This file contains bothe the "A" and "B" bursts. //////////////////////////////////////////////////////////////////////// TITLE: GCN CIRCULAR NUMBER: 8021 SUBJECT: GRB 080727: Swift detection of a burst DATE: 08/07/27 06:16:46 GMT FROM: David Palmer at LANL S. Immler (CRESST/GSFC/UMD), W. H. Baumgartner (GSFC/UMBC), N. Gehrels (NASA/GSFC), S. D. Hunsberger (PSU), W.B Landsman (GSFC), C. B. Markwardt (CRESST/GSFC/UMD), K. L. Page (U Leicester), D. M. Palmer (LANL), A. M. Parsons (GSFC), D. Perez (U Leicester), T. Sakamoto (NASA/UMBC) and T. N. Ukwatta (GSFC/GWU) report on behalf of the Swift Team: At 05:57:39 UT, the Swift Burst Alert Telescope (BAT) triggered and located GRB 080727 (trigger=318094). Swift slewed immediately to the burst. The BAT on-board calculated location is RA, Dec 208.389, -18.549 which is RA(J2000) = 13h 53m 33s Dec(J2000) = -18d 32' 55" with an uncertainty of 3 arcmin (radius, 90% containment, including systematic uncertainty). The BAT light curve showed a single peak structure with a duration of about 5 sec. The peak count rate was ~700 counts/sec (15-350 keV), at ~2 sec after the trigger. The XRT began observing the field at 05:59:28.5 UT, 109.2 seconds after the BAT trigger. Using promptly downlinked data we find a fading, uncatalogued X-ray source with an enhanced position: RA, Dec 208.39099, -18.54505 which is equivalent to: RA(J2000) = 13h 53m 33.84s Dec(J2000) = -18d 32' 42.2" with an uncertainty of 2.7 arcseconds (radius, 90% containment). This location is 15 arcseconds from the BAT onboard position, within the BAT error circle. A power-law fit to a spectrum formed from promptly downlinked event data gives a column density consistent with the Galactic value of 6.75e+20 cm^-2 (Kalberla et al. 2005). UVOT took a finding chart exposure of 100 seconds with the White (160-650 nm) filter starting 114 seconds after the BAT trigger. No afterglow candidate has been found in the initial data products. The 2.7'x2.7' sub-image covers 25% of the BAT error circle and 100% of the XRT error circle. The typical 3-sigma upper limit has been about 18.5 mag. 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 0.07. Burst Advocate for this burst is S. Immler (immler 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: 8022 SUBJECT: GRB 080727B: Swift detection of a bright burst DATE: 08/07/27 08:30:44 GMT FROM: David Palmer at LANL S. Immler (CRESST/GSFC/UMD), W. H. Baumgartner (GSFC/UMBC), A. P. Beardmore (U Leicester), P. A. Evans (U Leicester), C. Guidorzi (INAF-OAB), S. D. Hunsberger (PSU), W.B Landsman (GSFC), C. B. Markwardt (CRESST/GSFC/UMD), K. L. Page (U Leicester), D. M. Palmer (LANL), A. M. Parsons (GSFC), D. Perez (U Leicester), T. Sakamoto (NASA/UMBC) and R. L. C. Starling (U Leicester) report on behalf of the Swift Team: At 08:13:24 UT, the Swift Burst Alert Telescope (BAT) triggered and located GRB 080727B (trigger=318101). Swift slewed immediately to the burst. The BAT on-board calculated location is RA, Dec 276.870, +1.172 which is RA(J2000) = 18h 27m 29s Dec(J2000) = +01d 10' 20" with an uncertainty of 3 arcmin (radius, 90% containment, including systematic uncertainty). The BAT light curve showed a double-peaked structure with a duration of about 10 sec. The peak count rate was ~18,000 counts/sec (15-350 keV), at 6 sec after the trigger. The XRT began observing the field at 08:15:05.9 UT, 101.2 seconds after the BAT trigger. Using promptly downlinked data we find a fading, uncatalogued X-ray source with an enhanced position: RA, Dec 276.85898, 1.16304 which is equivalent to: RA(J2000) = 18h 27m 26.16s Dec(J2000) = +01d 09' 47.0" with an uncertainty of 2.8 arcseconds (radius, 90% containment). This location is 51 arcseconds from the BAT onboard position, within the BAT error circle. A power-law fit to a spectrum formed from promptly downlinked event data gives a column density in excess of the Galactic value (3.64e+21 cm^-2, Kalberla et al. 2005), with an excess column of 4.7 (+4.37/-3.38) x 10^21 cm^-2 (90% confidence). UVOT took a finding chart exposure of 100 seconds with the White (160-650 nm) filter starting 105 seconds after the BAT trigger. No afterglow candidate has been found in the initial data products. The 2.7'x2.7' sub-image covers 25% of the BAT error circle and 100% of the XRT error circle. The typical 3-sigma upper limit has been about 18.5 mag. No correction has been made for the expected extinction corresponding to E(B-V) of 1.94. Burst Advocate for this burst is S. Immler (immler 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: 8023 SUBJECT: GRB 080727B: REM prompt observations DATE: 08/07/27 09:11:06 GMT FROM: Paolo D'Avanzo at INAF-OAB P. D'Avanzo, S. Covino, L.A. Antonelli, 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. 