//////////////////////////////////////////////////////////////////////// TITLE: GCN CIRCULAR NUMBER: 7362 SUBJECT: GRB 080307: Swift detection of a burst DATE: 08/03/07 12:01:53 GMT FROM: David Palmer at LANL S. T. Holland (CRESST/USRA/GSFC), S. D. Barthelmy (GSFC), D. N. Burrows (PSU), J. R. Cummings (NASA/UMBC), G. Cusumano (INAF-IASFPA), P. A. Evans (U Leicester), N. Gehrels (NASA/GSFC), O. Godet (U Leicester), C. Guidorzi (INAF-OAB), S. D. Hunsberger (PSU), J. A. Kennea (PSU), V. Mangano (INAF-IASFPA), C. B. Markwardt (CRESST/GSFC/UMD), A. Moretti (INAF-OAB), P. T. O'Brien (U Leicester), J. P. Osborne (U Leicester), C. Pagani (PSU), K. L. Page (U Leicester), D. M. Palmer (LANL), D. Perez (U Leicester), P. Romano (INAF-IASFPA), G. Sato (GSFC/ISAS), M. Stamatikos (NASA/ORAU), R. L. C. Starling (U Leicester) and E. Troja (U Leicester/INAF-IASFPA) report on behalf of the Swift Team: At 11:23:30 UT, the Swift Burst Alert Telescope (BAT) triggered and located GRB 080307 (trigger=305011). Swift slewed immediately to the burst. The BAT on-board calculated location is RA, Dec 136.633, +35.168 which is RA(J2000) = 09h 06m 32s Dec(J2000) = +35d 10' 06" with an uncertainty of 3 arcmin (radius, 90% containment, including systematic uncertainty). The BAT light curve showed a FRED structure with a duration of at least 30 sec. The peak count rate was ~600 counts/sec (15-350 keV), at ~0 sec after the trigger. The XRT began observing the field at 11:25:10.1 UT, 99.3 seconds after the BAT trigger. Using promptly downlinked data we find a bright, fading uncatalogued X-ray source with an enhanced position: RA, Dec 136.62833, 35.13866 which is equivalent to: RA(J2000) = 09h 06m 30.80s Dec(J2000) = +35d 08' 19.2" with an uncertainty of 2.6 arcseconds (radius, 90% containment). This location is 106 arcseconds from the BAT onboard position, within the BAT error circle. No prompt spectrum is yet available to assess possible redshift constraints using X-ray spectroscopy and the nH-z relation from Grupe et al. (2007). The initial flux in the 2.5 s image was 7.63e-10 erg cm^-2 s^-1 (0.2-10 keV). UVOT took a finding chart exposure of 100 seconds with the White (160-650 nm) filter starting 105 seconds after the BAT trigger. A possible fading source that is not present in the DSS has been found in the initial data products at RA(J2000.0) = 09:06:25.5 Dec(J2000.0) = +35:08:39 with an estimated uncertainty of 0.6 arcsec (radius, 90% confidence). This source is approximately 1 arcminute from the XRT position, which is too far away to be consistent with the X-ray source. The estimated white magnitude is 19.6 +/- 0.1. No correction has been made for the expected extinction corresponding to E(B-V) of 0.03 mag. Burst Advocate for this burst is S. T. Holland (sholland AT milkyway.gsfc.nasa.gov). 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: 7363 SUBJECT: GRB 080307: Optical observation with DMC/KANATA DATE: 08/03/07 12:33:44 GMT FROM: Makoto Uemura at Hiroshima U M. Doi, S. Sako, J. Hayano, Y. Ihara, N. Takanashi, H. Kuncarayakti (The Univresity of Tokyo), D. Kuroda (NAOJ), K. S. Kawabata, and M. Uemura (Hiroshima Univ.) report on behalf of the DMC team: We took optical CCD images of the field of GRB 080307 (GCNC 7362) with Dichroic Mirror Camera (DMC; http://www.ioa.s.u-tokyo.ac.jp/dmc/) attached to the 1.5-m KANATA telescope. DMC enables us to simultenaously obtain 15 band images in the optical range (typical delta lambda = 35 nm). We started observations at 11:31:18 (UT) 7 March 2008, 467 s after the burst. The exposure time was 60 s. No candidate of its optical afterglow brighther than r=17.13 mag (USNO B1.0 1251-0170228; RA=09:06:33.62, Dec=+35:08:44.1) was found in our all images. YYYYDDMM(UT) limit mag. center of wavelengths 20080307.4804 17.13 r 641nm (chanel 07 of