//////////////////////////////////////////////////////////////////////// TITLE: GCN GRB OBSERVATION REPORT NUMBER: 801 SUBJECT: IPN triangulation of GRB000926 DATE: 00/09/27 20:05:35 GMT FROM: Kevin Hurley at UCBerkeley/SSL K. Hurley, on behalf of the Ulysses GRB team, E. Mazets and S. Golenetskii, on behalf of the Konus-Wind GRB team, and T. Cline, on behalf of the Konus-Wind and NEAR GRB teams, report: Ulysses, Konus, and NEAR observed this burst at 85773 s. As observed by Ulysses, it had a duration ~25 s, a 25-100 keV fluence of We have triangulated it to a preliminary, 3 sigma error box whose area is approximately 35 sq. arcmin. and whose coordinates are RA(2000) DEC(2000) 17 h 4 m 15.05 s 51 o 46 ' 34.93 " (CENTER) 17 h 4 m 2.88 s 51 o 46 ' 10.91 " (CORNER) 17 h 4 m 31.05 s 51 o 38 ' 13.48 " (CORNER) 17 h 3 m 59.06 s 51 o 54 ' 56.51 " (CORNER) 17 h 4 m 27.22 s 51 o 46 ' 58.88 " (CORNER) This box may be improved. //////////////////////////////////////////////////////////////////////// TITLE: GCN GRB OBSERVATION REPORT NUMBER: 802 SUBJECT: IPN triangulation of GRB000926 DATE: 00/09/27 20:10:46 GMT FROM: Kevin Hurley at UCBerkeley/SSL K. Hurley reports: Because I am logged in from an unfamiliar terminal, the tilde characters caused a line to be erased from the previous message (GCN 801). The 25-100 keV fluence was approx. 2.2E-5 erg/cm^2, and the peak flux over 0.25 s was approx. 1.3E-6 erg/cm^2 s. //////////////////////////////////////////////////////////////////////// TITLE: GCN GRB OBSERVATION REPORT NUMBER: 803 SUBJECT: Optical candidate for GRB000926 DATE: 00/09/28 00:40:30 GMT FROM: Javier Gorosabel at LAEFF-INTA, Madrid J. Gorosabel (DSRI, Copenhagen), J.M. Castro Ceron (ROA, San Fernando), A.J. Castro-Tirado (IAA-CSIC, Granada), J. Greiner (AIP, Potsdam), C. Wolf (MPIA, Heidelberg), N. Lund (DSRI, Copenhagen) report on behalf of a larger European collaboration: Starting at 27.859UT SEP 2000 we obtained R- ,V-, I- and B-band images of the IPN error box for GRB 000926 (Hurley et al., GCN #801) with the 2.2m. telescope at the Calar Alto Observatory. A comparison with the Digital Sky Survey-2 revealed a new bright point-like source located at: RA(J2000)= 17h 04m 09.70s DEC(J2000)= +51o 47' 10.2" Our uncertainty is 2". These object's coordinates agree with the ones reported independently by Dall et al. It is clearly detected in the R-, V-, and I-bands. We derive a preliminary magnitude of 19.5 +/- 0.3 based on a zero point calculated with USNO-2.0 stars in the field. Further multicolour imaging is in progress. This message may be cited. [GCN OPS NOTE 28Sep00: The last two authors were added to the list at the first author's request.] //////////////////////////////////////////////////////////////////////// TITLE: GCN GRB OBSERVATION REPORT NUMBER: 804 SUBJECT: GRB 000926: Optical candidate DATE: 00/09/28 00:41:00 GMT FROM: Johan U. Fynbo at Inst. Phys. and Astro., Aarhus,Denmark T. Dall (NOT and University of Aarhus), J.P.U. Fynbo (ESO), H. Pedersen, B.L. Jensen, J. Hjorth (U. of Copenhagen) and J. Gorosabel (DSRI, Copenhagen) report on behalf of a larger European GRB Collaboration: "Using the ALFOSC on the 2.5m Nordic Optical Telescope, we have obtained U,B,R and I-band imaging of the field of GRB 000926 (Hurley et al., GCN #801) on 2000 September 27.8-28.1 UT. Comparing with DSS-2 (red) we find a bright point source not visible on the DSS-2 exposure. The coordinates of this object are: RA(J2000) : 17 04 09.62 Dec(J2000) : +51 47 11.2 (with an uncertainty of about 2") These coordinates are consistent with those reported independently by Gorosabel et al. This object is detected in both U,B,R and I-band images. A 1hr spectrum covering the region 3500AA-7000AA has been obtained showing a blue spectrum with strong absorption lines. The redshift has not yet been determined. A preliminary magnitude for the object is: R=19.3 +- 0.2. Ingvar Svaerdh and Charlotte Moeller are acknowledged for help with the observations." //////////////////////////////////////////////////////////////////////// TITLE: GCN GRB OBSERVATION REPORT NUMBER: 805 SUBJECT: GRB000926, radio observations DATE: 00/09/28 04:40:23 GMT FROM: Dale A. Frail at NRAO D. A. Frail (NRAO) and E. Berger (Caltech) report on behalf of a larger collaboration: "Beginning on September 28.16 we observed the IPN error box of GRB000926 (GCN #801) with the VLA at 8.46 GHz and 4.86 GHz. A quick-look analysis of the 8.46 GHz data reveals a ~0.5 mJy radio source positionally coincident with the optical candidate reported by Gorosabel et al. (GCN #803) and Dall et al. (GCN #804). Further observations are planned." This message may be cited. //////////////////////////////////////////////////////////////////////// TITLE: GCN GRB OBSERVATION REPORT NUMBER: 806 SUBJECT: GRB 000926, Optical Observation DATE: 00/09/28 07:15:17 GMT FROM: Jules Halpern at Columbia U. J. P. Halpern, N. Mirabal (Columbia U.), D. Turnshek & J. Busche (U. Pittsburgh) report on behalf of the MDM Observatory GRB follow-up team: "We observed the optical candidate for GRB 000926 (Gorosabel et al. GCN #803; Dall et al. GCN #804) in R and B on Sep. 28.177 UT using the MDM 2.4m. We measure the position of the optical candidate to be (J2000) RA 17:04:09.749, Dec +51:47:09.97 in the Guide Star Catalog system, relative to eight stars having an rms dispersion of 0".15. A preliminary magnitude for the optical candidate is measured as R = 19.89 +/- 0.02, referenced to a USNO-A2.0 star at (J2000) RA 17:04:01.206, Dec +51:46:19.88 which is listed as having R = 17.1. Since this measurement was made from an unprocessed image, it is subject to additional systematic error, and should not be used in serious analyses. The decay rate is therefore still unknown." //////////////////////////////////////////////////////////////////////// TITLE: GCN GRB OBSERVATION REPORT NUMBER: 807 SUBJECT: Spectroscopic Redshift of GRB 000926 DATE: 00/09/28 14:03:26 GMT FROM: Jens Hjorth at U.Copenhagen Spectroscopic Redshift of GRB 000926 J. P. U. Fynbo, P. Moller (ESO), T. Dall (NOT and U. of Aarhus), H. Pedersen, B. L. Jensen, J. Hjorth (U. of Copenhagen) and J. Gorosabel (DSRI, Copenhagen) report on behalf of a larger European GRB Collaboration: "We have analysed the spectrum of the optical afterglow of GRB 000926 (GCN #803, GCN #804) reported by Dall et al. (GCN #804). The spectrum was obtained 22.2 hours after the burst with ALFOSC at the Nordic Optical Telescope and covered the wavelength range from the atmospheric cut-off to 8800 A. We find two significant absorption systems: One at z = 