//////////////////////////////////////////////////////////////////////// TITLE: GCN CIRCULAR NUMBER: 9879 SUBJECT: GRB 090904: Swift detection of a burst DATE: 09/09/04 01:18:05 GMT FROM: Scott Barthelmy at NASA/GSFC M. Perri (ASDC), S. D. Barthelmy (GSFC), W. H. Baumgartner (GSFC/UMBC), D. N. Burrows (PSU), V. D'Elia (ASDC), S. T. Holland (CRESST/USRA/GSFC), J. A. Kennea (PSU), F. E. Marshall (NASA/GSFC), M. H. Siegel (PSU), M. Stamatikos (OSU/NASA/GSFC), M. A. Stark (PSU) and T. N. Ukwatta (GSFC/GWU) report on behalf of the Swift Team: At 01:01:06 UT, the Swift Burst Alert Telescope (BAT) triggered and located GRB 090904 (trigger=361830). Swift slewed immediately to the burst. The BAT on-board calculated location is RA, Dec 100.882, +50.206 which is RA(J2000) = 06h 43m 32s Dec(J2000) = +50d 12' 23" with an uncertainty of 3 arcmin (radius, 90% containment, including systematic uncertainty). The BAT light curve shows a small peak at T_zero and then two large peaks at T+130 and T+175 sec with a duration of at least 200 sec. The peak count rate was ~2500 counts/sec (15-350 keV), at ~T+130 sec after the trigger. The XRT began observing the field at 01:05:38.6 UT, 271.7 seconds after the BAT trigger. XRT found a bright, uncatalogued, fading X-ray source located at RA, Dec 100.8816, +50.2040 which is equivalent to: RA(J2000) = 06h 43m 31.58s Dec(J2000) = +50d 12' 14.4" with an uncertainty of 5.2 arcseconds (radius, 90% containment). This location is 7.3 arcseconds from the BAT onboard position, within the BAT error circle. No event data are yet available to determine the column density using X-ray spectroscopy. The XRT prompt light curve shows a large flare peaking about 30s after the start of the XRT observations. The initial flux in the 2.5 s image was 1.71e-09 erg cm^-2 s^-1 (0.2-10 keV). UVOT took a finding chart exposure of 150 seconds with the White filter starting 141 seconds after the BAT trigger. No credible afterglow candidate has been found in the initial data products. Because part of the 2.7'x2.7' sub-image was not received, the overlap with the XRT error circle is uncertain. 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 expected extinction corresponding to E(B-V) of 0.10. Burst Advocate for this burst is M. Perri (perri AT asdc.asi.it). 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: 9880 SUBJECT: GRB 090904A: ROTSE-III Optical Limits DATE: 09/09/04 01:25:32 GMT FROM: Shashi Bhushan Pandey at ROTSE S. B. Pandey (U Mich), W. Rujopakarn (Steward), W. Zheng (U Mich) report on behalf of the ROTSE collaboration: ROTSE-IIId, located at the Turkish National Observatory at Bakirlitepe, Turkey, responded to GRB 090904A (Swift trigger 361830; Perri M., GCN 9879), producing images beginning 9.5 s after the GCN notice time. An automated response took the first image at 01:02:31.6 UT, 84.7 s after the burst, and during the gamma-ray emission, under fair 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. Individual images have limiting magnitudes ranging from 15.8-16.6; we set the following specific limits. start UT end UT t_exp(s) mlim t_start-tGRB(s) Coadd? -------------------------------------------------------------------- 01:02:31.5 01:02:36.5 5 15.8 84.6 N 01:04:48.1 01:09:27.0 278 17.8 221.2 Y //////////////////////////////////////////////////////////////////////// TITLE: GCN CIRCULAR NUMBER: 9884 SUBJECT: GRB 090904A: NOT observations DATE: 09/09/04 10:50:17 GMT FROM: Pall Jakobsson at U of Iceland D. Malesani (DARK/NBI), P. Jakobsson (U. Iceland), N. Tanvir (U. Leicester) and I. Ilyin (AIP) report on behalf of a larger collaboration: We observed the field of GRB 090904A (Perri et al., GCN 9879) with the Nordic Optical Telescope equipped with StanCam. Observations were carried out on 2009 Sept 4.17 (3.1 hr after the GRB) in the R- and I-bands. No objects are detected inside the XRT error circle to a limit of R > 23. However, just outside the error circle at RA(J2000) = 06:43:32.33 Dec(J2000) = +50:12:12.4 there is an object with R = 22 +/- 0.2 mag (calibrated against several nearby USNO-B1 stars). If weather permits, further observations are planned