//////////////////////////////////////////////////////////////////////// TITLE: GCN CIRCULAR NUMBER: 8217 SUBJECT: GRB 080913: Swift detection of a burst DATE: 08/09/13 07:03:29 GMT FROM: David Palmer at LANL P. Schady (MSSL-UCL), A. P. Beardmore (U Leicester), J. R. Cummings (NASA/UMBC), P. A. Evans (U Leicester), O. Godet (U Leicester), C. Gronwall (PSU), C. B. Markwardt (CRESST/GSFC/UMD), K. L. Page (U Leicester), D. M. Palmer (LANL), A. M. Parsons (GSFC), D. Perez (U Leicester), R. L. C. Starling (U Leicester) and E. Troja (INAF-IASFPA) report on behalf of the Swift Team: At 06:46:54 UT, the Swift Burst Alert Telescope (BAT) triggered and located GRB 080913 (trigger=324561). Swift slewed immediately to the burst. The BAT on-board calculated location is RA, Dec 65.725, -25.110 which is RA(J2000) = 04h 22m 54s Dec(J2000) = -25d 06' 36" with an uncertainty of 3 arcmin (radius, 90% containment, including systematic uncertainty). The BAT light curve showed a double-peaked structure with a duration of about 10 sec. The peak count rate was ~800 counts/sec (15-350 keV), at ~0 sec after the trigger. The XRT began observing the field at 06:48:33.6 UT, 99.5 seconds after the BAT trigger. Using promptly downlinked data we find a fading, uncatalogued X-ray source with an enhanced position: RA, Dec 65.72800, -25.12945 which is equivalent to: RA(J2000) = 04h 22m 54.72s Dec(J2000) = -25d 07' 46.0" with an uncertainty of 2.4 arcseconds (radius, 90% containment). This location is 70 arcseconds from the BAT onboard position, within the BAT error circle. A power-law fit to a spectrum formed from promptly downlinked event data gives a column density consistent with the Galactic value of 3.17e+20 cm^-2 (Kalberla et al. 2005). UVOT took a finding chart exposure of 100 seconds with the White (160-650 nm) filter starting 105 seconds after the BAT trigger. No afterglow candidate has been found in the initial data products. The 2.7'x2.7' sub-image covers 25% of the BAT error circle and 100% of the XRT error circle. The 3-sigma upper limit at the XRT position is 20.7 mag. The 8'x8' region for the list of sources generated on-board covers 100% of the BAT error circle. The list of sources is typically complete to about 18 mag. No correction has been made for the expected extinction corresponding to E(B-V) of 0.04. Burst Advocate for this burst is P. Schady (ps AT mssl.ucl.ac.uk). Please contact the BA by email if you require additional information regarding Swift followup of this burst. In extremely urgent cases, after trying the Burst Advocate, you can contact the Swift PI by phone (see Swift TOO web site for information: http://www.swift.psu.edu/too.html.) //////////////////////////////////////////////////////////////////////// TITLE: GCN CIRCULAR NUMBER: 8218 SUBJECT: GRB 080913: GROND observation of a high-z optical/NIR afterglow candidate DATE: 08/09/13 09:07:05 GMT FROM: Jochen Greiner at MPI A. Rossi (Tautenburg Obs.), J. Greiner, T. Kruehler, A. Yoldas (all MPE), S. Klose (Tautenburg Obs.), A. Kuepcue Yoldas (ESO) report on behalf of the GROND team: We observed the field of GRB 080913 (Swift trigger 324561; Schady et al., GCN #8217), simultaneously in g'r'i'z'JHK with GROND (Greiner et al. 2008, PASP 120, 405) mounted at the 2.2m ESO/MPI telescope at La Silla Observatory (Chile). Observations started at 06:50 UT on September 13, 2008, 3 min after the GRB trigger. We detect a faint optical object inside the 2.4 arcsec Swift/XRT error box (Schady et al., GCN #8217). We detect the