//////////////////////////////////////////////////////////////////////// TITLE: GCN CIRCULAR NUMBER: 10148 SUBJECT: GRB 091109B: Swift detection of a short burst DATE: 09/11/09 22:10:18 GMT FROM: Scott Barthelmy at NASA/GSFC S. R. Oates (UCL-MSSL), S. D. Barthelmy (GSFC), W. H. Baumgartner (GSFC/UMBC), A. P. Beardmore (U Leicester), P. A. Evans (U Leicester), N. Gehrels (NASA/GSFC), S. T. Holland (CRESST/USRA/GSFC), J. A. Kennea (PSU), H. A. Krimm (CRESST/GSFC/USRA), C. B. Markwardt (CRESST/GSFC/UMD), F. E. Marshall (NASA/GSFC), P. T. O'Brien (U Leicester), K. L. Page (U Leicester), D. M. Palmer (LANL), A. Rowlinson (U Leicester), T. Sakamoto (NASA/UMBC), M. H. Siegel (PSU), M. Stamatikos (OSU/NASA/GSFC), M. A. Stark (PSU), T. N. Ukwatta (GSFC/GWU) and L. Vetere (PSU) report on behalf of the Swift Team: At 21:49:03 UT, the Swift Burst Alert Telescope (BAT) triggered and located GRB 091109B (trigger=375409). Swift slewed immediately to the burst. The BAT on-board calculated location is RA, Dec 112.717, -54.080 which is RA(J2000) = 07h 30m 52s Dec(J2000) = -54d 04' 48" with an uncertainty of 3 arcmin (radius, 90% containment, including systematic uncertainty). The BAT light curve shows a single spike with a duration of about 0.4 sec. The peak count rate was ~30,000 counts/sec (15-350 keV), at ~0 sec after the trigger. The XRT began observing the field at 21:50:21.1 UT, 78.1 seconds after the BAT trigger. Using promptly downlinked data we find an uncatalogued X-ray source with an enhanced position: RA, Dec 112.7349, -54.0896 which is equivalent to: RA(J2000) = 07h 30m 56.39s Dec(J2000) = -54d 05' 22.7" with an uncertainty of 3.6 arcseconds (radius, 90% containment). This location is 51 arcseconds from the BAT onboard position, within the BAT error circle. This position may be improved as more data are received; the latest position is available at http://www.swift.ac.uk/sper. A power-law fit to a spectrum formed from promptly downlinked event data gives a column density consistent with the Galactic value of 9.23e+20 cm^-2 (Kalberla et al. 2005). UVOT took a finding chart exposure of 250 seconds with the U filter starting 296 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 3-sigma upper limit is 20.3 mag. The coverage of the XRT error circle by the 8'x8' region for the list of sources generated on-board is uncertain because the large number of sources filled the available telemetry. No correction has been made for the expected extinction corresponding to E(B-V) of 0.17. Burst Advocate for this burst is S. R. Oates (sro AT mssl.ucl.ac.uk). 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: 10149 SUBJECT: GRB 091109B: ROTSE-III Optical Limits DATE: 09/11/09 22:25:08 GMT FROM: Brad Schaefer at LSU B. E. Schaefer (Louisiana State), E.S. Rykoff (UCSB), T. Guver (U Arizona), H. Flewelling (IfA/Hawaii), 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 091109B (Swift trigger 375409; S. R. Oates et al., GCN 10148), producing images beginning 9.4 s after the GCN notice time. An automated response took the first image at 21:49:24.5 UT, 21.6 s after the burst, under excellent conditions. We took 10 5-sec, 10 20-sec and 10 60-sec exposures. These unfiltered images are calibrated relative to USNO A2.0 (R). Imaging is on going. Comparison to the DSS (second epoch) reveals no new sources within the 3-sigma Swift/BAT error circle or the XRT error circle, for both single images and coadding