Gamma-ray Burst 050124

(All information courtesy of the instrument teams.)

Previous IAU Circulars

• none

• GCN notice #2972
  C. Markwardt (GSFC/UMD), S. Barthelmy, L. Barbier (GSFC), J. Cummings (GSFC), E. Fenimore (LANL), N. Gehrels (GSFC), D. Hullinger (GSFC/UMD), H. Krimm (GSFC/USRA), K. McLean (LANL), T. McMahon (Langston U.), D. Palmer (LANL), A. Parsons (GSFC), G. Sato (ISAS), P. Schady (MSSL), T. Sakamoto (GSFC), M. Suzuki (Saitama), J. Tueller (GSFC) on behalf of the Swift-BAT team:
  At 11:30:03 UT, the Swift Burst Alert Telescope (BAT) triggered and located on-board GRB050124. The spacecraft did not autonomously slew to the burst because automatic operations were disabled for weekend operations. The spacecraft will be repointed via a Target of Opportunity command.
  The BAT on-board calculated location is RA,Dec 192.879, +13.026 (J2000) with an uncertainty of 6 arcmin (radius, 3-sigma, including a systematic uncertainty). This is a high significance burst. The structure of the burst is double-peaked with a duration of ~4 seconds.
• GCN notice #2973
  J. Cummings (GSFC), S. Barthelmy, L. Barbier (GSFC), A. Breeveld (MSSL), J. Cannizzo (GSFC/UMBC), E. Fenimore (LANL), N. Gehrels (GSFC), D. Hullinger (GSFC/UMD), H. Krimm (GSFC/USRA), C. Markwardt (GSFC/UMD), K. McLean (LANL), T. McMahon (Langston U.), D. Palmer (LANL), A. Parsons (GSFC), G. Sato (ISAS), P. Schady (MSSL), T. Sakamoto (GSFC), A. Smale (NASA HQ), M. Suzuki (Saitama), J. Tueller (GSFC)
  This is a followup report on Swift/BAT GRB050124 (GCN Circ. 2972, Markwardt et al.) The ground-calculated BAT location is RA, Dec 192.884, 13.024 degrees (J2000). At 43 degrees from the BAT boresight, we expect the uncertainty to be primarily systematic due to currently uncalibrated image distortion (Swift/BAT image calibration activities are still in progress). The systematic uncertainty is approximately 3 arcmin (radius).
  Further analysis yields a fluence of (2.1 +- 0.2) x 10^-6 ergs/cm2 and a 1-second peak flux of (6.8 +- 0.4) ph/cm2/s in the 15-350 keV band. The power-law photon index is 1.48 in the 20 - 150 keV band.
  T90 is 4.1 seconds and T50 is 2.1 seconds. The burst had 2 peaks, the first 2 seconds long with a rise in 0.1 seconds from a baseline that was slightly elevated for about 1.4 seconds, and the second about 1 second long. There is a low-significance (3.6 sigma image) hint of a 1-second precursor at -16 seconds from the trigger.
• GCN notice #2974
  C. Pagani (OAB), J. Kennea, D. N. Burrows, J. E. Hill, J. A. Nousek (PSU), G. Chincarini, G. Tagliaferri, A. Moretti, P. Romano, S. Campana (OAB), M. Goad, K. Page, A. Wells, J. Osborne, A. Beardmore (U. Leicester), M. Chester (PSU), S. Barthelmy, N. Gehrels, N. White (GSFC), P. Schady (MSSL), M. Tripicco (GSFC), L. Cominsky (Sonoma State U.), P. Giommi (ASDC) on behalf of the Swift XRT team.
  The Swift X-Ray Telescope (XRT) was pointed at GRB010124 ( GCN 2972, Markwardt et al.; GCN 2973, Cummings et al.) on 2005/01/24 at 14:34 UT. The spacecraft did not autonomously slew to the burst since automated slewing was not enabled at the time the burst occurred. The observation was performed as a Target of Opportunity beginning about 3 hours after the burst. The first XRT exposure was at 14:35:16 UT. The observation continued until 15:17:12 UT. The XRT was in Auto State and the ToO was performed as if it were an automated burst observation. XRT attempted to determine a prompt centroid but found insufficient counts. It took one frame in Piled-up Photodiode mode, one in Low-rate Photodiode mode, and then settled into Windowed Timing mode (1-D position resolution, 2 ms timing) for the bulk of the observation (1100 frames), with about 220 frames in Photon-Counting mode (2-D position resolution, 2.5s timing).
  We processed the data on the ground and detect a bright X-ray source in this field. The X-ray centroid has an approximate location of:

  RA(J2000) = 12:51:31.1
  Dec(J2000) = 13:02:34.3.
  