1.378 (based on Al II 1670, Fe II 2344, Fe II 2374, Fe II 2382, Fe II 2586) and one at z = 2.066 (based on Ly alpha 1215, Si IV 1393, Si IV 1402, C IV 1548/1550, Fe II 1608, Al II 1670). The redshift of GRB 000926 is likely to be z = 2.066 due to the high column density of this absorption system. In an Omega_m = 0.3, Omega_Lambda = 0.7, H_0 = 65 km s^-1 Mpc^-1 cosmology the 25 - 100 keV fluence of 2.2 10^-5 erg cm^-2 (Hurley et al. GCN #801, GCN #802) corresponds to an isotropic energy release of 2.6 10^53 erg". //////////////////////////////////////////////////////////////////////// TITLE: GCN GRB OBSERVATION REPORT NUMBER: 808 SUBJECT: GRB 000926 HST/Chandra TOO Status DATE: 00/09/28 20:41:06 GMT FROM: Shri Kulkarni at Caltech Dear Colleagues: This note is to inform you that, under the aegis of our AO-9 program, we have requested observations of GRB 000926 (GCN 801) with the Hubble Space Telescope and Chandra X-ray Observatory. This burst with a bright optical (GC 803, 804) and radio (GCN 805) afterglow appears to be particularly well suited for detailed studies of the afterglow and the circumburst medium. We encourage intensive ground based observations of this burst so that it will become a very well studied GRB. Particularly valuable are intensive lightcurves at early times since the earliest HST observation is at least a week away (as is the requested Chandra observation). We ourselves are planning to supplement the HST and CXO observations with detailed multiwavelength observations at facilities to which our group has access (e.g. Keck, Palomar, MDM, HET). In the radio, we will be undertaking observations at VLA and OVRO and possibly other facilities as well. Shri Kulkarni, on behalf of a large international GRB collaboration. //////////////////////////////////////////////////////////////////////// TITLE: GCN GRB OBSERVATION REPORT NUMBER: 809 SUBJECT: GRB 000926: Preliminary R-band Lightcurve DATE: 00/09/28 22:35:11 GMT FROM: Johan U. Fynbo at Inst. Phys. and Astro., Aarhus,Denmark GRB 000926: Preliminary R-band Lightcurve J. Hjorth, B. L. Jensen, and H. Pedersen (U. of Copenhagen), J. U. P. Fynbo and P. Moller (ESO), J. Gorosabel (DSRI, Copenhagen) report on behalf of a larger European GRB collaboration: "Using the ALFOSC on the 2.56-m Nordic Optical Telescope we have obtained R-band imaging of the optical afterglow of GRB 000926 (GCN #801-#808) on 2000 September 27.8-28.9 UT. We find the following preliminary R-band magnitudes of the object using the reference star of Halpern et al. (GCN #806) : Sept. 2000 UT R 1 sigma -------------------------------- 27.8547 19.414 0.015 27.8594 19.428 0.011 27.8639 19.411 0.011 27.8684 19.433 0.008 27.8729 19.437 0.011 27.8774 19.453 0.010 27.8820 19.441 0.010 27.9658 19.618 0.011 27.9705 19.595 0.014 27.9750 19.641 0.015 27.9795 19.609 0.017 27.9840 19.619 0.021 28.8356 20.778 0.023 28.8911 20.834 0.034 These magnitudes show that the object identified as the optical afterglow is decaying. The temporal power-law decay index appears to progressively steepen from -1.2 on Sep 27.85 to -1.85 between Sep 28.2 (GCN #806) and Sep 28.9, indicating a 'break' in the lightcurve." //////////////////////////////////////////////////////////////////////// TITLE: GCN GRB OBSERVATION REPORT NUMBER: 810 SUBJECT: CONCAM crude optical limits before and after GRB000926 DATE: 00/09/29 01:03:57 GMT FROM: Robert Nemiroff at Michigan Tech. R. J. Nemiroff, D. Perez-Ramirez, J. B. Rafert, W. E. Pereira, C. Ftaclas, and J. Fernandez (Michigan Tech) report on behalf of the CONCAM collaboration: "The CONtinuous CAMera (CONCAM) operating on the roof of the RMT building at Kitt Peak National Observatory in Arizona has recorded data that provides very crude limits on the attributes of the OT through non-detection. Before the GRB Trigger From (2000 September 26.135) to (2000 September 26.263), spanning from roughly 20.6 hours to 17.5 hours before the Konus trigger, no obvious optical transient brighter than visual magnitude 4 was recorded. After the GRB Trigger From (2000 September 27.100) to (2000 September 27.252), spanning from roughly 2.6 hours to 6.2 hours after the Konus trigger, no obvious optical transient brighter than visual magnitude 4 was recorded. These above results were derived from a visual inspection of a series of two-minute exposures of the nearly 2 pi steradian CONCAM field. A more detailed inspection of the data might improve these magnitude limits to approximately visual magnitude 6. Data remains freely available at http://concam.net . //////////////////////////////////////////////////////////////////////// TITLE: GCN GRB OBSERVATION REPORT NUMBER: 811 SUBJECT: GRB000926: Optical observations DATE: 00/09/29 03:00:25 GMT FROM: Paul Price at RSAA, ANU at CIT P.A. Price, O. Pevunova, B.F. Madore, A. Diercks and J.S. Bloom (Caltech) report on behalf of a larger collaboration: "We have observed the optical transient candidate of Dall et. al. (GCN #804) and Gorosabel et. al. (GCN #803) with the Palomar 60-inch telescope in B, R and I. Photometry was performed relative to the USNO-A2.0 star U1350_09071131 at J2000 coordinates RA 17:04:01.21, Dec +51:46:19.9 (as per Halpern et. al., GCN #806). Results are as follows: Filter Epoch Relative Reference Magnitude B Sep 28.193 2.427 +/- 0.049 mag 17.8 mag 20.227 +/- 0.049 R Sep 28.213 2.934 +/- 0.037 mag 17.1 mag 20.034 +/- 0.037 I Sep 28.173 2.917 +/- 0.052 mag Unknown (Errors are statistical only.) Further observations are planned." This message may be cited. //////////////////////////////////////////////////////////////////////// TITLE: GCN GRB OBSERVATION REPORT NUMBER: 812 SUBJECT: GRB000926: X-ray afterglow by BeppoSAX & plan of BSAX & Chandra obs. DATE: 00/09/29 10:20:21 GMT FROM: Luigi Piro at IAS/CNR Frascati L. Piro (BeppoSAX Mission Scientist) on behalf of a large collaboration reports: A BeppoSAX TOO observation of GB000926 has started on Sept. 28.979, i.e. about 2 days after the GRB. Preliminary analysis of the first three orbits shows a relatively bright (flux about 0.5 10**-12 erg/cm2/s) unknown source in the MECS(1.6-10 keV) image. The position is RA(2000)=17h 04m 07s Decl.