//////////////////////////////////////////////////////////////////////// TITLE: GCN CIRCULAR NUMBER: 8964 SUBJECT: GRB 090309: Swift detection of a burst DATE: 09/03/09 23:50:52 GMT FROM: David Burrows at PSU/Swift P. A. Evans (U Leicester), W. H. Baumgartner (GSFC/UMBC), D. N. Burrows (PSU), C. Guidorzi (U Ferrara), S. T. Holland (CRESST/USRA/GSFC), W.B Landsman (GSFC), F. E. Marshall (NASA/GSFC), C. Pagani (PSU), K. L. Page (U Leicester), D. M. Palmer (LANL), A. M. Parsons (GSFC), B. A. Rowlinson (U Leicester), T. Sakamoto (NASA/UMBC), M. H. Siegel (PSU), T. N. Ukwatta (GSFC/GWU) and L. Vetere (PSU) report on behalf of the Swift Team: At 23:29:13 UT, the Swift Burst Alert Telescope (BAT) triggered and located GRB 090309 (trigger=345945). Swift slewed immediately to the burst. The BAT on-board calculated location is RA, Dec 284.981, -25.264 which is RA(J2000) = 18h 59m 55s Dec(J2000) = -25d 15' 50" with an uncertainty of 3 arcmin (radius, 90% containment, including systematic uncertainty). The BAT light curve showed a peak with a with a duration of about 3 sec. There is a hint of a secondary peak around T+25 sec with a duration of 10 sec. The peak count rate was ~1400 counts/sec (15-350 keV), at ~1 sec after the trigger. The XRT began observing the field at 23:30:32.5 UT, 79.3 seconds after the BAT trigger. Using promptly downlinked data we find an uncatalogued X-ray source with an enhanced position: RA, Dec 284.9730, -25.2611 which is equivalent to: RA(J2000) = 18h 59m 53.51s Dec(J2000) = -25d 15' 39.8" with an uncertainty of 3.3 arcseconds (radius, 90% containment). This location is 28 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 1.07e+21 cm^-2 (Kalberla et al. 2005). UVOT took a finding chart exposure of 150 seconds with the White filter starting 81 seconds after the BAT trigger. No credible afterglow candidate has been found in the initial data products. The 2.7'x2.7' sub-image covers 100% of the XRT error circle. The typical upper limit for this image is approximately white = 19 mag. No correction has been made for the expected extinction corresponding to E(B-V) of 0.23. Burst Advocate for this burst is P. A. Evans (pae9 AT star.le.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: 8967 SUBJECT: GRB 090309, Swift-BAT refined analysis DATE: 09/03/10 14:02:00 GMT FROM: Takanori Sakamoto at NASA/GSFC D. M. Palmer (LANL), 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), 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+362 sec from the recent telemetry downlink, we report further analysis of BAT GRB 090309 (trigger #345945) (Evans, et al., GCN Circ. 8964). The BAT ground-calculated position is RA, Dec = 284.978, -25.274 deg which is RA(J2000) = 18h 59m 55.5s Dec(J2000) = -25d 16' 42.0" with an uncertainty of 2.3 arcmin, (radius, sys+stat, 90% containment). The partial coding was 61%. The mask-weighted light curve shows a single peak starting at T-1 sec, peaking around T+1 sec, and ending at T+2 sec. T90 (15-350 keV) is 3.0 +- 1.4 sec (estimated error including systematics). The time-averaged spectrum from T-0.8 to T+2.2 sec is best fit by a simple power-law model. The power law index of the time-averaged spectrum is 1.36 +- 0.33. 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+0.18 sec in the 15-150 keV band is 0.9 +- 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/345945/BA/ //////////////////////////////////////////////////////////////////////// TITLE: GCN CIRCULAR NUMBER: 8969 SUBJECT: GRB 090309: Enhanced Swift-XRT position DATE: 09/03/10 15:00:31 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 1230 s of XRT Photon Counting mode data and 3 UVOT images for GRB 090309, 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 = 284.97425, -25.26099 which is equivalent to: RA (J2000): 18h 59m 53.82s Dec (J2000): -25d 15' 39.6" with an uncertainty of 2.0 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: 8970 SUBJECT: GRB 090309: Swift-XRT refined analysis DATE: 09/03/10 15:43:56 GMT FROM: Phil Evans at U of Leicester P. A. Evans (U Leicester) reports on behalf of the Swift-XRT team: We have analysed 5.5 ks of XRT data for GRB 090309 (Evans et al. GCN Circ. 8964), from 86 s to 12.4 ks after the BAT trigger. The data are entirely in Photon Counting (PC) mode. The enhanced XRT position for this burst was given by Goad et al. (GCN. Circ 8969). The light curve can be modelled with a power-law decay with a decay index of alpha=0.38 (+0.08, -0.09). A spectrum formed from the PC mode data can be fitted with an absorbed power-law with a photon spectral index of 2.2 (+/-0.3). The best-fitting absorption column is 2.8 (+1.5, -1.1) x 10^21, in excess of the Galactic value of 1.1 x 10^21 cm^-2 (Kalberla et al. 2005). The counts to observed (unabsorbed) 0.3-10 keV flux conversion factor deduced from this spectrum is 4.0 x 10^-11 (6.8 x 10^-11) erg cm^-2 count^-1. If the light curve continues to decay with a power-law decay index of 0.38, the count rate at T+24 hours will be 0.012 count s^-1, corresponding to an observed (unabsorbed) 0.3-10 keV flux of 4.8 x 10^-13 (8.2 