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 080727B (Immler et al. GCN 8022) on July 27 starting at 08:14:25 UT (61 seconds after the burst). Observations were carried out at high airmass. In a series of 10s and 30s exposures we do not see any afterglow candidate inside the XRT error box down to R > 16.0 and H > 13.0 (3sigma c.l.). //////////////////////////////////////////////////////////////////////// TITLE: GCN CIRCULAR NUMBER: 8024 SUBJECT: GRB 080727B: KAIT observations DATE: 08/07/27 10:03:20 GMT FROM: Weidong Li at UC Berkeley KAIT/LOSS W. Li, R. Chornock, D. A. Perley, J. S. Bloom, and A. V. Filippenko, University of California at Berkeley, on behalf of the KAIT GRB team, report: The robotic 0.8-m KAIT located at Lick Observatory responded to GRB 080727B (Immler et al. GCN 8022) automatically on July 27 starting at 08:14:12 UT (48 seconds after the burst). A series of images were taken in the V, I, and clear filters. We detected a fading new object at the following location: RA (J2000) = 18h27m26.05s +/- 0.3" Dec (J2000) = +01d09'47.7" +/- 0.3" , suggesting that this is the optical afterglow of the GRB. We report the following preliminary photometry (calibrated to USNO B1): UT start exptime filter mag err 08:14:12 2 s clear 18.20 0.16 08:14:17 2 s clear 18.38 0.16 08:14:20 2 s clear 18.45 0.23 The power-law decay index between t = 49 s and 72 s after the burst is -1.44 +/- 0.59. Further analysis is ongoing. //////////////////////////////////////////////////////////////////////// TITLE: GCN CIRCULAR NUMBER: 8025 SUBJECT: GRB 080727A: Enhanced Swift-XRT position DATE: 08/07/27 10:30:36 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 2786 s of XRT Photon Counting mode data and 1 UVOT images for GRB 080727A, 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 = 208.39050, -18.54479 which is equivalent to: RA (J2000): 13h 53m 33.72s Dec (J2000): -18d 32' 41.2" with an uncertainty of 1.9 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 http://www.swift.ac.uk/xrt_positions/Goad.pdf), the current algorithm is an extension of this method. This circular was automatically generated, and is an official product of the Swift-XRT team. //////////////////////////////////////////////////////////////////////// TITLE: GCN CIRCULAR NUMBER: 8026 SUBJECT: GRB 080727B: Enhanced Swift-XRT position DATE: 08/07/27 11:40:28 GMT FROM: Phil Evans at U of Leicester M.R. Goad, J.P. Osborne, A.P. Beardmore and P.A. Evans (U. Leicester) report on behalf of the Swift-XRT team. Using 2097 s of XRT Photon Counting mode data and 1 UVOT images for GRB 080727B, 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 = 276.85851, +1.16272 which is equivalent to: RA (J2000): 18h 27m 26.04s Dec (J2000): +01d 09' 45.8" with an uncertainty of 1.9 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 http://www.swift.ac.uk/xrt_positions/Goad.pdf), the current algorithm is an extension of this method. This circular was automatically generated, and is an official product of the Swift-XRT team. //////////////////////////////////////////////////////////////////////// TITLE: GCN CIRCULAR NUMBER: 8027 SUBJECT: GRB080727A: Swift/UVOT Upper Limits DATE: 08/07/27 14:38:23 GMT FROM: Wayne Landsman at GSFC/SSAI W.B. Landsman (NASA/GSFC/Adnet) and S. Immler (PSU) report on behalf of the Swift/UVOT team: The Swift/UVOT observed the field of GRB080727A starting 113s after the BAT trigger (Immler et al., GCN Circ. 8021). We do not find any source, in any of the UVOT observations, at the UVOT-enhanced XRT position of the afterglow (Evans et al. GCN Circ. 8025). The 3-sigma upper limits for detecting a source at this location in the co-added images are: Filter T_start T_stop Exp(s) Mag (3-sigma upper limit) ----------------------------------------------------------------- v 219 7675 1165 >20.6 b 700 7083 471 >20.9 u 675 6878 490 >20.6 uvw1 650 6673 491 >20.5 uvm2 1541 6468 236 >20.0 uvw2 730 7486 471 >20.8 white 113 7284 623 >21.8 ----------------------------------------------------------------- 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} = 0.07 mag. All photometry is on the UVOT flight system described in Poole et al. (2008, MNRAS, 383, 627). //////////////////////////////////////////////////////////////////////// TITLE: GCN CIRCULAR NUMBER: 8028 SUBJECT: GRB 080727A: Swift-XRT refined analysis DATE: 08/07/27 15:30:20 GMT FROM: Kim Page at U.of Leicester K.L. Page, J.P. Osborne (U. Leicester) and S. Immler (CRESST/GSFC/UMD) report on behalf of the Swift-XRT team: We have analysed the first three orbits of data obtained for GRB 080727A (Immler et al., GCN Circ. 8021), covering 7 ks of Photon Counting mode data. The UVOT-enhanced position has been given by Evans et al. (GCM Circ. 8025). During the first orbit (117s - 1.9 ks after the trigger), the light-curve shows a number of small flares, superimposed on a power-law decay of alpha= 2.01 +0.18/-0.17. The source is no longer detected in the combined second and third orbits of data (5.3 ks of exposure time, starting 5 ks after the trigger). Although the upper limit is consistent with the continued decay of alpha = 2.01, it is not possible to determine whether a break has occurred. The spectrum from the first orbit of data can be fitted with a power-law of Gamma = 1.43 +0.20/-0.19, absorbed by the Galactic column in this direction (6.75x10^20 cm^-2). The average observed (unabsorbed) flux over this time