(2000)= +51 47' 42" which is 0.7' from the optical counterpart (Gorosabel et al. GCN 803, Dall et al. GCN 804, Halpern et al. GCN 806) and consistent with it within our errors. We identify this new X-ray source (1SAXJ1704.1+5147) as the X-ray afterglow of GB000926. This is an updated status of X-ray observations programmed on this source: 1- This BeppoSAX observation will last upto Sept. 29.046 (T_GRB+2 days) 2- A fast Chandra TOO (Cycle 1 program by Piro et al) has been scheduled for Sept. 29.67 (T_GRB+2.7 days) 3- On the basis of the results of these 2 observation we will decide whether to plan another BeppoSAX observation around T_GRB+6 days 4- Another Chandra observation should be performed by Kulkarni et al (GCN808) at later times //////////////////////////////////////////////////////////////////////// TITLE: GCN GRB OBSERVATION REPORT NUMBER: 813 SUBJECT: GRB 000926, optical observation by Oksanen (vsnet-grb) DATE: 00/09/29 11:55:19 GMT FROM: Taichi Kato at Kyoto U GRB 000926, optical observation by Oksanen (vsnet-grb) The following observation has been reported to vsnet-grb No. 14 (http://www.kusastro.kyoto-u.ac.jp/vsnet/Mail/vsnet-grb/maillist.html) Subject: [vsnet-grb 14] Re: GRB 000926, Oksanen's image Re: GRB 000926, Oksanen's image >On Oksanen's image, a very faint source near the position of the >candidate of the afterglow of GRB 000926 (vsnet-grb 10) is shown. >It is not shown in the DSS 2 R image. Further analysis is >undergoing. The precise astrometry using 43 USNO_A2.0 stars yields: R.A. = 17h04m09s.71 +/- 0s.05, Decl. = +51o47'10".0 +/- 0".5 (2000.0), which shows quite good agreement with the reported positions. Oksanen reports that every POSS scan examined at USNO server does not show this object. Thus it is highly probable that this object is the same object as a candidate of the afterglow of GRB 000926. The magnitude was about 20.0CR at Sept. 28.8 UT (comparison star is USNO_A2.0 star at 17h04m01s.21, +51o46'19".9 (2000.0), rmag = 17.1, same as Halpern et al. (GCN 806)). Note that it is somewhat brighter than Hjorth et al. (GCN 809) report. Sincerely Yours, Hitoshi Yamaoka, Kyushu Univ., Japan yamaoka@rc.kyushu-u.ac.jp //////////////////////////////////////////////////////////////////////// TITLE: GCN GRB OBSERVATION REPORT NUMBER: 814 SUBJECT: GRB 000926: Lightcurve Update and Predictions DATE: 00/09/29 13:00:56 GMT FROM: Brian Lindgren Jensen at U.of Copenhagen J. Hjorth, B. L. Jensen, and H. Pedersen (U. of Copenhagen), J. U. P. Fynbo and P. Moller (ESO), J. Gorosabel (DSRI, Copenhagen) report on behalf of a larger European GRB collaboration: Further to GCN #809, we report an additional NOT R-band data point obtained on Sept. 28.9595 UT: R=20.889+-0.035. We note that if we exclude the preliminary data point of Halpern et al. (GCN #806) and include the data point of Price et al. (GCN #811) the lightcurve is consistent with a pure power law decay with a decay index of -1.66 +- 0.02. Further monitoring of the optical afterglow is needed to distinguish a pure power law and a broken power law decay. A finding chart, a lightcurve and predictions for the coming days are posted at http://www.astro.ku.dk/~brian_j/grb/grb000926/ ." //////////////////////////////////////////////////////////////////////// TITLE: GCN GRB OBSERVATION REPORT NUMBER: 816 SUBJECT: J and K band observations of GRB 000926 DATE: 00/09/29 13:23:20 GMT FROM: Angelo Antonelli at Obs. Astro. di Roma A. Di Paola, R. Speziali, L.A. Antonelli, F. Pedichini, F. D'Alessio, G.L. Israel, D. Lorenzetti, L. Stella, Osservatorio Astronomico di Roma, Italy, on behalf of a larger collaboration report: "We observed the optical transient candidate of GRB 000926 (Gorosabel et al., GCN #803; Dall et. al., GCN #804) with the AZT-24 1.1-meter telescope at Campo Imperatore (AQ). The J-band observation started at September 28.8481 UT and the field was imaged for a total exposure time of 1800 sec. We observed a source at a position: RA(J2000)= 17h 04m 09.11s DEC(J2000)= +51o 47' 09.3" (uncertainty is 2") consistent with the optical transient of GRB 000926 (GCN #803) having a magnitude of J=18.6+/-0.3 mag with a S/N=5. The K-band observation started at Sep. 28.9345 UT and the field was imaged for a total exposure time of 1800 sec. The limiting magnitude reached in the K-band was K=17.0 mag (S/N=3) with an average FWHM of 2.5", no sources were detected at the above position. The J-band image is posted at http://argos.mporzio.astro.it/angelo/grb000926/ This message is citable." //////////////////////////////////////////////////////////////////////// TITLE: GCN GRB OBSERVATION REPORT NUMBER: 817 SUBJECT: Re: GRB 000926, optical observation by Oksanen (vsnet-grb) DATE: 00/09/29 13:24:22 GMT FROM: Taichi Kato at Kyoto U Addendum to GCN No. 813: Important information was missing, sorry. The observation referred in GCN 813 was done by Arto Oksanen, Nyrola Observatory, Finland. (http://www.ursa.fi/sirius/nytt/nytt_info.html) The observation was done using a 40-cm f6.3 SCT telescope. The image was combined from 17 240s unfiltered exposures around September 28 19:00 UT. Regards, Taichi Kato //////////////////////////////////////////////////////////////////////// TITLE: GCN GRB OBSERVATION REPORT NUMBER: 818 SUBJECT: GRB000926 - Optical observations DATE: 00/09/29 22:11:05 GMT FROM: Christian Veillet at CFHT GRB000926 - Optical observations The optical counterpart of GRB000926 has been observed using the CFH12K CCD mosaic camera at the prime focus of the 3.6-m CFH Telescope. One 600s exposure with moderate seeing (image quality between 0.9" and 1.0") has been obtained and a preliminary reduction using the reference star of Halpern et al. (GCN #806) with R=17.1 gives the following measurement for GRB000926: Sept. 29.3075 R = 21.23 +/- 0.05 Added to the R-band data points used in the analysis by Hjorth et al. (GCN #814), this new point confirms a pure power law decay with a decay value of 1.69 +/- 0.03, which is not significantly different from Hjorth et al.'s determination. An image of the area around the GRB can be found at http://www.cfht.hawaii.edu/~veillet/grb.html Kocevski, Donovan and G. Luppino are acknowledged for their help in this observation. This message may be cited. ************************************************************ Dr. Christian Veillet, CFHT Senior Resident Astronomer Phone: (808) 885-3161 http://www.cfht.hawaii.edu/~veillet/ ************************************************************ //////////////////////////////////////////////////////////////////////// TITLE: GCN GRB OBSERVATION REPORT NUMBER: 819 SUBJECT: GRB000926 optical observations DATE: 00/09/29 23:42:30 GMT FROM: Fredrick J. Vrba at USNO On behalf of the USNO GRB team, F. Vrba and B. Canzian, report two additional R-band photometric measurements of the GRB 000926 optical counterpart, discovered by Gorosabel et al. (GCN 803) and Dall et al. (GCN 804). Our observations were obtained with the USNO, Flagstaff Station, 1.0-m telescope. These