Gamma-ray Burst 041223

(All information courtesy of the instrument teams.)

Previous IAU Circulars

• none

• GCN notice #2898
  

  TITLE:   GCN GRB OBSERVATION REPORT
  NUMBER:  2898
  SUBJECT: GRB041223: Swift-BAT detection of a bright long burst
  DATE:    04/12/23 17:58:52 GMT
  FROM:    Scott Barthelmy at NASA/GSFC  
  

  J. Tueller, L. Barbier, S. Barthelmy (GSFC), A. Beardmore (U.Leicester), L. Cominsky (Sonoma State U), J. Cummings (GSFC), E. Fenimore (LANL), N. Gehrels (GSFC), S.T. Holland (GSFC/USRA), D. Hullinger (GSFC/UMD), H. Krimm (GSFC/USRA), C. Markwardt (GSFC/UMD), K. McLean, D. Palmer (LANL), A. Parsons (GSFC), G. Sato (ISAS), M. Suzuki (Saitama), G. Tagliaferri (OAB) on behalf of the Swift BAT team:
  At 14:06:18 UT, the Swift Burst Alert Telescope (BAT) triggered and located on-board GRB041223. The spacecraft did not autonomously slew to the burst since automated slewing was not yet enabled.
  The BAT ground-calculated location is RA,Dec 100.183,-37.066 (J2000) with an uncertainty of 7 arcmin (radius, 3-sigma, including systematic uncertainty using a preliminary bore-sight alignment calibration). This is 27 degrees off the BAT bore sight and was in the partially encoded field of view.
  The burst lightcurve is multi-peaked with structure within the peaks with the main emission lasting ~60 sec. The peak flux was 7.5 events/cm^2/sec (1-sec sampling; unsaturated; ~15 to 100 keV; ~28 Crab). The total duration was ~130 sec. The fluence was ~2e-5erg/cm^2. A reduced energy band is being quoted because of our response uncertainty in the >100 keV band, and because of strong emission by this burst in this band.
• GCN notice #2899
  E. Rykoff (U. Michigan) reports on behalf of the ROTSE collaboration:
  ROTSE-IIIc, located at the H.E.S.S. site at Mt. Gamsberg, Namibia, responded to Swift GRB041223 (GCN #2898). A manual response was initiated at 18:27 UT, around 4.5 hours after the burst. We took 10 5-s exposures followed by 200 20-s exposures. The first images were taken during twilight, and all the images were taken with >90% moon illumination. The unfiltered images were calibrated relative to USNO A2.0. Individual images had limiting magnitudes around 16.8. Comparison to DSS (second epoch) reveals no new sources within the 3-sigma error circle to a limiting magnitude of 18.4 for a stack of the first 90 images.
• GCN notice #2901
  D. N. Burrows, J. E. Hill, J. Racusin, J. Kennea, D. Morris, J. A. Nousek (PSU), G. Chincarini, G. Tagliaferri, A. Moretti, P. Romano, S. Campana, D. Malesani, C. Pagani (OAB), A. Wells, J. Osborne, A. Beardmore, K. Page (U. Leicester), P. Giommi (ASI), M. Chester (PSU), S. Barthelmy, N. Gehrels, N. White (GSFC), K. Mason (MSSL), on behalf of the Swift XRT team.
  The Swift X-Ray Telescope (XRT) was pointed at GRB041223 (GCN 2898, Tueller et al.) on 2004/12/23 at 18:43:59 UT for 1490 s, at 20:16:24.4s for 1600 s, and at 21:50:40 for 430 s. The spacecraft did not autonomously slew to the burst since automated slewing is not yet enabled and the XRT is in the midst of engineering measurements. The observation was performed as a Target of Opportunity beginning about 4.5 hours after the burst.
  We detect a fading X-ray source about 3.5 arcminutes from the BAT position. The ground-calculated positions were checked through two independent data processing and analysis techniques, which yielded consistent sky positions within 22 arcseconds. Our best estimate of the X-ray afterglow position is 06:40:49.2, -37:04:21.5 (J2000) for the first observation. The position determined independently for the second observation was within 4 arcseconds of these coordinates. The XRT alignment is not yet fully calibrated, and we estimate a systematic uncertainty of about 15 arcseconds in this position. Checks against SIMBAD, DSS and X-ray catalogs from ROSAT, ASCA, XMM, and Chandra yielded no known source at this position on the sky.
  We have a total of about 580 counts from this object in the first two observations. A simple power-law fit to the spectrum gives a photon index of 1.43 +/- 0.09 and model fluxes of 1.7E-12 ( 0.5-2 keV) and 4.7E-12 (2-10 keV) ergs/cm**2/s. We caution that the instrument is not yet fully calibrated and that these fluxes may have systematic uncertainties of 15%. The light curve based on all three observations is well fit with a power-law index of 2.2 +/- 0.3.
• GCN notice #2902
  E. Berger (Carnegie Observatories), W. Krzeminski and M. Hamuy (Las Campanas Observatory) report:
  "We imaged the 7-arcmin radius error circle of GRB 041223 (GCN 2898) with the Swope 40-inch telescope at Las Campanas Observatory starting on December 24.185 UT (14.4 hours after the burst) in r-band for a total of 20 minutes. We find a new bright source not present in the DSS which is located at (J2000):

