Gamma-ray Burst 050915

(All information courtesy of the instrument teams.)

Previous IAU Circulars

• none

• GCN/BACODINE POSITION NOTICE
  

  TITLE:           GCN/SWIFT NOTICE
  NOTICE_DATE:     Thu 15 Sep 05 11:23:03 UT
  NOTICE_TYPE:     Swift-BAT GRB Position
  TRIGGER_NUM:     155242,   Seg_Num: 0
  GRB_RA:           81.714d {+05h 26m 51s} (J2000),
                    81.770d {+05h 27m 05s} (current),
                    81.220d {+05h 24m 53s} (1950)
  GRB_DEC:         -28.030d {-28d 01' 48"} (J2000),
                   -28.026d {-28d 01' 32"} (current),
                   -28.072d {-28d 04' 17"} (1950)
  GRB_ERROR:       4.00 [arcmin radius, statistical only]
  GRB_INTEN:       4443 [cnts]    Image_Peak=186 [image_cnts]
  TRIGGER_DUR:     1.024 [sec] 
  TRIGGER_INDEX:   146     E_range: 25-100 keV
  BKG_INTEN:       29357 [cnts]
  BKG_TIME:        40944.00 SOD {11:22:24.00} UT
  BKG_DUR:         8 [sec]
  GRB_DATE:        13628 TJD;   258 DOY;   05/09/15
  GRB_TIME:        40962.31 SOD {11:22:42.31} UT
  GRB_PHI:         -148.00 [deg]
  GRB_THETA:        30.08 [deg]
  SOLN_STATUS:     0x3
  RATE_SIGNIF:     10.53 [sigma]
  IMAGE_SIGNIF:    7.68 [sigma]
  MERIT_PARAMS:     +1  +0  +0  +0  +2  +0  +0  +0  +4  +1 
  SUN_POSTN:       173.31d {+11h 33m 15s}   +2.89d {+02d 53' 21"}
  SUN_DIST:         92.72 [deg]
  MOON_POSTN:      320.08d {+21h 20m 19s}  -20.11d {-20d 06' 41"}
  MOON_DIST:       105.90 [deg]
  MOON_ILLUM:      90 [%]
  GAL_COORDS:      231.28,-29.85 [deg] galactic lon,lat of the burst (or transient)
  ECL_COORDS:       78.30,-51.13 [deg] ecliptic lon,lat of the burst (or transient)
  COMMENTS:        SWIFT-BAT GRB Coordinates.  
  COMMENTS:        This is a rate trigger.  
  COMMENTS:        A point_source was found.  
  COMMENTS:        This does not match any source in the on-board catalog.  
  COMMENTS:        This does not match any source in the ground catalog.  
  COMMENTS:        This is a GRB.  
  

• red DSS finding chart ps-file
  
  
• GCN/SWIFT NOTICE
  

  TITLE:           GCN/SWIFT NOTICE
  NOTICE_DATE:     Thu 15 Sep 05 11:24:17 UT
  NOTICE_TYPE:     Swift-XRT Nack-Position
  TRIGGER_NUM:     155242,   Seg_Num: 0
  POINT_RA:         81.739d {+05h 26m 57s} (J2000)
  POINT_DEC:       -28.025d {-28d 01' 28"} (J2000)
  GRB_DATE:        13628 TJD;   258 DOY;   05/09/15
  GRB_TIME:        41048.79 SOD {11:24:08.79} UT
  COUNTS:          15    Min_needed= 20
  STD_DEV:         0.00   Max_StdDev_for_Good=28.44 [arcsec]
  PH2_ITER:        4    Max_iter_allowed= 4
  ERROR_CODE:      1
  COMMENTS:        SWIFT-XRT Nack Position.  
  COMMENTS:        No source found in the image.  
  

