//////////////////////////////////////////////////////////////////////// TITLE: GCN CIRCULAR NUMBER: 10138 SUBJECT: GRB 091109: Swift detection of a burst with optical afterglow DATE: 09/11/09 05:11:55 GMT FROM: David Palmer at LANL S. R. Oates (UCL-MSSL), S. D. Barthelmy (GSFC), A. P. Beardmore (U Leicester), N. Gehrels (NASA/GSFC), J. A. Kennea (PSU), H. A. Krimm (CRESST/GSFC/USRA), C. B. Markwardt (CRESST/GSFC/UMD), K. L. Page (U Leicester), D. M. Palmer (LANL), M. H. Siegel (PSU), M. Stamatikos (OSU/NASA/GSFC) and L. Vetere (PSU) report on behalf of the Swift Team: At 04:57:43 UT, the Swift Burst Alert Telescope (BAT) triggered and located GRB 091109 (trigger=375246). Swift slewed immediately to the burst. The BAT on-board calculated location is RA, Dec 309.265, -44.176 which is RA(J2000) = 20h 37m 04s Dec(J2000) = -44d 10' 34" with an uncertainty of 3 arcmin (radius, 90% containment, including systematic uncertainty). The BAT light curve showed a spiky structure with a duration of about 25 sec. The peak count rate was ~800 counts/sec (15-350 keV), at ~20 sec after the trigger. The XRT began observing the field at 05:00:14.1 UT, 150.7 seconds after the BAT trigger. Using promptly downlinked data we find a fading, uncatalogued X-ray source located at RA, Dec 309.25854, -44.15853 which is equivalent to: RA(J2000) = 20h 37m 2.05s Dec(J2000) = -44d 09' 30.7" with an uncertainty of 3.8 arcseconds (radius, 90% containment). This location is 65 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 in excess of the Galactic value (2.99e+20 cm^-2, Kalberla et al. 2005), with an excess column of 3 (+1.84/-1.63) x 10^21 cm^-2 (90% confidence). UVOT took a finding chart exposure of 150 seconds with the White filter starting 155 seconds after the BAT trigger. There is a candidate afterglow in the rapidly available 2.7'x2.7' sub-image at RA(J2000) = 20:37:01.81 = 309.25755 DEC(J2000) = -44:09:29.6 = -44.15821 with a 90%-confidence error radius of about 0.69 arc sec. This position is 2.7 arc sec. from the center of the XRT error circle. The estimated magnitude is 19.92 with a 1-sigma error of about 0.18. No correction has been made for the expected extinction corresponding to E(B-V) of 0.03. 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: 10139 SUBJECT: GRB091109: REM detection of the NIR afterglow DATE: 09/11/09 06:14:55 GMT FROM: Angelo Antonelli at Obs. Astro. di Roma L.A. Antonelli, S. Covino, P. D'Avanzo, D. Fugazza, L. Calzoletti, S. Campana, G. Chincarini, M.L. Conciatore, S. Cutini, V. D'Elia, F. D'Alessio, F. Fiore, P. Goldoni, D. Guetta, C. Guidorzi, G.L. Israel, E. Maiorano, N. Masetti, A. Melandri, E.J.A. Meurs, L. Nicastro, E. Palazzi, E. Pian, S. Piranomonte, L. Stella, G. Stratta, G. Tagliaferri, G. Tosti, V. Testa, S.D. Vergani, F. Vitali report on behalf of the REM team: "The robotic 60-cm REM telescope located at La Silla (Chile) observed automatically the field of the GRB 091109 (Oates et al. GCN10138) starting about 77 s after the burst. We detect a faint object in the XRT error circle in our first H-band images at H~14.8 at coordinates: RA(J2000) 20:37:02.2; Dec(J2000) -44:09:30.4 with 1 arcsec error. This message can be cited" //////////////////////////////////////////////////////////////////////// TITLE: GCN CIRCULAR NUMBER: 10140 SUBJECT: GRB 091109: Enhanced Swift-XRT position DATE: 09/11/09 09:42:18 GMT FROM: Phil Evans at U of Leicester A.P. Beardmore, P.A. Evans, M.R. Goad and J.P. Osborne (U. Leicester) report on behalf of the