is 5.56 (6.02) x 10^-12 erg cm^-2 s^-1. The counts to observed flux conversion is 5.3 x 10^-11 erg cm^-2 count^-1. With the limited information available from a detection only in the first orbit, we are unable confidently to predict the flux at 24 hours. This is an official product of the Swift-XRT team. //////////////////////////////////////////////////////////////////////// TITLE: GCN CIRCULAR NUMBER: 8029 SUBJECT: GRB 080727A, Swift-BAT refined analysis DATE: 08/07/27 16:47:32 GMT FROM: Takanori Sakamoto at NASA/GSFC K. McLean (GSFC/UMD), S. D. Barthelmy (GSFC), W. Baumgartner (GSFC/UMBC), J. Cummings (GSFC/UMBC), E. Fenimore (LANL), N. Gehrels (GSFC), H. Krimm (GSFC/USRA), C. Markwardt (GSFC/UMD), D. Palmer (LANL), A. Parsons (GSFC), T. Sakamoto (GSFC/UMBC), G. Sato (ISAS), M. Stamatikos (GSFC/ORAU), J. Tueller (GSFC), T. Ukwatta (GWU) (i.e. the Swift-BAT team): Using the data set from T-239 to T+963 sec from the recent telemetry downlink, we report further analysis of BAT GRB 080727A (trigger #318094) (Immler, et al., GCN Circ. 8021). The BAT ground-calculated position is RA, Dec = 208.416, -18.572 deg which is RA(J2000) = 13h 53m 39.9s Dec(J2000) = -18d 34' 18.6" with an uncertainty of 2.4 arcmin, (radius, sys+stat, 90% containment). The partial coding was 97%. The mask-weighted light curve shows a single weak pulse starting at T+~0 and ending a T+~5 sec. T90 (15-350 keV) is 4.9 +- 1.0 sec (estimated error including systematics). The time-averaged spectrum from T-0.1 to T+5.1 sec is best fit by a simple power-law model. The power law index of the time-averaged spectrum is 1.25 +- 0.34. The fluence in the 15-150 keV band is 1.3 +- 0.3 x 10^-07 erg/cm2. The 1-sec peak photon flux measured from T+1.20 sec in the 15-150 keV band is 0.3 +- 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/318094/BA/ //////////////////////////////////////////////////////////////////////// TITLE: GCN CIRCULAR NUMBER: 8030 SUBJECT: GRB 080727B, Swift-BAT refined analysis DATE: 08/07/27 17:12:48 GMT FROM: Takanori Sakamoto at NASA/GSFC W. Baumgartner (GSFC/UMBC), S. D. Barthelmy (GSFC), J. Cummings (GSFC/UMBC), E. Fenimore (LANL), N. Gehrels (GSFC), H. Krimm (GSFC/USRA), C. Markwardt (GSFC/UMD), K. McLean (GSFC/UMD), D. Palmer (LANL), A. Parsons (GSFC), T. Sakamoto (GSFC/UMBC), G. Sato (ISAS), M. Stamatikos (GSFC/ORAU), J. Tueller (GSFC), T. Ukwatta (GWU) (i.e. the Swift-BAT team): Using the data set from T-120 to T+182 sec from the recent telemetry downlink, we report further analysis of BAT GRB 080727B (trigger #318101) (Immler, et al., GCN Circ. 8022). The BAT ground-calculated position is RA, Dec = 276.871, 1.173 deg which is RA(J2000) = 18h 27m 29.1s Dec(J2000) = +01d 10' 23.2" with an uncertainty of 1.0 arcmin, (radius, sys+stat, 90% containment). The partial coding was 69%. The mask-weighted light curve shows two big FRED-like pulses from T-0.5 to T+3 sec and from T+5.5 to T+9.5 sec. There are several pulses starting at T+2.5, T+7.2, T+7.5, and T+8.8 sec. T90 (15-350 keV) is 8.6 +- 0.2 sec (estimated error including systematics). The time-averaged spectrum from T-0.2 to T+9.4 sec is best fit by a power law with an exponential cutoff. This fit gives a photon index 0.80 +- 0.17, and Epeak of 226.6 +- 120.2 keV (chi squared 43.60 for 56 d.o.f.). For this model the total fluence in the 15-150 keV band is 3.1 +- 0.1 x 10^-06 erg/cm2 and the 1-sec peak flux measured from T-0.04 sec in the 15-150 keV band is 7.6 +- 0.2 ph/cm2/sec. A fit to a simple power law gives a photon index of 1.12 +- 0.04 (chi squared 54.09 for 57 d.o.f.). 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/318101/BA/ //////////////////////////////////////////////////////////////////////// TITLE: GCN CIRCULAR NUMBER: 8031 SUBJECT: GRB 080727B: Swift-XRT refined analysis DATE: 08/07/27 17:16:40 GMT FROM: Phil Evans at U of Leicester P.A. Evans (U. Leicester) and S. Immler (CRESST/GSFC/UMD) report on behalf of the Swift-XRT team: We have analysed 1.6 ks of XRT data for GRB 080727B (Immler et al., GCN Circ 8022). The data were taken in two snapshots; the first started 105 s after the trigger and contained 51 s of Windowed Timing mode data followed by 500 s of Photon Counting (PC) mode data. The second snapshot began at T0+11 ks, and contained 1.2 ks of data, all in PC mode. The UVOT-enhanced XRT position has been given by Goad et al. (GCN Circ. 8026). The light curve shows an initial steep decay with a power-law index of 2.47 (+1.38, -0.39), with a break to a shallower decay of 1.05 (+0.20, -0.13). The break occurred at T0+267 (+89, -100) s. A spectrum formed from all available PC mode data can be modelled by an absorbed power law with a photon index on 1.61 (+0.43, -0.38). The best fitting absorption column is 8.7 (+4.1, -2.9) x 10^21 cm^-2, in excess of the Galactic value in the direction of the burst (3.6 x 10^21, Kalberla et al. 2005). The counts to observed 0.3-10 keV flux conversion factor deduced from this spectrum is 5.0 x 10^-11 erg cm^-2 s^-1 count^-1. If the light curve continues to decay with a slope of 1.05, the count rate at 24 hours