  This position is not corrected for stellar aberration, and we estimate an uncertainty of about 30 arcseconds as a result. A more accurate position will be available once the data are processed by the XRT pipeline software.
  Checks against SIMBAD and the HEASARC master X-ray catalog yielded no known source at this position on the sky. The XRT position is about 70 arcseconds from the refined BAT positions (GCN 2973).
  We have a total of about 600 counts from this object in the first observation set. The spectrum appears consistent with a power-law, but detailed fitting awaits the pipeline-processed data. Additional automated observations are in progress when the afterglow field is observable by Swift.
• GCN notice #2975
  J. P. Osborne, K. Page, M. Goad (UL), A. Beardmore, A. F. Abbey, A. A. Wells (U. Leicester), S. Campana, A. Moretti, C. Pagani, P. Romano, G. Tagliaferri, G. Chincarini (OAB), L. Angelini, F. Marshall, N. Gehrels (NASA/GSFC), J. E. Hill, J. Kennea, D. N. Burrows, J. A. Nousek, P. Roming, P. Meszaros (PSU), G. Cusumano, V. Mangano (IFSFC), P. Schady (MSSL), and S. Piranomonte (ASDC) report on behalf of the Swift XRT team:
  We have obtained a refined XRT position, using the ground-based pipeline processing software, including stellar aberration correction. The refined position for the X-ray afterglow is: RA(J2000) = 12:51:30.4, Dec(J2000) = +13:02:39.0. We estimate a remaining uncertainty of about 8 arcseconds, including a systematic error of about 5 arcseconds due to residual alignment offsets that have not been fully calibrated yet.
  We now have data from 3 orbits. Data were collected between 14:35:15 and 15:17:12 UT, between 16:11:35 and 16:53:41 UT, and between 17:48:02 and 18:30:03. The point source is clearly fading, with average observed count rates 0.20 cps, 0.14 cps, and 0.09 cps in the three observations.
  A preliminary spectral fit to data from the first orbit gives a spectral power law photon index of 1.3 +/- 0.1, assuming Galactic absorption (2E20 cm^-2). The average estimated unabsorbed 1-5 keV flux is then about 6E-12 erg cm^-2 s^-1 at about 3.5 hours post-burst.
• GCN notice #2976
  GRB 050124 : Lulin R-band follow-up observation
  Z.Y. Lin, K.Y. Huang, W.H. Ip (NCU), Y. Urata, T. Tamagawa (RIKEN), Y. Qiu (BAO), Y.Q. Lou(THCA) on behalf of the East Asian collaboration report:
  "We have observed the error range of GRB 050124 reported by Markwardt et al.(GCN 2972) using Lulin 1-m telescope at Taiwan. The R band dithering observations started from 4.37 to 5.17 hours after the burst. No obvious source was found at the bright X-ray source position (Pagani et al. GCN 2974). There are no new source brighter than 20 magnitude during our observations."
  This message may be cited.
  
• GCN notice #2977
  S.Maeno,E.Sonoda,Y.Matsuo,M.Yamauchi (University of Miyazaki)
  "We have observed the field covering the error box of GRB 050124 (GCN 2972;Swift-BAT Trigger time is 11:30:03 UT) with the unfiltered CCD camera on the 30-cm telescope at University of Miyazaki. The observation was started 17:41:25 UT on Jan.24. Observed field of view is 43 arcmin centerd on

  R.A.=12h 50m 28s
  Dec= 13d 07' 30"
  

  After co-adding a set of 2 images of 30 sec exposures, we have compared with the USNO A2.0 catalog. Preliminary analysis shows there is no new source brighter than 17.0 mag.
• GCN notice #2978
  E. Berger (Carnegie Observatories) and S.R. Kulkarni (Caltech) report on behalf of a larger collaboration:
  "We imaged the 8-arcsec XRT error circle (GCN 2975) of GRB 050124 (GCN 2972) with NIRC on the Keck I telescope on January 25.504 UT (24.6 hours after the burst). A total of 9 min were obtained in the Ks band. We find two sources within the XRT error circle, which we designate C1 and C2. Object C1 is point-like and is located at (J2000):

          RA = 12:51:30.7
          DEC= 13:02:42  
  

  Object C2, 8.4" to the southwest, appears extended. Further observations are planned to check for variability. A finding chart is available at: http://www.ociw.edu/~eberger/grb050124_finder.ps
  This message may be cited.
• GCN notice #2979
  Y. Yatsu and N. Kawai (Tokyo Tech) report on behalf of MITSUME collaboration,
  "We observed the field of GRB050124 (GCN 2972, Markwardt et al.) with the 50 cm Mitsume Telescope at Akeno, Japan in I band starting at 3.8 hours after the trigger.
  We detected no new objects with following upper limits, as estimated by comparison with the USNO A2.0 catalog.
  Start Time stacked frames upper limit

  15:17:17 UT   30 sec x 100       I > 18.0   
  16:11:07 UT   30 sec x 100       I > 18.5
  17:04:18 UT   30 sec x 98        I > 18.8
  