DMC) //////////////////////////////////////////////////////////////////////// TITLE: GCN CIRCULAR NUMBER: 7364 SUBJECT: GRB 080307 : BOAO optical afterglow observation DATE: 08/03/07 13:35:23 GMT FROM: Yuji Urata at Saitama U M. Im, I. Lee, W.K. Zheng, K.Y. Huang, Y. Urata on behalf of EAFON report: "We have been imaging the GRB 080307 optical afterglow (Holland et al. #7362) using the 1.8 m telescope of the Bohyunsan Optical Astronomy Observatory, Korea. The optical afterglow brightness at 67 min after the burst is R~20.3 mag. Further deeper imaging are encouraged." We thank J. Seo, and Y. Jeon for their assistance with the BOAO observation. This message may be cited. //////////////////////////////////////////////////////////////////////// TITLE: GCN CIRCULAR NUMBER: 7365 SUBJECT: GRB 080307, Preliminary Swift-BAT refined analysis DATE: 08/03/07 13:52:56 GMT FROM: Scott Barthelmy at NASA/GSFC D. Palmer (LANL), S. D. Barthelmy (GSFC), J. Cummings (GSFC/UMBC), E. Fenimore (LANL), N. Gehrels (GSFC), S. T. Holland (CRESST/USRA/GSFC), H. Krimm (GSFC/USRA), C. Markwardt (GSFC/UMD), K. McLean (GSFC/UMD), T. Sakamoto (GSFC/UMBC), G. Sato (GSFC/ISAS), M. Stamatikos (GSFC/ORAU), J. Tueller (GSFC), T. Ukwatta (GWU) (i.e. the Swift-BAT team): Using only a small amount of data set from the first telemetry downlink (from T-119 to T+183 sec), we report preliminary analysis of BAT GRB 080307 (trigger #305011) (Holland, et al., GCN Circ. 7362). The BAT ground-calculated position is RA, Dec = 136.626, 35.156 deg, which is RA(J2000) = 09h 6m 30.2s Dec(J2000) = 35d 9' 20" with an uncertainty of 1.7 arcmin, (radius, sys+stat, 90% containment). The partial coding was 81%. The mask-weighted light curve shows an initial FRED-like peak starting at T+0 sec, and ending around T+80 sec. There is evidence for emission out to T+135 sec (and the end of the downlinked data ends at T+183 sec). T90 (15-350 keV) is 64 +- 22 sec (estimated error including systematics). Using this partial data set, the time-averaged spectrum from T-7.4 to T+56.6 sec is best fit by a simple power-law model. The power law index of the time-averaged spectrum is 1.41 +- 0.19. The fluence in the 15-150 keV band is 7.3 +- 0.9 x 10^-7 erg/cm2. The 1-sec peak photon flux measured from T+16.06 sec in the 15-150 keV band is 0.2 +- 0.0 ph/cm2/sec. 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/305011/BA/ This burst satisfies Sakamoto/Ukwatta Swift-BAT possible high-z criteria (Ukwatta et al. arXiv:0802.3815): 1) The power law photon index (= 1.41) is less than 2, 2) The 1-s peak photon flux (= 0.19) is less than 1.0 ph/cm2/s, 3) The light curve variance (= 2.11e-05 is less than 0.0001, 4) The T90/Peak_photon_flux (= 336) is greater than 100. Based on a limited sample of bursts, these criteria yield an 85% chance it has a redshift greater than 3.5. We must stress however, that we have downlinked data out to only T+180 sec and there is evidence of continued emissin out to T+135 sec. So if there is further activity in this burst past T+180 sec, then the spectral and temporal values used in this hi-z indicator test may change and no longer fit the hi-z criteria. We are publishing this preliminary refined circular on that chance the hi-z indicator is correct and follow-up observsers can choose to make observations sooner. We will issue the regular 'refined' circular when the full data set becomes available. //////////////////////////////////////////////////////////////////////// TITLE: GCN CIRCULAR NUMBER: 7366 SUBJECT: GRB 080307: Enhanced Swift-XRT position DATE: 08/03/07 14:19:41 GMT FROM: Phil Evans at U of Leicester M.R. Goad, J.P. Osborne, A.P. Beardmore and P.A. Evans (U. Leicester) report on behalf of the Swift-XRT team. Using 161 s of overlapping XRT Photon Counting mode and UVOT data for GRB 080307, 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 = 