          RA = 06:40:47.31
          DEC= -37:04:22.5
  

  This object is located 22.5 arcsec away from the nominal position of the X-ray counterpart detected with the XRT (GCN 2901), or about 1.5 times the 15-arcsec uncertainty radius.
  Further analysis and observations are in progress"
• GCN notice #2903
  D. Malesani, G. Tagliaferri, G. Chincarini, S. Campana, S. Covino, L.A. Antonelli, M. Della Valle, F. Fiore, L. Stella, F.M. Zerbi, P. D'Avanzo, A. Moretti, and P. Romano report on behalf of the MISTICI collaboration:
  We observed the field of GRB041223 (Tueller et al., GCN 2898; Burrows et al., GCN 2901) with the ESO-VLT-UT1 equipped with the ISAAC camera, starting on 2004 Dec 24.256 (~16 hours after the GRB). The observing conditions were good, with a seeing of 0.6". Twelve one-minute exposures were acquired in the J band, with a mean UT 24.261.
  The source reported by Berger et al. (GCN 2902) is clearly detected in our images, with a magnitude J = 19.51+-0.05, based on comparison with 3 nearby bright nonsaturated stars from the 2MASS catalog.
  We warmly thank the ESO staff at Paranal, in particular Olivier Marco and Jonathan Smoker, for carefully performing the observations in service mode.
  This message can be cited.
• GCN notice #2907
  S. Covino, F.M. Zerbi, E. Palazzi, G. Chincarini, G. Tagliaferri, E.=20 Molinari, V. Testa, G. Tosti, A. Monfardini, A. Di Paola, M. Rodon=F2,=20 L.A. Antonelli, P. Conconi, G. Cutispoto, P. D'Avanzo, L. Nicastro, on=20 behalf of the REM/ROSS team, report:
  We imaged the field of GRB 041223 (Tueller et al., GCN 2898; Burrows et=20 al., GCN 2901) with the robotic 60-cm REM telescope located at La Silla,=20 Chile. Observations were carried both in the NIR and in the optical, on=20 2004 Dec 24 from 02:37 UT to 03:11 UT (i.e. ~12 hours after the burst).=20 REM was equipped with the REMIR near-IR camera (10x10 sq arcmin FoV, JHK=20 filters) and the ROSS optical spectrograph/imager (10x10 sq arcmin FoV,=20 VRI filters).
  Observations were performed under good seeing conditions. The net=20 exposure times were: J: 500s; H: 500s; K: 500s; V: 150s; R: 150s; I: 150s.
  The comparison with the 2MASS catalog did not reveal new infrared=20 sources with S/N>5 at the limit of the catalog. In particular no source=20 is present at the position of the X-ray afterglow detected by Swift-XRT=20 (Burrows et al. GCN 2901) and of the optical transient reported by=20 Berger et al. (GCN 2902) and Malesani et al. (GCN 2903).
  Also the optical observations, partly affected by the bright Moon, did=20 not show any convincing candidate. The 3-sigma upper limit in the R band=20 is R ~ 18.
  This message is citeable.
• GCN notice #2909
  GRB041223 Fluence measured by Swift-BAT
  C. Markwardt (GSFC/UMD), M. Suzuki (Saitama), L. Barbier, S. Barthelmy (GSFC), J. Cummings (GSFC), E. Fenimore (LANL), N. Gehrels (GSFC), D. Hullinger (GSFC/UMD), H. Krimm (GSFC/USRA), K. McLean, D. Palmer (LANL), A. Parsons (GSFC), G. Sato (ISAS), J. Tueller (GSFC), on behalf of the Swift BAT team:
  GRB 041223 (Tueller et al., GCN #2898) was a spectrally hard burst. Fits to the total Swift-BAT burst spectrum are consistent with a power law, with a photon index of 1.05-1.15.
  The BAT team did not quote a total band fluence in GCN 2898, due to uncertainty in the response at high energies. Now, with further simulations and spectral analysis, we estimate that the 15-350 keV fluence was ~5E-5 erg/cm^2. The peak flux was 3E-6 erg/cm^2/s (15-350 keV; 1 s sampling), which is dominated by the highest energy band.
• GCN notice #2910
  G. Tagliaferri, A. Moretti, P. Romano, D. Malesani, G. Chincarini, S. Campana, C. Pagani (OAB), D.N. Burrows, J.E. Hill, J. Racusin, J. Kennea, D. Morris, J.A. Nousek (PSU), A. Wells, J. Osborne, A. Beardmore, K. Page (U. Leicester), P. Giommi (ASI), M. Chester (PSU), L. Angelini, S. Barthelmy, N. Gehrels, N. White (GSFC), K. Mason (MSSL), on behalf of the Swift XRT team, report:
  We have posted online the results of the analysis of the X-ray afterglow of GRB 041223 (Tueller et al., GCN 2898; Burrows et al., GCN 2901). Plots displaying the lightcurve and the spectrum can be seen at
  http://www.merate.mi.astro.it/~taglia/GRB041223
  At the same page, a finding chart for the afterglow is also shown, reporting a refined X-ray position obtained after running the XRT pipeline processing software. The coordinates are