tonight to estimate whether the object is fading. //////////////////////////////////////////////////////////////////////// TITLE: GCN CIRCULAR NUMBER: 9885 SUBJECT: GRB 090904A: Enhanced Swift-XRT position DATE: 09/09/04 12:16:03 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 1030 s of XRT Photon Counting mode data and 1 UVOT images for GRB 090904A, 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 = 100.88052, +50.20366 which is equivalent to: RA (J2000): 06h 43m 31.33s Dec (J2000): +50d 12' 13.2" 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) 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: 9886 SUBJECT: GRB090904A: Correction to enhanced XRT position DATE: 09/09/04 12:32:00 GMT FROM: Phil Evans at U of Leicester P.A. Evans (U. Leicester) reports on behalf of the Swift-XRT team: The automatic enhanced XRT position (GCN 9885) was incorrect and should be disregarded. The position was obtained by averaging all the PC data from the first orbit, however the degree of pile up in this period changes by much more than is normal (see the light curve at: http://www.swift.ac.uk/xrt_curves/00361830/). As a result, the PSF of the image did not match any of our calibrated PSFs. We apologise for any confusion. The best XRT position available is the enhanced SPER position, which was distributed as an XRT Position Update GCN notice about at 01:27 UT. This position is RA, Dec = 100.8858, 50.2038, which corresponds to RA(J2000.0) = 06h 43m 32.59s Dec (J2000.0) = +50d 12' 13.6" with an uncertainty of 2.3 arcsec (radius, 90% confidence). This circular is an official product of the Swift-XRT team. //////////////////////////////////////////////////////////////////////// TITLE: GCN CIRCULAR NUMBER: 9888 SUBJECT: GRB 090904A: Swift-BAT refined analysis DATE: 09/09/04 13:16:39 GMT FROM: Scott Barthelmy 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), M. Perri (ASDC), 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 090904A (trigger #361830) (Perri, et al., GCN Circ. 9879). The BAT ground-calculated position is RA, Dec = 100.855, 50.235 deg, which is RA(J2000) = 06h 43m 25.2s Dec(J2000) = +50d 14' 06.9" with an uncertainty of 3.0 arcmin, (radius, sys+stat, 90% containment). The partial coding was 75%. The mask-weighted light curve shows low level emission starting at ~T-40 sec, with a small peak at ~T+5 sec. Then there was a larger peak at ~T+50 sec, and then the largest peak (FRED-like) starting at ~T+123 sec, peaking at ~T+128 sec. Riding on that tail is a peak ~T+173. The event is over in the BAT energy band at ~T+240 sec. T90 (15-350 keV) is 122 +- 10 sec (estimated error including systematics). The time-averaged spectrum from T+29.3 to T+186.3 sec is best fit by a simple power-law model. The power law index of the time-averaged spectrum is 2.01 +- 0.10. The fluence in the 15-150 keV band is 3.0 +- 0.2 x 10^-6 erg/cm2. The 1-sec peak photon flux measured from T+127.07 sec in the 15-150 keV band is 1.9 +- 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/361830/BA/ //////////////////////////////////////////////////////////////////////// TITLE: GCN CIRCULAR NUMBER: 9891 SUBJECT: GRB 090904A: Enhanced Swift XRT position DATE: 09/09/04 14:28:45 GMT FROM: Phil Evans at U of Leicester P.A. Evans (U. Leicester) reports on behalf of the Swift-XRT team. With 6 ks of XRT data, and 5 UVOT images from recent data downlinks we have generated an enhanced XRT position for GRB 090904A, which does not include the problematic first image and is thus reliable. The enhanced position is RA, Dec = 100.88480, +50.20300 which is equivalent to: RA (J2000): 06h 43m 32.35s Dec (J2000): +50d 12' 10.8" with an uncertainty of 1.6 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 is an official product of the Swift-XRT team. [GCN OPS NOTE(04sep09): Per operator's desire, the Subject-line was changed from "090404A" to "090904A". F.Marshall noticed this.] //////////////////////////////////////////////////////////////////////// TITLE: GCN CIRCULAR NUMBER: 9894 SUBJECT: GRB 090904A: Swift-XRT refined analysis DATE: 09/09/04 16:56:03 GMT FROM: Matteo Perri at ISAC/ASDC M. Perri, V. D'Elia, G. Stratta (ASDC) report on behalf of the Swift-XRT team: We have analysed the first 12 ks of XRT data for GRB 090904A (Perri et al., GCN Circ. 9879), from 134 s to 29.6 ks after the BAT trigger. The enhanced XRT position for this burst was given by Evans (GCN. Circ. 9891). During the first Swift orbit, the light-curve shows a steep decay with a large superimposed flare peaking at about T+300 s. Starting from T+1000 s, the curve is well described by a broken power-law model with temporal decay indices alpha1=0.2+/-0.1, alpha2=0.9+/-0.3 and a temporal break at around T+12 ks. A spectrum extracted from the PC mode data from T+460 s to T+29.6 ks can be fitted with an absorbed power-law model with a photon spectral index of 2.46 (+0.16,-0.26) and an absorption column density of 1.03 (+0.66,-0.64)e21 cm-2 in excess of the Galactic value of 9.3e20 cm-2 (Kalberla et al. 2005). The counts-to-observed (-unabsorbed) 0.3-10 keV flux conversion factor deduced from this spectrum is 3.3e-11 (6.2e-11) erg cm-2 count-1. Errors are given at the 90% confidence level. If the light curve continues to decay with a power-law index of 0.9, the count rate at T+24 hours will be 6e-3 count s-1, corresponding to an observed (unabsorbed) 0.3-10 keV flux of 2.0e-13 (3.7e-13) erg cm-2 s-1. The results of the XRT-team automatic analysis are available at http://www.swift.ac.uk/xrt_products/00361830. This circular is an official product of the Swift-XRT team. //////////////////////////////////////////////////////////////////////// TITLE: GCN CIRCULAR NUMBER: 9899 SUBJECT: GRB 090904A: Swift/UVOT Refined Analysis DATE: 09/09/05 05:46:33 GMT FROM: Tyler Pritchard at PSU T. A. Pritchard (PSU), C. A. Swenson (PSU) and M. Perri (ASDC) report on behalf of the Swift/UVOT team: The Swift/UVOT began settled observations of GRB 090904A, 141 seconds after the BAT trigger (M. Perri et al., GCN Circ. 9879). We do not detect any source at the UVOT-enhanced XRT position (M.R. Goad, GCN Circ. 9885). The 3-sigma upper limits for the exposures are: Filter T_start(s) T_stop(s) Exp(s) Mag (3-sigma upper limit) ------------------------------------------------------------- white 141 1189 341 > 21.57 v 629 1078 58 > 18.72 b 555 1177 58 > 19.59 u 299 1152 285 > 20.43 uvw1 679 1127 58 > 19.11 uvm2 827 847 19 > 17.61 uvw2 605 1054 58 > 19.17 ------------------------------------------------------------- The quoted upper limits have not been corrected for the expected Galactic extinction corresponding to a reddeningalong the line of sight of E_(B-V) = 0.1 mag (Schlegel et al., 1998, ApJS, 500, 525). All photometry is on the UVOT photometric system described in Poole et al. (2008, MNRAS, 383, 627). //////////////////////////////////////////////////////////////////////// TITLE: GCN CIRCULAR NUMBER: 10000 SUBJECT: GRB 090904A: afterglow confirmation DATE: 09/10/08 05:16:08 GMT FROM: Daniele Malesani at Dark Cosmology Centre, Niels Bohr Inst Daniele Malesani (DARK/NBI), Pall Jakobsson (Univ. Iceland), and Ilya Ilyin (AIP), report on behalf of a larger collaboration: We observed again the field of GRB 090904A (Perri et al., GCN 9879) with the NOT equipped with StanCam. Observations were carried out in the R band, for a total exposure time of 30 min, with a mean time September 6.218 UT (2.176 days after the GRB trigger). The object identified in our previous epoch of imaging (Malesani et al., GCN 9884) has clearly faded and is hardly detectable, if at all. A faint source is visible at its position, with magnitude R = 24.0 +- 0.3. If real, the inferred decay slope is alpha = 0.55 +- 0.12, assuming F(t) propto t^-alpha. The value of alpha is shallower than usually found at late times, and may indicate some host contribution or an unusual light curve. The position of the transient is consistent with the latest available UVOT-enhanced XRT position (Goad et al., GCN 9885; see also http://www.swift.ac.uk/xrt_positions/index.php). We thus identify the object as the optical afterglow of GRB 090904A. A finding chart comparing the two epochs can be found at the following URL: http://www.astro.ku.dk/~malesani/GRB/090904A/GRB090904A_finder_NOT.jpg