  The observing condition was not optimum due to the full moon and the low elevation angle, but it improved with the increase of the target elevation."
• GCN notice #2981
  B. E. Cobb and C. D. Bailyn (Yale), part of the larger SMARTS consortium, report:
  Using the ANDICAM instrument on the 1.3m telescope at CTIO, we obtained optical/IR imaging of the error region of GRB 050124 (GCN 2972, Markwardt et al.) beginning ~20.2 hours post-burst (2005-01-25 07:42:48 UT). Total summed exposure times amounted to 180s in BRIYJK and 120s in H and V. Preliminary visual comparison of the optical images to the SDSS and the IR images to 2MASS frames does not reveal any new sources brighter than our detection limits (listed below).
  The following approximate upper limits on detection were estimated by comparison with the USNO B1.0 and 2MASS catalogs:

           B > 20.1
           R > 20.6
           I > 20.4
           J > 18.3
           K > 16.9
  

• GCN notice #2982
  S. Hunsberger (PSU), A. Breeveld (MSSL), P. Roming (PSU), K. Mason, P. Schady (MSSL), M. Ivanushkina (PSU), K. McGowan, T. Poole (MSSL), C. Gronwall (PSU), M. De Pasquale, A. Blustin (MSSL), P. Brown (PSU), S. Rosen, C. James (MSSL), P. Boyd, S. T. Holland, M. Still, W. Landsman (GSFC), P. Smith, B. Hancock (MSSL), S. Koch (PSU), M. Carter, H. Huckle (MSSL), P. Broos (PSU), T. Kennedy (MSSL), S. Barthelmy (GSFC), D. Burrows, J. Nousek, M. Chester (PSU), N. Gehrels (GSFC), K. Hurley (UCB), G. Chincarini (OAB) on behalf of the Swift UVOT team.
  The Swift Ultra-Violet/Optical Telescope (UVOT) began observations of GRB050124 (GCN 2972) on January 24, 2005, at 14:34:56 UT. The spacecraft did not autonomously slew to the burst since automated slewing was not enabled. The observation was performed as a Target of Opportunity beginning about 3 hours after the burst. Based on comparisons to the USNO-B1.0 Catalogue, we detect no source down to a magnitude of 17.4 in the V-filter for a 100 second UVOT Finding Chart exposure. We caution that the instrument is not yet fully calibrated and that this magnitude limit is an estimate.
• GCN notice #2983
  E. Berger (Carnegie Observatories) and S.R. Kulkarni (Caltech) report on behalf of a larger collaboration:
  "We re-observed the 8-arcsec XRT error circle (GCN 2975) of GRB 050124 (GCN2972) with Keck/NIRC on January 26.47 UT. A total of 18 min were obtained in the Ks band. We find that object C1 in our previous Keck/NIRC image (GCN 2978) has faded by about 0.5 mag, while object C2 remained constant in flux. We therefore conclude that C1 is the afterglow of GRB 050124."
  This message may be cited.
• GCN notice #2989
  J. P. U. Fynbo, B. L. Jensen (NBI), B. Thomsen (U. Aarhus), J. Hjorth (NB= I), E. =D6rndahl, H. Hyv=F6nen (U. Turku) and M. I. Andersen (AIP) report:
  "We imaged the 8-arcsec Swift/XRT error circle (GCN 2975) of GRB 050124 (GCN 2972) in the K band with NOT/NOTCam on January 25.11 UT. Object C1,=20 suggested to be the NIR afterglow of GRB 050124 (GCN 2978, 2983), was considerably brighter in the NOTCam image at t+15h than in the Keck/NIRSp= ec=20 image at t+24h (GCN 2978). This confirms the transient nature of the sour= ce and strengthens the afterglow candidacy."
• GCN notice #3000
  A. M. Soderberg (Caltech) and D. A. Frail (NRAO) report on behalf of a larger collaboration:
  "On 2005 January 29.41 UT we carried out follow-up observations with the VLA centered on the NIR afterglow candidate reported by Berger et al. (GCN #2978) for GRB 050124 (GCN #2972). At a frequency of 8.46 GHz no emission was detected above a 2-sigma level of 99 microJy."
• GCN Circular #5269
  L.J. Pellizza (CEA Saclay, France & IAFE, Argentina), P.-A. Duc (CEA Saclay, France), E. Le Floc'h (Steward Obs., USA), & I.F. Mirabel (ESO), on behalf of the MISTICI collaboration.
  We imaged the field of GRB 050124 (Markwardt et al. 2005, GCN 2972) on April 29, 2005 and May 10, 2005. R (10 x 308 seconds) and Ks (42 x 60 seconds) frames were obtained respectively with FORS1 and ISAAC at VLT. In the combined R image we detect a single object within the revised XRT error circle (Moretti et al. 2006, A&A, 448, L9), down to our limiting magnitude R_lim ~ 26. No object is detected in our combined Ks image down to a limiting magnitude Ks_lim ~ 21. The position of the possible host galaxy is RA(J2000) = 12:51:30.45, DEC(J2000) = +13:02:43.0 (0.2 arcsec error). Its magnitude is R = 23.9 (uncertainty ~0.5 mag). Astrometry was performed using USNO B1.0 stars, while photometry was calibrated against 2MASS and USNO B1.0 (second epoch) magnitudes.