Gamma-ray Burst 000418

On April 18, 2000 at 9:53:10 UT a burst was detected by Ulysses, NEAR, and KONUS.

(All information courtesy of the instrument teams.)

Previous IAU Circulars

• none

• GCN notice #642
  K. Hurley, on behalf of the Ulysses GRB team, and T. Cline and E. Mazets, on behalf of the NEAR and KONUS-Wind teams, report:
  Ulysses, NEAR, and KONUS observed GRB000418 at 35590 s UT. As observed by Ulysses, this burst had a duration of ~30 s, and a 25-100 keV fluence of ~1.3x10^-5 erg/cm^2. We have triangulated it to an ~ 35 sq. arcmin. error box at the following 3 sigma, preliminary position:

      RA(2000)                 DEC(2000)
   12 h 25 m 21.17 s     20 o  5 '   3.61 "  (CENTER)
   12 h 25 m 33.03 s     20 o  4 '  17.15 "  (CORNER)
   12 h 24 m 49.69 s     20 o 13 '  17.39 "  (CORNER)
   12 h 25 m 52.50 s     19 o 56 '  49.93 "  (CORNER)
   12 h 25 m  9.30 s     20 o  5 '  50.00 "  (CORNER)
  

  This position can be refined.
• GCN notice #645
  S. Klose, B. Stecklum (Thueringer Landessternwarte Tautenburg), O. Fischer (Universitaets-Sternwarte Jena), J. Gorosabel (DSRI, Copenhagen), C. Sanchez-Fernandez (LAEFF-INTA, Madrid), A. Castro-Tirado (LAEFF-INTA, Madrid, and IAA-CSIC, Granada), D. Butler (Max-Planck-Institut fuer Extraterrestrische Physik, Garching), S. Hippler, Th. Ott, M. Kasper, R. Weiss (Max-Planck-Institut fuer Astronomie, Heidelberg), L. Montoya, A. Aguirre (Max-Planck-Institut fuer Astronomie, Heidelberg, and Calar Alto observatory), F. J. Vrba, A. A. Henden, C. B. Luginbuhl, B. Canzian, S. E. Levine, H. H. Guetter, J. A. Munn (U.S. Naval Observatory, Flagstaff), D. H. Hartmann (Clemson University, Clemson), and J. Greiner (AIP Potsdam) report:
  The central part of the error box of GRB 000418 (Hurley et al., GCN #642) was imaged with the Calar Alto 3.5-m telescope on April 20, 20:55 UT - 21:54 UT, using the near-infrared camera Omega Cass. The limiting magnitude of the K'-band image is about K'=17 after adding all images taken at different position angles of a wire-grid polarizer. A second observing run was performed on April 22, 02:22 UT - 03:23 UT, using the same telescope and the same instrumentation.
  The same region of the error box was also covered by K'-band (April 20, 22:06 UT - 22:46 UT and April 24, 21:36 UT - 22:30 UT) and J-band images (April 21, 22:23 UT - 22:48 UT) taken with the Calar Alto 1.23-m telescope using the near-infrared camera MAGIC. Additional frames covering the whole error box (Hurley et al. GCN #642) are being processed and the results will be reported soon.
  A comparison between the April 20 and April 22 images and a cross-check with the 1.23-m images has revealed a potentially fading source within the central GRB error box at RA, DEC (J2000) = 12:25:19.3, 20:06:12 (+/- 1 arcsec). This source (K' ~ 16) is visible on the 3.5-m and 1.23-m frames obtained during the first night. It has no counterpart on the corresponding DSS2-red image. Since standard stars are not available at the moment we can only provide a rough estimate of the brightness of the source. Further data reduction is in progress.
  The K'-band image from April 22 will be posted on the Tautenburg Web page at http://www.tls-tautenburg.de/research/grb000418.html.
• GCN notice #646
  N. Mirabal, J. P. Halpern, J. Kemp, & D. J. Helfand (Columbia U.) report on behalf of the MDM Observatory GRB follow-up team:
  The potential K-band counterpart of GRB 000418 reported by Klose et al. (GCN #645) is present in an R-band image which we obtained on the MDM 2.4m telescope on April 21, 03:33 UT. Its position is (J2000) RA 12 25 19.30, Dec. +20 06 11.1, with an uncertainty of 0."5. Under non-photometric conditions we measure R = 21.52 +/- 0.12 for this candidate, referenced to a USNO star at (J2000) RA 12 25 25.62, Dec. +20 04 57.8 which is listed as R = 15.4. An additional systematic uncertainty of 0.2 mag should be assumed based on the dispersion among other USNO star magnitudes in this field.
  Further observations are needed to determine if this object is fading.
• GCN notice #650
  N. Mirabal, J. P. Halpern (Columbia U.), R. M. Wagner (Ohio State U.) report on behalf of the MDM Observatory GRB follow-up team:
  We reobserved the suggested afterglow candidate for GRB 000418 (Klose et al., GCN #645) in the R-band using the MDM 2.4m telescope. The object at position (J2000) RA 12:25:19.30, Dec. +20:06:11.1 has faded to R = 22.59 +/- 0.23 on April 27.26 UT from our previous detection at R = 21.52 +/- 0.12 on April 21.15 UT (Mirabal et al., GCN #646). The second measurement was made with a non-standard broad R filter. Both magnitudes are referenced to the same USNO star at (J2000) RA 12:25:25.62, Dec +20:04:57.8 which is listed as R = 15.4. The corresponding power-law decay index would be -0.84 +/- 0.20. The magnitude of the decline and its rate are plausible for a GRB afterglow, but further confirmation is desired.
• GCN notice #652
  A. Henden (USRA/USNO) and H. Harris (USNO), on behalf of the USNO GRB team, S. Klose, (Thueringer Landessternwarte Tautenburg), on behalf of a much larger European team, report:
  We have observed the error box of GRB 000418 with the NOFS 1.3-m automated telescope on 000426 UT with a total exposure time of 1800 seconds in Cousins R. At the position of the proposed afterglow candidate (Klose et. al. GCN #645) we find a faint source near our limiting magnitude. With respect to the USNO-A2.0 star used by Mirabal et. al. (GCN #646, #650), we obtain