136.62799, +35.13896 which is equivalent to: RA (J2000): 09h 06m 30.72s Dec (J2000): +35d 08' 20.3" with an uncertainty of 1.8 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). This circular was automatically generated, and is an official product of the Swift-XRT team. //////////////////////////////////////////////////////////////////////// TITLE: GCN CIRCULAR NUMBER: 7367 SUBJECT: GRB 080307: retraction of UVOT candidate DATE: 08/03/07 14:44:30 GMT FROM: Patricia Schady at MSSL/Swift P. Schady (MSSL/UCL) and S. T. Holland (CRESST/USRA/GSFC) report on behalf of the Swift UVOT team: There was a typo in the position for the optical afterglow candidate for GRB 080307 reported by Holland et al., (GCN 7362), and this should, in fact, be RA(J2000.0) = 09:06:25.5 Dec(J2000.0) = +35:08:29 with an estimated uncertainty of 1 arcsec. However, we note that the new UVOT position is 0.2" from a known source, and is therefore unlikely to be the optical afterglow of GRB 080307. //////////////////////////////////////////////////////////////////////// TITLE: GCN CIRCULAR NUMBER: 7368 SUBJECT: GRB 080307: BOAO imaging - retraction and new limit DATE: 08/03/07 14:56:48 GMT FROM: Myungshin Im at Seoul Nat U M. Im, I. Lee, W.K. Zheng, K.Y. Huang, Y. Urata on behalf of EAFON team. Earlier, we reported the detection of the after glow of GRB080307 (GCN Circular, #7364). Our reported afterglow at the UVOT position turned out to be a known star, and we retract our earlier report. We do not detect the GRB afterglow at the enhanced XRT position (GCN Circular #7366), and we place the limit of R > 21.2 at 3 sigma. Further analysis is ongoing. This message may be cited. //////////////////////////////////////////////////////////////////////// TITLE: GCN CIRCULAR NUMBER: 7369 SUBJECT: GRB 080307: Gemini-N i-band observations - candidate afterglow DATE: 08/03/07 15:05:05 GMT FROM: Nial Tanvir at IofA U.Cambridge N. R. Tanvir (U. Leicester) reports on behalf of a larger collaboration. We observed the field of GRB 080307 with Gemini-N/GMOS, beginning at 12:50 (UT), approximately 85 minutes post-burst. We detect a point source in the i-band image within the XRT error circle (GCN 7366) with (J2000) coordinates: 09 06 30.78 +35 08 20.0 Provisional photometry relative to field SDSS stars gives a magnitude of i=22.4 at this time. We thank the Gemini staff, particularly Ricardo Schiavon, for support in obtaining these observations. //////////////////////////////////////////////////////////////////////// TITLE: GCN CIRCULAR NUMBER: 7370 SUBJECT: GRB080307: Optical upper limits DATE: 08/03/07 15:59:54 GMT FROM: Michitoshi Yoshida at Okayama Astrophysical Obs M. Yoshida, K. Yanagisawa, Y. Shimizu, S. Nagayama, H. Toda (OAO, NAOJ) and N. Kawai (Tokyo Tech) report on behalf of the MITSuME collaboration: We performed optical imaging observations (g', Rc, and Ic) of the field of GRB 080307 (Holland et al. GCN 7362) with the 50cm MITSuME telescope at Okayama Astrophysical Observatory from UT 11:25:50 to UT 12:47:00 on March 7 2008. Flux calibration was made using USNO B1.0 catalog. We could not identify any new source at the XRT position (Holland et al. GCN 7362) or the UVOT positions (Schady et al. GCN 7367). Three sigma upper limits are listed below. mid-UT exp.time g' Rc Ic ------------------------------------------------------- 2008-03-07 11:31:20 10 min. >19.6 >19.3 >18.7 2008-03-07 12:12:00 57 min. >20.5 >20.3 >19.5 ------------------------------------------------------- //////////////////////////////////////////////////////////////////////// TITLE: GCN CIRCULAR NUMBER: 7371 SUBJECT: GRB 080307: TNT optical observation DATE: 08/03/07 16:49:51 GMT FROM: W.K. Zheng at NAOC L.P. Xin, X.M. Meng, M. Zhai, J.S. Deng, Y.L. Qiu, J.Y. Wei, J.Y. Hu, J. Wang, W.K. Zheng Y. Urata, M. Im, I. Lee, K.Y. Huang, Y. on behalf of EAFON