//////////////////////////////////////////////////////////////////////// TITLE: GCN CIRCULAR NUMBER: 9101 SUBJECT: GRB 090407: Swift detection of a burst DATE: 09/04/07 10:48:08 GMT FROM: David Burrows at PSU/Swift H. Ziaeepour (UCL-MSSL), S. D. Barthelmy (GSFC), W. H. Baumgartner (GSFC/UMBC), A. P. Beardmore (U Leicester), D. N. Burrows (PSU), P. A. Evans (U Leicester), N. Gehrels (NASA/GSFC), O. Godet (U Leicester), C. Guidorzi (U Ferrara), S. T. Holland (CRESST/USRA/GSFC), J. A. Kennea (PSU), N. P. M. Kuin (MSSL), J. Mao (INAF-OAB), P. T. O'Brien (U Leicester), S. R. Oates (UCL-MSSL), J. P. Osborne (U Leicester), K. L. Page (U Leicester), D. M. Palmer (LANL), P. Romano (INAF-IASFPA), B. A. Rowlinson (U Leicester), B. Sbarufatti (INAF-IASFPA), P. Schady (MSSL-UCL) and G. Stratta (ASDC) report on behalf of the Swift Team: At 10:28:25 UT, the Swift Burst Alert Telescope (BAT) triggered and located GRB 090407 (trigger=348650). Swift slewed immediately to the burst. The BAT on-board calculated location is RA, Dec 68.959, -12.665 which is RA(J2000) = 04h 35m 50s Dec(J2000) = -12d 39' 53" with an uncertainty of 3 arcmin (radius, 90% containment, including systematic uncertainty). The BAT light curve showed a multiple-peaked structure with a duration of at least 150 sec, including a small peak at T+135 sec, during the XRT/UVOT observations. The peak count rate was ~2390 counts/sec (15-350 keV), at ~1 sec after the trigger. The XRT began observing the field at 10:29:58.7 UT, 93.0 seconds after the BAT trigger. Using promptly downlinked data we find a fading, uncatalogued X-ray source located at RA, Dec 68.98074, -12.67921 which is equivalent to: RA(J2000) = 04h 35m 55.38s Dec(J2000) = -12d 40' 45.2" with an uncertainty of 3.8 arcseconds (radius, 90% containment). This location is 91 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 (3.68e+20 cm^-2, Kalberla et al. 2005), with an excess column of 2.5 (+1.79/-1.62) x 10^21 cm^-2 (90% confidence). UVOT took a finding chart exposure of 150 seconds with the White filter starting 97 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 25% of the BAT error circle and 0% of the XRT error circle. The typical 3-sigma upper limit has been about 19.6 mag. The 8'x8' region for the list of sources generated on-board covers 100% of the BAT and XRT error circles. 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 H. Ziaeepour (hz 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: 9102 SUBJECT: GRB 090407: ROTSE-III Optical Limits DATE: 09/04/07 11:06:47 GMT FROM: Brad Schaefer at LSU B. E. Schaefer (Louisiana State), F. Yuan (U Mich), report on behalf of the ROTSE collaboration: ROTSE-IIIa, located at Siding Spring Observatory, Australia, responded to GRB 090407 (Swift trigger 348650; H. Ziaeepour et al., GCN 9101), producing images beginning 8.8 s after the GCN notice time. An automated response took the first image at 10:29:05.8 UT, 40.2 s after the burst, and during the gamma-ray emission, under fair conditions. We took 10 5-sec, 10 20-sec and 33 60-sec exposures. These unfiltered images are calibrated relative to USNO A2.0 (R). Imaging is on going but the source is getting low. 