object only in the z'-band and NIR, but not in i'-band or bluer. Preliminary photometry yields the following magnitudes calibrated against USNO-B1 and 2MASS field stars in stacked images: r' > 23.2 mag, i' > 23.0 mag, z' = 22.4 mag, not corrected for the expected Galactic foreground reddening of E(B-V) = 0.05 mag (Schlegel et al., 1998). The non-detection in i' and bluer may indicate a redshift of about 6. We caution however, that the drop-out is only 0.6 mag in depth between our i' and z' bands, and our lack of better sensitivity could make this a wrong interpretation. We encourage deeper observations. //////////////////////////////////////////////////////////////////////// TITLE: GCN CIRCULAR NUMBER: 8219 SUBJECT: GRB 080913: Enhanced Swift-XRT position DATE: 08/09/13 09:10:38 GMT FROM: Phil Evans at U of Leicester A.P. Beardmore, P.A. Evans, M.R. Goad and J.P. Osborne (U. Leicester) report on behalf of the Swift-XRT team. Using 2223 s of XRT Photon Counting mode data and 1 UVOT images for GRB 080913, we find an astrometrically corrected X-ray position (using the XRT-UVOT alignment and matching UVOT field sources to the USNO-B1 catalogue): RA, Dec = 65.72775, -25.12950 which is equivalent to: RA (J2000): 04h 22m 54.66s Dec (J2000): -25d 07' 46.2" with an uncertainty of 1.9 arcsec (radius, 90% confidence). This position may be improved as more data are received. The latest position can be viewed at http://www.swift.ac.uk/xrt_positions. Position enhancement is described by Goad et al. (2007, A&A, 476, 1401 http://www.swift.ac.uk/xrt_positions/Goad.pdf), the current algorithm is an extension of this method. This circular was automatically generated, and is an official product of the Swift-XRT team. //////////////////////////////////////////////////////////////////////// TITLE: GCN CIRCULAR NUMBER: 8220 SUBJECT: GRB 080913: REM NIR early observations DATE: 08/09/13 09:58:37 GMT FROM: Paolo D'Avanzo at INAF-OAB P. D'Avanzo, S. Covino, L.A. Antonelli, D. Malesani, D. Fugazza, L. Calzoletti, S. Campana, G. Chincarini, M.L. Conciatore, S. Cutini, V. D'Elia, F. D'Alessio, F. Fiore, P. Goldoni, D. Guetta, C. Guidorzi, G.L. Israel, E. Maiorano, N. Masetti, A. Melandri, E. Meurs, L. Nicastro, E. Palazzi, E. Pian, S. Piranomonte, L. Stella, G. Stratta, G. Tagliaferri, G. Tosti, V.Testa, S.D. Vergani, F. Vitali report on behalf of the REM team: The robotic 60-cm REM telescope located at La Silla (Chile) observed automatically the field of the GRB 080913 (Schady et al. GCN 8217) on Sep 13 starting about 6 min after the burst. Observations were carried out at high airmass. Coadding a series of 10s, 30s and 60s exposures, at a mean t-t0 ~ 40 min we do not see the object reported by Rossi et al. (GCN 8218) or any other afterglow candidate inside the refined XRT error box (Beardmore et al.; GCN 8219) down to J > 17.1, H > 17.2 and K > 15.8 (3sigma c.l.). //////////////////////////////////////////////////////////////////////// TITLE: GCN CIRCULAR NUMBER: 8221 SUBJECT: GRB 080913: VLT/FORS2 observations DATE: 08/09/13 10:58:48 GMT FROM: Paul Vreeswijk at Dark Cosmology Centre,U.of Copenhagen P.M. Vreeswijk, J.P.U. Fynbo, D. Malesani (DARK/NBI) report on behalf of a larger collaboration: The field of GRB 080913 (Swift trigger 324561; Schady et al., GCN #8217) was observed in target-of-opportunity mode with VLT+FORS2 using the imaging sequence RzIVBR, starting at 7:31 UT on September 13, 2008, i.e. 45 minutes after the GRB. In the z-band image a faint source is detected within the