• GCN/SWIFT NOTICE
  

  TITLE:           GCN/SWIFT NOTICE
  NOTICE_DATE:     Thu 15 Sep 05 11:26:14 UT
  NOTICE_TYPE:     Swift-UVOT Source List
  TRIGGER_NUM:     155242,   Seg_Num: 0
  POINT_RA:         81.739d {+05h 26m 57s} (J2000)
  POINT_DEC:       -28.025d {-28d 01' 29"} (J2000)
  POINT_ROLL:      88.201d
  GRB_DATE:        13628 TJD;   258 DOY;   05/09/15
  GRB_TIME:        41046.96 SOD {11:24:06.96} UT
  FILTER:          3, V
  BKG_MEAN:        0.000000
  N_STARS:         36
  X_OFFSET:        476 [pixels]
  Y_OFFSET:        555 [pixels]
  X_MAX:           1435 [pixels]
  Y_MAX:           1514 [pixels]
  DET_THRESH:      5
  PHOTO_THRESH:    2
  SL_URL:          sw00155242000msufc.fits
  SUN_POSTN:       173.31d {+11h 33m 15s}   +2.89d {+02d 53' 20"}
  SUN_DIST:         92.70 [deg]
  MOON_POSTN:      320.09d {+21h 20m 22s}  -20.11d {-20d 06' 22"}
  MOON_DIST:       105.91 [deg]
  MOON_ILLUM:      90 [%]
  GAL_COORDS:      231.28,-29.82 [deg] galactic lon,lat of the pointing direction
  ECL_COORDS:       78.34,-51.13 [deg] ecliptic lon,lat of the pointing direction
  COMMENTS:        SWIFT-UVOT Source List.  
  

• GCN/SWIFT NOTICE
  

  TITLE:           GCN/SWIFT NOTICE
  NOTICE_DATE:     Thu 15 Sep 05 11:26:56 UT
  NOTICE_TYPE:     Swift-UVOT Processed Source List
  TRIGGER_NUM:     155242,   Seg_Num: 0
  POINT_RA:         81.739d {+05h 26m 57s} (J2000)
  POINT_DEC:       -28.025d {-28d 01' 29"} (J2000)
  POINT_ROLL:      88.201d
  GRB_DATE:        13628 TJD;   258 DOY;   05/09/15
  GRB_TIME:        41046.96 SOD {11:24:06.96} UT
  FILTER:          3, V
  BKG_MEAN:        0.000000
  N_STARS:         36
  X_OFFSET:        476 [pixels]
  Y_OFFSET:        555 [pixels]
  X_MAX:           1435 [pixels]
  Y_MAX:           1514 [pixels]
  DET_THRESH:      5
  PHOTO_THRESH:    2
  SL_URL:          sw00155242000msufc.fits
  SUN_POSTN:       173.31d {+11h 33m 15s}   +2.89d {+02d 53' 20"}
  SUN_DIST:         92.70 [deg]
  MOON_POSTN:      320.09d {+21h 20m 22s}  -20.11d {-20d 06' 22"}
  MOON_DIST:       105.91 [deg]
  MOON_ILLUM:      90 [%]
  GAL_COORDS:      231.28,-29.82 [deg] galactic lon,lat of the pointing direction
  ECL_COORDS:       78.34,-51.13 [deg] ecliptic lon,lat of the pointing direction
  COMMENTS:        SWIFT-UVOT Processed Source List.  
  COMMENTS:        If you have elected to receive attachments:  
  COMMENTS:        The uvot_catalog_srclist.fits file does not exist; skipping the attachment.  
  

  
• GCN/SWIFT NOTICE
  

  TITLE:           GCN/SWIFT NOTICE
  NOTICE_DATE:     Thu 15 Sep 05 11:27:21 UT
  NOTICE_TYPE:     Swift-BAT GRB Lightcurve
  TRIGGER_NUM:     155242,   Seg_Num: 0
  GRB_RA:           81.714d {+05h 26m 51s} (J2000),
                    81.770d {+05h 27m 05s} (current),
                    81.220d {+05h 24m 53s} (1950)
  GRB_DEC:         -28.030d {-28d 01' 48"} (J2000),
                   -28.026d {-28d 01' 32"} (current),
                   -28.072d {-28d 04' 17"} (1950)
  GRB_DATE:        13628 TJD;   258 DOY;   05/09/15
  GRB_TIME:        40962.31 SOD {11:22:42.31} UT
  TRIGGER_INDEX:   146
  GRB_PHI:         -148.00 [deg]
  GRB_THETA:        30.08 [deg]
  DELTA_TIME:      65491.00 [sec]
  TRIGGER_DUR:     1.024 [sec] 
  LC_URL:          sw00155242000msb.lc
  SUN_POSTN:       173.31d {+11h 33m 15s}   +2.89d {+02d 53' 21"}
  SUN_DIST:         92.72 [deg]
  MOON_POSTN:      320.08d {+21h 20m 19s}  -20.11d {-20d 06' 41"}
  MOON_DIST:       105.90 [deg]
  MOON_ILLUM:      90 [%]
  GAL_COORDS:      231.28,-29.85 [deg] galactic lon,lat of the pointing direction
  ECL_COORDS:       78.30,-51.13 [deg] ecliptic lon,lat of the pointing direction
  COMMENTS:        SWIFT-BAT GRB Lightcurve.  
  COMMENTS:           
  COMMENTS:        The next comments were copied from the BAT_POS Notice:  
  COMMENTS:        This is a rate trigger.  
  COMMENTS:        A point_source was found.  
  COMMENTS:        This does not match any source in the on-board catalog.  
  COMMENTS:        This does not match any source in the ground catalog.  
  COMMENTS:        This is a GRB.  
  