  RA 12:25:19.30  DEC +20:06:11.6 +/- 0.3  J2000
  UT 000426.316  R=22.49 +/- 0.20 
  

  We will be calibrating this field in UBVRI over the weekend.
• GCN notice #653
  N. Mirabal, J. P. Halpern (Columbia U.), R. M. Wagner (Ohio State U.) report on behalf of the MDM Observatory GRB follow-up team:
  We obtained additional R-band images of the afterglow candidate for GRB 000418(Klose et al., GCN #645) using the MDM 2.4m telescope. The object located at (J2000) RA 12:25:19.30, Dec. +20:06:11.1 has an estimated magnitude R = 22.8 +/- 0.31 on April 28.3 UT, this magnitude is referenced to USNO star (J2000) RA 12:25:25.62, Dec +20:04:57.8 (R = 15.4). The decline is consistent with the -0.84 +/- 0.2 power-law derived from previous detections (Mirabal et al., GCN #646,#650). In addition we note that the OT appears to be slightly extended which might be an indication of residual light from an underlying host galaxy.
• GCN notice #654
  B. Stecklum, S. Klose (Thueringer Landessternwarte Tautenburg), O. Fischer (Universitaets-Sternwarte Jena), J. Gorosabel (DSRI, Copenhagen), C. Sanchez-Fernandez (LAEFF-INTA, Madrid), A. Castro-Tirado (LAEFF-INTA, Madrid, and IAA-CSIC, Granada), D. Butler (Max-Planck-Institut fuer Extraterrestrische Physik, Garching), S. Hippler, Th. Ott, M. Kasper, R. Weiss (Max-Planck-Institut fuer Astronomie, Heidelberg), L. Montoya, A. Aguirre (Max-Planck-Institut fuer Astronomie, Heidelberg, and Calar Alto observatory), A. Henden (USRA/USNO), on behalf of the USNO GRB team, D. H. Hartmann (Clemson University, Clemson), and J. Greiner (AIP Potsdam) report:
  As a supplement to our previous GCN report (Klose et al., GCN #645) we can provide now a more accurate estimate of the K'-band magnitude of the afterglow of GRB 000418. It is based on the assumption that the B-R colours of three USNO stars on the detection image are representative for their spectral types. A value of K' = 17.5 was found with an uncertainty of 0.5 mag.
  In addition, in GCN #645 one should read: The limiting magnitude of the (3.5-m) K'-band images is about 18.5.
• GCN notice #655
  D. A. Frail (NRAO) reports on behalf of a larger collaboration:
  Beginning on April 29.07 UT we observed GRB000418 with the VLA at a frequency of 8.46 GHz. At the position of the IR/optical transient reported by Klose et al. (GCN 645) and Mirabal et al. (GCN 650), we detect a bright radio source with a flux density of 850+/-33 microJy. We will continue to monitor this source.
• GCN notice #656
  A. Henden (USRA/USNO) reports on behalf of the USNO GRB team:
  We have acquired preliminary UBVRcIc all-sky photometry for the field of GRB000418 with the USNOFS 1.0-m telescope on one marginally photometric night. This 11x11arcmin field includes the proposed counterpart and extends a little fainter than V=20. All stars brighter than V=14 are saturated and should be used with care. We have placed the photometric data on our anonymous ftp site: ftp://ftp.nofs.navy.mil/pub/outgoing/aah/grb/grb000418.dat The current photometry has a potential external zero-point error of about three percent. The astrometry in this file is based on linear plate solutions with respect to USNO-A2.0. The internal errors are less than 100mas.
  We suggest the use of five comparison stars in the field until further photometry is obtained:

  ID   x    y     U       B       V       R       I
  A   000  000  16.726  16.682  16.037  15.686  15.313
                 0.009   0.004   0.002   0.003   0.004
  
  B  -158 +050  19.695  18.530  17.480  16.834  16.329
                 0.110   0.013   0.007   0.009   0.012
  
  C  -060 +134  18.899  19.172  18.302  17.874  17.369
                 0.063   0.024   0.014   0.021   0.029
  
  D  -094 -006    -     20.489  19.663  19.168  18.046
                         0.091   0.046   0.065   0.150
  
  E  -200 -042    -     19.874  18.982  18.549  18.046
                         0.044   0.025   0.036   0.050
  

  Notes: star A is the Mirabal et. al. comparison star located at RA 12:25:25.65, DEC +20:04:57.4 J2000; x,y offsets are in arcsec with respect to this star, positive east and north.
• GCN notice #661
  J. S. Bloom, A. Diercks, S. G. Djorgovski, D. Kaplan, and S. R. Kulkarni (Caltech) report on behalf of the larger Caltech-NRAO-CARA GRB collaboration:
  We observed the transient position of GRB 000418 (Klose et al. GCN #645) with the Echellette Spectrograph and Imager (ESI) on the Keck II 10-m Telescope on Mauna Kea at 2.318 May 2000 UT. In a 1200-s exposure we detect both broadband continuum and a strong doublet in emission at wavelengths Lambda = 7894.0,7899.4 Angstrom (preliminary reduction). Further observations of the source are in progress.
  We attribute this doublet to [OII] emission from the underlying host galaxy. If so, this would place GRB 000418 at a redshift of z=1.11854 +/- 0.0007, placing it near the median of GRB redshifts thus far obtained. Assuming a flat lambda cosmology of H_0 = 65 km/s/Mpc, Omega_m = 0.3, Omega_lam = 0.7 the luminosity distance to the GRB is D_L = 2.515 x 10^28 cm. Since the total fluence of the burst is 1.3 x 10^{-5} erg cm^{-2} (Hurley et al. GCN #642), we estimate the total isotropic energy release of the GRB to be E = 4.9 x 10^52 erg.
• GCN notice #662
  A. Henden (USRA/USNO) reports on behalf of the USNO GRB team:
  Final UBVRcIc all-sky photometry for the field of GRB000418 is now available on our anonymous ftp site: ftp://ftp.nofs.navy.mil/pub/outgoing/aah/grb/grb000418.dat. It has been acquired with the USNOFS 1.0-m telescope on three photometric nights. This 11x11arcmin field surrounds the proposed counterpart and extends a little fainter than V=21. All stars brighter than V=14 are saturated and should be used with care. The astrometry in this file is based on linear plate solutions with respect to USNO-A2.0. The internal errors are less than 100mas.
  The field is filled with galaxies. In fact, object C in the original list of comparison stars is a galaxy; it has been replaced in the updated table below with a stellar object (G) to the north of the optical counterpart:

  ID   x    y     U       B       V       R       I
  A   000  000  16.718  16.668  16.020  15.654  15.291
                 0.020   0.020   0.019   0.019   0.019
  
  B  -158 +050  19.559  18.529  17.447  16.802  16.281
                 0.192   0.030   0.027   0.027   0.027
  
  D  -094 -006    -     20.424  19.631  19.118  18.538
                         0.051   0.032   0.035   0.070
  
  E  -200 -042    -     19.856  18.988  18.484  18.043
                         0.021   0.021   0.061   0.078
  
  G  -102 +220  19.402  19.800  19.330  18.935  18.637
                 0.150   0.065   0.065   0.065   0.079
  

  Notes: star A is the Mirabal et. al. comparison star; x,y offsets are in arcsec with respect to this star, positive east and north.
• GCN notice #669
  M. R. Metzger (Caltech) and A. Fruchter (STScI) report:
  The suggested afterglow candidate for GRB 000418 (Klose et al. GCN645) was imaged in the R band with the Keck I telescope + LRIS on UT May 6.42. We measure R = 23.57 +- 0.10 for the object at this epoch. When combined with the photometry of Mirabal et al. (GCNs 646, 650, 653), this suggests that the decay rate has steepened to a t ^ -1.2 power law from the shallower slope of the early photometry. We also note that in our stacked image having approx. 0".6 FWHM seeing, the candidate PSF does not appear extended (is consistent with a point source PSF). This suggests that the continuum emission is still dominated by the afterglow, or that the underlying host galaxy (cf. Bloom et al. GCN 661) is compact.
• GCN notice #689
  J. S. Bloom, A. Diercks, T. J. Galama, A. Mahabal, S. R. Kulkarni, F. A. Harrison, and P. Mao (Caltech) on behalf of the larger Caltech-NRAO-CARA GRB collaboration report:
  We have detected two components of the putative host galaxy of GRB 000418 (Hurley et al. GCN #642; Klose et al. GCN #645): an optically bright component at the position of the transient and an extended red component.
  Our optical observations were conducted on 2 May 2000 UT with the Echellete Spectrograph Imager (ESI) on Keck II and on 29 May 2000 UT with COSMIC on the Palomar 200-inch Telescope. The light curve at the position of the optical transient has appeared to level off in R-band. Fitting the light curve with a power-law + constant flux, we find this component (at the position of the OT) has R = 24.0 +/- 0.3 mag (1-sigma) and the decay constant is alpha=-1.3 +/- 0.3 (1-sigma). This is consistent with the detection of strong emission lines at the position of the OT (Bloom et al. GCN #661).
  In the infrared, we obtained 92 minutes of Ks-band imaging on 13 May 2000 of the field of GRB 000418 with NIRC on the Keck I 10-m Telescope. In ~0.5 arcsec seeing (FWHM), we detect both the IR transient and a faint galaxy extended (3--4 arcsec) to the southeast from the transient. The transient appears to lie on the edge of the extended K-band emission.
  Together, the imaging and spectroscopic data suggest a possible association of the GRB with a bright star-forming region in an otherwise red galaxy.
• GCN notice #733
  M. Metzger, A. Fruchter, N. Masetti, E. Palazzi, E. Pian, S. Klose, and B. Stecklum report for a larger HST GRB Collaboration:
  The field of GRB 000418 was observed by the Hubble Space Telescope using the STIS camera in open (50CCD) mode on UT 2000 June 4.17. The position of the transient with respect to the STIS image was made by performing relative astrometry of early infrared images of the transient from the Calar Alto 3.5m (GCN 645) and optical images on Apr 20.9 UT from the Telescopio Nazionale Galileo 3.5m with deep late-time images from Keck (GCN 669). The transient position on the Keck images was then transformed to the STIS image.
  Near the position of the transient, a compact galaxy with half-light radius of 0.13 arcsec is detected with R = 23.9 +- 0.2 mag (where much of the photometric uncertainty is due to the uncertain spectral energy distribution of the galaxy). The best fit position of the OT is approx 0".08 +- 0".15 arcsec east of the center of this galaxy, which we infer is the likely host. The magnitude measured is within a few tenths of a magnitude of the May 6 Keck measurement (GCN 669), and thus the OT does not likely contribute significant flux to the host in the STIS image.
  The next nearest galaxies to the transient is a pair approx 2 arcsec southeast of the host and are detected in both the STIS and Keck images at total R magnitude of 26.2 +- 0.3 mag. The pair shows no significant extension toward the host galaxy in either the STIS or Keck images.
  A reduced image of the STIS field, with transient location indicated, can be obtained at http://www.stsci.edu/~fruchter/GRB/000418.
• Light curve and finding chart from Klose et al. (astro-ph/0007201)
  