Swift-XRT team. Using 3018 s of XRT Photon Counting mode data and 5 UVOT images for GRB 091109, 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 = 309.25767, -44.15872 which is equivalent to: RA (J2000): 20h 37m 1.84s Dec (J2000): -44d 09' 31.4" 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 was automatically generated, and is an official product of the Swift-XRT team. //////////////////////////////////////////////////////////////////////// TITLE: GCN CIRCULAR NUMBER: 10141 SUBJECT: GRB 091109: Swift-BAT refined analysis DATE: 09/11/09 11:34:40 GMT FROM: Scott Barthelmy at NASA/GSFC H. A. Krimm (GSFC/USRA), S. D. Barthelmy (GSFC), W. H. Baumgartner (GSFC/UMBC), J. R. Cummings (GSFC/UMBC), E. E. Fenimore (LANL), N. Gehrels (GSFC), C. B. Markwardt (GSFC/UMD), S. R. Oates (UCL-MSSL), 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 091109 (trigger #375246) (Oates, et al., GCN Circ. 10138). The BAT ground-calculated position is RA, Dec = 309.252, -44.177 deg, which is RA(J2000) = 20h 37m 00.5s Dec(J2000) = -44d 10' 36.0" with an uncertainty of 2.1 arcmin, (radius, sys+stat, 90% containment). The partial coding was 19%. The mask-weighted light curve shows a couple overlapping peaks. The first starts at ~T-15 sec, peaks at ~T+10 sec. The second (weaker) peaks at ~T+40 sec and ends at ~T+60 sec. T90 (15-350 keV) is 48 +- 17 sec (estimated error including systematics). The time-averaged spectrum from T-0.8 to T+51.5 sec is best fit by a simple power-law model. The power law index of the time-averaged spectrum is 1.31 +- 0.25. The fluence in the 15-150 keV band is 1.6 +- 0.2 x 10^-6 erg/cm2. The 1-sec peak photon flux measured from T+8.20 sec in the 15-150 keV band is 1.3 +- 0.4 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/375246/BA/ //////////////////////////////////////////////////////////////////////// TITLE: GCN CIRCULAR NUMBER: 10142 SUBJECT: GRB 091109: Faulkes Telescope South observations DATE: 09/11/09 12:12:49 GMT FROM: Cristiano Guidorzi at Ferrara U,Italy C. Guidorzi (U. Ferrara), R.J. Smith, C.G. Mundell, D. Bersier, A. Melandri, Z. Cano, S. Kobayashi, C.J. Mottram, I.A. Steele (Liverpool JMU), A. Gomboc (U. Ljubljana) report on behalf of a large collaboration: On 2009 November 9 at 09:26:10 UT the 2-m Faulkes Telescope South began observing GRB 091109 (Oates et al., GCN Circ. 10138) using the R and i' filters. We detect the UVOT optical afterglow candidate at a position consistent with that reported by Oates et al. (but not consistent with the object reported by REM Antonelli et al., GCN Circ. 10139), with the following magnitudes: Mid Time from GRB Total Exp Filter Magnitude (hours) (s) ----------------------------------------------------- 4.74 600 i' 21.7 +- 0.3 5.29 600 R 21.95 +- 0.25 ----------------------------------------------------- Magnitudes have been calibrated from the nearby USNOB-1 star 20:37:02.508, -44:09:33.68, using R2=17.52 and I=17.61. //////////////////////////////////////////////////////////////////////// TITLE: GCN CIRCULAR NUMBER: 10143 SUBJECT: GRB 091109: Swift/UVOT observations DATE: 09/11/09 12:24:27 GMT FROM: Samantha Oates at MSSL S. R. Oates (MSSL-UCL) reports on behalf of the Swift/UVOT team: The Swift/UVOT began observerving the field of GRB 091109 156s after the BAT trigger (Oates et al., GCN Circ. 10138). We detect the optical afterglow in the white filter only, which faded rapidly. The refined UVOT position is: RA (J2000) 20:37:01.80 Dec (J2000) -44: 9:29.6 with an estimated uncertainty of 