  
• GCN/SWIFT NOTICE
  

  TITLE:           GCN/SWIFT NOTICE
  NOTICE_DATE:     Thu 15 Sep 05 11:27:04 UT
  NOTICE_TYPE:     Swift-UVOT Image
  TRIGGER_NUM:     155242,   Seg_Num: 0
  POINT_RA:         81.739d {+05h 26m 57s} (J2000)
  POINT_DEC:       -28.025d {-28d 01' 29"} (J2000)
  ROLL:            88.201d
  GRB_DATE:        13628 TJD;   258 DOY;   05/09/15
  GRB_TIME:        41046.96 SOD {11:24:06.96} UT
  FILTER:          3, V
  EXPOSURE_ID:     2265
  X_OFFSET:        796 [pixels]
  Y_OFFSET:        875 [pixels]
  WIDTH:           160 [pixels]
  HEIGHT:          160 [pixels]
  X_GRB_POS:       956
  Y_GRB_POS:       1035
  BINNING_INDEX:   1
  IM_URL:          sw00155242000msuni.fits
  SUN_POSTN:       173.31d {+11h 33m 15s}   +2.89d {+02d 53' 20"}
  SUN_DIST:         92.70 [deg]
  MOON_POSTN:      320.09d {+21h 20m 22s}  -20.11d {-20d 06' 22"}
  MOON_DIST:       105.91 [deg]
  MOON_ILLUM:      90 [%]
  GAL_COORDS:      231.28,-29.82 [deg] galactic lon,lat of the pointing direction
  ECL_COORDS:       78.34,-51.13 [deg] ecliptic lon,lat of the pointing direction
  COMMENTS:        SWIFT-UVOT Image.  
  COMMENTS:        The GRB Position came from the Window Position in the Mode Command.  
  COMMENTS:        The image has 2x2 binning (compression).  
  

  
• GCN/SWIFT NOTICE
  

  TITLE:           GCN/SWIFT NOTICE
  NOTICE_DATE:     Thu 15 Sep 05 11:27:28 UT
  NOTICE_TYPE:     Swift-UVOT Processed Image
  TRIGGER_NUM:     155242,   Seg_Num: 0
  POINT_RA:         81.739d {+05h 26m 57s} (J2000)
  POINT_DEC:       -28.025d {-28d 01' 29"} (J2000)
  ROLL:            88.201d
  GRB_DATE:        13628 TJD;   258 DOY;   05/09/15
  GRB_TIME:        41046.96 SOD {11:24:06.96} UT
  FILTER:          3, V
  EXPOSURE_ID:     2265
  X_OFFSET:        796 [pixels]
  Y_OFFSET:        875 [pixels]
  WIDTH:           160 [pixels]
  HEIGHT:          160 [pixels]
  X_GRB_POS:       956
  Y_GRB_POS:       1035
  BINNING_INDEX:   1
  IM_URL:          sw00155242000msuni.fits
  SUN_POSTN:       173.31d {+11h 33m 15s}   +2.89d {+02d 53' 20"}
  SUN_DIST:         92.70 [deg]
  MOON_POSTN:      320.09d {+21h 20m 22s}  -20.11d {-20d 06' 22"}
  MOON_DIST:       105.91 [deg]
  MOON_ILLUM:      90 [%]
  GAL_COORDS:      231.28,-29.82 [deg] galactic lon,lat of the pointing direction
  ECL_COORDS:       78.34,-51.13 [deg] ecliptic lon,lat of the pointing direction
  COMMENTS:        SWIFT-UVOT Processed Image.  
  COMMENTS:        If you have elected to receive attachments:  
  COMMENTS:        The uvot_catalog_image.fits file does not exist; skipping the attachment.  
  