measurements are based on a preliminary photometric calibration from a limited number of standard stars. UT Date Magnitude Sep 28.097 R = 19.70 +/- .03 Sep 29.146 R = 21.05 +/- .04 If weather permits at a later date, we will produce a fully-calibrated UBVRI standard sequence, as we have for several earlier GRB fields. //////////////////////////////////////////////////////////////////////// TITLE: GCN GRB OBSERVATION REPORT NUMBER: 820 SUBJECT: GRB000926 : increasing optical decay slope DATE: 00/09/30 00:47:57 GMT FROM: Johan U. Fynbo at ESO,Garching J. P. U. Fynbo, P. Moller (ESO), J. Gorosabel (DSRI, Copenhagen), J. Hjorth, B. L. Jensen, and H. Pedersen (U. of Copenhagen), report on behalf of a larger European GRB Collaboration: "Using the ALFOSC on the 2.5m Nordic Optical Telescope, we have obtained further R-band imaging of the Optical Transient (OT) of GRB 000926 (GCN #801, #803, #804) on 2000 September 29.84-29.95 UT. We find the following R-band magnitudes of the OT using the reference star of Halpern et al. (GCN #806) : UT R-band 1sigma ----------------------------- 29.8414 21.779 0.042 29.9478 21.890 0.082 An updated lightcurve including the NOT measurements (black circles) and the measurements of Halpern et al. (GCN #806), Price et al. (#811) and Veillet (GCN ~818) (open diamonds) can be seen at www.obs.aau.dk/~jfynbo/grb/grb000926/lightcurve.gif. The new NOT measurements fall below the extrapolation of the power-law decline found at earlier epochs. We conclude therefore that the decay slope of the afterglow is increasing. //////////////////////////////////////////////////////////////////////// TITLE: GCN GRB OBSERVATION REPORT NUMBER: 821 SUBJECT: GRB000926 K'-band Observation DATE: 00/09/30 07:37:08 GMT FROM: Naoto Kobayashi at SUBARU, NAOJ Naoto Kobayashi, Miwa Goto, Hiroshi Terada, Daigo Tomono (Subaru Telescope, National Astronomical Observatory of Japan), reported on behalf of SUBARU Telescope team and SUBARU IRCS team On 29 Sept, 5:20-6:00 UT (29.24 UT), we have obtained 1800-sec K' image of the field around the proposed optical transient (OT) of GRB000926 (GCNC #803, Gorosabel et al.). We used the Subaru 8.2m Telescope atop Mauna kea with a near-infrared camera and spectrograph (IRCS) during its second engineering run. The candidate OT was clearly detected in our image. http://www.SubaruTelescope.org/Latestnews/200010/GRB/grb000926.jpg Seeing was about 0".7 in the K'-band. No associated host galaxy was detected in our image. Since we did not have time to observe standards, here we just show the relative magnitudes of the OT to a number of field stars: relative relative position K'-magnitude to OT OT 0.00 +- 0.04 StarA 42"E -0.45 +- 0.03 StarB 30"E,34"S -2.06 +- 0.01 StarC 32"W -0.80 +- 0.03 Assuming a probable V-K color of StarB (US170412+514636, R=18.6,B=20.9), we have estimated rough K'-magnitude of the OT at about K'=19 mag. We have also uploaded the co-added fits image on the same web site shown above. http://www.SubaruTelescope.org/Latestnews/200010/GRB/grb000926.fits Please feel free to use it for detailed photometry if you have any information on K'-magnitudes of the field stars. The original pixel scale of our image is 0.058 arcsec/pix, but the posted image is binned by 4-pix and the resultant pixel scale should be 0.233 arcsec/pix. North is to the top, East is to the left. This message is quotable in publications. //////////////////////////////////////////////////////////////////////// TITLE: GCN GRB OBSERVATION REPORT NUMBER: 823 SUBJECT: GRB000926 - Optical observations DATE: 00/09/30 21:14:00 GMT FROM: Christian Veillet at CFHT Content-Type: text/plain; charset=us-ascii Content-Transfer-Encoding: 7bit GRB000926 - Optical observations The optical counterpart of GRB000926 has been observed using the CFH12K CCD mosaic camera at the prime focus of the 3.6-m CFH Telescope. One 600s exposure with moderate seeing (image quality 0.8") has been obtained and a preliminary reduction using the reference star of Halpern et al. (GCN #806) with R=17.1 gives the following measurement for GRB000926: Sept. 30.3075 R = 22.19 +/- 0.06 Added to the R-band data points used in the analysis by Hjorth et al. (GCN #814), to the previous CFHT observation and to the last data by Fynbo et al. (GCN #820), this new point confirms the change in decay rate announced in GCN #820. The decay value is now 2.44 +/- 0.07, using data past Sept 29.2, while the decay is 1.67 +/- 0.04 with data prior to Sept 29.2. A graph of the light curve in R with the linear fits can be found at http://www.cfht.hawaii.edu/~veillet/grb.html D. Kocevski, D. Donovan and G. Luppino are acknowledged for their help in this observation. This message may be cited. -- ************************************************************ Dr. Christian Veillet, CFHT Senior Resident Astronomer Phone: (808) 885-3161 http://www.cfht.hawaii.edu/~veillet/ ************************************************************ //////////////////////////////////////////////////////////////////////// TITLE: GCN GRB OBSERVATION REPORT NUMBER: 824 SUBJECT: GRB 000926, Optical Observations DATE: 00/09/30 22:04:07 GMT FROM: Jules Halpern at Columbia U. J. P. Halpern, N. Mirabal (Columbia U.), D. Turnshek & J. Busche (U. Pittsburgh) report on behalf of the MDM Observatory GRB follow-up team: "We processed and calibrated the MDM R and B data reported previously in GCN #806, now using Landolt standard stars, and we acquired new R and B observations on the MDM 2.4. The comparison star at (J2000) RA 17:04:01.21, Dec +51:46:19.9, previously assumed to have R = 17.1, is now measured at R = 17.06, B = 18.50. In this new system, we find the following magnitudes for the OT: Sep. 28.183 B = 20.89 +/- 0.04 Sep. 28.177 R = 19.86 +/- 0.02 Sep. 29.176 B = 22.11 +/- 0.09 Sep. 29.196 R = 21.14 +/- 0.03 Sep. 30.179 B = 23.07 +/- 0.06 Sep. 30.211 R = 22.11 +/- 0.06 Correcting the observed B-R for the Galactic extinction A_B = 0.101, A_R = 0.063 of Schlegel et al., we find that B-R = 0.95 +/- 0.05 consistently for these three nights. This color corresponds to spectral slope beta = -1.51 +/- 0.12, which indicates that there may be intrinsic extinction. Our latest R-band measurement confirms the steepening of the decay reported by Fynbo et al. (GCN #820) and Veillet (GCN #823). For the first 2 days the decay slope was consistent with alpha = -1.65 +/- 0.02. After 2.2 days, alpha = -2.51 +/- 0.17. Images of this field and an updated decay curve are posted at http://www.astro.columbia.edu/~jules/grb/000926 This message may be