post-trigger will be 1.8 x 10^-3, corresponding to an observed (unabsorbed) flux of 9.0 x 10^-14 (4.2 x 10^-13) erg cm^-2 s^-1. This circular is an official product of the Swift-XRT team. //////////////////////////////////////////////////////////////////////// TITLE: GCN CIRCULAR NUMBER: 8033 SUBJECT: GRB 080727B: Swift/UVOT Upper Limits DATE: 08/07/27 18:25:27 GMT FROM: Wayne Landsman at GSFC/SSAI W.B. Landsman (NASA/GSFC/Adnet) and S. Immler (PSU) report on behalf of the Swift/UVOT team: The Swift/UVOT observed the field of GRB 080727B starting 105s after the BAT trigger (Immler et al., GCN Circ. 8022). We do not find any source, in any of the UVOT observations, at either the UVOT-enhanced XRT position of the afterglow (Goad et al. GCN Circ. 8026) or the proposed KAIT afterglow position (Li et al., GCN 8024). The 3-sigma upper limits for detecting a source at this location in single exposures are: Filter T_start Exp(s) Mag (3-sigma upper limit) ---------------------------------------------------------- v 211 393 >20.6 uvw1 642 15 >17.9 uvm2 617 19 >17.6 white 105 98 >21.0 ---------------------------------------------------------- The quoted upper limits have not been corrected for the expected Galactic extinction along the line of sight corresponding to a large reddening of E_{B-V} = 1.9 mag. All photometry is on the UVOT flight system described in Poole et al. (2008, MNRAS, 383, 627). Combining the UVOT upper limits with the KAIT detection at R~18.3 (Li et al., GCN 8024) suggest that there is either high extinction, very fast decline in brightness (the UVOT observations began 57 seconds after the KAIT observations ), or high redshift. The UVOT results are obtained at shorter wavelengths, and for example, the UVOT v filter is expected to suffer an additional ~1.4 mag of extinction, assuming that E(B-V) = 1.9 and that the KAIT clear filter corresponds roughly to the R band. The results may also be consistent with a high redshift burst (5.5 < z <6.5) which is only observable at wavelengths longward of ~6000 A. //////////////////////////////////////////////////////////////////////// TITLE: GCN CIRCULAR NUMBER: 8035 SUBJECT: GRB 080727C: Swift detection of a burst DATE: 08/07/27 23:28:30 GMT FROM: Scott Barthelmy at NASA/GSFC A. M. Parsons (GSFC), S. D. Barthelmy (GSFC), W. H. Baumgartner (GSFC/UMBC), A. P. Beardmore (U Leicester), D. N. Burrows (PSU), S. T. Holland (CRESST/USRA/GSFC), E. A. Hoversten (PSU), S. D. Hunsberger (PSU), J. A. Kennea (PSU), C. B. Markwardt (CRESST/GSFC/UMD), F. E. Marshall (NASA/GSFC), K. L. Page (U Leicester), D. M. Palmer (LANL), D. Perez (U Leicester), T. Sakamoto (NASA/UMBC), R. L. C. Starling (U Leicester), M. C. Stroh (PSU) and T. N. Ukwatta (GSFC/GWU) report on behalf of the Swift Team: At 23:07:35 UT, the Swift Burst Alert Telescope (BAT) triggered and located GRB 080727C (trigger=318170). Swift slewed immediately to the burst. The BAT on-board calculated location is RA, Dec 32.645, +64.151 which is RA(J2000) = 02h 10m 35s Dec(J2000) = +64d 09' 05" with an uncertainty of 3 arcmin (radius, 90% containment, including systematic uncertainty). The BAT light curve shows multiple peaks with a duration of about 100 sec. The peak count rate was ~3500 counts/sec (15-350 keV), at ~25 sec after the trigger. The XRT began observing the field at 23:08:47.9 UT, 72.5 seconds after the BAT trigger. Using promptly downlinked data we find a bright, fading, uncatalogued X-ray source with an enhanced position: RA, Dec 32.63384, 64.13771 which is equivalent to: RA(J2000) = 02h 10m 32.12s Dec(J2000) = +64d 08' 15.8" with an uncertainty of 2.8 arcseconds (radius, 90% containment). This location is 50 arcseconds from the BAT onboard position, within the BAT error circle. A power-law fit to a spectrum formed from promptly downlinked event data gives a column density in excess of the Galactic value (6.78e+21 cm^-2, Kalberla et al. 2005), with an excess column of 7.7 (+7.98/-6.22) x 10^21 cm^-2 (90% confidence). The initial flux in the 2.5 s image was 1.30e-09 erg cm^-2 s^-1 (0.2-10 keV). UVOT took a finding chart exposure of 100 seconds with the White (160-650 nm) filter starting 81 seconds after the BAT trigger. No 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 18.5 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 large, but uncertain extinction expected. We note that the Galactic latitude of this source is 2.6 deg, but we believe this to be a GRB based on the BAT and XRT lightcurves and the spectral information. Burst Advocate for this burst is A. M. Parsons (parsons 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: 8037 SUBJECT: GRB 080727B: REM NIR afterglow prompt detection DATE: 08/07/28 07:27:46 GMT FROM: Paolo D'Avanzo at INAF-OAB P. D'Avanzo, S. Covino, L.A. Antonelli, D. Malesani, 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. 