  R.A. =  06:40:47.4
  Dec. = -37:04:22.3
  

  This position is just 1.5" far from the optical/NIR afterglow (Berger et al., GCN 2902; Malesani et al., GCN 2903).
  This message can be cited.

  The figures are copied below:

  The decay is well fitted by a powerlaw with index 2.2. ± 0.3.
  Spectrum of the afterglow (sum of the first two segments). Please note that at this stage the calibration is still preliminary, therefore the above results should be taken with care.
  Finding chart for GRB 041223. The position of the optical (Berger et al., GCN 2902) and near-infrared (Malesani et al., GCN 2903) is indicated by the arrow. The leftmost circle represents the XRT errorbox (15" radius) communicated in GCN 2901. The rightmost circle corresponds to a refined XRT position, derived by running the pipeline processing software. The center of this errorbox (yellow dot: RA=06:40:47.4, Dec=-37:04:22.3) is just 1.5" far away from the optical counterpart. J-band VLT image taken from Malesani et al. (GCN 2903).
• GCN notice #2913
  D. Malesani, S. Covino, P. D'Avanzo, G. Tagliaferri, G. Chincarini, L.A. Antonelli, S. Campana, M. Della Valle, F. Fiore, L. Stella, and F.M. Zerbi report on behalf of the MISTICI collaboration:
  We observed again the field of the Swift GRB 041223 (Tueller et al., GCN 2898; Burrows et al., GCN 2901), using the ESO-VLT at Paranal. Optical and NIR observations were performed under excellent conditions (seeing 0.4") during the night of 2004 Dec 24 (~1.5 days after the GRB). We clearly detect the candidate afterglow reported by Berger et al. (GCN 2902), for which we measure J = 20.43 +- 0.05 on 2004 Dec 25.07. The object is pointlike at the resolution of the VLT images, and clearly faded since our previous observation (Malesani et al., GCN 2903), confirming that this is indeed the afterglow of GRB 041223. The decay index is alpha = 1.6 +- 0.1 (F = K*t^-alpha).
  The photometric SED derived from our optical and NIR observations is well represented by a hard powerlaw with a spectral index beta = 0.38 +- 0.05 (F = K * nu^-beta), after correcting for Galactic extinction (A_V = 0.394 mag). Such hard values are not common for afterglows at these stages (even without any reddening correction, the spectrum is still hard with beta = 0.65). We note that this value is very similar to the X-ray spectral index ~6 hours after the GRB reported by Burrows et al. (GCN 2901), namely alpha = 0.43 +- 0.09.
  This message can be cited.