cited." //////////////////////////////////////////////////////////////////////// TITLE: GCN GRB OBSERVATION REPORT NUMBER: 825 SUBJECT: GRB 000926: optical observations DATE: 00/10/01 01:16:56 GMT FROM: Johan U. Fynbo at ESO,Garching J. P. U. Fynbo, P. Moller (ESO), J. Gorosabel (DSRI, Copenhagen) J. Hjorth, B. L. Jensen, and H. Pedersen (U. of Copenhagen), report on behalf of a larger European GRB Collaboration: "Using the ALFOSC on the 2.5m Nordic Optical Telescope, we have obtained further R-band imaging of the Optical Transient (OT) of GRB 000926 (GCN #801, #803, #804) on 2000 September 30.83 UT. We also report the results of B-band imaging on 2000 September UT 27.88 - 30.85. We find the following magnitudes of the OT using R=17.06 and B=18.50 for the reference star of Halpern et al. (GCN #806, #824) : UT -------------------------- 30.83 R=22.45+-0.05 27.89 B=20.41+-0.03 29.86 B=22.83+-0.08 30.85 B=23.46+-0.10 We note that the colour of the OT, B-R=0.95+-0.05 (Halpern et al., GCN #824), is similar to that of the OT of GRB 000301C at z=2.04, B-R=0.91+-0.03 (Jensen et al., astro-ph/0005609). The estimated intrinsic extinction for this OT was in the range A(V)=0.11-0.35." //////////////////////////////////////////////////////////////////////// TITLE: GCN GRB OBSERVATION REPORT NUMBER: 826 SUBJECT: GRB000926 - Optical observations DATE: 00/10/01 19:34:03 GMT FROM: Christian Veillet at CFHT GRB000926 - Optical observations The optical counterpart of GRB000926 has been observed using the CFH12K CCD mosaic camera at the prime focus of the 3.6-m CFH Telescope for the third night. One 600s exposure has been obtained with an excellent seeing (0.5"). Using the new R magnitude of 17.06 by Halpern et al. (GCN #824) for the reference star, the three R magnitudes of the GRB for our observations are: Sept. 29.3075 R = 21.19 +/- 0.05 Sept. 30.3075 R = 22.15 +/- 0.06 Oct. 01.2593 R = 22.57 +/- 0.08 The last observation by Fynbo et al. (GCN #825) and this new CFHT data point sugest that the GRB is no longer on the decay reported by Fynbo et al. (GCN #820), Veillet (GCN #823) and Halpern et al. (GCN #824). We could see a flare out as suggested by Dar in a private communication (see also astro-ph/0008474), though more observations would definitely be welcome at this stage... A new graph of the light curve in R can be found at http://www.cfht.hawaii.edu/~veillet/grb.html D. Kocevski, D. Donovan and G. Luppino are acknowledged for their help in this observation. This message may be cited. -- ************************************************************ Dr. Christian Veillet, CFHT Senior Resident Astronomer Phone: (808) 885-3161 http://www.cfht.hawaii.edu/~veillet/ ************************************************************ //////////////////////////////////////////////////////////////////////// TITLE: GCN GRB OBSERVATION REPORT NUMBER: 827 SUBJECT: GRB000926 - Optical observations DATE: 00/10/02 22:09:20 GMT FROM: Christian Veillet at CFHT Content-Type: text/plain; charset=us-ascii Content-Transfer-Encoding: 7bit GRB000926 - Optical observations The optical counterpart of GRB000926 has been observed using the CFH12K CCD mosaic camera at the prime focus of the 3.6-m CFH Telescope for the fourth night. One 600s exposure has been obtained with a decent seeing (0.7"). Using the new R magnitude of 17.06 by Halpern et al. (GCN #824) for the reference star, the R magnitude of the GRB is found as: Oct. 02.2626 R = 22.82 +/- 0.08 The last two days of data from Halpern et al. (GCN #284), Fynbo et al. (GCN #825), and the previous CFHT measurement (GCN #826) suggest a new decay phase with a decay rate of 1.47 +/- 0.10 . A new graph of the light curve in R can be found at http://www.cfht.hawaii.edu/~veillet/grb.html D. Kocevski, D. Donovan and G. Luppino are acknowledged for their help in this observation. This message may be cited. -- ************************************************************ Dr. Christian Veillet, CFHT Senior Resident Astronomer Phone: (808) 885-3161 http://www.cfht.hawaii.edu/~veillet/ ************************************************************ //////////////////////////////////////////////////////////////////////// TITLE: GCN GRB OBSERVATION REPORT NUMBER: 829 SUBJECT: GRB 000926, Optical Decay DATE: 00/10/03 18:37:24 GMT FROM: Jules Halpern at Columbia U. J. P. Halpern, N. Mirabal (Columbia U.), D. Turnshek & J. Busche (U. Pittsburgh) report on behalf of the MDM Observatory GRB follow-up team: "Using the MDM 2.4m, we obtained 5x900 s exposures in the R band centered on Oct. 2.16 UT. Using the comparison star previously measured at R = 17.06 (GCN #824), we find for the OT R = 23.17 +/- 0.09 (1 sigma). This is significantly fainter than the measurement made by Veillet just after ours (GCN #827, R = 22.82 +/- 0.08 on Oct. 2.26), which constitutes an interesting discrepancy. Our own measurement is consistent with a constant decay slope alpha = -2.23 +/- 0.07 after day 2, and would predict that R = 23.9 +/- 0.1 on Oct. 4.0 UT. This image and an updated decay curve are posted at http://www.astro.columbia.edu/~jules/grb/000926 This message may be cited." [GCN OPS NOTE 03oct00: At the author's request the value for the alpha value was changed from the original value of -2.33 to -2.23. The original value was a typo.] //////////////////////////////////////////////////////////////////////// TITLE: GCN GRB OBSERVATION REPORT NUMBER: 830 SUBJECT: GRB000926 - Optical observations DATE: 00/10/04 05:10:14 GMT FROM: Christian Veillet at CFHT Content-Type: text/plain; charset=us-ascii Content-Transfer-Encoding: 7bit GRB000926 - Optical observations The optical counterpart of GRB000926 has been observed using the CFH12K CCD mosaic camera at the prime focus of the 3.6-m CFH Telescope for the fifth night on Oct. 3.2304 . Following GCN #829 by Halpern et al., a more accurate reduction of the CFHT data has been made, with the problems encountered when none of the observations is made in photometric reduction. A fist full reduction of the images leads to a more constant slope. The change seen previously in the decay rate (GCN #825, #826 and #827) doesn't seem to be real. Even if there are still discrepancies between the MDM and CFHT data, there are now smaller, thanks to the work on the secondary reference stars made by F. Vrba (USNO). The 5 nights of observations at CFHT lead to a decay slope of 2.16 +/- 0.03 but it's not really possible to link accurately the CFHT magnitudes to others as long as there is no calibration of the field stars made. A graph of the light curve in R from CFHT observations can be found at http://www.cfht.hawaii.edu/~veillet/grb.html