into sets of 10; the field is not crowded. Individual images have limiting magnitudes ranging from 15.9-17.0; we set the following specific limits. start UT end UT t_exp(s) mlim t_start-tGRB(s) Coadd? -------------------------------------------------------------------- 21:49:24.5 21:49:29.5 5 16.0 21.6 N 21:49:24.4 21:50:40.5 76 16.9 21.5 Y //////////////////////////////////////////////////////////////////////// TITLE: GCN CIRCULAR NUMBER: 10150 SUBJECT: GRB 091109B: Optical limits from Watcher DATE: 09/11/09 23:47:07 GMT FROM: Petr Kubanek at AIO M. JelĂ­nek (IAA-CSIC), A. de Ugarte Postigo (INAF-OAB), R. Felletti, L. Hanlon (UCD Dublin), H. Van Heerden (UOVS, Bloemfontein), P. KubĂĄnek (IPL UV, IAA-CSIC) reports on behalf of a large collaboration: Watcher telescope, located at Boyden Observatory, South Africa, observed autonomously GRB 091109B (S. R. Oates et al., GCN 10148). We obtained a set of 5s exposures in clear filter, starting 78s after the GRB (65s after the notice). We see no new sources in the XRT error box down to the single-image limiting magnitude of 16.5. Coaddition of first 120s (mean exposure time 153s after the GRB) of imaging data improves this limit to ~17.7 calibrated against field USNO-A2.0 R-band stars. Those results are consistent with ROTSE-III non-detection (Schaefer et al. GCN 10149). We note that there is a R~15.3 galaxy 8" North-West of the XRT position, posibly the host of this short GRB. Further observations are ongoing. This message can be quoted. //////////////////////////////////////////////////////////////////////// TITLE: GCN CIRCULAR NUMBER: 10151 SUBJECT: GRB 091109B: Enhanced Swift-XRT position DATE: 09/11/10 03:10:55 GMT FROM: Phil Evans at U of Leicester P.A. Evans, M.R. Goad, J.P. Osborne and A.P. Beardmore (U. Leicester) report on behalf of the Swift-XRT team. Using 1173 s of XRT Photon Counting mode data and 1 UVOT images for GRB 091109B, 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 = 112.73603, -54.08983 which is equivalent to: RA (J2000): 07h 30m 56.65s Dec (J2000): -54d 05' 23.4" with an uncertainty of 2.8 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 was automatically generated, and is an official product of the Swift-XRT team. //////////////////////////////////////////////////////////////////////// TITLE: GCN CIRCULAR NUMBER: 10153 SUBJECT: GRB 091109b: Magellan Observations DATE: 09/11/10 05:28:28 GMT FROM: Edo Berger at Harvard E. Berger (Harvard), K. Covey (Cornell), A. A. West, J. M. Andersen (BU), and M. McDonald (U. Maryland, College Park) report: "We observed the XRT error circle (GCN #10151) of the short GRB 091109b (GCN #10152) with IMACS on the Magellan/Baade 6.5-m telescope starting on 2009 Nov. 10.167 UT (6.2 hours after the burst). In a 1200-sec stacked R-band image we find no optical sources within the XRT error circle to a 3-sigma limit of R~23 mag in comparison to several nearby stars in the USNO-B catalog. We further note that the object claimed to be a galaxy north-west of the XRT position (GCN #10150) appears to be resolved into two point sources in our image (with a seeing of about 1.1 arcsec)." //////////////////////////////////////////////////////////////////////// TITLE: GCN CIRCULAR NUMBER: 10154 SUBJECT: GRB 091109B: VLT observations DATE: 09/11/10 05:33:34 GMT FROM: Andrew Levan at U.of Leicester A.J. Levan (Warwick), N.R. Tanvir (Leicester), J. Hjorth, D. Malesani (DARK/NBI), A. de Ugarte