  
• GCN notice #3977
  D. Grupe (PSU), A. Beardmore (U. Leicester), D. Burrows (PSU), J. Cummings (GSFC/NRC), K. Page (U. Leicester), D. Palmer (LANL), P. Roming (PSU), E. Rol (U. Leicester) N. Gehrels (GSFC) on behalf of the Swift Team
  At 11:22:42 UT, Swift-BAT triggered and located GRB050915 (trigger=155242). The BAT on-board calculated location is RA,Dec 81.714d, -28.030d {05h 26m 51s, -28d 01' 48"} (J2000), with an uncertainty of 3 arcmin (radius, 90% containment, stat+sys). The BAT light curve showed a multi-peak structure with at least 4 well-separated peaks and a total duration of 25 sec. The peak count rate was ~1500 counts/sec (15-350 keV), at ~14 seconds after the trigger.
  The spacecraft slewed immediately and the XRT began observing the BAT position at 11:24:09 UT (T+87 s). The count rate was too low for an on-board centroid, but the spectrum and lightcurve strongly suggest that XRT observed a rapidly-fading X-ray source in the field. The XRT position will be available following the next ground station data dump.
  UVOT finds no obvious new sources in the BAT error circle in a 100 sec image starting at T+85 s. Further analysis will follow.
• GCN notice #3978
  S.A. Yost, E.S. Rykoff (U Mich), B. Schaefer (Louisiana State), D.A. Smith (Guilford), T. Guver (U. Istanbul) report on behalf of the ROTSE collaboration:
  ROTSE-IIIb, located at McDonald Observatory, Texas, responded to GRB 050915 (Swift trigger 155242), producing images beginning 7.5 s after the GCN notice time. An automated response took the first image at 11:23:10.5 UT, 28.2 s after the burst, under fair conditions. We took 10 5-sec, 10 20-sec and 20 60-sec eposures. These unfiltered images are calibrated relative to USNO A2.0 (R). With the arrival of morning twilight, few further images are expected.
  Comparison to the DSS (second epoch) reveals no new sources within the 3-sigma error circle, for both single images and coadding into sets of 10. Individual images have limiting magnitudes ranging from 16.0-17.4; we set the following specific limits.

  start UT 		end UT 	t_exp(s) 	mlim 	t_start-tGRB(s) Coadd?
  --------------------------------------------------------------------
  11:23:10.5 	11:24:32.5 	82 	17.4 		28.2		 Y
  11:24:33.4 	11:29:34.4 	301 	18.0 		111.1 	 Y
  

• GCN notice #3979
  J.A. Kennea, D.N. Burrows, D. Grupe and C. Pagani (PSU) report on behalf of the Swift/XRT team:
  We have analysed ground processed data from the burst GRB050915 (BAT trigger 155242). We find a bright fading uncatalogued X-ray source at the following coordinates:

  RA(J2000):   05 26 44.8
  Dec(J2000): -28 00 55.8
  

  with an estimated uncertainty of 8 arcseconds (90% containment). This position lies 100 arcseconds from the BAT position reported in GCN 3977.
• GCN notice #3980
  P. Kilmartin and A. Gilmore (Canterbury) report on behalf of the AAVSO International High Energy Network:
  We observed the localization of the Swift burst GRB050915 (Grupe et al. GCN 3977) with the 60cm OCS telescope of Mount John Observatory. 600 seconds of stacked unfiltered observations with mipoint at 050915.542 (1.6hrs after the burst) reached a limiting magnitude of CR=18.0 estimated from USNO-A2.0 stars. No new object is present by comparison with DSS2-R. Observations are continuing.
  The AAVSO thanks the Curry Foundation for their continued support of the AAVSO International High Energy Network.
• GCN notice #3981
  S. Bradley Cenko (Caltech) and Derek B. Fox (Penn State) report on behalf of a larger collaboration:
  We have imaged the error circle of GRB 050915 (Grupe et al., GCN 3977) with the automated Palomar 60-inch telescope. Observations began approximately 4 minutes after the burst in the Kron R and Gunn i filters. Inside the XRT error circle (Kennea et al., GCN 3979), we find no source present.
  Using the USNO-B object located at 05:26:48.6, -28:00:48.9 (J2000.0, R2 = 17.90, I2 = 17.88) as a reference, we find the following 3-sigma upper limits for any point-source in the XRT error circle:

  Filter		Int Time (s)	Mean UT		Tb (min)	Mag
  ---------------------------------------------------------------------------
  R		540		11:41		18		> 21.0
  i		540		11:43		20		> 20.5
  