0.7 arcsec (radius, 90% confidence). This position is consistent with the XRT refined position (Beardmore et al., GCN Circ 10140). Preliminary magnitudes and the 3 sigma upper limits are reported below. Filter T_start(s) T_stop(s) Exposure Mag Err ########################################################### white 156 306 147 19.88 +\- 0.14 white 5371 5571 197 > 21.26 v 4345 5981 393 > 19.94 b 5166 5365 197 > 20.49 u 314 6572 615 > 20.97 uvw1 4755 6392 393 > 20.59 uvm2 4550 6186 393 > 20.46 uvw2 4140 5777 393 > 20.68 ########################################################### The above magnitudes are not corrected for the Galactic extinction corresponding to a reddening of E_{B-V} = 0.03 mag (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: 10144 SUBJECT: GRB 091109: BOOTES-3 observations DATE: 09/11/09 13:41:34 GMT FROM: Antonio Deugarte at IAA-CSIC A. de Ugarte Postigo (INAF-OAB), A.J. Castro-Tirado, M. Jelinek (IAA-CSIC), P. Kubanek (IPL UV, IAA-CSIC), J. Gorosabel, R. Cunniffe, S. Guziy (IAA-CSIC), P. Yock (Auckland Univ.), W.H. Allen (Vintage Lane Obs.), I. Bond (Massey Univ.), G. Christie (Stardome Obs.), report on behalf of a larger collaboration: We have observed the field of GRB 091109 (Oates et al. GCN 10138) using the 0.6 Yock-Allen robotic telescope (BOOTES-3) located in Bleinheim, New Zealand. Due to bad weather conditions, observations did not start until 11:03 UT (6.1h after the burst). A combination of the first 30x60s unfiltered exposures does not show any source at the UVOT postion down to a 3-sigma limiting magnitude of R~20.0, consistent with the limits given by UVOT (Oates et al. GCN 10143) and the fainter detection by Faulkes Telescope South (Guidorzi et al. GCN 10142). Further observations are ongoing. //////////////////////////////////////////////////////////////////////// TITLE: GCN CIRCULAR NUMBER: 10145 SUBJECT: GRB 091109: Swift-XRT refined analysis DATE: 09/11/09 16:10:35 GMT FROM: Andy Beardmore at U Leicester A. P. Beardmore (U. Leicester) and S. R. Oates (UCL-MSSL) report on behalf of the Swift-XRT team: We have analysed 7.9 ks of Swift-XRT data for GRB 091109 (Oates et al. GCN Circ. 10138), from 154 s to 18.1 ks after the BAT trigger. The data span four orbits, comprising 37 s in Windowed Timing (WT) mode with the remainder in Photon Counting (PC) mode. The enhanced XRT position for this burst was given by Beardmore et al. (GCN. Circ 10140). The light curve can be modelled by a broken power-law with an initial decay slope of 2.9 +0.5 -0.4, breaking at T+358 s to a shallower decay of 0.86 +0.07 -0.08. A spectrum formed from the PC mode data (from 175 s to 18.1 ks after the trigger) can be fitted with an absorbed power-law, giving a photon index of 2.10 +/- 0.19. The best-fitting absorption column is (9.9 +2.1 -4.4) x 10^20 cm^-2, in excess of the Galactic value of 3.0 x 10^20 cm^-2 (Kalberla et al. 2005) in the direction of the burst. The counts to observed (unabsorbed) 0.3-10 keV flux conversion factor deduced from this spectrum is 3.6 x 10^-11 (4.8 x 10^-11) erg cm^-2 count^-1. If the light curve continues to decay with a power-law decay index of 0.86, the count rate at T+24 hours will be 4.7 x 10^-3 count s^-1, corresponding to an observed (unabsorbed) 0.3-10 keV flux of 1.7 x 10^-13 (2.3 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/00375246. This circular is an official product of the Swift-XRT team. //////////////////////////////////////////////////////////////////////// TITLE: GCN CIRCULAR NUMBER: 10147 