Swift/XRT error circle, with magnitude z(AB) = 23.1 (based on a very preliminary calibration), while this object is not detected in any of the other optical filters. Comparison with the z-band magnitude reported by Rossi et al. (GCN #8218) suggests that the object has faded between 3 and 45 minutes after the burst, and therefore is likely the afterglow of GRB 080913. We are very grateful for the excellent support by the Paranal observatory staff, in particular Rachel Gilmour and Heidi Korhonen. [GCN OPS NOTE(06nov08): Per author's request, "Heidi Schmidt" was changed to "Hiedi Korhonen".] //////////////////////////////////////////////////////////////////////// TITLE: GCN CIRCULAR NUMBER: 8222 SUBJECT: GRB 080913, Swift-BAT refined analysis DATE: 08/09/13 16:07:01 GMT FROM: Jay R. Cummings at NASA/GSFC/Swift M. Stamatikos (GSFC/ORAU), S. D. Barthelmy (GSFC), W. Baumgartner (GSFC/UMBC), J. Cummings (GSFC/UMBC), E. Fenimore (LANL), N. Gehrels (GSFC), H. Krimm (GSFC/USRA), C. Markwardt (GSFC/UMD), K. McLean (GSFC/UMD), D. Palmer (LANL), A. Parsons (GSFC), T. Sakamoto (GSFC/UMBC), G. Sato (ISAS), P. Schady (MSSL-UCL), J. Tueller (GSFC), T. Ukwatta (GWU) (i.e. the Swift-BAT team): Using the data set from T-239 to T+963 sec from the recent telemetry downlink, we report further analysis of BAT GRB 080913 (trigger #324561) (Schady, et al., GCN Circ. 8217). The BAT ground-calculated position is RA, Dec = 65.741, -25.127 deg which is RA(J2000) = 04h 22m 57.9s Dec(J2000) = -25d 07' 38.6" with an uncertainty of 1.5 arcmin, (radius, sys+stat, 90% containment). The partial coding was 39%. The mask-weighted light curve shows multiple overlapping peaks, somewhat smooth in character. T90 (15-350 keV) is 8 +- 1 sec (estimated error including systematics). The time-averaged spectrum from T-3.8 to T+5.2 sec is best fit by a power law with an exponential cutoff. This fit gives a photon index 0.46 +- 0.70, and Epeak of 93.1 +- 56.1 keV (chi squared 38.53 for 56 d.o.f.). For this model the total fluence in the 15-150 keV band is 5.6 +- 0.6 x 10-07 erg/cm2 and the 1-sec peak flux measured from T+0.11 sec in the 15-150 keV band is 1.4 +- 0.2 ph/cm2/sec. A fit to a simple power law gives a photon index of 1.36 +- 0.15 (chi squared 44.56 for 57 d.o.f.). All the quoted errors are at the 90% confidence level. The results of the batgrbproduct analysis are available at http://gcn.gsfc.nasa.gov/notices_s/324561/BA/ //////////////////////////////////////////////////////////////////////// TITLE: GCN CIRCULAR NUMBER: 8223 SUBJECT: GRB 080913: GROND photo-z DATE: 08/09/13 16:39:12 GMT FROM: Jochen Greiner at MPI J. Greiner, T. Kruehler (both MPE), A. Rossi (Tautenburg Obs.) report on behalf of the GROND team: We have analyzed more data of our GROND observing run (Rossi et al. 2008, GCN #8218) of GRB 080913 (Schady et al. 2008, GCN #8217; Stamatikos et al. 2008, GCN #8222). The object reported previously is clearly detected in several epochs. The position is RA (2000.0) = 04:22:54.74 Decl. (2000.) = -25:07:46.2 with an uncertainty of 0.5 arcsec. This position is consistent with the astrometrically corrected Swift X-ray position (Beardmore et al. 2008, GCN #8219). z'-band data spanning the time period from 3 min to 3 hrs after the burst clearly show a fading source and are well fit with a power law of decay slope 0.6 +- 0.3. This confirms the fading seen with the VLT (Vreeswijk et al. 2008, GCN #8221). If this fading continues, we predict z(AB) ~ 25 mag at 24 hrs after the GRB. The afterglow is