  
  
• GCN notice #1061
  A. Fruchter and M. Metzger report for a larger HST GRB Collaboration:
  The field of GRB 000418 was re-observed by the Hubble Space Telescope starting on UT 2001 Feb 11.64 using the STIS camera in open (50CCD) mode. The individual exposures were combined using Drizzle for a total exposure time of 5120 s.
  When this image is subtracted from that obtained by HST on 2000 June 4.17 a small residual of magnitude R~28 is found at the position of the compact galaxy believed to be the host galaxy (GCN 669); however, the residual is sufficiently faint to be consistent with no detection at about the 2 sigma level. Taking into account the varying brightness of the host galaxy we find an upper limit to the brightness of the OT on 2000 June 4.2 of R > 27.5.
  This upper limit on the R-band flux implies that the decay of the optical transient steepened to at least t ^ -1.75 to -2 at late times, in agreement with the result obtainted primarily from radio data by Berger et al (20001, astro-ph/0102278).
  The images of the STIS field, with transient location indicated, can be seen at http://www.stsci.edu/~fruchter/GRB/000418.
  This message may be cited.
• GCN notice #1182
  E. Berger (Caltech), L. Cowie, H. Aussel, A. Barger (U of Hawaii), S. R. Kulkarni (Caltech), and D. A. Frail (NRAO), report:
  We observed the position of GRB000418 with the Sub-millimeter Common User Bolometer Array (SCUBA) on the James Clark Maxwell Telescope (JCMT) at 850 and 450 microns on the nights of Oct 30th through Nov 1st, 2001. We find a source with a flux density of 3.4+/-0.8 mJy at 850 microns and 38+/-10 mJy at 450 microns. The spectral index between 850 and 450 microns, beta~3.8 (F_nu~nu^beta), is indicative of thermal emission from dust, as observed from other SCUBA galaxies.
  In addition, observations with the VLA conducted during the month of June reveal a 4-sigma source at 8.46 GHz at the position of GRB000418, whereas an extrapolation of the power-law decay of the afterglow indicates that the flux density of the afterglow at this frequency should be well below the detection limit of the VLA (Berger et al. 2001).
  Based on the astrometric accuracy of the of the VLA detection (+/-0.6 arcsec) and the spectral characteristics of the SCUBA source, we conclude that we have detected the host galaxy of GRB000418. This is the third GRB host galaxy, the other two being GRB980703 (Berger, Kulkarni, & Frail 2001) and GRB010222 (Frail et al. 2001), which shows significant emission at submillimeter and centimeter wavelengths, indicating the presence of high levels of star formation. The star formation rate estimated in the usual manner (Carilli & Yun, 1999) is ~500-1000 Msun/yr (using a Salpeter IMF), typical of the sample of dusty, high redshift starburst galaxies (Smail et al. 2000).
  References:

  Berger, E., et al., 2001, ApJ, 556, 556.
  Berger, E., Kulkarni, S. R., and Frail, D. A. 2001, ApJ, 560, 652.
  Carilli, C. L., and Yun, M. S. 1999, ApJ, L13.
  Frail, D. A., et al. 2001, Accepted to ApJ; astro-ph/0108436.
  Smail, I., et al. 2000; astro-ph/0008237