Gamma-ray Burst 991208

On December 8, 1999, 04:36:52 UT a very bright GRB was detected by Ulysses, KONUS and NEAR and localized by triangulation to a 14 arcmin^2 error box.

(All information courtesy of the instrument teams.)

Previous IAU Circulars

• IAUC 7332 optical afterglow discovery
• IAUC 7333 IRAM detection at 240 GHz

• GCN notice #450
  K. Hurley (UCB SSL), on behalf of the Ulysses GRB team, and T. Cline (NASA GSFC), on behalf of the KONUS and NEAR GRB teams, report:
  Ulysses, KONUS, and NEAR observed an extremely intense, 60 s long gamma-ray burst on December 8, 1999, at 04:36:52 UT. Preliminary estimates indicate a fluence >25 keV of ~10^-4 erg/cm^2, and considerable flux was observed by NEAR >100 keV. We have localized this burst to a 14 sq. arcmin. error box whose corners are:

  RA(2000)        Decl.(2000)
  
  16 h 33 m 47 s   +46 o 27 ' 43 "
  16 h 34 m 08 s   +46 o 20 ' 19 "
  16 h 33 m 43 s   +46 o 32 ' 52 "
  16 h 34 m 04 s   +46 o 25 ' 29 "
  

  This error box can be refined considerably.
• GCN notice #451
  D. A. Frail (NRAO) reports on behalf of a larger collaboration:
  Beginning 1999 December 10.92 UT we imaged the IPN error box (Hurley et al. GCN #450) of GRB 991208 with the Very Large Array (VLA) at 4.86 GHz and 8.46 GHz. Near the center of the IPN box, at R.A.=16 33 53.50, dec.=+46 27 20.9 (J2000), there is a previously uncataloged source. The source is unresolved at a resolution of 0.8 arcsec and has a spectral index of +1.4. Based on the source location, its inverted spectrum and compactness we consider this to be a strong candidate for the afterglow from GRB 991208. This GRB is located in the daytime sky, making optical observations all but impossible at this time. We urge further radio observations to determine whether the source is variable.
• GCN notice #452
  Alberto Castro-Tirado, LAEFF-INTA (Madrid) and IAA-CSIC (Granada), Javier Gorosabel, LAEFF-INTA (Madrid) and Univ of Amsterdam (UoA), Jochen Greiner, AIP (Potsdam), Holger Pedersen, KUO (Copenhagen), Elena Pian, ITESRE (Bologna), Paul Vreeswijk (UoA) on behalf of a larger European Collaboration, Chris Blake and Gavin Dalton (Oxford Univ. and INT Group, La Palma), Georg Feulner and Ulrich Hopp, Universitat Sternwarte (Hamburg and Munich), Nick Rattenbury (Univ. of Auckland, New Zealand) report:
  We have obtained several exposures of the IPN error box for GRB 991208 (Hurley et al. GCN 450) with the 2.5-m Isaac Newton telescope at La Palma and with the 2.2-m telescope at the German- Spanish Calar Alto Observatory. The images were taken on Dec 10.27 (I-band) and Dec 11.25 UT (R- and I-band filters). After a visual comparison with the Digital Sky Survey, a new source is clearly detected with R = 19.1 +/- 0.1 (Dec 11.27). Its position is AR(2000) = 16h 33m 53.51s, Dec(2000) = +46 27 21.5 (+/- 1"). We note that this object coincides with the radio source reported by Frail et al. (GCN 451) and therefore is the optical afterglow to GRB 991208. Further multiwavelength imaging and spectroscopy are encouraged. A finding chart will be posted at http://www.laeff.esa.es/~ajct/GRBs/GRB991208.
  