• GCN notice #3982
  S. Barthelmy (GSFC), L. Barbier (GSFC), J. Cummings (GSFC/NRC), E. Fenimore (LANL), N. Gehrels (GSFC), D. Hinshaw (GSFC-SPSYS), D. Hullinger (UMD), H. Krimm (GSFC/USRA), C. Markwardt (GSFC/UMD), P. Meszaros (PSU), D. Palmer (LANL), A. Parsons (GSFC), T. Sakamoto (GSFC/NRC), G. Sato (ISAS), J. Tueller (GSFC), on behalf of the Swift-BAT team:
  Using the data set from T-100 to T+300 sec from the recent telemetry downlink, we report further analysis of Swift-BAT GRB 050915 (trigger #155242) (Grupe, et al., GCN 3977). The refined BAT ground position is RA,Dec = 81.682d,-28.010d {5h26m43.7s,-28d0'36"} [J2000] +/- 1.4 arcmin, (radius, sys+stat, 90% containment). This position is 25 arcsec from the XRT afterglow position reported in Kennea, et al. (GCN circ. 3979). The partial coding was 75%.
  The light curve shows about seven 2-second long peaks from T-10 to T+20 sec and one more peak at about T+43 sec. T90 (15-350 keV) is 53 +- 3 sec (estimated error including systematics).
  The time-averaged spectrum from T-8 to T+56 sec is well fit by a simple power law. The power law index is 1.36 +- 0.16. The fluence in the 15-150 keV band is 8.8 +- 0.9 x 10^-7 erg/cm2. The 1-sec peak photon flux measured from T+13.7 sec in the 15-150 keV band is 0.8 +- 0.2 ph/cm2/sec. All the quoted errors are at the 90% confidence level.
• GCN notice #3983
  D. Grupe, J. Kennea, D. Burrows (PSU), and N. Gehrels GSFC) on report behalf of the Swift XRT team:
  We have analyzed the Swift XRT data of the first three orbits of GRB050915 (Grupe et al. GCN 3977, BAT trigger 155242). The new refined position based on the SDC quicklook data is:

  RA (J2000) =  05h26m44.6s
  DEC(J2000) = -28d01m01.0s
  

  This position is 5.8 arcsec away from the XRT position reported by Kennea et al. (GCN 3979) based on the preliminary data analysis and 29 arcsec from the refined BAT position (Barthelmy et al., GCN 3982).
  The WT data show a spectrum that can be fitted by a single power law with excess absorption above the Galactic value. The X-ray energy spectral slope is beta-x =3D 1.33+/-0.23. The integrated 0.3-10.0 keV Flux during the WT observation was 4.6e-10 ergs/s/cm2 (corrected for absorption).
  The XRT light curve started 87s after the burst and shows a rapidly decaying source after a light increased in flux at the beginning. The decay slope is alpha-1 =3D 3.00+/-0.14. The light curves shows a clear break in the PC mode data at 210s after the burst and flattens to a decay slope alpha-2=0.75 =B10= .04. Extrapolating this light curve we estimate the 0.3-10.0 flux to be in the order of 5e-13 ergs/s/cm2 24 hours after the burst. However, this estimate does not take any late time break, which are usually observed in GRBs several hours after the burst, into consideration.
• GCN notice #3984
  J. S. Bloom and K. Alatalo (UC Berkeley), on behalf of a larger collaboration, reports:
  "Starting at 2005-09-15 11:33:18 UTC, the 1.3m PAIRITEL on Mt. Hopkins began imaging the field of GRB 050915 (Swift trigger 155242; GCN 3977). In a stack of exposures amounting to 1130 sec of integration time we detect a red source at (J2000):

     RA     05:26:44.83
     DEC -28:00:59.5
  

  The position is uncertain to about 400 ms but may be improved with further analysis. This source appears to be consistent with the revised XRT position (Grupe et al. GCN 3983). Since the source is significantly more faint than the 2MASS detection level, we make no claims about variability at this time. Further analysis is in progress."
  An image will be posted to: http://astro.berkeley.edu/~jbloom/grb050915_jhk.gif
  This message may be cited.
  