detected in z'JHK, but not in g'r'i-bands. After correction for foreground extinction of A_V=0.129, we obtain (AB system) g > 23.3 +- 0.1 r > 23.3 +- 0.1 i > 23.0 +- 0.1 z = 22.52 +- 0.15 J = 20.90 +- 0.06 H = 20.67 +- 0.09 K = 20.54 +- 0.21 at 07:13 UT (mid-time of 12 min exposure), 26 min after the GRB. A fit to this simultaneously obtained 7-filter spectral energy distribution, using Hyper-z (Bolzonella et al. 2000) results in a photometric redshift of z = 6.44 +- 0.3. The SED-fit is shown on http://www.mpe.mpg.de/~jcg/grb080913.html //////////////////////////////////////////////////////////////////////// TITLE: GCN CIRCULAR NUMBER: 8224 SUBJECT: GRB080913: Swift/UVOT Upper Limits DATE: 08/09/13 16:40:12 GMT FROM: Samantha Oates at MSSL S. R. Oates and P. Schady report on behalf of the Swift/UVOT team. The Swift/UVOT began settled observations of the field of GRB 080913 starting 105s after the BAT trigger (Schady et al., GCN 8217). We do not detect an afterglow in any of the UVOT filters inside the UVOT-enhanced XRT error circle (Beardmore et al., GCN 8219). The 3 sigma upper limits for the finding charts (fc) and summed images are given below: Filter T_start(s) T_stop(s) Expo(s) Magnitude (3 sigma UL) ----------------------------------------------------------------- White (fc) 105 205 98 >20.92 White 105 1964 238 >21.26 v (fc) 211 611 393 >20.08 v 211 1858 865 >20.39 b 691 1957 97 >19.62 u 666 1932 117 >19.36 w1 641 1907 117 >19.48 m2 616 1882 78 >18.84 w2 721 1833 58 >18.99 ---------------------------------------------------------------- The above magnitudes are not corrected for the Galactic extinction corresponding to a reddening of E_{B-V} = 0.04 mag (Schlegel et al., 1998, ApJS, 500, 525). The photometry is on the UVOT flight system described in Poole et al. (2008,MNRAS,383,627). //////////////////////////////////////////////////////////////////////// TITLE: GCN CIRCULAR NUMBER: 8225 SUBJECT: GRB 080913: VLT/FORS spectrum DATE: 08/09/13 17:28:26 GMT FROM: Jochen Greiner at MPI J.P.U. Fynbo (DARK/NBI), J. Greiner, T. Kruehler (both MPE), A. Rossi (Tautenburg Obs), P. Vreeswijk, D. Malesani (both DARK/NBI) report on behalf of a larger collaboration Based on the rapid determination of an i'-band drop out we triggered VLT/ToO observations (program-ID 081.A-0135; PI Greiner) and obtained spectroscopy with FORS2+Gris600z of the afterglow of GRB080913 (Schady et al. 2008, GCN #8217; Stamatikos et al. 2008, GCN #8222). Observations started at 8:30, about 100 min after the GRB, and continued until morning twilight. We detect a red continuum that disappears bluewards of a break around 9400 AA. Interpreting this break as the onset of the Lyman-alpha forest we infer a redshift of about z=6.7 consistent with the photometric redshift determined by GROND (Greiner et al., GCN #8223). We are very grateful for the excellent support by the Paranal observatory staff, in particular Rachel Gilmour and Heidi Korhonen. [GCN OPS NOTE(06nov08): Per author's request, "Heidi Schmidt" was changed to "Hiedi Korhonen".] //////////////////////////////////////////////////////////////////////// TITLE: GCN CIRCULAR NUMBER: 8226 SUBJECT: GRB 080913: Swift-XRT refined analysis DATE: 08/09/13 17:30:12 GMT FROM: Andy Beardmore at U Leicester A.P. Beardmore (U. Leicester) and P. Schady (MSSL-UCL) report on behalf of the Swift-XRT team : The Swift-XRT started observing the field of GRB 080913 (trigger number 324561, Schady et al., GCN Circ. 8217) at 2008-09-13 06:48:30 UT, 94 s after the