SUBJECT: GRB091109: Correction to GCN 10139 DATE: 09/11/09 19:08:33 GMT FROM: Angelo Antonelli at Obs. Astro. di Roma L.A. Antonelli, S. Covino, P. D'Avanzo, report on behalf of the REM team: "We have to correct the position of the object reported in our previous GCN 10139: due to a typo the R.A. position of the putative NIR afterglow of GRB091109 reported is RA(J2000) 20:37:02.02 instead of RA(J2000) 20:37:02.2. However, we note that the correct position is still about 2" far away from the UVOT position (Oates, GCN 10143). The observed source in the REM H band early images is very faint and close to the detection limit of our images. So due to the misplacement with the UVOT position the observed object may be a background fluctuation not related to GRB091109. A detailed analysis is in progress." //////////////////////////////////////////////////////////////////////// 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: 10152 SUBJECT: GRB 091109B: Swift-BAT refined analysis DATE: 09/11/10 03:19:30 GMT FROM: Hans Krimm at NASA-GSFC C. B. Markwardt (GSFC/UMD), S. D. Barthelmy (GSFC), W. H. Baumgartner (GSFC/UMBC), J. R. Cummings (GSFC/UMBC), E. E. Fenimore (LANL), N. Gehrels (GSFC), H. A. Krimm (GSFC/USRA), S. R. Oates (UCL-MSSL), 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-60 to T+243 sec from the recent telemetry downlink, we report further analysis of BAT GRB 091109B (trigger #375409) (Oates, et al., GCN Circ. 10148). The BAT ground-calculated position is RA, Dec = 112.750, -54.092 deg which is RA(J2000) = 07h 30m 59.9s Dec(J2000) = -54d 05' 30.6" with an uncertainty of 1.2 arcmin, (radius, sys+stat, 90% containment). The partial coding was 76%. The mask-weighted light curve shows a single symmetrical peak of duration 0.32 seconds. There is no sign of extended emission. T90 (15-350 keV) is 0.3 +- 0.03 sec (estimated error including systematics). The time-averaged spectrum from T-0.0 to T+0.3 sec is best fit by a simple power-law model. The power law index of the time-averaged spectrum is 0.71 +- 0.13. The fluence in the 15-150 keV band is 1.9 +- 0.2 x 10^-7 erg/cm2. The 1-sec peak photon flux measured from T-0.33 sec in the 15-150 keV band is 5.4 +- 0.4 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/375409/BA/ [GCN OPS NOTE(09nov09): Per author's request, the "B" was added to the GRB name and the reference was filled in.] //////////////////////////////////////////////////////////////////////// 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: 10158 SUBJECT: GRB 091109A: GROND and VLT observations DATE: 09/11/10 14:59:13 GMT FROM: Thomas Kruehler at MPE/MPI P. Afonso, T. Kruehler, A. Rau, and J. Greiner (all MPE Garching) report on behalf of the GROND team: GROND (Greiner et al. 2008, PASP 120, 405), mounted at the 2.2m ESO/MPI telescope at La Silla Observatory (Chile), observed the field of GRB 091109A (Oates et al., GCN #10138) simultaneously in the g'r'i'z'JHK bands. Observations were done under clear sky conditions, starting on Nov 10 at 00:07 UTC, 19.1 h after the burst and lasted for 1.8 hours. In stacked images corresponding to a total integration time of 60 min in JHK and 75 min in g'r'i'z', we detect the optical afterglow (Oates et al., GCN #10138, Guidorzi et. al, GCN #10142) in the g'r'i'z' bands and obtain the following preliminary magnitudes and upper limits (all in the AB system): g' = 24.5 +/- 0.1 r' = 23.6 +/- 0.1 i' = 23.4 +/- 0.1 z' = 23.3 +/- 0.2 J > 22.2 H > 21.8 K > 21.2 which were derived using the GROND zero