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: Following the KAIT detection of the optical afterglow of GRB 080727B (Li et al. GCN 8024) we performed a detailed off-line analysis of our REM images (D'Avanzo et al., GCN 8023). While we confirm the non-detection of the optical afterglow in the R-band down to the 16th magnitude (30 s of total exposure), we find a barely visible object in our coadded H-band frame (50 s of total exposure) with a magnitude of H = 11.8 ± 0.2 (calibrated against the 2MASS catalogue) at a position consistent with the one reported by Li et al. Unfortunately, just after taking the first R and H-band images, the telescope experienced tracking problems, due to the low altitude of the object with respect to the horizon, and we do not have more images of this GRB. The inferred unabsorbed color (R-H = 3.24 mag) is consistent with the hypothesis of an highly absorbed or high redshift event (Landsman et al. GCN 8033). //////////////////////////////////////////////////////////////////////// TITLE: GCN CIRCULAR NUMBER: 8038 SUBJECT: GRB 080727C: Enhanced Swift-XRT position DATE: 08/07/28 07:40:27 GMT FROM: Phil Evans at U of Leicester J.P. Osborne, A.P. Beardmore, P.A. Evans and M.R. Goad (U. Leicester) report on behalf of the Swift-XRT team. Using 1905 s of XRT Photon Counting mode data and 1 UVOT images for GRB 080727C, 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 = 32.63485, +64.13754 which is equivalent to: RA (J2000): 02h 10m 32.36s Dec (J2000): +64d 08' 15.2" with an uncertainty of 1.5 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 http://www.swift.ac.uk/xrt_positions/Goad.pdf), the current algorithm is an extension of this method. This circular was automatically generated, and is an official product of the Swift-XRT team. //////////////////////////////////////////////////////////////////////// TITLE: GCN CIRCULAR NUMBER: 8039 SUBJECT: GRB 080727A: VLT upper limits DATE: 08/07/28 08:05:37 GMT FROM: Daniele Malesani at Dark Cosmology Centre, Niels Bohr Inst D. Malesani (DARK), P. Jakobsson (Univ. Hertfordshire), A. J. Levan (Univ. Warwick), E. Rol (Univ. Leicester), J. P. U. Fynbo (DARK), report on behalf of a larger collaboration. We observed the field of GRB 080727A (Immler et al., GCN 8021) with the ESO VLT equipped with FORS1. Observations started on 2008 Jul 27.979 UT, 17.5 hr after the burst, for a total exposure time of 900 s in the R filter. Inside the refined XRT error circle (Evans et al., GCN 8025), we detect no new source down to a limiting magnitude R~26. Calibration was based on tabulated zeropoints and is in rough agreement with USNO-B1 stars. We acknowledge kind support from the observing staff at Paranal, particularly Suzanna Randall, Karla Aubel, and Alain Smette. //////////////////////////////////////////////////////////////////////// TITLE: GCN CIRCULAR NUMBER: 8040 SUBJECT: GRB 080727C: Liverpool Telescope observations DATE: 08/07/28 10:01:03 GMT FROM: Cristiano Guidorzi at INAF-OAB C. Guidorzi (INAF-OAB), S. Kobayashi, M.J. Burgdorf (Liverpool JMU) and N. Tanvir (U. Leicester) report on behalf of a larger collaboration: On 2008 July 28 (01:35:55 UT) we began observing the field of GRB 080727C (Parsons et al. GCN Circ. 8035) with the Liverpool Telescope. Observations consisted of 6x300s exposures acquired using the SDSS-i' filter. In our coadded frame we do not detect any source inside the refined XRT error box (Osborne et al. GCN Circ. 8038) down to the limiting magnitude reported below. Telescope Filter T_mid[s] Exposure[s] M_lim (3-sigma) ------------------------------------------------------------- Liverpool SDSS-i' 9830 6x300 22.8 ------------------------------------------------------------- The calibration was performed using the I magnitudes of several USNOB-1 catalogue field objects. The value derived by us is consistent with that given by Bikmaev et al. (GCN Circ. 8036). //////////////////////////////////////////////////////////////////////// TITLE: GCN CIRCULAR NUMBER: 8041 SUBJECT: GRB 080727C: Swift XRT refined analysis DATE: 08/07/28 11:53:51 GMT FROM: Rhaana Starling at U of Leicester R.L.C. Starling (U. Leicester) and A.M. Parsons (GSFC) report on behalf of the Swift XRT team: We have analysed the first five orbits of Swift XRT data for GRB 080727C (trigger=318170, Parsons et al. GCN Circ. 8035) beginning at T0+79 s until T0+22.6 ks. The enhanced XRT position is given in Osborne et al. (GCN Circ. 8038). Up to approximately T0+110 s the light curve appears to be flat. Thereafter the light curve can be fitted with a broken power law with alpha1 = 1.5+/-0.1, breaking at Tbk = 740 +1880/-370 s to a slightly shallower decay of alpha2 = 1.2 +0.1/-0.3. The Photon Counting mode spectrum consisting of 502 s of data during the first orbit is well fitted with an absorbed power law of photon index Gamma = 1.4+/-0.3 and intrinsic absorption (assuming z=0) of N_H = (1.2 +0.5/-0.2) e22 cm-2 in addition to the high Galactic absorption in this direction of N_H = 6.8e21 cm-2 (Kalberla et al. 2005). We measure an average observed (unabsorbed) 0.3-10 keV flux over this time of 1.1e-10 (1.7e-10) erg/cm2/s corresponding to an observed count rate to flux conversion of 1 count/s = 9.9e-11 erg/cm2/s. The predicted count rate at T+24 hr is 0.001 count/s corresponding to an observed 0.3-10 keV