trigger. The best XRT position is the UVOT-enhanced position reported by Beardmore et al. (GCN Circ. 8219). The X-ray light curve presently spans 5 orbits of photon counting mode data from T+108 s to T+23 ks. The light curve shows a number of small flares in the first orbit, with the largest giving a factor of ~7 increase in count rate at T+1.8 ks, on top of a power-law decay of index 1.20 +0.16 -0.13. A 2.7 ks exposure X-ray spectrum from T+108 s to T+7.6 ks can be well fit by an absorbed power-law with a photon index of 1.69 +0.46 -0.41 and a column density consistent with the Galactic value of 3.2 x 10^20 cm^-2 in the direction of the burst. The observed 0.3-10.0 keV flux is (3.2 +0.9 -1.6) x 10^-12 erg cm^-2 s^-1 which corresponds to an unabsorbed flux of (3.7 +1.6 -1.7) x 10^-12 erg cm^-2 s^-1. The count to flux conversion factor is 4.6 x 10^-11 erg cm^-2 count^-1. Providing the source continues to decay at the same rate, we predict a count rate of 2.8 x 10^-4 count s^-1 at T+1 day. This circular is an official product of the Swift-XRT team. //////////////////////////////////////////////////////////////////////// TITLE: GCN CIRCULAR NUMBER: 8256 SUBJECT: GRB 080913: Konus-Wind and Swift/BAT joint spectral analysis DATE: 08/09/17 09:41:53 GMT FROM: Valentin Pal'shin at Ioffe Inst V. Pal'shin, S. Golenetskii, R.Aptekar, E. Mazets, D. Frederiks, and T. Cline on behalf of the Konus-Wind team, T. Sakamoto (GSFC/UMBC), S. D. Barthelmy (GSFC), W. Baumgartner (GSFC/UMBC), A. P. Beardmore (U Leicester), J. Cummings (GSFC/UMBC), E. Fenimore (LANL), N. Gehrels (GSFC), H. Krimm (GSFC/USRA), C. Markwardt (GSFC/UMD), K. McLean (GSFC/UMD), D. Palmer (LANL), G. Sato (GSFC/ISAS), M. Stamatikos (GSFC/ORAU), J. Tueller (GSFC), and T. Ukwatta (GWU) on behalf of the Swift-BAT team, report: We performed the Konus-Wind and the Swift/BAT joint spectral analysis of GRB 080913 (Swift/BAT trigger #324561: Schady et al., GCN Circ. 8217, Stamatikos et al. GCN Circ. 8222). Since the Konus-Wind observed this GRB in the waiting mode, we only have 3 channel spectral data for the Konus-Wind which cover the energy range from 20 keV to 1.3 MeV. Therefore, the joint spectral analysis of the Konus-Wind and the Swift/BAT data enables to derive the broad-band spectral parameters of this burst. The time interval of the spectral data for each instrument is chosen from T0(BAT)-4.1 to T0(BAT)+4.7 sec where T0(BAT) is the trigger time of BAT at 06:46:54.1 UTC. The energy ranges which we used in the joint spectral analysis are 20-1300 keV and 14-150 keV for the Konus-Wind and the Swift/BAT respectively. The spectral data of two instruments are fit with the spectral model multiplied by the constant factor to take into account the systematic effective area uncertainties in the response matrices of each instrument. The spectrum is well fit with a power-law with exponential cutoff model: dN/dE ~ E^{alpha}*exp(-(2+alpha)*E/Epeak). The constant factors of each instrument agree within 5%. No systematic residual from the best fit model is seen in the spectral data of each instrument. The best fit spectral parameters are: alpha = -0.89(-0.46, +0.65) and Epeak = 131 (-48/+225) keV (chi2/dof = 43.7/58). The best fit spectral parameters for the Band function fixing beta=-2.5 are: alpha = -0.82(-0.53, +0.75) and Epeak = 121 (-39/+232) keV (chi2/dof = 43.9/58). The energy fluence in the 15-1000 keV band calculated by a power-law with exponential cutoff model for this 8.8 sec interval is 8.5(-2.2, +6.0)x10^-7 erg/cm2 