report: We have imaged the field of GRB080307 (Holland et al., GCN 7362) using the TNT 0.8 telescope at Xinglong observatory under good condition. A set of White and R band images were obtained. Preliminary result shows we margianally detected the afterglow candidate (Tanvir, GCN 7369) in our combined images. By performing PSF photometry, we have the following magnitude calibrated to the USNO B1.0 R2 mag: T_mid(min) Mag Band Exp Merr ------------------------------------- 15.71 20.9 W 10*20s 0.3 24.50 21.3 R 10*60s 0.3 70.28 22.1 R 8*300s 0.3 The source faded during our observation epoch, we confirm this is the afterglow of GRB 080307. This message may be cited. For more information about Xinglong GRBs Follow-up observations, please visit the website: http://www.xinglong-naoc.org/grb/ //////////////////////////////////////////////////////////////////////// TITLE: GCN CIRCULAR NUMBER: 7372 SUBJECT: GRB080307 - SDSS Pre-Burst Observations DATE: 08/03/07 17:47:58 GMT FROM: Richard J. Cool at U.of AZ/Steward Obs Richard J. Cool (Arizona), Daniel J. Eisenstein (Arizona), David W. Hogg (NYU), Michael R. Blanton (NYU), David J. Schlegel (LBNL), J. Brinkmann (APO), Donald Q. Lamb (Chicago), Donald P. Schneider (PSU), and Daniel E. Vanden Berk (PSU) report: The Sloan Digital Sky Survey (SDSS) imaged the field of burst GRB080307 prior to the burst. As these data should be useful as a pre-burst comparison and for calibrating photometry, we are supplying the images and photometry measurements for this GRB field to the community. Data from the SDSS, including 5 FITS images, 3 JPGS, and 3 files of photometry and astrometry, are being placed at http://mizar.as.arizona.edu/~grb/public/GRB080307 We supply FITS images in each of the 5 SDSS bands of a 8'x8' region centered on the GRB position (ra=136.633 (09:06:31.9), dec=35.1680 (35:10:04.8); Swift-BAT TRIGGER 305011), as well as 3 gri color-composite JPGs (with different stretches). The units in the FITS images are nanomaggies per pixel. A pixel is 0.396 arcsec on a side. A nanomaggie is a flux-density unit equal to 10^-9 of a magnitude 0 source or, to the extent that SDSS is an AB system, 3.631e-6 Jy. The FITS images have WCS astrometric information. In the file GRB080307_sdss.calstar.dat, we report photometry and astrometry of 301 bright stars (r<20.5) within 15' of the burst location. The magnitudes presented in this file are asinh magnitudes as are standard in the SDSS (Lupton 1999, AJ, 118, 1406). Beware that some of these stars are not well-detected in the u-band; use the errors and object flags to monitor data quality. In the files GRB080307_sdss.objects_flux.dat and GRB080307_sdss.objects_magnitudes.dat, we report photometry of 1032 objects detected within 6' of the GRB position. We have removed saturated objects and objects with model magnitudes fainter than 23.0 in the r-band. The fluxes listed in GRB080307_sdss.objects_flux.dat are in nanomaggies while the magnitudes listed in GRB080307_sdss.objects_magnitudes.dat are asinh magnitudes. **Be aware that at least a portion of the photometry provided in this release has been flagged as non-photometric. As photometry for objects with this flag set may have non-optimal calibration, we do not recommend these objects be used for photometric calibration. Non-photometric imaging may still be valuable as a pre-burst comparison and for astrometric calibration. All quantities reported are standard SDSS photometry, meaning that they are very close to AB zeropoints and magnitudes are quoted in asinh magnitudes. Photometric zeropoints are known to about 2% rms. None of the photometry is corrected for dust extinction. The Schlegel, Finkbeiner, and Davis (1998) predictions for this region are A_U=0.137 mag, A_g=0.101 mag, A_r = 0.073 mag, A_i=0.055 mag, and A_z=0.039 mag. The file GRB080307_sdss.spectro.dat