flux of 1.35e-13 erg/cm2/s, assuming the decay continues with alpha=1.2. This is an official product of the Swift-XRT team. //////////////////////////////////////////////////////////////////////// TITLE: GCN CIRCULAR NUMBER: 8042 SUBJECT: Konus-Wind observation of GRB 080727B DATE: 08/07/28 12:43:57 GMT FROM: Valentin Pal'shin at Ioffe Inst S. Golenetskii, R.Aptekar, E. Mazets, V. Pal'shin, D. Frederiks, P. Oleynik, M. Ulanov, D. Svinkin, and T. Cline on behalf of the Konus-Wind team, report: The long GRB 080727B (Swift-BAT trigger #318101: Immler et al., GCN 8022, Baumgartner et al., GCN 8030) triggered Konus-Wind at T0=29609.825 s UT (08:13:29.825). The burst light curve shows two multipeaked pulses with a total duration of ~9 s. As observed by Konus-Wind the burst had a fluence of 9.46(-0.84, +0.98)x10^-6 erg/cm2, and a 64-ms peak flux measured from T0+6.080 s of 5.14(-0.10, +0.11)x10^-6 erg/cm2/s (both in the 20 keV - 2 MeV energy range). The time-integrated spectrum of the burst (from T0 to T0+8.448 s) is well be fitted (in the 20 keV - 2 MeV range) by a power law with exponential cutoff model: dN/dE ~ (E^alpha)*exp(-E*(2+alpha)/Ep) with alpha = -0.85(-0.18, +0.16), and Ep = 282(-37, +52) keV (chi2 = 56.6/60 dof). Fitting by GRBM (Band) model yields: the low-energy photon index is alpha = -0.73(-0.24, +0.29), the high energy photon index beta < -2.08, the peak energy Ep = 242(-48, +69) keV (chi2 = 54.8/59 dof). All the quoted errors are at the 90% confidence level. The Konus-Wind light curve of this GRB is available at http://www.ioffe.rssi.ru/LEA/GRBs/GRB080727_T29609/ //////////////////////////////////////////////////////////////////////// TITLE: GCN CIRCULAR NUMBER: 8043 SUBJECT: GRB 080727C: Swift/UVOT Upper Limits DATE: 08/07/28 19:41:18 GMT FROM: Erik Hoversten at Swift/Penn State E. A. Hoversten (PSU) and A. M. Parsons (GSFC) report on behalf of the Swift/UVOT team: The Swift/UVOT began observing the field of GRB 080727C starting 82 seconds after the BAT trigger (Parsons, et al. GCN Circ. 8035). We do not detect any source in any of the filters at the UVOT-enhanced XRT position (Osborne, et al., GCN Circ. 8038). The 3-sigma upper limits at this position for single exposures are: Filter T_start T_stop Exp(s) Mag (3-sigma upper limit) ----------------------------------------------------- white 82.1 181.0 97.3 > 20.81 white 3987.1 4186.8 196.6 > 21.58 v 187.4 587.2 393.5 > 19.89 v 4397.7 4597.5 196.6 > 19.93 b 668.8 673.4 4.6 > 17.79 u 643.0 662.8 19.5 > 18.32 uvw1 618.4 638.2 19.5 > 18.11 uvm2 593.5 613.3 19.5 > 17.61 uvw2 4192.9 4392.7 196.6 > 20.17 The quoted upper limits have not been corrected for the expected Galactic extinction along the line of sight corresponding to a large reddening of E_{B-V} = 1.1 mag. All photometry is on the UVOT flight system described in Poole et al. (2008, MNRAS, 383, 627). //////////////////////////////////////////////////////////////////////// TITLE: GCN CIRCULAR NUMBER: 8044 SUBJECT: GRB 080727C, Swift-BAT refined analysis DATE: 08/07/28 20:46:16 GMT FROM: Scott Barthelmy at NASA/GSFC E. Fenimore (LANL), S. D. Barthelmy (GSFC), W. Baumgartner (GSFC/UMBC), J. Cummings (GSFC/UMBC), N. Gehrels (GSFC), H. Krimm (GSFC/USRA), C. Markwardt (GSFC/UMD), K. McLean (GSFC/UMD), D. Palmer (LANL), A. Parsons (GSFC), T. Sakamoto (GSFC/UMBC), G. Sato (ISAS), M. Stamatikos (GSFC/ORAU), J. Tueller (GSFC), T. Ukwatta (GWU) (i.e. the Swift-BAT team): Using the data set from T-239 to T+843 sec from recent telemetry downlinks, we report further analysis of BAT GRB 080727C (trigger #318170) (Parsons, et al., GCN Circ. 8035). The BAT ground-calculated position is RA, Dec = 32.638, 64.130 deg which is RA(J2000) = 02h 10m 33.2s Dec(J2000) = +64d 07' 48.6" with an uncertainty of 1.0 arcmin, (radius, sys+stat, 90% containment). The partial coding was 77%. The mask-weighted light curve shows several overlapping peaks starting at ~T-5 sec and ending at ~T+200 sec. T90 (15-350 keV) is 79.7 +- 8.8 sec (estimated error including systematics). The time-averaged spectrum from T-3.3 to T+116.3 sec is best fit by a power law with an exponential cutoff. This fit gives a photon index 0.87 +- 0.20, and Epeak of 143.2 +- 50.0 keV (chi squared 66 for 56 d.o.f.). For this model the total fluence in the 15-150 keV band is 5.2 +- 0.2 x 10^-6 erg/cm2 and the 1-sec peak flux measured from T+15.23 sec in the 15-150 keV band is 2.3 +- 0.2 ph/cm2/sec. A fit to a simple power law gives a photon index of 1.30 +- 0.05 (chi squared 81 for 57 d.o.f.). 