' sub-image covers 100% of the XRT error circle. The typical 3-sigma upper limit has been about 19.6 mag. The 8'x8' region for the list of sources generated on-board covers 100% of the XRT error circle. The list of sources is typically complete to about 18 mag. No correction has been made for the expected extinction corresponding to E(B-V) of 0.22. We note the possibility of a faint source on the northern edge of the XRT error circle. Further analysis is forthcoming. Burst Advocate for this burst is H. A. Krimm (krimm AT milkyway.gsfc.nasa.gov). Please contact the BA by email if you require additional information regarding Swift followup of this burst. In extremely urgent cases, after trying the Burst Advocate, you can contact the Swift PI by phone (see Swift TOO web site for information: http://www.swift.psu.edu/too.html.) //////////////////////////////////////////////////////////////////////// TITLE: GCN CIRCULAR NUMBER: 10284 SUBJECT: GRB 091221: ROTSE-III Detection of Optical Counterpart DATE: 09/12/21 21:37:02 GMT FROM: Shashi Bhushan Pandey at ROTSE GRB 091221: ROTSE-III Detection of Optical Counterpart W. Zheng, F. Yuan and S. B. Pandey (U Mich), report on behalf of the ROTSE collaboration: ROTSE-IIIc, located at the H.E.S.S. site at Mt. Gamsberg, Namibia, responded to GRB 091221 (Swift trigger 380311, GCN 10283 Krimm et al.). The first image was at 20:53:18.1 UT, 25.8 s after the burst (9.1 s after the GCN notice time). The unfiltered images are calibrated relative to USNO A2.0. We detect a 17.4 magnitude, source with coordinates: 03:43:11.47 +23:14:29.38 (J2000), with positional uncertainty of 1" or better start UT mag mlim(of image) ---------------------------------- 20:54:49.5 17.4 18.0 This source is not visible in DSS (second epoch), 2MASS or the MPChecker database. A jpeg image is available at http://www.rotse.net/images/gsb380311_3c011-020_key.jpg, the candidate is marked as 110. Continuing observations are in progress. //////////////////////////////////////////////////////////////////////// TITLE: GCN CIRCULAR NUMBER: 10285 SUBJECT: GRB 091221: UVOT Confirmation of an Optical Afterglow DATE: 09/12/21 22:12:23 GMT FROM: Stephen Holland at USRA/NASA/GSFC/SSC S. T. Holland (CRESST/GSFC/USRA), M. de Pasquale (MSSL), P. Kuin (MSSL), and H. A. Krimm (CRESST/GSFC/USRA) report on the behalf of the Swift/UVOT team: The Swift/UVOT observed the field of GRB 091221 (Krimm et al. 2009, GCN Circ. 10283) starting approximately 80 s after the BAT detection. We confirm the optical afterglow detected by Krimm et al. 2009, GCN Circ 10283 and Zheng et al. 2009, GCN Circ. 10284. The preliminary UVOT position is RA = 03:43:11.47 = 55.79771 deg Dec = +23:14:28.9 = +23.24136 deg with a preliminary error estimate of 0.6 arcsec (radius, 90% containment). The preliminary white magnitude is Filter TSTART TSTOP EXPOSURE Mag Err --------------------------------------------------------- White 80 230 150 20.22 0.28 --------------------------------------------------------- The quoted upper limits have not been corrected for the expected Galactic extinction along the line of sight corresponding to a reddening of E_{B-V} = 0.22 mag (Schlegel et al., 1998, ApJS, 500, 525). All photometry is on the UVOT photometry system described in Poole et al. (2008, MNRAS, 383, 627). //////////////////////////////////////////////////////////////////////// TITLE: GCN CIRCULAR NUMBER: 10286 SUBJECT: GRB 091221, GROND observations DATE: 09/12/22 03:20:01 GMT FROM: Sylvio Klose at TLS Tautenburg R. Filgas, P. Afonso (both MPE Garching), S. Klose (TLS Tautenburg), and J. Greiner (MPE Garching), report on behalf of the GROND team: GROND (Greiner et al. 2008, PASP 120, 405), the 7-channel imager mounted at the 2.2m ESO/MPI telescope at La Silla Observatory (Chile), started