All the quoted errors are at the 90% confidence level. Assuming z = 6.7 (Fynbo et al., GCN Circ. 8225) and a standard cosmology model with H_0 = 71 km/s/Mpc, Omega_M = 0.27, Omega_Lambda = 0.73, the isotropic energy release is E_iso ~7x10^52 erg in 1 keV to 10 MeV at the GRB rest frame extrapolating the best Band function fit fixing beta=-2.5. Looking only at the parameters of the prompt emission, namely T90~1 sec and Ep ~900 keV in the GRB rest frame, this burst could be classified as a short burst. //////////////////////////////////////////////////////////////////////// TITLE: GCN CIRCULAR NUMBER: 8267 SUBJECT: GRB080913: Swift-BAT spectral lag DATE: 08/09/18 14:15:23 GMT FROM: Dong Xu at DARK,NBI Dong Xu (DARK/NBI) reports The Swift/BAT data were reduced in a standard way. Making use of the Cross Correlation Function (CCF) for different energy bands over 15-150 keV, we found negligible spectral time lags, being consistent with the values/range of previous Swift short-duration GRBs. Also we note the rest-frame energy band which BAT corresponds to for this burst (z~6.7, Fynbo et al. GCN 8225) is higher than that for previous GRBs. DX is grateful to R. L. C. Starling, P. T. O'Brien, and K. Page through the SPARTAN program on Swift data reduction. //////////////////////////////////////////////////////////////////////// TITLE: GCN CIRCULAR NUMBER: 8280 SUBJECT: GRB 080913B: Fermi GBM detection DATE: 08/09/21 15:32:20 GMT FROM: Bill Paciesas at UAH Bill Paciesas (UAH), Alexander van der Horst (NASA/MSFC) and Adam Goldstein (UAH), report on behalf of the Fermi Gamma-ray Burst Monitor Team: "At 17:38:31 UT on 13 September 2008, the Fermi Gamma-Ray Burst Monitor (GBM) triggered and located GRB 080913B (trigger 243020312 / 080913.735). The on-ground calculated location, using the GBM trigger data, is RA = 46.3, Dec = -4.6 (J2000 degrees) (equivalent to J2000 3h 05m, -4d 36'), with an uncertainty of 3.3 degrees (radius, 1-sigma containment, statistical only; there is additionally a systematic error which is currently estimated to be 2 to 3 degrees). The angle from the Large Area Telescope (LAT) boresight is 71 degrees. This GRB was about 140 s long consisting of several peaks with a main emission period of 30 seconds. The time-averaged spectrum from T-2 to T+28 s is best fit by a power law with exponential cut-off, with a power-law index of -0.69 +/- 0.16 and a cut-off energy, parameterized as Epeak, of 114 +/- 14 keV. The fluence between 50 and 300 keV over these 30 seconds is (2.2 +/- 0.5) x 10^-6 erg/cm^2. The spectral analysis results presented above are preliminary; the final results will be published in the GBM GRB Catalog." //////////////////////////////////////////////////////////////////////// TITLE: GCN CIRCULAR NUMBER: 9279 SUBJECT: GRB 090423: pseudo burst at z=1 and its relation to GRB 080913 DATE: 09/04/29 00:10:01 GMT FROM: Binbin Zhang at UNLV Bin-Bin Zhang and Bing Zhang (University of Nevada Las Vegas) report: GRB 090423 is a second, high-z, intrinsically short GRB after GRB 080913. Following the similar procedure discussed in Zhang, B et al 2009, http://arxiv.org/abs/0902.2419 , we have simulated a pseudo GRB by shifting GRB 090423 to z=1. The following three factors, i.e, specific flux (f_\nu) amplification due to a smaller luminosity distance, blue-shift of spectrum, and temporal compression of the lightcurve (de-dilation), have been considered. We notice that there is an early X-ray flare in GRB 090423 (again similar to GRB 080913), which should be