contains a list of the 2 objects with SDSS spectroscopy within 6 arcminutes of the GRB position. In addition to the redshift and 1-sigma error for each object, this file also lists the object spectroscopic classification. SDSS astrometry is generally better than 0.1 arcsecond per coordinate. Users requiring high precision astrometry should take note that the SDSS astrometric system can differ from other systems such as those used in other notices; we have not checked the offsets in this region. More detailed information pertaining to our SDSS GRB releases can be found in our initial data release paper (Cool et al. 2006, PASP 118, 733). See the SDSS DR4 documentation for more details: http://www.sdss.org/dr5. These data have been reduced using a slightly different pipeline than that used for SDSS public data releases. We cannot guarantee that the values here will exactly match those in the data release in which these data are included. In particular, we expect the photometric calibrations to differ by of order 0.01 mag. This note may be cited, but please also cite the SDSS data release paper, Adelman-McCarthy et al. (2007, ApJS, 172, 634), when using the data or referring to the technical documentation. //////////////////////////////////////////////////////////////////////// TITLE: GCN CIRCULAR NUMBER: 7373 SUBJECT: GRB 080307, Swift-BAT refined analysis DATE: 08/03/07 18:47:06 GMT FROM: Goro Sato at GSFC G. Sato (GSFC/ISAS), S. D. Barthelmy (GSFC), J. Cummings (GSFC/UMBC), E. Fenimore (LANL), N. Gehrels (GSFC), S. T. Holland (CRESST/USRA/GSFC), H. Krimm (GSFC/USRA), C. Markwardt (GSFC/UMD), K. McLean (GSFC/UMD), D. Palmer (LANL), A. Parsons (GSFC), T. Sakamoto (GSFC/UMBC), M. Stamatikos (GSFC/ORAU), 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 080307 (trigger #305011) (Holland, et al., GCN Circ. 7362, and Palmer, et al., GCN Circ. 7365). The BAT ground-calculated position is RA, Dec = 136.629, 35.151 deg which is RA(J2000) = 9h 6m 31.0s Dec(J2000) = 35d 9' 4" with an uncertainty of 1.6 arcmin, (radius, sys+stat, 90% containment). The partial coding was 81%. The mask-weighted light curve shows an initial FRED-like peak starting at T+0 sec, and ending around T+140 sec. A strong spectral evolution can be seen in the BAT four energy band light curves. T90 (15-350 keV) is 125.9 +- 24.6 sec (estimated error including systematics). The time-averaged spectrum from T+1.7 to T+146.1 sec is best fit by a simple power-law model. The power law index of the time-averaged spectrum is 1.78 +- 0.21. The fluence in the 15-150 keV band is 8.7 +- 1.2 x 10^-07 erg/cm2. The 1-sec peak photon flux measured from T+1.90 sec in the 15-150 keV band is 0.4 +- 0.1 ph/cm2/sec. 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/305011/BA/ This burst satisfies Sakamoto/Ukwatta Swift-BAT possible high-z criteria (Ukwatta et al. arXiv:0802.3815): 1) The power law photon index (= 1.78) is less than 2, 2) The 1-s peak photon flux (= 0.4) is less than 1.0 ph/cm2/s, 3) The light curve variance (= 9.4e-06) is less than 0.0001, 4) The T90/Peak_photon_flux (= 350) is greater than 100. Based on a limited sample of bursts, these criteria yield an 85% chance it has a redshift greater than 3.5. //////////////////////////////////////////////////////////////////////// TITLE: GCN CIRCULAR NUMBER: 7374 SUBJECT: GRB 080307: Early RAPTOR Limits DATE: 08/03/07 18:59:18 GMT FROM: James Wren at LANL J. Wren, W.T. Vestrand, P.R. Wozniak, H. Davis of Los Alamos National Laboratory report: Our Raptor telescopes responded to Swift trigger 305011 (Holland et al., GCN 7362) at 11:24:30.8 UTC, 60.0 seconds after the trigger and 7.3 seconds after receipt of the GCN packet. We detect no new optical source at the Swift XRT position. Five sigma limiting magnitudes are given for three of our unfiltered response images