• GCN notice #453
  B. Stecklum, S. Klose (Thueringer Landessternwarte Tautenburg), O. Fischer (Universitaets-Sternwarte Jena), 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), A. Castro-Tirado (LAEFF-INTA, Madrid, and IAA-CSIC, Granada), J. Greiner (AIP Potsdam), J. Gorosabel (LAEFF-INTA, Madrid, and University of Amsterdam), and A. Riffeser (Universitaets-Sternwarte Muenchen) report:
  The error box of GRB 991208 (Hurley et al., GCN 450) was observed with the Tautenburg Schmidt telescope on 1999 Dec. 11.21 UT in the I band. An object was found whose position corresponds to that of the VLA radio source which is a strong candidate for the afterglow from GRB 991208 (Frail et al. 1999, GCN #451). This optical source is not visible in the Digitized Sky Survey. The detection of the radio and optical sources which coincide in their positions within the astrometric errors strongly supports the view that their origin is the afterglow of the GRB. Photometric calibration of the I-band image is in progress. The comparison of the brightness of the newly found object with nearby USNO stars indicates an I magnitude of about 19...19.5 mag. The presence of the optical source is confirmed by independent observations of Castro-Tirado et al. (GCN 452). The image can be found at http://www.tls-tautenburg.de/research/grb991208.html
• GCN notice #454
  B. L. Jensen, J. Hjorth, H. Pedersen (University of Copenhagen), H. E. Kristen (CfA), L. Tomassi (Universita di Milano), E. Pian (ITESRE, Bologna) and K. Hurley (UCB SSL) report on behalf of a larger European collaboration:
  We have imaged a significant fraction of the errorbox of GRB 991208 (Hurley & Cline GCN #450) with the 2.5-m Nordic Optical Telescope. Three 5-min R-band exposures were obtained with ALFOSC on 10.27 December 1999 UT and three 3-min R-band exposures were obtained with StanCam on 11.85 December 1999 UT. On both occasions the data were obtained during twilight, at high (3 - 4) airmass and in bad seeing (2.5" - 3" FWHM). At the location of the new radio (Frail GCN #451) and optical (Castro-Tirado et al. GCN #452) source we detect a transient optical source [at RA(J2000) = 16:33:53.52, Dec = +46:27:21.0 (+- 0.4")], thus confirming its proposed identification with the afterglow of GRB 991208. We have performed PSF photometry on the images using DAOPHOT II/ALLSTAR and tied our photometric zeropoint to the USNO-A2.0 star 1350-08916561 which has R = 15.8. On this system we find that the magnitudes of the optical transient were R = 18.7 +- 0.1 on 10.27 Dec and 20.0 +- 0.2 on 11.85 Dec. We caution however that the latter data point may be affected by systematic uncertainties due to the difficult observing conditions. If the optical transient follows a power law decay, the decay index is -2.15 and the predicted magnitude on 12.25 Dec is R = 20.2 +- 0.3. If we discard the 11.85 Dec data point and use R = 19.1 +- 0.1 on 11.25 Dec (GCN #452), the decay index is -0.98 and the predicted magnitude on 12.25 Dec is R = 19.4 +- 0.2.
  The NOT images will be posted at http://www.astro.ku.dk/~brian_j/grb991208/.
• GCN notice #455
  D. S. Shepherd, S. Jogee, S. R. Kulkarni and D. A. Frail on behalf of the Caltech-NRAO-Keck GRB effort report the detection of the radio afterglow of GRB 991208 at millimeter wavelengths.
  We undertook observations of the afterglow of GRB 991208 (Frail, GCN 451) with the Owens Valley Millimeter Array. The mean epoch of the observations is UT 1999 December 11.58. We detected a source with a flux of 3.8 +/- 0.8 mJy at position alpha(J)=16:33:53.5 and delta(J) = +46:27:21.2. This is coincident (within errors) with the radio afterglow of GRB 991208 first discovered at the VLA (GCN 451). This the brightest afterglow detected at millimeter wavelengths to date. We urge observations at higher frequencies.
• GCN notice #456
  Peter Garnavich (CfA/Notre Dame) and Alberto Noriega-Crespo (IPAC/CalTech)
  We imaged the field of GRB991208 with the Vatican Advanced Technology Telescope (VATT) on 1999 Dec 12.52 (UT) in an R filter. The optical afterglow (GCN 453) was detected in 3x600s exposures and using a single set of Landolt standards we estimate the R-band brightness to be 20.5+/-0.1 mag. This is consistent with the brightness predicted by Jensen et al. (GCN 454) for the steeper of their two suggested decay rates, that is a decay index of -2.15. A bright star 43" West and 24" South of the optical transient is estimated to have R=15.9+/-0.1.
• GCN notice #457
  Guy Pooley, MRAO, University of Cambridge, reports two observations of GRB991208 (first detected by Frail, GCN 451, with the VLA), using the Ryle Telescope at 15 GHZ:

  99 Dec 11.6 UT    2.1 +- 0.3 mJy (sigma)
  99 Dec 12.5 UT    2.1 +- 0.4 mJy
  

  More observations are planned.
• GCN notice #458
  J. P. Halpern & D. J. Helfand (Columbia U.) report on behalf of the MDM Observatory GRB follow-up team:
  We imaged the field of GRB 991208 in the R band on Dec. 13.53 UT using the MDM 2.4m telescope. A single 10 minute exposure was obtained in non-photometric conditions. The seeing was 1.1 arcseconds. The afterglow was detected at R = 20.92 +/- 0.06, referenced to the comparsion star quoted in GCNs 454 and 456 as having R = 15.9. The decay index between our measurement and that of Garnavich & Noriega-Crespo one day earlier (GCN 456) is -1.9 +/- 0.4.
• GCN notice #459
  Michael Bremer (IRAM Grenoble), Frank Bertoldi (MPIfR Bonn), Ute Lisenfeld (IRAM Granada), Alberto Castro-Tirado (LAEFF-INTA Madrid and IAA-CSIC Granada), Titus Galama (Caltech, Pasadena), and Ernst Kreysa (MPIfR) report:
  The afterglow of GRB 991208 was detected at 240 GHz with the Max-Planck Millimeter Bolometer (MAMBO) array (80 GHz bandwidth, 10.7 arcsec HPBW) at the IRAM 30 m telescope on Pico Veleta, at the position reported by Frail et al. (GCN 451). Three on-off integrations yield the following flux densities:

   UT December 11.77, 1999        2.6 +/- 0.8 mJy
   UT December 12.38, 1999        1.9 +/- 0.6 mJy
   UT December 14.35, 1999        2.2 +/- 0.7 mJy
  

  Combining all data we obtain a flux density 2.4 +/- 0.5 mJy. The source intensity appears to remain nearly constant. We will continue to monitor its flux.
• GCN notice #460
  A. Diercks, J. S. Bloom, S. G. Djorgovski, L. Hillenbrand, and J. Carpenter (Caltech) report on behalf of the Caltech-NRAO-CARA GRB collaboration:
  A 1500-s spectrum of the afterglow of GRB 991208 (GCN #450; GCN #451; GCN #452) was obtained on the night of 14 Dec 1999 UT at the Keck II 10-m Telescope on Mauna Kea by L. Hillenbrand and J. Carpenter (Caltech). The observations were conducted using the Low-Resolution Imaging Spectrometer (LRIS; Oke et al. 1995) with a 400 line/mm grating blazed at ~8500 Ang giving an effective wavelength coverage of ~6250 - 9050 Ang. A previously-measured instrument response function was used for an approximate flux calibration.
  Interestingly, the spectrum appears very blue, in contrast with theoretical expectations for an afterglow. Though the spectrograph slit was aligned close to the parallactic angle, the observations were performed at an airmass of ~3.6 and with a bright dawn sky foreground. However, we do not think that the observed spectral slope can be entirely explained by the differential slit losses. The extreme blueness is so puzzling that we strongly encourage multiband photometric or additional spectrophotometric observations to check this potentially interesting result.
• GCN notice #461
  S. Dodonov, V. Afanasiev, V. Sokolov, V. Komarova, T. Fatkhullin, A. Moiseev report:
  One 2700-sec spectrum and one 4500-sec spectrum of the optical transient of GRB 991208 detected by A.Castro-Tirado et al., (GCN #452) were obtained on the nights of the 13th and 14th Dec 1999 UT respectfully with the SAO RAS 6-meter telescope at the Northern Caucasus. Observational conditions on the night of the 13th of December were poor. The seeing was 3 arcsec and the transparency was not good. On the 14th of December the observational conditions were good: the seeing ~1.5 arcsec (at a zenithal distance of 60 degrees), a good transparency. So, the first spectrum is with a poor S/N ratio, the second one is much better. The observations were carried out with the integral field spectrograph (Multi Pupil Fiber Spectrograph, MPFS http://www.sao.ru:8100/~gafan/devices/mpfs/mpfs_main.htm) with 300 lines/mm grating blazed at 6000 A giving a spectral resolution of about FWHM=14A/px and effective wavelength coverage of 4100 - 9200 A. A spectrophotometric standards HZ44 and BD+75d325 (Oke et al. 1995) were used for the flux calibration. The spectra show a blue continuum and in the second one with better S/N there are possible two emission lines. The data are being processed.
  In the second night (on Dec 14.14 UT) simultaneously with spectroscopic observations at the 6-meter telescope we imaged the field of GRB991208 in the R_c band (Cousins) with the SAO RAS 1-m telescope (Zeiss-1000). Two 10-minute exposures were obtained at an airmass of ~1.6 in good photometric conditions. The seeing was of ~2 arcseconds. The brightness estimate was made for optical counterpart of GRB 991208: R_c = 21.6 +/- 0.3. For photometric calibration Landolt standards were used.
• GCN notice #462
  N. Masetti, E. Palazzi, E. Pian, F. Frontera (ITESRE, CNR, Bologna), S. Benetti, A. Magazzu' (TNG), A.J. Castro-Tirado (LAEFF-INTA and IAA-CSIC) and B.L. Jensen (Univ. of Copenhagen), on behalf of a larger collaboration, report:
  R images of the optical afterglow of GRB991208 (GCN #452 and #453) were obtained between Dec. 12.29 and Dec. 15.29 UT at Roque de Los Muchachos (Canary Islands, Spain) with the 3.58-meter Telescopio Nazionale Galileo (TNG) + OIG CCD camera. We clearly detected the optical transient in all R images. The following table shows the results of these observations:

       Date (UT)       Exptime      Magnitude     Seeing
                                                       
    1999 Dec 12.29     500 sec    20.25 +- 0.15    1".8
    1999 Dec 13.29     360 sec    20.3  +- 0.2     1".6
    1999 Dec 14.29     600 sec    21.25 +- 0.15    1".5
    1999 Dec 15.29     900 sec    21.6  +- 0.3     1".5 (clouds)
  

  Photometric calibration was tied to the USNO A2.0 star 1350-08916561 (R = 15.85 +- 0.1 was assumed). Preliminary analysis of R data shows that these are consistent with a power-law decay with index alpha = -2.15 (GCN #454 and #456) with the exception of the observation of Dec. 13.29, which may however be affected by uncertainties associated with the observing conditions and with the shorter exposure time.
• GCN notice #464
  J. S. Bloom, A. Diercks, S. G. Djorgovski, S. R. Kulkarni (Caltech), A. V. Filippenko (UCB), on behalf of the Caltech-NRAO-CARA GRB Collaboration report:
  On 15.638 December 1999 UT, A. Filippenko obtained a 900-s spectrum using the Low-Resolution Imaging Spectrometer (LRIS; Oke et al. 1995) on the Keck II 10-m telescope of the transient associated with GRB 991208 (GCN #450; GCN #451; GCN #452). The grating was 300 l/mm giving an effective wavelength coverage of 3850 Ang to 8850 Ang with a dispersion of ~2.47 Ang/pixel. The optical transient is better detected in this spectrum compared to the observations of December 14, 1999 and reported earlier (GCN #460). Reductions of the December 15 data reveal an emission line at lambda=8541 Ang (preliminary wavelength calibration). The presence of continuum emission blueward of this line effectively rules out a Ly-alpha origin.
  The two most likely candidate identifications of this emission line are [OII] 3727 Ang or H-alpha 6563 Ang. If the former, then the redshift implied, presumably that of the host galaxy, is z=1.29. Coupled with the bright fluence above 25 keV (10^-4 erg cm^-2; GCN #450) this implies an isotropic emission (restframe 30-2000 keV) of ~4 x 10^{53} erg (Omega=0.2, Lambda=0, H_0 = 65 km/s/Mpc). Such high energetics could be relaxed by collimated emission as suggested by the steep decay in the optical light curve.
  If instead we associate the emission line with H-alpha 6563 Ang, then the implied redshift is z=0.30, making it the lowest redshift of all cosmological GRBs. The associated isotropic energy loss would be ~2 x 10^{52} erg (Omega=0.2, Lambda=0, H_0 = 65 km/s/Mpc), consistent with the energies of GRB 970508, 970228, and GRB 980613. We disfavor this low-redshift hypothesis since the [OIII] 4959,5007 lines should be present in our spectrum but we have not detected these lines. Nevertheless, if the low redshift proves correct, then GRB 991208 would be an excellent candidate for a detectable supernova component in the the coming month.
• GCN notice #467
  Vijay Mohan, Anil K. Pandey, Ram Sagar and S.B. Pandey (from UPSO, Nainital) and Alberto J. Castro-Tirado (INTA, Madrid and IAA, Granada) -on behalf of a larger European collaboration- report:
  We have imaged the field of GRB 991208 with the 2k x 2k CCD camera mounted on the UPSO 104-cm telescope on 1999 Dec 12.0 (UT); Dec 13.0 (UT) and Dec 14.0 (UT) in I photometric passband during photometric sky conditions. The optical transient of the GRB 991208 (Castro-Tirado et al. GCN 452) is fading rapidly about 0.5 mag between Dec 12 and 13. This indicates a power decay index of -2.0. The object has become so faint for our telescope that it is barely visible on the 1 hour CCD image. Thus flux decay in I is almost similar to that in R filter (Jensen et al. GCN 454; Garnavich et al. GCN 456). Calibration of the field is in progress.
• GCN notice #475
  S.N. Dodonov, V.L. Afanasiev, V.V. Sokolov, A.V. Moiseev (SAO-RAS) and Alberto J. Castro-Tirado (INTA, Madrid and IAA, Granada) report:
  A BTA/MPSF 4500-s spectrum of the optical transient of GRB 991208 (GCN #452) was obtained on 14.14 Dec 1999 UT with the the SAO-RAS 6-m telescope. The observational conditions on 14 Dec were already given in GCN #461. The data were obtained with the integral field spectrograph (Multi Pupil Fiber Spectrograph, MPFS, http://www.sao.ru:8100/~gafan/devices/mpfs/mpfs_main.htm ) with 300 lines/mm grating blazed at 6000 A giving a spectral resolution of about 5 A/pix and effective wavelength coverage of 4100 - 9200 A. Emission lines at lambda = 6350 A, 8550 A and 8470 A are present, with the most likely identifications of these emission lines being: [OII] 3727 A, [OIII] 4959,5007 A at a redshift of z = 0.707 +/-0.002, presumably that of the host galaxy.
• GCN notice #480
  J. S. Bloom, A. Diercks, S. R. Kulkarni, S. G. Djorgovski, N. Z. Scoville, D. T. Frayer (Caltech) report on behalf of the Caltech-NRAO-CARA GRB Collaboration:
  On 16 December 1999 UT N. Scoville and D. Frayer observed the field of GRB 991208 with the slit-viewing camera of the Near-Infrared Echelle Spectrograph (NIRSPEC; McLean et al. SPIE, 1998) at the Keck II 10-m Telescope on Mauna Kea, Hawaii. In a stacked 1560-s imaging exposure we detect a K-band source at the position of the transient afterglow (GCN #450, GCN #451, GCN #452) of GRB 991208. We find no clear extension of this presumed IR afterglow with respect to other stars in the field. We note the presence of a faint extended galaxy ~8.3" W of the source. Comparison with standard star SJ 9162 (Persson, AJ, 1998) yields a preliminary magnitude of the afterglow of K=19.31 +/- 0.15 mag (16.68 Dec 1999 UT).
  Extrapolating the R-band light curve using the reported decay slope from Masetti et al. (GCN #462), on 16.68 Dec 1999, we find R - K = 2.7 (including the small Galactic extinction) implying a spectral index beta = -0.77 +/- 0.14 (statistical uncertainty). We note this optical-IR spectral index is inconsistent with reports of an apparent blue spectrum from preliminary reductions of optical spectroscopy (GCN #460, GCN #461).
  A K-band finding chart can be found at http://astro.caltech.edu/~jsb/GRB/grb991208/
• GCN notice #481
  S. G. Djorgovski, A. Dierks, J. S. Bloom, S. R. Kulkarni (Caltech), A. V. Filippenko (UC Berkeley), L. A. Hillenbrand, and J. Carpenter (Caltech), report on behalf of the Caltech-CARA-NRAO GRB collaboration:
  We recalibrated and combined the Keck spectra of GRB 991208 obtained on 14 and 15 Dec 1999 UT, for which preliminary results were reported earlier (GCN #460, GCN #464). Addition of the spectra improved the total S/N as expected. We confirm the existence of emission lines at the observed wavelengths 6356, 8454, and 8545 Ang, reported by Dodonov et al. (GCN #475). We agree with their proposed identifications as [O II] 3727, and [O III] 4959, 5007, giving the redshift z = 0.7055 +- 0.0005. However, we note that the proximity of the strong night sky lines (especially for the tentative 8454 Ang line), and additional spectroscopic observations are still needed in order to firm up this result.
  Assuming z = 0.7055, and the standard Friedmann cosmology with h = 0.65, Omega_0 = 0.2, and Lambda_0 = 0, the luminosity distance is 1.30E28 cm. Assuming the integrated gamma-ray fluence of >~ 1.E-4 erg/cm2 (GCN #450), the implied isotropic energy is ~ 1.3E53 erg, which of course may be affected by beaming.
  We also performed a power-law fit to the fully calibrated and extinction corrected spectrum from UT Dec. 15.64. For F_nu ~ nu ** beta, we obtain beta = -0.9 +- 0.15, in a good agreement with the photometric measurement reported by Bloom et al. (GCN #480).
• GCN notice #531
  C. Garcia-Miro (LAEFF-INTA, Madrid and IAA-CSIC, Granada), J. Gorosabel (DSRI, Copenhagen), J. Calvo (INSA, Madrid) and A.J. Castro-Tirado (LAEFF-INTA, Madrid and IAA-CSIC, Granada) report:
  We scanned at 8.42-GHz the position of the afterglow reported for GRB 991208 (GCN 451) with the 70-m radio-telescope of the Madrid Deep Space Communication Center (MDSCC, NASA-INTA) located at Robledo de Chavela, Madrid. The observations were based on two observing runs carried out on Dec 22.2491-22.6488 UT and Dec 23.3243-23.6095 UT 1999. We derive a 1 sigma upper limit for the flux density of 3.5 mJy for the afterglow. The authors wish to thank the MDSCC staff and the JPL scheduler for their enthusiastic support.
• GCN notice #631
  A. Henden (USRA/USNO) reports on behalf of the USNO GRB team:
  We have acquired UBVRcIc all-sky photometry for the field of GRB 991208 with the USNOFS 1.0-m telescope on two photometric nights. This 11x11arcmin field covers the optical transient and extends a little fainter than V=21. 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/grb991208.dat
  The astrometry in this file is based on linear plate solutions with respect to USNO-A2.0; estimated errors are +/- 0.1 arcsec on the brighter stars.
• GCN notice #764
  A. Diercks, J. S. Bloom, T. J. Galama, and S. R. Kulkarni report on behalf of the larger Caltech-NRAO-CARA collaboration:
  We observed the field of GRB 991208 (Hurley et al. 1999, GCN #450) with the with the Echellette Spectrograph and Imager (ESI) on the Keck II 10-m Telescope on Mauna Kea at 4 April 2000 UT. A 1200-s Gunn r-band image with 0.75 arsec seeing (FWHM) reveals a galaxy at the location (Frail et al. 2000, GCN #451) of the afterglow. This galaxy, the putative host of GRB 991208, is likely responsible for the nebular emission lines previously observed spectra of the transient (Dodonov et al. 1999, GCN 475; Bloom et al. 1999, GCN 464). The galaxy appears extended with an ellipticity of ~0.3 and PA= 106 +/- 6 degrees. Using differential astrometry with respect to our early K-band image when the transient was bright (Bloom et al. 1999, GCN #480), we find the GRB was 66 +/- 63 mas (1 sigma) from the center of the galaxy; i.e. the GRB location is consistent with no offset from its host.
  A 39" x 39" image of the field surrounding the host galaxy is posted at http://astro.caltech.edu/~ad/grb991208-host.ps
• GCN notice #872
  A. Fruchter, (STScI), P. Vreeswijk (Amsterdam), V. Sokolov (SAO RAS) and A. Casto-Tirado (IAA-Granada, INTA-Madrid) report on behalf of the larger HST GRB collaboration report:
  We observed the field of GRB 991208 with the HST STIS CCD on August 3, 2000, or approximately 8 months after outburst. A total exposure time of 5210s was obtained in the (50CCD) clear aperture. At the position of the burst we find a very compact galaxy with a magnitude of V= 24.6 +/- 0.15, where a conservative error bar is given due to the very wide bandpass of the filter. The full-width at half-maximum (FWHM) of the galaxy is measured as 0."095, only marginally larger than the intrinsic 0."08 of the STIS PSF. However, both curve-of-growth analysis and direct subtaction of a STIS PSF indicate that the object is indeed resolved. We estimate the intrinsic FWMH of the core of the galaxy is less than 0."06.
  Comparison of the HST image with ground-based images (Castro-Tirado et al., A&A submitted, see also GCN 452) shows the position of the optical transient to be offset from the center of the host by less than the 0."1 one-sigma uncertainty in the relative positions.
  We believe the ellipticity and position angle reported for the host by Bloom et al. (GCN 764) is due to the presence of a fainter, small object located approximagely 1" to the ESE of the host. It is not clear from the HST image whether these two objects are merely close due to a projection effect or whether they are indeed physically related.
  The wider (50") field of the STIS CCD shows a rich association of spiral galaxies surrounding the position of the OT. While some of the spirals show grand design or prominent bulges, and are up to 5" across, we cannot rule out the possibility that the host of the GRB (which is at a redshift of 0.7, Dodonov et al., GCN 475) is a member of this apparent group of galaxies.
  The images can be seen at http://www.stsci.edu/~fruchter/GRB/991208.