harder and observable by BAT if it were at z=1. Following the similar procedure described in Zhang et al. (2009), we manipulate the XRT data of GRB 090423 to simulate the BAT band extended emission of the pseudo burst. The constructed BAT band lightcurve of the pseudo GRB at z=1 is shown in the figure at http://grb.physics.unlv.edu/gcns/090423/pseudo.jpg . This psuedo burst appears as a short duration GRB with extended emission. On the other hand, both high-z GRBs have high isotropic luminosity and energy, which make them following the Amati/Yonetoku correlation defined by GRBs that are of the massive star origin (Type II or long population). Although it is possible to have NS-NS and NS-BH mergers (Type I or short population) at such a high-z (Belczynski et al. 2009), the difficulty is to have two such energetic merger events at high-z. The Type I model has difficulty to accommodate both low-z, low-L Type I events and these events in terms of luminosity function (Zhang et al. 2009). Based on the multiple criteria analysis, we cannot address the physical category of GRB 090423 and GRB 080913 using more definite criteria (e.g. SN association, host galaxy property, etc). On the other hand, one can use less definite criteria (Amati/Yonetoku relation and energetics) to judge that both bursts are Type II (massive star collapse) candidates. A judging flow chart using Fig. 8 of Zhang et al. (2009) is posted at http://grb.physics.unlv.edu/gcns/090423/flowchart.jpeg . We also noticed the interesting discussions by Krimm et al. (GCN 9241) and Nava et al. (GCN 9235), which are broadly consistent with our conclusion here. Finally, using the three samples (Type II Gold, Type I Gold, and Other Short/Hard) defined in Zhang et al. (2009), we plot the intrinsic duration (T_{90}/(1+z)) as a function of z (see http://grb.physics.unlv.edu/gcns/090423/t90z.png ). It is interesting to note that the two high-z bursts are intrinsically shorter than the majority of Type II GRBs. If these observations persist in the future, it may suggest an intrinsic trend of short duration for Type II GRBs at high-z. This message can be cited. //////////////////////////////////////////////////////////////////////// TITLE: GCN CIRCULAR NUMBER: 9321 SUBJECT: GRB 080913: 250 GHz upper limit for a z=6.7 GRB with MAMBO-2 at the IRAM 30m DATE: 09/05/04 18:16:48 GMT FROM: Dominik A. Riechers at Caltech D. A. Riechers (Caltech), F. Walter (MPIA Heidelberg), F. Bertoldi (AIfA Bonn), C. L. Carilli (NRAO), P. Cox (IRAM) report: "We used the Max-Planck-Millimeter Bolometer (MAMBO-2) array at the IRAM 30-m telescope to observe the field of view toward the host galaxy of GRB 080913 (GCN 8217) at redshift z=6.7 (GCN 8225), RA 04:22:54.74, Dec -25:07:46.2 (J2000) at 250 GHz. Observations were carried out for 3.7 hr between 2008 November 13 and 15. We obtained a non-detection of S_nu(250 GHz,1.20 mm) = 0.34 +/- 0.45 mJy (1 sigma error), i.e. a 3 sigma upper flux density limit of 1.35 mJy on the dust continuum in the GRB host galaxy at 1.2 mm (rest-frame 156 um). The 117-element MAMBO-2 bolometer detectors cover 210-290 GHz (half power). The bolometers have a FWHM beam size of 10.7 arcsec, at a pixel spacing of 20 arcsec. Observations were carried out in ON-OFF observing mode under good weather conditions. Calibrations were performed on J0348-278 and J0609-157. We acknowledge the excellent support of the staff at IRAM. IRAM is supported by INSU/CNRS (France), MPG (Germany), and IGN (Spain). This message may be cited."