• GCN notice #3985
  W. Li, University of California, Berkeley, on behalf of the KAIT GRB team, report:
  "The robotic 0.76-m Katzman Automatic Imaging Telescope (KAIT) at Lick Observatory observed GRB 050915 (Swift trigger 155242; Grupe et al. GCN 3977). A series of images was automatically obtained from 11:27:32 UT (290s after the burst) to 12:21:36 UT (3534s after the burst). The sequence includes a combination of images taken with the V and I filters, as well as some that are unfiltered. We did not detect a new object in our images when compared to the DSS II images. In particular, no new object was found within the error circle of the revised XRT position (Grupe et al. GCN 3983). Our first 15s unfiltered image started at 290s after the burst has a 3-sigma limiting magnitude of about 18.2 when compared to the USNO-B1.0 catalog."
• GCN notice #3986
  A. J. Blustin (UCL-MSSL), D. Grupe (PSU), T. Poole (UCL-MSSL), P. Roming (PSU), N. White (GSFC), D. Hinshaw (GSFC-SPSYS), N. Gehrels (GSFC) report on behalf of the Swift-UVOT team:
  The Swift/UVOT began observing the field of GRB050915 85 s after the BAT trigger (Grupe et al. GCN 3977). No new source is detected at the position of the refined XRT error circle (Grupe et al. GCN 3983) in the initial 100 s V-band image down to a 3-sigma upper limit of 19.0, or in summed exposures with any of the filters down to the following 3-sigma magnitude upper limits:

  Filter T_range (s) Exp (s) 3sig UL
  
  V      85-6154     1049    20.3
  B      230-17031   324     20.6
  U      216-12846   958     20.9
  W1     203-11939   958     20.5
  M2     188-6743    640     20.2
  W2     246-677     59      19.6
  

  The magnitudes are uncorrected for extinction.
• GCN notice #3990
  J. S. Bloom (UC Berkeley) reports:
  "Further imaging of the field of GRB 050915a (GCNs 3977, 3979, 3983) with the PAIRITEL 1.3m began at 2005-09-16 10:58:38 UTC. We confirm that the source present in the first epoch (GCN 3984) has faded and is thus the likely IR afterglow of GRB 050915a. In particular, the mean H-band magnitude of the source during the first epoch was H=18.25 +/- 0.16. The source was undetected in the second epoch, with an approximate 3-sigma detection threshold of H(upper limit)=18.55 mag.
  An improved astrometric solution was obtained for the imaging on 2005-09-15 UTC, yielding a J2000 position of the IRT of:

      RA    =  05:26:44.804
      DEC = -28:00:59.27
  

  The 1 sigma uncertainties relative to the 2MASS catalog are 0.18" and 0.09" in RA and DEC, respectively. This position is 3.2" from the revised XRT position reported by Grupe et al. (GCN 3983).
  We encourage deep z band and NIR imaging."
  This message may be cited.
• GCN notice #4001
  P. B. Cameron (Caltech) and D. A. Frail (NRAO) report on behalf of a larger collaboration:
  "VLA observations were made toward the XRT position (GCN 3983) of GRB 050915a at a frequency of 8.46 GHz on September 18.58 UT. No radio sources are seen in the error circle above a 3-sigma level of 93 uJy. The flux density at the position of the IR transient reported by Bloom (GCN 3990) is 43 +/- 31 uJy.
  No further observations are planned.
  The National Radio Astronomy Observatory is a facility of the National Science Foundation operated under cooperative agreement by Associated Universities, Inc."
• 0803.0376from 4 Mar 2008
  : Search for gravitational waves associated with GRB 050915a using the Virgo detector
  Abstract: In the framework of the expected association between gamma-ray bursts and gravitational waves, we present results of an analysis aimed to search for a burst of gravitational waves in coincidence with gamma-ray burst 050915a. This was a long duration gamma-ray burst detected by Swift during September 2005, when the Virgo gravitational wave detector was engaged in a commissioning run during which the best sensitivity attained in 2005 was exhibited. This offered the opportunity for Virgo's first search for a gravitational wave signal in coincidence with a gamma-ray burst. The result of our study is a set of strain amplitude upper-limits, based on the loudest event approach, for different but quite general types of burst signal waveforms. The best upper-limit strain amplitudes we obtain are h_{rss}=O(10^{-20})Hz^{-1/2} around 200-1500 Hz. These upper-limits allow us to evaluate the level up to which Virgo, when reaching nominal sensitivity, will be able to constrain the gravitational wave output associated with a long burst. Moreover, the analysis here presented plays the role of a prototype, crucial in defining a methodology for gamma-ray burst triggered searches with Virgo and opening the way for future joint analyses with LIGO.
• New/revised redshift from the TOUGH project, in particular: 1205.3162 1205.3490 1205.3779 1205.4036