Postigo, P. D'Avanzo (INAF-OAB) report on behalf of a larger collaboration: We observed the location of the short GRB 091109B (Oates et al. GCNC 10148), with the VLT/FORS2. Observations began at 03:34 UT, approximately 5.7 hours after the burst. Within the X-ray localisation (Evans et al. GCNC 10151) we identify a faint source (Source A) at: RA: 07:30:56.61 Dec: -54:05:22.85 We also identify a second, fainter source (Source B) just outside the X-ray localisation, at: RA: 07:30:56.46 Dec: -54:05:25.56 Both positions have errors of ~0.5" in each axis. Source A has R~25, and appears pointlike. At this stage we cannot make any claim of variability in either source A or B, although further observation are planned. Additionally, we note that the apparently extended object to the NW is actually a blend of two stars, and a possible galaxy, rather than a single object, and hence its relation to GRB 091109B is currently unclear. We thank P. Lyman and the staff of VLT for their assistance with these observations. //////////////////////////////////////////////////////////////////////// TITLE: GCN CIRCULAR NUMBER: 10155 SUBJECT: GRB 091109B: Swift-XRT Team refined analysis DATE: 09/11/10 07:33:26 GMT FROM: Kim Page at U.of Leicester K.L. Page (U. Leicester) and S.R. Oates (UCL-MSSL) report on behalf of the Swift-XRT team: We have analysed 9.7 ks of XRT data for GRB 091109B (Oates et al. GCN Circ. 10148), from 86 s to 22.9 ks after the BAT trigger. The data are entirely in Photon Counting (PC) mode. The enhanced XRT position for this burst was given by Evans et al. (GCN. Circ 10151). The light curve can be modelled with a power-law decay with a decay index of alpha=0.62 (+0.11, -0.10). Although there is some evidence that there may be a steep, shallow, normal trend in the light-curve, as is often seen, there are not enough data points to warrant such additional modelling at this time. A spectrum formed from the PC mode data can be fitted with an absorbed power-law with a photon spectral index of 2.0 (+0.5, -0.4). The best-fitting absorption column is 1.2 (+1.4, -0.1) x 10^21 cm^-2, in excess of the Galactic value of 9.2 x 10^20 cm^-2 (Kalberla et al. 2005). The counts to observed (unabsorbed) 0.3-10 keV flux conversion factor deduced from this spectrum is 3.8 x 10^-11 (5.3 x 10^-11) erg cm^-2 count^-1. If the light curve continues to decay with a power-law decay index of 0.62, the count rate at T+24 hours will be 2.4 x 10^-3 count s^-1, corresponding to an observed (unabsorbed) 0.3-10 keV flux of 9.1 x 10^-14 (1.2 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/00375409. This circular is an official product of the Swift-XRT team. //////////////////////////////////////////////////////////////////////// TITLE: GCN CIRCULAR NUMBER: 10156 SUBJECT: GRB 091109B: VLT afterglow confirmation DATE: 09/11/10 10:00:29 GMT FROM: Daniele Malesani at Dark Cosmology Centre, Niels Bohr Inst D. Malesani (DARK/NBI), A. de Ugarte Postigo (INAF/OABr), A. J. Levan (Univ. Warwick), N. R. Tanvir (Univ. Leicester), J. Hjorth (DARK/NBI), P. D'Avanzo (INAF/Brera), report on behalf of a larger collaboration: Following the observations of GRB 091109B (Oates et al., GCN 10148) with the VLT reported by Levan et al. (GCN 10154), we obtained a further epoch of R-band imaging with mean time Nov 10.33 UT (10.22 hr after the burst), using the same instrument and configuration. Source "A" by Levan et al. (GCN 10154) is still