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 13.9-15.5; we set the following specific limits. start UT end UT t_exp(s) mlim t_start-tGRB(s) Coadd? -------------------------------------------------------------------- 10:29:05.8 10:29:10.8 5 14.1 40.2 N 10:29:05.8 10:31:19.0 133 16.1 40.2 Y //////////////////////////////////////////////////////////////////////// TITLE: GCN CIRCULAR NUMBER: 9104 SUBJECT: GRB 090407: Swift-BAT refined analysis DATE: 09/04/07 19:52:15 GMT FROM: Scott Barthelmy at NASA/GSFC T. N. Ukwatta (GWU) 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), C. B. Markwardt (GSFC/UMD), D. M. Palmer (LANL), T. Sakamoto (GSFC/UMBC), G. Sato (ISAS), M. Stamatikos (GSFC/ORAU), J. Tueller (GSFC), H. Ziaeepour (UCL-MSSL) (i.e. the Swift-BAT team): Using the data set from T-239 to T+627 sec from recent telemetry downlinks, we report further analysis of BAT GRB 090407 (trigger #348650) (Ziaeepour, et al., GCN Circ. 9101). The BAT ground-calculated position is RA, Dec = 68.979, -12.684 deg, which is RA(J2000) = 04h 35m 54.9s Dec(J2000) = -12d 41' 02.4" with an uncertainty of 2.2 arcmin, (radius, sys+stat, 90% containment). The partial coding was 84%. The mask-weighted light curve shows two clusters of peaks. The first cluster starts at ~T-15 sec, peaks at ~T+2 sec, and returns to baseline at ~T+10 sec. The second clutser starts at ~T+130 sec, peaks at ~T+140 sec, and returns to baseline at ~T+340 sec. T90 (15-350 keV) is 310 +- 70 sec (estimated error including systematics). The time-averaged spectrum from -17.7 to 368.6 sec is best fit by a simple power-law model. The power law index of the time-averaged spectrum is 1.73 +- 0.29. The fluence in the 15-150 keV band is 1.1 +- 0.2 x 10^-6 erg/cm2. The 1-sec peak photon flux measured from T+0.45 sec in the 15-150 keV band is 0.6 +- 0.1 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/348650/BA/ //////////////////////////////////////////////////////////////////////// TITLE: GCN CIRCULAR NUMBER: 9105 SUBJECT: GRB 090407: Enhanced Swift-XRT position DATE: 09/04/07 19:56:04 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 8297 s of XRT Photon Counting mode data and 13 UVOT images for GRB 090407, 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 = 68.97908, -12.67929 which is equivalent to: RA (J2000): 04h 35m 54.98s Dec (J2000): -12d 40' 45.5" with an uncertainty of 1.4 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, arXiv:0812.3662). This circular was automatically generated, and is an official product of the Swift-XRT team. //////////////////////////////////////////////////////////////////////// TITLE: GCN CIRCULAR NUMBER: 9106 SUBJECT: GRB 090407: Swift UVOT Upper Limits DATE: 09/04/07 21:34:44 GMT FROM: Samantha Oates at MSSL S. R. Oates (MSSL-UCL) and H. Ziaeepour (MSSL-UCL) report on behalf of the Swift/UVOT team: The Swift/UVOT began observing the field of GRB 090407 98 s after the BAT trigger (Ziaeepour et al., GCN Circ. 9101). No optical afterglow is detected in the initial UVOT exposures at the refined position of the X-ray afterglow (Evans et al., GCN Circ. 9105). The 3 sigma upper limits for the finding chart (fc) and summed exposures are reported below. Filter T_start (s) T_stop Exposure Mag/3UL ------------------------------------------------------------ white fc 98 248 147 <20.50 u fc 310 559 246 <19.89 white 590 2050 303 <21.04 v 640 5550 352 <19.25 u 713 2001 136 <19.61 b 565 2026 156 <19.99 uvw1 689 1977 136 <19.35 uvm2 664 5607 207 <19.49 uvw2 615 2071 170 <19.74 The above magnitudes are not corrected for the Galactic extinction corresponding to a reddening of E_{B-V} = 0.40 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: 9107 SUBJECT: GRB 090407: Swift-XRT refined analysis DATE: 09/04/08 00:10:35 GMT FROM: Andy Beardmore at U Leicester A.P. Beardmore (U. Leicester) and H. Ziaeepour (UCL-MSSL) report on behalf of the Swift-XRT team: We have analysed the first five orbits of Swift-XRT data obtained from GRB 090407 (trigger #348650; Ziaeepour, et al., GCN Circ. 9101), comprising 273 s taken in Windowed Timing (WT) mode, starting at T+96.7 s, followed by 10.2 ks in Photon Counting (PC) mode from T+398 s to T+24.2 ks. The UVOT-enhanced position was given by Evans et al. (GCN Circ. 9105). The 0.3-10 keV X-ray light curve shows a number of flares in the first 400 s, the largest occurring from T+120 s to T+180 s, reaching a peak rate of 90 count s^-1 at T+140 s. This flare is also seen by the Swift-BAT (Ukwatta et al., GCN Circ. 9104). Further flaring is seen from ~T+200s to ~T+350 s, ending with a steep decay of slope ~4.0. After T+950 s the X-ray light curve breaks to a much shallower decay slope of 0.28 +/- 0.06. The data show spectral evolution during the flaring intervals, after which the PC mode spectrum can be modelled by an absorbed powerlaw with a photon index of 2.43 +/- 0.13 and a total absorbing column density of (2.51 +/- 0.35) x 10^21 cm^-2, which is in excess of the Galactic value of 3.7 x 10^20 cm^-2 (Kalberla et al. 2005) in the direction of the burst. The observed 0.3-10 keV flux at this time (~T+6.2 ks) is (6.29 +0.41 -0.56) x 10^-12 erg cm^-2 s^-1, which corresponds to an unabsorbed flux of 1.3 x 10^-11 erg cm^-2 s^-1. The count to observed flux conversion factor for this spectrum is 3.5 x 10^-11 erg cm-^2 count^-1. If the light curve continues to decay with the same slope of 0.28 we predict an X-ray count rate of 0.047 count s^-1 at T+24 hours after the trigger, which corresponds to an observed 0.3-10 keV flux of 1.6 x 10^-12 erg cm^-2 s^-1. However, we note that it is unlikely the light curve decay will remain this shallow at T+24 hours. The results of the XRT-team automatic analysis are available at http://www.swift.ac.uk/xrt_curves/00348650. This circular is an official product of the Swift-XRT team. //////////////////////////////////////////////////////////////////////// TITLE: GCN CIRCULAR NUMBER: 9108 SUBJECT: GRB 090407: VLT observations DATE: 09/04/08 01:02:57 GMT FROM: Daniele Malesani at Dark Cosmology Centre, Niels Bohr Inst Daniele Malesani and Johan Peter Uldall Fynbo report on behalf of a larger collaboration: We observed the field of GRB 090407 (Ziaeepour et al., GCN 9101) with the ESO VLT equipped with FORS2. Observations were carried out with mean time Apr 8.0 UT (13.7 hr after the GRB), partially during evening twilight. Inside the X-ray error circle (Evans et al., GCN 9105), no source is detected down to limiting magnitudes R > 23.8 and z(AB) > 23.8, based on archival zeropoints (accurate up to ~0.2 mag). We encourage deeper observations, possibly in the near infrared. We acknowledge significant support from the ESO staff at Paranal, in particular Gianni Marconi and Elena Mason. //////////////////////////////////////////////////////////////////////// TITLE: GCN CIRCULAR NUMBER: 9109 SUBJECT: GRB 090407: GROND upper limits DATE: 09/04/08 02:19:56 GMT FROM: Paulo M. J. Afonso at MPE P. Afonso, F. Olivares, J. Greiner and T. Kruehler (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 090407 (H. Ziaeepour et al. 2009, GCN #9101) simultaneously in the g'r'i'z'JHK bands. Observations started on April 7, at 23:34 UTC (13.1 h after the burst) and lasted for 87 minutes. In stacked images of 24 min total integration time in griz and 20 min in JHK, we do not detect any new object inside the enhanced XRT error circle (Evans et al., GCN #9105), down to the following limiting magnitudes (all in the AB system): g' > 23.7 r' > 24.1 i' > 23.5 z' > 23.3 J > 21.6 H > 21.0 K > 20.4 The upper limits have been obtained using GROND zero points and 2MASS field stars as reference. No correction has been made for the expected extinction corresponding to E(B-V) of 0.07 mag.