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/318170/BA/ //////////////////////////////////////////////////////////////////////// TITLE: GCN CIRCULAR NUMBER: 8045 SUBJECT: GRB 080727B: GROND redshift limit DATE: 08/07/28 21:21:10 GMT FROM: Jochen Greiner at MPI T. Kruehler, J. Greiner, F. Schrey, C. Clemens, A. Yoldas (all MPE Garching), A. Kupcu Yoldas (ESO) and G. Szokoly (Eoetvoes Univ., Budapest) report on behalf of the GROND team: Since telescope pointing constraints did not allow a prompt observation of GRB 080727B (Swift trigger 318101, Immler et al. 2008, GCN #8022), GROND (Greiner et al. 2008, PASP 120, 405), mounted at the 2.2m ESO/MPI telescope at La Silla Observatory (Chile), started observations in g'r'i'z'JHK only on Jul 27, 23:08 UT, nearly 15 hrs after the burst. Under mediocre conditions a total of 90 min effective exposure in g'r'i'z' and 76 min in JHK was collected. Correcting for foreground extinction of A_V = 6.15 (Schlegel et al. 1998), we measure the following AB magnitudes/limits: g'>17.7, r'>19.7, i'>19.9, z'=19.8+-0.1, J=19.45+-0.15, H=19.2+-0.1, K=19.0+-0.15. The corresponding SED is well fit by a single power law with slope 0.85, with no evidence of additional (intrinsic) extinction, and with the i'-limit being consistent with that power law. Our SED power law has an extinction-corrected R-H=1.0. The best fit Hyper-z redshift to our data gives z=5.5-6.5, with a firm upper limit of 6.7. Given the non-constraining upper limits at i' and bluer, no lower limit can be placed. If the color R-H = 3.24 mag from the combination of KAIT (Li et al. 2008, GCN #8024) and REM data (D'Avanzo et al. 2008, GCN #8037) is correct, then the redshift of GRB 080727B would be larger than 5.8. //////////////////////////////////////////////////////////////////////// TITLE: GCN CIRCULAR NUMBER: 8046 SUBJECT: GRB 080727B: KAIT photometry and an early lightcurve break DATE: 08/07/28 23:49:10 GMT FROM: Weidong Li at UC Berkeley KAIT/LOSS W. Li, R. Chornock, D. A. Perley, J. S. Bloom, and A. V. Filippenko, University of California at Berkeley, on behalf of the KAIT GRB team; D. A. Kann, TLS Tautenburg, report: We have analyzed the KAIT observations of the OA of GRB 080727B as reported in Li et al. (GCN 8024). The imaging sequence started with 10 x 2 s unfiltered exposures, with the OA detected on each frame. A series of 20 s V, I, and unfiltered images were then obtained, and the OA was detected in the first couple of I and unfiltered images. Additional photometry (calibrated to USNO B1): UT start exptime filter mag err 08:14:46 2 s clear 18.98 0.28 08:16:03 20 s clear 19.64 0.07 08:17:35 20 s clear 20.68 0.23 Our GRB pipeline used more than 100 USNO B1 stars in calculating the photometric zero point. However, we suspect that the USNO B1 calibration for the GRB field may be significantly off. Based on our experience in the limiting magnitude of the KAIT 2 s and 20 s unfiltered images, we estimate that the above photometry and those reported in GCN 8024 should be made brighter by 1.0 - 2.0 mag. The corrected KAIT photometry, together with the REM NIR detection (D'Avanzo et al. GCN 8037), suggests an optical - NIR color of R-H (Vega) = 1.2 to 2.2 mag, which is consistent with the SED fit from the GROND observations (predicted R-H (AB) = 1.0 mag; Kruehler et al. GCN 8045). The KAIT unfiltered light curve of GRB 080727B can be well fit by a broken power-law with an index of 1.08 +/- 0.07 between t = 49 s to 169 s, and 1.88 +/- 0.21 between t= 169 s and 524 s. Such an early break in the light curve is quite extraordinary. We plan to obtain photometric calibrations of the GRB field in the upcoming photometric nights at Lick Observatory. //////////////////////////////////////////////////////////////////////// TITLE: GCN CIRCULAR NUMBER: 8047 SUBJECT: GRB 080727C: TAROT Calern observatory optical observations DATE: 08/07/29 11:55:52 GMT FROM: Bruce Gendre at LAM-OAMP Gendre, B. (LAM/CNRS), Klotz, A. (CESR-OMP), Boer M. (OHP), Atteia J.L. (LATT-OMP) report: We imaged the field of GRB 080727 detected by SWIFT (trigger 318170) with the TAROT robotic telescope (D=25cm) located at the Calern observatory, France. The observations started 790.7s after the GRB trigger (765.8s after the notice). The elevation of the field increased from from 38 degrees above horizon and weather conditions were good. The date of trigger : t0 = 2008-07-27T23:07:35.040 At the enhanced XRT position given by Osborne et al. (GCN #8038) we do not detect any optical transient. We co-added a series of exposures: t0+857.5s to t0+1850.1s : R > 18.5 Magnitudes were estimated with the nearby USNO-B1 stars and are not corrected for galactic dust extinction. N.B. Galactic coordinates are lon=131.4275 lat= +2.5930 and the galactic extinction in R band is 2.8 magnitudes estimated from D. Schlegel et al. 1998ApJ...500..525S. This message may be cited. //////////////////////////////////////////////////////////////////////// TITLE: GCN CIRCULAR NUMBER: 8048 SUBJECT: GRB 080727A: Early IR observations DATE: 08/07/29 15:12:05 GMT FROM: Andrew Levan at U.of Leicester A.J. Levan (U. Warwick) and K. Wiersema (U. Leicester) report for a larger collaboration: We observed the location of GRB 080727A (Immler et al. GCN 8021) using UKIRT. A series of K-band exposures were taken beginning at 06:24:51 UT, roughly 30 minutes after the burst, a total of 720s of observtions were taken (36x20s). We find no evidence for any source within the XRT error circle (Evans et al. GCN 8025) for GRB 080727A, down to a limit of K=19.8 mag (3-sigma). Comparing this limit to the extrapolated X-ray flux 30 minutes post-burst implies that the observed