detected, and decayed by 1.0+-0.3 mag during this time interval, implying a decay index of alpha = 1.7+-0.5. We hence conclude that the source is indeed the afterglow of GRB 091109B. We acknowledge excellent support from the ESO staff at Paranal, in particular Alain Smette and Paul Lynam. //////////////////////////////////////////////////////////////////////// TITLE: GCN CIRCULAR NUMBER: 10157 SUBJECT: GRB 091109B: Swift/UVOT Upper Limits DATE: 09/11/10 12:35:35 GMT FROM: Samantha Oates at MSSL S. R. Oates (MSSL-UCL) reports on behalf of the Swift/UVOT team: The Swift/UVOT began settled observations of the field of GRB 091109B 84s after the BAT trigger (Oates et al., GCN 10148). We do not detect any source at the enhanced Swift XRT position (Evans et al. GCN 10151) and at the location of source A detected by the VLT (Levan et al. GCN 10154, Malesani et al. GCN 10156) The 3-sigma upper limits for the finding chart exposures (FC) and summed images are: Filter T_start T_stop Exp(s) Mag (3-sigma upper limit) ------------------------------------------------------------- white (FC) 84 234 147 > 21.25 u (FC) 296 546 246 > 20.29 white 577 18629 1313 > 22.09 v 627 11274 1172 > 20.96 b 553 17890 1337 > 21.78 u 701 23171 1761 > 21.61 uvw1 677 22710 1988 > 21.44 uvm2 652 12179 1160 > 20.87 uvw2 603 7050 471 > 20.52 ------------------------------------------------------------- The quoted upper limits have not been corrected for the expected Galactic extinction along the line of sight of E_(B-V) = 0.17 mag. All photometry is on the UVOT photometric system described in Poole et al. (2008, MNRAS, 383, 627). //////////////////////////////////////////////////////////////////////// TITLE: GCN CIRCULAR NUMBER: 10168 SUBJECT: GRB 091109B: Suzaku WAM observation of the prompt emission DATE: 09/11/14 09:30:39 GMT FROM: Masanori Ohno at ISAS/JAXA M. Ohno, M. Suzuki, M. Kokubun, T. Takahashi (ISAS/JAXA), K. Yamaoka (Aoyama Gakuin U.), S. Sugita (Nagoya U.), Y. E. Nakagawa, T. Tamagawa (RIKEN), S. Hong (Nihon U.), N. Vasquez (Tokyo Tech.), N. Ohmori, E. Sonoda, K. Kono, H. Hayashi, A. Daikyuji, Y. Nishioka, K. Noda, M. Yamauchi (Univ. of Miyazaki), Y. Hanabata, T. Uehara, T. Takahashi, Y. Fukazawa (Hiroshima U.), W. Iwakiri, M. Tashiro, Y. Terada, A. Endo, K. Onda, T. Sugasahara (Saitama U.), Y. Urata, H.M Lin (NCU), T. Enoto, K. Nakazawa, K. Makishima (Univ. of Tokyo), on behalf of the Suzaku WAM team, report: The short GRB 091109B (Swift/BAT trigger #375409 ; Oates et al., GCN 10148) triggered the Suzaku Wide-band All-sky Monitor (WAM) which covers an energy range of 50 keV - 5 MeV at 2009-11-09 21:49:02.83 UT (=T0). The observed light curve shows a single peak starting at T0+0.3s, ending at T0+0.6s with a duration (T90) of about 0.19 seconds. The fluence in 100 - 1000 keV was 9.98(-3.69,+0.72) x 10^-7 erg/cm^2. The 1-s peak flux measured from T0 was 1.75(-0.59,+0.14) photons/ cm^2/s in the same energy range. Preliminary result shows that the time-averaged spectrum from T0s to T0+1s is well fitted by a power-law with exponential cutoff model: dN/dE ~ E^{-alpha} * exp(-(2-alpha)*E/Epeak) with alpha 0.91(-0.78,+0.42), and Epeak 1330(-610,+1120) keV (chi^2/d.o.f. = 24.6/24). All the quoted errors are at statistical 90% confidence level, in which the systematic uncertainties are not included. The light curves for this burst are available at: http://www.astro.isas.jaxa.jp/suzaku/HXD-WAM/WAM-GRB/grb/trig/grb_table.html