points and 2MASS catalog field stars as reference. No correction has been made for the expected extinction corresponding to a reddening of E(B-V) = 0.03 mag in the direction of the burst (Schlegel et al. 1998). Associating the blue g'-r' color with Lyman-alpha absorption in the host of the GRB, we obtain a photometric redshift of z = 3.5 +/- 0.4 assuming no intrinsic dust. In addition, we triggered VLT/FORS2 spectroscopy, that started Nov 10 at 02:23 UTC, 21.5 h post-burst. Two integrations of 1800 s each at a mean airmass of 2.1 were obtained using the 600RI grism that covers the wavelength range from 5300 to 8700 A. In the low S/N spectrum we find a tentative ~60A EW broad absorption feature around a wavelength of 5700A. If associated with Lyman-alpha absorption, the corresponding redshift of ~3.5 would be in agreement with the GROND photo-z. We note, however, that all observations are also consistent with a host galaxy at a redshift of z ~ 0.44. Given the absence of information about a possible host galaxy contribution we cannot distinguish these two possibilities at this point. We thank A. Smette and P. Lynam at Paranal for excellent support. //////////////////////////////////////////////////////////////////////// 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 //////////////////////////////////////////////////////////////////////// TITLE: GCN CIRCULAR NUMBER: 10246 SUBJECT: GRB 091109A: GROND confirmation of redshift z = 3.5 DATE: 09/12/04 17:32:12 GMT FROM: Paulo M. J. Afonso at MPE GRB 091109A: GROND confirmation of redshift z = 3.5 P. Afonso, T. Kruehler, A. Rau, and J. Greiner (all MPE Garching) report on behalf of the GROND team: GROND (Greiner et al. 2008, PASP 120, 405), mounted at the 2.2m ESO/MPI telescope at La Silla Observatory (Chile), reobserved the field of GRB 091109A (Oates et al., GCN #10138) simultaneously in the g'r'i'z'JHK bands. Observations started 2009-11-20 00:42, 10.8 days after the trigger and lasted for an effective exposure of 75 min in g'r'i'z' and 60 min in JHK. At the position of the optical afterglow (Guidorzi et al. GCN#10142, Oates GCN#10143, Afonso et al., GCN #10158) we do not detect any source down to a limiting magnitude of r' > 25.1. Comparing with the brightness of r' = 23.6 +- 0.1 mag (AB) reported for the 1st epoch (Afonso et al., GCN #10158), the last imaging clearly shows a fading of more than 1.5 magnitudes. The 1st epoch was hence dominated by afterglow light, favoring a redshift of around z = 3.5 +/- 0.4. A thorough analysis of the VLT data (GCN # 10158) was limited by the very low S/N of the optical spectrum and does not yield more precise redshift constraints. //////////////////////////////////////////////////////////////////////// TITLE: GCN CIRCULAR NUMBER: 10350 SUBJECT: GRB091109A: VLT/FORS2 spectroscopic redshift DATE: 10/01/19 22:11:33 GMT FROM: Arne Rau at MPE Arne Rau (MPE Garching), Johan Fynbo (DARK), and Jochen Greiner (MPE Garching): "We report on additional analysis of our VLT/FORS2 spectrum of the optical afterglow of GRB 091109A (Oates et al., GCN #10138, Guidorzi et al. GCN#10142, Oates GCN#10143, Afonso et al., GCN #10158 ). A careful search revealed absorption lines at 6227, 6308, and 6321 Angstroem which we identify with SiII and the CIV doublet a common redshift of z=3.076 +/- 0.002. Lyman-alpha absorption at this redshift is located shortwards of the blue wavelength cut-off and the earlier reported tentative detection at 5700A (Afonso et al., GCN #10158) is not confirmed."