where more information on the photometric reductions can be found. An accurate photometric calibration of stars 1 and 2 (see the image on the web page) is definitely needed. L. Wells, D. Woodworth and J. Luthe are acknowledged for their help in this observation. This message may be cited. -- ************************************************************ Dr. Christian Veillet, CFHT Senior Resident Astronomer Phone: (808) 885-3161 http://www.cfht.hawaii.edu/~veillet/ ************************************************************ //////////////////////////////////////////////////////////////////////// TITLE: GCN GRB OBSERVATION REPORT NUMBER: 831 SUBJECT: GRB000926 - Optical observations DATE: 00/10/05 04:04:33 GMT FROM: Christian Veillet at CFHT Content-Type: text/plain; charset=us-ascii Content-Transfer-Encoding: 7bit GRB000926 - Optical observations The optical counterpart of GRB000926 has been observed using the CFH12K CCD mosaic camera at the prime focus of the 3.6-m CFH Telescope for the sixth night on Oct. 4.25 . The two images were with variable transparency and poor seeing conditions (0.9 to 1"). Star 2 (see GCN #830 and the web page referenced below) is used as a reference with R=20.36 for the following photometric data: Sept. 29.3075 21.23 0.03 30.3075 22.10 0.04 Oct. 1.2593 22.71 0.04 2.2626 23.13 0.08 3.2304 23.45 0.10 4.2500 23.73 0.15 T is in UTC days after Sept. 0 . R magnitudes are given with their uncertainty. A photometric check on stars 1 and 2 leads to mg1 - mg2 = 0.658 +/- 0.01 over the 6 nights of observations. A graph of the light curve in R from CFHT observations can be found at http://www.cfht.hawaii.edu/~veillet/grb.html as well as the last image of the OT vanishing in the background... We are done at CFHT with the observations of the OT itself. The observing time used for GRB000926 has been taken from allocated time to colleagues from Canada and Hawaii who are once more acknowledged, with for last night special thanks to M. Brodwin. The field will be imaged again when CFH12K will be on the telescope for a final photometric calibration before running the last analysis and publishing the data. This run has been more hectic than the one on GRB000301C. Sorry for that... Aloha! This message may be cited. -- ************************************************************ Dr. Christian Veillet, CFHT Senior Resident Astronomer Phone: (808) 885-3161 http://www.cfht.hawaii.edu/~veillet/ ************************************************************ //////////////////////////////////////////////////////////////////////// TITLE: GCN GRB OBSERVATION REPORT NUMBER: 832 SUBJECT: GRB000926: X-ray afterglow by BeppoSAX. Refined analysis DATE: 00/10/05 20:00:05 GMT FROM: Luigi Piro at IAS/CNR Frascati L. Piro (BeppoSAX Mission Scientist, IAS/CNR Roma) & L. A. Antonelli (OaR) report on behalf of the BeppoSAX team: A BeppoSAX TOO observation of GB000926 started on Sept. 29.00, i.e. 2 days after the GRB and lasted for 12 hrs. Effective exposure times were MECS(1.6-10 keV): 20 ksec, LECS(0.1-10 keV):5 ksec. We confirm the relatively bright unknown source identified as the X-ray afterglow by Piro (GCN 812) The revised position is: RA(2000)=17h 04m 07s Decl.(2000)= +51 47' 18" with an error radius of 50", consistent with the previous preliminary position distributed in GCN 812 and with the optical counterpart (Gorosabel et al. GCN 803, Dall et al. GCN 804, Halpern et al. GCN 806). The average flux of the source in the MECS(1.6-10 keV) is (4.1+/-0.6) 10^-3 cts/s, corresponding to a F(1.6-10 keV)=(4.8+-0.7) 10^-13 erg/cm2/s. The spectrum is consistent with a power law with photon index=(1.9+/-0.7) and absorption by our Galaxy (NH=2.7 10^20 cm-2). The BeppoSAX observation occured in coincidence with the break of the optical light curve reported e.g by Fynbo (GCN820), Veillet (GCN 823) and Halpern et al (GCN824). In the X-ray band the source exhibits a substantial decay, decreasing by a factor of (1.7+/-0.5) in 6 hours. This would correspond to a power law decay F= c(T-T0)^d_X (where T0=26.99) with slope d_X=-4.3+/-1, i.e. steeper that that measured in the optical after the break (d_O=-2.5+/-0.2, Halpern et al., GCN 824). This behaviour is not immediately consistent with a jet-expansion, that predicts d_X=d_O. Chandra data, taken few hours after the end of the BeppoSAX observation, shall be crucial in confirming the X-ray light curve. //////////////////////////////////////////////////////////////////////// TITLE: GCN GRB OBSERVATION REPORT NUMBER: 833 SUBJECT: GRB000926: X-ray afterglow by BeppoSAX: revised fluxes (fwd) DATE: 00/10/06 14:50:33 GMT FROM: Luigi Piro at IAS/CNR Frascati L. Piro (BeppoSAX Mission Scientist, IAS/CNR Roma) & L. A. Antonelli (OaR) report on behalf of the BeppoSAX team: We have found an error in the application of a conversion factor which underestimates the fluxes distributed in GCN n.832 The correct value of the average flux (at T=29.25) is F(1.6-10 keV)= (2.6+\-0.6) 10^-13 erg/cm2/s We have also carefully checked different background subtraction methods, finding that the corresponding systematic effect amouts to less than about 15%. This has been included in the flux error quoted above. All the other results on the fading behaviour and on the spectral shape presented in GCN 832 remain unaffected. //////////////////////////////////////////////////////////////////////// TITLE: GCN GRB OBSERVATION REPORT NUMBER: 834 SUBJECT: Public availability of BeppoSAX data of GRB000926 DATE: 00/10/06 14:57:41 GMT FROM: Luigi Piro at IAS/CNR Frascati L. Piro (BeppoSAX Mission Scientist) reports: The observation of the X-ray afterglow of GRB000926 reported by Piro et al. in BeppoSAX mails n. 00/21, 00/22, 00/23 and GCN n. 812 , 832, 833 was performed as a BeppoSAX Project TOO (i.e. the equivalent of Director Discretionary Time) and as such falls under the responsibility of the BeppoSAX Mission Scientist. These data are usually property of the BeppoSAX team. However, taking into account the considerable interest of this GRB, we have decided to make these data immediately public to the scientific community. Reduced data sets (image, spectrum, light curve) and cleaned photon list can be accessed through the BeppoSAX archive at: http://www.sdc.asi.it/archive/00000059/ //////////////////////////////////////////////////////////////////////// TITLE: GCN GRB OBSERVATION REPORT NUMBER: 836 SUBJECT: GRB 000926 Chandra Observation DATE: 00/10/06 21:27:15 GMT FROM: Gordon Garmire at Penn State U TITLE: GCN GRB OBSERVATION REPORT NUMBER: GCN 836 SUBJECT: GRB000926: X-ray afterglow by Chandra X-ray Observatory DATE: 00/10/06 22:29:00 GMT FROM: G. Garmire at Penn State University G. Garmire and A. Garmire (Penn State U), L. Piro (IAS/CNR Roma) and M. R. Garcia (CfA) A Chandra X-ray Observatory TOO observation of the afterglow from GRB000926 began September 29.67375 and ended on 29.85125, but with a total good time of observation of 9979s. The source position determined by CXO is: RA(2000)=17h 04m 09.6s Decl. (2000)= +51 47' 8.6" with an uncertainty of ~2", consistant with the optical position by Gorosabel et al. GCN 803, Dall et al. GCN 804, Halpern et al. GCN 806. The average flux of the source is (3.08+/-.017) 10^-2 cts/s, corresponding to a flux F(1.6-10 keV)=(9.4+/-0.95)10^-14 erg/cm2/s. The spectrum is found to fit a powerlaw with powerlaw index =(1.76+/-0.2) consistant with the slope of Piro et al. GCN 832, and the absorption by our Galaxy (NH=2.7 10^20 cm-2). This very large decrease in flux in such a short time is unprecedented, decreasing by a factor of ~3 in only ~12 hours from the BeppoSAX measurement! To obtain a better measure of the slope with time for a law of the form F=c(T-T0)^d_X with T0=26.99 will require a more refined analysis, since taking average values leads to a slope of -5! //////////////////////////////////////////////////////////////////////// TITLE: GCN GRB OBSERVATION REPORT NUMBER: 840 SUBJECT: GRB 000926 : the host galaxy DATE: 00/10/09 17:12:45 GMT FROM: Johan U. Fynbo at ESO,Garching J. P. U. Fynbo (ESO), M. I. Andersen (University of Oulu), J. Gorosabel (DSRI, Copenhagen), J. Hjorth, B. L. Jensen, H. Pedersen (University of Copenhagen), T. Pursimo, M.T. Hanski (University of Turku), R. Oestensen, J.-E. Solheim (University of Tromsoe) report: "Using the ALFOSC on the 2.5m Nordic Optical Telescope we have obtained further R-band imaging of the Optical Transient (OT) of GRB 000926 (GCN #801, #803, #804) on 2000 October 2.84 and 6.87 UT. We find the following magnitudes of the OT using R = 17.06 for the reference star of Halpern et al. (GCN #806, #824): Date (UT) R ------------------------------ Oct 2.84 23.28 +- 0.13 Oct 6.87 23.87 +- 0.25 The emission at the position of the OT in the Oct 6.87 image is (although at low signal-to-noise ratio) significantly elongated with a position angle of about 90 degrees. This indicates a contribution from a galaxy, possibly the GRB host. The light-curve shape also indicates a flattening consistent with a late time decay slope of alpha=2.5+-0.15 and an underlying galaxy with a magnitude of about R=24. An updated light-curve based on the NOT points only can be found at: http://www.ifa.au.dk/~jfynbo/grb/grb000926/GRB000926_lc.gif" //////////////////////////////////////////////////////////////////////// TITLE: GCN GRB OBSERVATION REPORT NUMBER: 844 SUBJECT: GRB000926 - Amateur Optical Observations DATE: 00/10/11 00:54:03 GMT FROM: AAVSO GRB Network at AAVSO Janet A. Mattei, AAVSO Director, reports: On the evening of September 28 UT, in response to an alert on the AAVSO's GRB mailing list, Joe Dellinger, Fort Bend Astronomy Club (FBAC), Texas, took a sequence of unfiltered CCD images of the GRB000926 field. He used the FBAC's 46 cm reflector at the Houston Museum of Natural Science's George Observatory, and an SBIG ST-9e camera on generous loan from Rice University. He could not see any optical transients on individual four-minute images when comparing them with a DSS-derived finder chart. Fellow FBAC member Bill Dillon combined the best seven of Joe's four-minute images into an equivalent 28 minute image. The combined image's UT mid-point time was 03:16:16. From positions and annotated images reported by professional astronomers, he realized that the OT had been imaged, near the threshold of detection. Using Astrometrica and the USNO-A2.0 catalog, the OT's position was measured at: RA 17h 04m 09.76s, DEC +51d 47' 10.6" with a magnitude of roughly 19.1. On the evening of October 3 UT, Randy Pepper and Bill Dillon did follow-up imaging of the GRB000926 field using the same telescope and camera. The OT had faded below detectability on a image made by combining 31 one-minute exposures. Joe, Bill, and Randy are all members of the FBAC's Gamma Ray Burst Extended Team, formed as the result of the NASA-MSFC/AAVSO High Energy Astrophysics Workshop held this April in Huntsville, Alabama. More information and imagery associated with this detection are available at http://www.geocities.com/amicustellarum/grb/grb000926.html This message may be cited. //////////////////////////////////////////////////////////////////////// TITLE: GCN GRB OBSERVATION REPORT NUMBER: 850 SUBJECT: V,R,I band observations of GRB000926 DATE: 00/10/14 18:11:47 GMT FROM: Evert Rol at U.Amsterdam E. Rol, P. M. Vreeswijk (U. of Amsterdam) and N. Tanvir (U. of Hertfordshire), on behalf of a larger collaboration, report: We have obtained Sloan i and Harris R & V band images of the field of GRB 000926 (GCN #801), using the Wide Field Camera on the 2.5m Isaac Newton Telescope at La Palma. Using aperture photometry (with a radius twice the FWHM), we find the magnitude of the OT, relative to the reference star of Halpern et al. (GCN #824), to be as follows: date (UT) filter rel-mag error exp-time (Sept 2000) (secs) - ------------------------------------------------ 27.919 i 2.406 0.007 300 27.924 i 2.439 0.007 300 27.929 i 2.454 0.008 300 30.850 i 5.403 0.009 600 27.892 R 2.369 0.007 300 27.896 R 2.386 0.007 300 27.901 R 2.396 0.008 300 27.906 V 2.271 0.009 300 27.910 V 2.298 0.009 300 27.915 V 2.301 0.010 300 30.839 V 5.352 0.096 600 (errors are statistical only) We have fitted the R band data, together with all published data (GCNs #809, #814, #816, #819, #820, #824, #825, GCN #829, #831, #840), with a smoothly broken power-law, and a constant flux (presumably from the underlying host galaxy). The fitted function is F(t) = { F_1^(-n) + F_2^(-n) }^(-1/n) + F_host, with F_i = k_i t ^(-a_i), n > 0; i = 1, 2. a_1 and a_2 correspond to the early and late time power-law indices, respectively. The break time t_0 corresponds to the time when F_1 = F_2. (see e.g. Beuermann, K., et al 1999, A&A, 352, L26-L30) We obtain the following parameters for the R band data, with n fixed at 1: a_1 = 1.1 +- 0.2 a_2 = 3.2 +- 0.4 t_0 = 2.0 +- 0.4 host: R = 24.2 +- 0.3 Errors are 1 sigma; chi^2/DOF = 69/31. Excluding the host, we find a chi^2/DOF = 83/32. The fit shows a rather large increase in the decay-rate of the OT flux around two days after the burst (from a power-law index of 1.1 to 3.2). Fitting for n as well (which can be