follow-up observations of GRB 091221 (Krimm et al. 2009, GCN 10283) on Dec 22, at 01:27 UT (4.5 hrs after the burst). For the suggested GRB afterglow (Zheng et al. 2009, GCN 10284; Holland et al. 2009, GCN 10285), based on a first 8 min exposure, we estimate the following preliminary magnitudes (in the AB system): g' = 22.90 +/- 0.30 r' = 22.27 +/- 0.30 i' = 21.95 +/- 0.30 z' = 22.20 +/- 0.30 J = 20.16 +/- 0.20 H > 19.9 K > 19.1 using GROND zeropoints and 2MASS catalog (airmass 1.8). Observations are ongoing. Taking into account a Galactic reddening of E(B-V)=0.22 mag (Holland et al. 2009, GCN 10285), we estimate a photometric redshift of z<3.5. At present we cannot decide if the z'-band magnitude is indicating to a broad-band absorption feature or if we underestimate the magnitude error in this band (where the source is very faint). //////////////////////////////////////////////////////////////////////// TITLE: GCN CIRCULAR NUMBER: 10287 SUBJECT: GRB 091221: Enhanced Swift-XRT position DATE: 09/12/22 09:17:25 GMT FROM: Phil Evans at U of Leicester P.A. Evans and M.R. Goad (U. Leicester) report on behalf of the Swift-XRT team: Using 3.7 ks of XRT Photon Counting mode data and 7 UVOT images, we find an astrometrically corrected X-ray position (using the XRT-UVOT alignment and matching UVOT field sources to the USNO-B1 catalogue): RA, Dec = 55.79749, 23.24119 which is equivalent to: RA (J2000): 03 43 11.40 Dec (J2000): +23 14 28.3 with an uncertainty of 1.7 arcsec (radius, 90% confidence). This position may be improved as more data are received. The latest position can be viewed at http://www.swift.ac.uk/xrt_positions. Position enhancement is described by Goad et al. (2007, A&A, 476, 1401) and Evans et al. (2009, MNRAS, 397, 1177). This circular is an official product of the Swift-XRT team. //////////////////////////////////////////////////////////////////////// TITLE: GCN CIRCULAR NUMBER: 10288 SUBJECT: GRB 091221: Swift-XRT refined analysis DATE: 09/12/22 10:50:17 GMT FROM: Jirong Mao at INAF-OAB J. Mao (INAF-OAB) and H. A. Krimm (CRESST/GSFC/USRA) report on behalf of the Swift-XRT team: We have analysed 4.7 ks of XRT data for GRB 091221 (Krimm et al. GCN Circ. 10283), from 78 s to 11.6 ks after the BAT trigger. The data comprise 332 s in Windowed Timing (WT) mode with the remainder in Photon Counting (PC) mode. The UVOT-enhanced XRT position was given in Evans et al. (GCN Circ. 10287). The light curve shows a flare feature from T0+90 s to T0+200 s, the peak value is about 55 count/s at T0+106 s. After that, the light curve can be modelled with a power-law decay with a decay index of alpha=1.07 ± 0.05. A spectrum formed from the WT mode data can be fitted with an absorbed power-law with a photon spectral index of 2.52 (+0.16, -0.17). The best-fitting absorption column is 3.6 (+/- 0.4) x 1021 cm^-2, in excess of the Galactic value of 1.1 x 1021 cm^-2 (Kalberla et al. 2005). The counts to observed (unabsorbed) 0.3-10 keV flux conversion factor deduced from this spectrum is 4.4 x 10^-11 (7.2 x 10^-11) erg cm^-2 count^-1. The spectrum formed from the PC mode data can be fitted with an absorbed power-law with a photon spectral index of 1.68 (+0.45, -0.51). The best-fitting absorption column is about 1.1 x 1021 cm^-2, in consistent with the Galactic value. If the light curve continues to decay with a power-law decay index of 1.07, the count rate at T0+24 hours will be 2.3 x 10^-3 count s^-1, corresponding to an observed (unabsorbed) 0.3-10 keV flux of 1.4 x 10^-13 (1.6 x 10^-13) erg cm^-2 s^-1. The results of the XRT-team automatic analysis are available at http://www.swift.ac.uk/xrt_products/00380311. This circular is an official product of the Swift-XRT team. //////////////////////////////////////////////////////////////////////// TITLE: GCN CIRCULAR NUMBER: 10289 SUBJECT: GRB 091221: Swift/UVOT refined analysis DATE: 09/12/22 13:58:52 GMT FROM: Massimiliano de Pasquale at MSSL-UCL M. De Pasquale (MSSL/UCL) and H. Krimm (CRESST/GSFC/USRA) report on behalf of the Swift/UVOT team: The Swift/UVOT began settled observations of the field of GRB091221 80s after the BAT trigger with a 150s finding chart exposure in the White filter. We detect the optical afterglow in the finding chart exposure. The refined UVOT position is RA = 55.79750, Dec = 23.24119 (J2000), corresponding to RA = 03h 43m 11.40s, Dec = +23d 14m 28.3s (J2000) with an estimated uncertainty of 0.6 arcsec (radius, 90% confidence). This position is consistent with the XRT enhanced position (Evans et al., GCN 10287) and ground-based detections (Zheng et al., GCN 10284; Klose et al., GCN 10286). The afterglow is not detected anymore in single or summed exposures in all filters. Preliminary magnitudes and 3 sigma upper limits are reported below. Filter T_start(s) T_stop(s) Exposure(s) Mag Err ----------------------------------------------------------------------- white 80 230 149.8 20.19 +/- 0.27 white 3657 11605 927.1 >21.62 v 4068 5704 393.2 >19.56 b 3452 11054 1278.4 >21.11 u 4683 10142 1083.4 >20.68 uvw1 4478 6075 354.4 >19.96 uvm2 4273 5909 393.3 >19.79 uvw2 3863 5499 393.3 >20.07 ------------------------------------------------------------------------ The values quoted above are not corrected for the heavy Galactic extinction corresponding to the reddening of E(B-V) = 0.22 in the direction of the burst (Schlegel et al. 1998, ApJS, 500, 525). The photometry is on the UVOT photometric system described in Poole et al. (2008, MNRAS, 383, 627). //////////////////////////////////////////////////////////////////////// TITLE: GCN CIRCULAR NUMBER: 10290 SUBJECT: GRB091221: Swift/UVOT refined analysis, correction. DATE: 09/12/22 14:06:10 GMT FROM: Massimiliano de Pasquale at MSSL-UCL M. De Pasquale (MSSL/UCL) reports: GCN circular 10289 title is wrong. It should be GRB091221: Swift/UVOT refined analysis not GRB091208B. I apologize for any confusion. //////////////////////////////////////////////////////////////////////// TITLE: GCN CIRCULAR NUMBER: 10291 SUBJECT: GRB 091221 Swift-BAT refined analysis DATE: 09/12/22 16:44:09 GMT FROM: Jay R. Cummings at NASA/GSFC/Swift J. R. Cummings (GSFC/UMBC), S. D. Barthelmy (GSFC), W. H. Baumgartner (GSFC/UMBC), E. E. Fenimore (LANL), N. Gehrels (GSFC), H. A. Krimm (GSFC/USRA), C. B. Markwardt (GSFC/UMD), D. M. Palmer (LANL), A. M. Parsons (GSFC), T. Sakamoto (GSFC/UMBC), G. Sato (ISAS), M. Stamatikos (GSFC/ORAU), J. Tueller (GSFC), T. N. Ukwatta (GWU) (i.e. the Swift-BAT team): Using the data set from T-240 to T+962 sec from the recent telemetry downlink, we report further analysis of BAT GRB 091221 (trigger #380311) (Krimm, et al., GCN Circ.#10283). The BAT ground-calculated position is RA, Dec = 55.798, 23.243 deg which is RA(J2000) = 03h 43m 11.6s Dec(J2000) = +23d 14' 35.2" with an uncertainty of 1.4 arcmin, (radius, sys+stat, 90% containment). The partial coding was 62%. The mask-weighted light curve shows a weak peak from T-45 to T-20 sec and a stronger, slow-rise, complex peak from T-10 to T+42 sec. T90 (15-350 keV) is 68.5 +- 5.5 sec (estimated error including systematics). The time-averaged spectrum from T-43.6 to T+41.1 sec is best fit by a simple power-law model. The power law index of the time-averaged spectrum is 1.59 +- 0.06. The fluence in the 15-150 keV band is 5.7 +- 0.2 x 10^-06 erg/cm2. The 1-sec peak photon flux measured from T+20.70 sec in the 15-150 keV band is 3.0 +- 0.2 ph/cm2/sec. All the quoted errors are at the 90% confidence level. The results of the batgrbproduct analysis are available at http://gcn.gsfc.nasa.gov/notices_s/380311/BA/ //////////////////////////////////////////////////////////////////////// TITLE: GCN CIRCULAR NUMBER: 10293 SUBJECT: GRB 091221: Fermi GBM Observation DATE: 09/12/23 21:02:35 GMT FROM: Colleen A. Wilson at NASA/MSFC/NSSTC Colleen A. Wilson-Hodge (NASA/MSFC) reports on behalf of the Fermi GBM Team: "At 20:52:57.22 UT on 21 December 2009, the Fermi Gamma-Ray Burst Monitor triggered and located GRB 091221 (trigger 283121579 / 091221870) which also triggered the SWIFT-BAT (Krimm et al. 2009, GCN 10283) The GBM on-ground location is consistent with the Swift position. The angle from the Fermi LAT boresight is 53 degrees. The GBM light curve shows/consists of single structured peak with a duration (T90) of about 32 s (8-1000 keV). The time-averaged spectrum from T0-2 s to T0+30 s is adequately fit by a Band function with Epeak = 207 (+22/-17) keV, alpha = -0.69 +/- 0.07, and beta = -2.3 (+0.2/-0.3) (C-Stat 724.6 for 481 d.o.f.). The event fluence (8-1000 keV) in this time interval is (1.38 +/- 0.05)E-05 erg/cm^2. The 1-sec peak photon flux measured starting from T0+11.3 s in the 8-1000 keV band is 5.1 +/- 0.4 ph/s/cm^2. During this burst, A0535+262 (currently in a bright outburst at an intensity of ~3xCrab 12-50 keV) and the Crab rose from Earth occultation, causing a significant rise in the background level. This likely adds additional systematic errors to the results, especially T90. The spectral analysis results presented above are preliminary; final results will be published in the GBM GRB Catalog." //////////////////////////////////////////////////////////////////////// TITLE: GCN CIRCULAR NUMBER: 10294 SUBJECT: GRB 091221: Skynet/PROMPT Detections DATE: 09/12/23 22:11:00 GMT FROM: Josh Haislip at U.North Carolina J. Haislip, D. Reichart, K. Ivarsen, A. LaCluyze, R. Egger, A. Foster, J. Moore, A. Oza, M. Schubel, J. Styblova, A. Trotter, J. A. Crain, and M. Nysewander report: Skynet observed the Swift/BAT localization of GRB 091221 (Palmer et al., GCN 10283) with four of the 16" PROMPT telescopes at CTIO beginning 4.3 hours after the trigger in BVRI. We detect the afterglow (Palmer et al., GCN 10283; Zheng et al., GCN 10284). Stacking only images that increase the limiting magnitude yields: mean 1-sig. 1-sig. time sys. stat. since cal. cal. cal. trig. tel. exp. fil. magnitude stars unc. unc. (h) (# x s) (mag) (mag) 4.9 PROMPT-5 44 x 80 I > 21.1 (3 sigma) 143 USNO B1 0.338 0.000 + 1 x 40 4.9 PROMPT-4 42 x 80 R 21.49 +0.27 -0.22 139 USNO B1 0.362 0.000 4.9 PROMPT-3 41 x 80 B > 21.5 (3 sigma) 82 USNO B1 0.154 0.000 4.9 PROMPT-1 41 x 80 V 21.41 +0.42 -0.31 27 NOMAD 0.193 0.000 7.3 PROMPT-3 136 x 80 B > 22.1 (3 sigma) 79 USNO B1 0.153 0.000 7.3 PROMPT-5 134 x 80 I > 21.8 (3 sigma) 120 USNO B1 0.337 0.000 7.3 PROMPT-4 139 x 80 R 22.44 +0.38 -0.28 112 USNO B1 0.392 0.000 7.4 PROMPT-1 145 x 80 V > 22.0 (3 sigma) 28 NOMAD 0.112 0.000 //////////////////////////////////////////////////////////////////////// TITLE: GCN CIRCULAR NUMBER: 10295 SUBJECT: GRB 091221 : IRSF NIR upper limit DATE: 09/12/25 14:42:23 GMT FROM: Kenta Nishimoto at Nagoya U/MOA-II K. Nishimoto, T. Sako, H. Naito, D. Suzuki (Nagoya Univ.) on behalf of the MOA Collaboration, M. Kurita (Nagoya Univ.), Y.Ita (NAOJ) on behalf of the IRSF Collaboration report: We searched for a NIR afterglow of GRB 091221 (GCN 10283, Krimm et al.) starting from 22:27:49.7 UT on 2009 Dec 21 (95 minutes after the burst) with the SIRIUS on the IRSF 1.4m telescope at SAAO in South Africa. In images of a 150sec exposure with J, H and Ks filters, we did not find any object within the error circle of the Swift XRT source position ( GCN 10287, Evans et al.) Three sigma upper limits are the followings. J > 19.5 H > 18.4 K > 17.0 This photometry was done by using the DoPhot and calibrated against the 2MASS cataloged stars.