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/00345945. This circular is an official product of the Swift-XRT team. //////////////////////////////////////////////////////////////////////// TITLE: GCN CIRCULAR NUMBER: 8971 SUBJECT: GRB 090309B: Fermi GBM detection DATE: 09/03/10 16:12:00 GMT FROM: Alexander van der Horst at NASA/MSFC A.J. van der Horst (NASA/MSFC/ORAU) reports on behalf of the Fermi GBM Team: "At 18:25:07.19 UT on 9 March 2009, the Fermi Gamma-ray Burst Monitor (GBM) triggered and located GRB 090309B (trigger 258315909 / 090309.767). The on-ground calculated location, using the Fermi GBM trigger data, is RA = 168.4, Dec = -55.0 (J2000 degrees, equivalent to J2000 11h13m, -55d01'), with a statistical uncertainty of 2.6 degrees (radius, 1-sigma containment, statistical only; there is additionally a systematic error which is currently estimated to be 2 to 3 degrees). The angle from the Fermi LAT boresight is 26 degrees. The GBM light curve consists of two main peaks, with durations of ~10 and ~25 seconds, and no significant emission above background level in between for ~25 seconds. The time-averaged spectrum over the two peaks, from T0-4.1 to T0+5.1 s and from T0+32.8 to T0+54.3 s, is best fit by a power law with an exponential high-energy cutoff. The index is -1.52 +/- 0.10 and the cutoff energy, parameterized as Epeak, is 197 +/- 65 keV (chi squared 358 for 360 d.o.f.). The fluence (8-1000 keV) in this time interval is (4.7 +/- 0.4)E-6 erg/cm^2. The 1-sec peak photon flux measured starting from T0+37.9s in the 8-1000 keV band is 4.43 +/- 0.17 ph/s/cm^2. The spectral and temporal analysis results presented above are preliminary; final results will be published in the GBM GRB Catalog." //////////////////////////////////////////////////////////////////////// TITLE: GCN CIRCULAR NUMBER: 8973 SUBJECT: GRB 090309: Swift/UVOT Upper Limits DATE: 09/03/10 22:03:58 GMT FROM: Wayne Landsman at GSFC/SSAI W.B. Landsman (NASA/GSFC) and P. Evans (U. Leicester) report on behalf of the Swift/UVOT team: The Swift/UVOT observed the field of GRB 090309 starting 82 s after the BAT trigger (Evans et al., GCN Circ. 8964). No optical afterglow is detected in the initial UVOT exposures at the refined position of the X-ray afterglow (Goad et al., GCN Circ. 8969). An r~19 field star ( GSC S9QR039837) is detected 3" from the XRT position. Three-sigma upper limits using the UVOT photometric system (Poole et al. 2008, MNRAS, 383, 627) in a 2" radius aperture for the first finding chart (FC) exposure and subsequent exposures are: Filter T_start(s) T_stop(s) Exp(s) Mag white (FC) 82 231 147 >21.0 white 82 6136 564 >21.8 v 624 17530 1317 >20.7 b 549 23995 1088 >21.4 u 294 23315 2241 >21.5 uvw1 673 22401 1998 >21.6 uvm2 648 18210 1875 >21.6 uvw2 599 16617 1318 >21.6 The values quoted above are not corrected for the Galactic extinction due to the reddening of E(B-V) = 0.23 in the direction of the burst (Schlegel et al. 1998). //////////////////////////////////////////////////////////////////////// TITLE: GCN CIRCULAR NUMBER: 8975 SUBJECT: GRB 090309A: GROND upper limits DATE: 09/03/11 00:24:38 GMT FROM: Adria C. Updike at Clemson U A. C. Updike (Clemson University), C. Clemens, and J. Greiner (MPE Garching) report on behalf of the GROND team: We observed the field of the possibly short/hard GRB 090309 (Swift trigger 345945; Evans et al., GCN #8964) simultaneously in g'r'i'z'JHK with GROND (Greiner et al. 2008, PASP 120, 405) mounted at the 2.2 m ESO/MPI telescope at La Silla Observatory (Chile). Observations started at 07:22 UT on March 10th, 7.9 hours after the GRB trigger and continued for 2.5 hours at an average seeing of 1.5" and an average airmass of 1.5. In one hour of stacked exposures, we do not detect a source within the Swift-XRT enhanced error circle (Goad et al., GCN #8969) down to g' > 23.4, r' > 23.8, i' > 23.2, z' > 23.0, J > 21.3, H > 21.0 and K > 20.3 The given limits in the AB system are derived based on calibrating the images against GROND zeropoints and 2MASS field stars and are not corrected for the Galactic foreground extinction corresponding to a reddening of E_(B-V)= 0.23 in the direction of the burst (Schlegel et al. 1998). //////////////////////////////////////////////////////////////////////// TITLE: GCN CIRCULAR NUMBER: 8982 SUBJECT: GRB 090309, Swift-BAT lag analysis DATE: 09/03/13 09:58:16 GMT FROM: Takanori Sakamoto at NASA/GSFC T. Sakamoto (GSFC/UMBC), J. P. Norris, T. N. Ukwatta (GWU/GSFC), S. D. Barthelmy (GSFC), N. Gehrels (GSFC), M. Stamatikos (GSFC/ORAU) (for the Swift-BAT team): For GRB 090309 (Evans et al. GCN Circ. 8964), we are unable to determine if this is a short or long burst. The reasons are as follows: (1) the spectral lag is 0.044 +/- 0.16 sec (between the 50-100 and 15-25 keV). (2) The T90 duration is 3.0 +- 1.4 sec (Palmer et al. GCN Circ. 8967) which is midway between the two T90 distributions. (3) The photon index is 1.36 +/- 0.33 (Palmer et al. GCN Circ. 8967) is also in the middle of the short and hard distributions (Figure 13 of Sakamoto et al., ApJS, 175, 179).