used to define the sharpness of the break) gives the same results as above, with n = 1.1 +- 0.8. Graphs of these fits can be found at http://www.astro.uva.nl/~evert/grb000926/ We acknowledge the help of the observers Chris Blake and Steve Rawlings (U. of Oxford), and the ING staff. //////////////////////////////////////////////////////////////////////// TITLE: GCN GRB OBSERVATION REPORT NUMBER: 851 SUBJECT: GRB 000926: Improved Absorber Redshift DATE: 00/10/14 23:58:55 GMT FROM: George Djorgovski at Caltech/Palomar Sandra M. Castro, S. G. Djorgovski, S. R. Kulkarni, J. S. Bloom, T. J. Galama, F. A. Harrison (Caltech), and D. A. Frail (NRAO), report on behalf of a large collaboration: We analysed high-resolution spectra of the optical afterglow of GRB 000926 kindly obtained at the WMKO Keck-II telescope by L. Cowie, A. Barger, et al. on UT 2000 September 29.26, using the ESI instrument (an Echelle spectrograph). Our preliminary analysis yields a single absorption system including the following lines: Si II 1526.7, C IV 1548.2 and 1550.5, Al II 1670.8, Si II 1808.0, Al III 1854.7 and 1862.8, Zn II 2026.1, Fe II 2344.2, 2373.7, 2382.8, 2586.6, and 2600.2, Mg II 2796.3 and 2803.5, and Mg I 2853.0. The mean redshift is z = 2.0369 +- 0.0007, presumably corresponding to the system identified by Fynbo et al. (GCN 807) as having z ~ 2.066. However, we see no evidence for any other absorption systems in these data; in particular, the ostensible system at z = 1.378 proposed by Fynbo et al. is likely due to line misidentifications. We note that the line equivalent widths appear to be unusually strong in comparison to the general population of metallic line absorbers seen in the spectra of quasars, suggesting a high column density and/or metallicity of the intervening gas. A more detailed analysis is in progress. This note can be cited. //////////////////////////////////////////////////////////////////////// TITLE: GCN GRB OBSERVATION REPORT NUMBER: 871 SUBJECT: GRB000926: R-image of the host galaxy DATE: 00/11/01 17:23:20 GMT FROM: Johan U. Fynbo at ESO,Garching J. P. U. Fynbo, P. Moller (ESO, Garching) I. Burud (University of Liege), M. I. Andersen (University of Oulu), J. Gorosabel (DSRI, Copenhagen), J. Hjorth, B. L. Jensen, H. Pedersen (U. of Copenhagen) report : "Using the ALFOSC on the 2.5m Nordic Optical Telescope, we have obtained 4700sec of further R-band imaging of the Optical Transient (OT) of GRB 000926 (GCN #801, #803, #804) on 2000 October 27. The seeing was 1.1 arcsec. Near the position of the OT we detect extended emission, which most likely is from the host galaxy of GRB000926. There are several knots of emission. One of these knots coincides with the precise position of the OT. The magnitude of the galaxy measured in a circular aperture with diameter 5.7 arcsec is about R=23.9 in good agreement with estimates based on the flattening of the OT light-curve (GCN #840, #850). A 10.5x10.5 arcsec^2 section of the combined R-band image centred on the position of the OT (marked by a circle) can be seen at http://www.astro.ku.dk/~brian_j/grb/grb000926" //////////////////////////////////////////////////////////////////////// TITLE: GCN GRB OBSERVATION REPORT NUMBER: 1088 SUBJECT: GRB000926 Host Galaxy Observations DATE: 01/08/22 15:38:47 GMT FROM: Fiona Harrison at CalTech F. A. Harrison, T. J. Galama, J. S. Bloom, S. M. Castro, S. R. Kulkarni (Caltech) report on behalf of the CIT-NRAO-CARA collaboration: "We have obtained HST WFPC2 images of the host of GRB 000926 in three filters. The observations spanned from UT May 19 19.63 - 19.86 2001, 238 days after the event. The images reaveal a compact knot of emission the center of which is consistent with the location of the optical transient. We interpret this to be the host galaxy of GRB 000926. The knot is reasonably bright, corresponding to about 25 mag in R, and appears to be marginally extended, with a FWHM of 0.3 arcsec." An image of the host may be found at: http://www.srl.caltech.edu/~fiona/grb000926host.eps This message may be cited. //////////////////////////////////////////////////////////////////////// TITLE: GCN GRB OBSERVATION REPORT NUMBER: 1091 SUBJECT: GRB000926, Host Galaxy Observations DATE: 01/09/08 07:45:25 GMT FROM: Vladimir Sokolov at SAO RAS S. Dodonov, T. Fatkhullin, V. Sokolov (SAO RAS), Andrew Fruchter (STScI), V. Komarova, A. Moiseev (SAO RAS), A. Cherepashchuk, K. Postnov (SAI-MSU Moscow) report: "On July 24 and 25, 2001 UT, we have observed the field of the optical transient of GRB 000926 (Fynbo et al., 2001, A&A, 373, 796). We have obtained B, V, Rc, Ic images with the SCORPIO (http://www.sao.ru/~moisav/scorpio/scorpio.html) at the 6-m telescope of SAO RAS. Photometric conditions were good and the seeing was about 1.3 arcsec. Photometric calibration was performed using Stetson standards in Landolt standard field PG1633. At the position of the optical transient we have detected an object - a host galaxy. At about 3" to the East from the OT position an extended emission is clearly seen. This extended emission is most likely the galaxy seen in early HST image (see Price et al., 2001, ApJ, 549, L7) and its association with the host is unclear. The exposure times and magnitudes of the object are: Filter Exposure (sec.) Magnitude Aperture --------------------------------------------------------- B 2500 26.13 +/- 0.17 2.0 arcsec V 1500 25.85 +/- 0.22 2.0 arcsec Rc 1260 26.31+/- 0.25 2.0 arcsec Ic 1800 24.7 +/- 0.4 2.0 arcsec --------------------------------------------------------- The faint R-band magnitude can be explained by a graphite band as on the Galactic extinction curves. Indeed, for the redshift z=2.0369 (Castro et al., GCN #851) this band (2200A) goes to the observed R-band. If so, then this is the second case of direct observations of this feature (see Sokolov et al., 2001, A&A, 372, 438, the case of the HG GRB 980703). We also performed the photometry of entire system of the objects using an aperture of 4.5 arcsec. Below we present the obtained magnitudes: Filter Exposure (sec.) Magnitude Aperture --------------------------------------------------------- B 2500 24.73 +/- 0.11 4.5 arcsec V 1500 24.81 +/- 0.19 4.5 arcsec Rc 1800* 24.38+/- 0.10 4.5 arcsec Ic 1800 23.68 +/- 0.30 4.5 arcsec --------------------------------------------------------- * The R-band data obtained on 25 Aug. are coadded. Images can be seen at http://www.sao.ru/~sokolov/GRB/HOSTS/GRB000926/GRB000926.html This message may be cited". -Vladimir Sokolov, on behalf of the RAS Special Astrophysical Observatory GRB followup team.