X-ray to optical/IR spectral slope was beta_KX < ~0.8, thus the non-detection in the IR is likely down to the rapid fading of the afterglow, rather than suppression of the optical/IR flux. We thank the staff of UKIRT for their rapid response to these alerts. //////////////////////////////////////////////////////////////////////// TITLE: GCN CIRCULAR NUMBER: 8049 SUBJECT: GRB 080727B: IR photometry DATE: 08/07/29 15:15:00 GMT FROM: Andrew Levan at U.of Leicester A.J. Levan (U. Warwick) and K. Wiersema (U. Leicester) report for a larger collaboration: We observed the location of GRB 080727B (Immler et al. GCN 8022) using UKIRT. The automatic observations begin at 08:27:13 UT, roughly 800 seconds after the burst. An initial set of K-band observations were acquired, followed by a shallower JHK sequence. At the location of the X-ray (Goad et al. GCN 8026) and optical/IR afterglows (D'Avanzo et al. GCN 8023; Li et al. GCN 8024) we clearly identify the fading afterglow of GRB080727B in all filters. The photometry, calibrated against several 2MASS stars within the field of view is shown below: =========================================== T_s T_s-T_b Band Mag err =========================================== 08:27:13 0.00959 K 13.952 0.03 08:31:38 0.01266 K 14.243 0.03 08:36:03 0.01573 K 14.392 0.03 08:50:08 0.02551 K 14.952 0.05 09:00:10 0.03248 K 15.276 0.05 09:10:09 0.03940 K 15.549 0.05 =========================================== 08:47:04 0.023389 H 16.144 0.06 08:58:06 0.031042 H 16.560 0.06 09:07:05 0.037280 H 16.775 0.08 ========================================== 08:43:13 0.02071 J 17.855 0.10 08:53:15 0.02767 J 18.300 0.10 09:03:16 0.03463 J 18.626 0.11 =========================================== *Data have not been corrected for the significant foreground extinciton The K-band is suggestive of a break occurring at t_b ~ 1600s, with pre- and post-break slopes of alpha_1 =0.84 and alpha_2 =1.26. The initial slope is significantly shallower than that suggested by the KAIT observations (Li et al GCN 8046), and implies either that the afterglow decay flatenned after those observations, or that the optical and IR were not tracking eachother in this case. We thank the staff of UKIRT for their rapid response to these alerts. //////////////////////////////////////////////////////////////////////// TITLE: GCN CIRCULAR NUMBER: 8050 SUBJECT: GRB 080727C: Suzaku WAM observation of the prompt emission DATE: 08/08/01 11:12:42 GMT FROM: Kazutaka Yamaoka at Aoyama Gakuin U K. Yamaoka, S. Sugita (Aoyama Gakuin U.), M. Ohno, M. Kokubun, M. Suzuki, T. Takahashi (ISAS/JAXA), Y.E. Nakagawa, T. Tamagawa (RIKEN), T. Uehara, T. Takahashi, Y. Fukazawa, C. Kira, Y. Hanabata (Hiroshima U.), M. Tashiro, Y. Terada, Y. Urata, A. Endo, K. Onda, N. Kodaka, K. Morigami, T. Sugasahara, W. Iwakiri (Saitama U.), T. Enoto, K. Nakazawa, K. Makishima (Univ. of Tokyo), E. Sonoda, M. Yamauchi, H. Tanaka, R. Hara, N. Ohmori (Univ. of Miyazaki), S. Hong (Nihon U.), on behalf of the Suzaku WAM team, report: The long 080727C (Swift/BAT trigger #318170; Parsons et al., GCN 8035) triggered the Suzaku Wide-band All-sky Monitor (WAM) which covers an energy range of 50 keV - 5 MeV at 23:07:51.558 UT (=T0). The observed light curve shows two peaks, starting at T0-13s, ending at T0+70s, with a duration (T90) of about 54 seconds. The fluence in 150 - 1000 keV was (6.0 +/- 0.7) x 10^-6 erg/cm^2. The 1-s peak flux measured from T0+9s was 0.78 +/- 0.12 photons/cm^2/s in the same energy range. Preliminary result shows that the time-averaged spectrum from T0-7s to T0+47s is fitted by a single power-law with a photon index of 1.83 +/- 0.18 in the 150 - 1000 keV range (chi^2/d.o.f = 6.1/11). All the quoted errors are at statistical 90% confidence level, in which the systematic uncertainties are not included. The light curves with 1/64 sec time resolution for this burst are now available at: http://www.astro.isas.jaxa.jp/suzaku/HXD-WAM/WAM-GRB/grb/trig/grb_table.html //////////////////////////////////////////////////////////////////////// TITLE: GCN CIRCULAR NUMBER: 8074 SUBJECT: GRB 080727B: Late VLT imaging DATE: 08/08/06 05:38:15 GMT FROM: Thomas Kruehler at MPE/MPI T. Kruehler, J. Greiner (MPE Garching) and S. Klose (Tautenburg) report: We triggered VLT/FORS imaging of the field of the Swift GRB 080727B (Immler et al. 2008, GCN #8022). A series of exposures were obtained in Rc (6*120s), Bessel I (5*120s) and Gunn z (4*120s) starting from 06:19 UT on 2008-07-29, roughly 46 hours after the burst. We marginally detect the optical afterglow (Li et al, 2008, GCN #8024) in the stacked I and z frames at 24.7 +- 0.3 mag (I) and 23.9 +- 0.5 mag (z), calibrated against USNO-B1 stars. Given the large errors and the uncertain and high foreground extinction, this is consistent with the power law reported in Kruehler et al (2008, GCN #8045) and puts the upper redshift limit to ~5. The 3 sigma upper limit in Rc (>25.5 mag) is above that power law and does not constrain the shape of the spectral energy distribution or the redshift. We thank the ESO/VLT staff for the perfect support.