in the table below. Calibration was performed using the USNO B1.0 R-band magnitudes. T-start (UTC) T-exp (s) mag limit ------------------------------------------------- 2008-03-07 11:24:30.81 5 16.9 2008-03-07 11:25:53.96 10 17.3 2008-03-07 11:30:12.01 30 18.0 //////////////////////////////////////////////////////////////////////// TITLE: GCN CIRCULAR NUMBER: 7375 SUBJECT: GRB 080307: Swift/UVOT Upper Limits DATE: 08/03/07 20:20:40 GMT FROM: Stephen Holland at USRA/NASA/GSFC/SSC S. T. Holland (CRESST/GSFC/USRA) reports on the behalf of the Swift UVOT team: The Swift/UVOT observed the field of GRB 080307 starting 105 s after the BAT trigger (Holland et al. 2008, GCN Circ. 7362). We do not find any source, in any of the UVOT observations, at the location of the Gemini-North source (Tanvir, 2008 GCN Circ. 7369). The 3-sigma upper limits for detecting a source at this location in the co-added images are: Filter T_start T_stop Exp(s) Mag (3-sigma upper limit) ----------------------------------------------------------------- v 212 5754 676 >20.7 b 691 6574 412 >21.4 u 666 6369 432 >21.1 uvw1 642 6164 432 >20.9 uvm2 618 5959 413 >20.6 uvw2 721 6816 245 >20.7 white 105 6779 599 >22.3 ----------------------------------------------------------------- The quoted upper limits have not been corrected for the expected Galactic extinction along the line of sight corresponding to a reddening of E_{B-V} = 0.03 mag. All photometry is on the UVOT flight system described in Poole et al. (2008, MNRAS, 383, 627). //////////////////////////////////////////////////////////////////////// TITLE: GCN CIRCULAR NUMBER: 7376 SUBJECT: GRB 080307: Swift-XRT Team refined analysis DATE: 08/03/07 21:37:34 GMT FROM: Kim Page at U.of Leicester K.L. Page, J.P. Osborne (U. Leicester) & S.T. Holland (CRESST/GSFC/USRA) report on behalf of the Swift-XRT team: We have analysed the first four orbits of data obtained for GRB 080307 (Holland et al., GCN Circ. 7362), which includes 509 seconds in Windowed Timing (WT) mode and 7.9 ks in Photon Counting (PC mode). The UVOT-enhanced XRT position has been given by Goad et al. in GCN Circ 7366. In the first orbit of the XRT data, the emission rises slowly, peaking around 200-300 seconds after the BAT trigger, after which the decay can be modelled with a single power-law with alpha = 1.83 +/- 0.08. The shape of the early light-curve is reminiscent of GRB 060218 (Campana, S. et al, 2006, Nature, 442, 1008). As the X-ray emission rises, it also softens; the hardness ratio then becomes close to constant as the light-curve decay sets in. The PC data at the end of the first orbit can be fitted with an absorbed power-law, with Gamma = 1.74 +0.23/-0.21 and NH = (1.5 +0.8/-0.6)e21 cm^-2, which is in excess of the Galactic value of 2.37e20 cm^-2. From the relation in Grupe et al. (2007, AJ, 133, 2216), this indicates a redshift of less than 4.0. The mean observed (unabsorbed) flux for the PC data at the end of the first orbit (615-1030 seconds) is 7.86e-11 (9.83e-11) erg cm^-2 s^-1. The corresponding counts to (observed) flux conversion is 1 count s^-1 = 4.9e-11 erg cm-2 s^-1. If the light-curve continues to decay following a power-law of 1.83, the count rate at 24 hours is predicted to be 3.6e-4 count s^-1 (an observed flux of 1.8e-14 erg cm^-2 s^-1). This circular is an official product of the Swift-XRT team. //////////////////////////////////////////////////////////////////////// TITLE: GCN CIRCULAR NUMBER: 7378 SUBJECT: GRB080307 BOAO optical afterglow observation - detection of a possible OT DATE: 08/03/08 08:12:01 GMT FROM: Myungshin Im at Seoul Nat U M. Im, I. Lee, Y. Urata, W.K. Zheng, K.Y. Huang, on behalf of EAFON team. We re-analyzed the I-band images taken with the 1.8m telescope of the Bohyunsan Optical Astronomy Observatory, Korea. The I-band observation started at 76.1 min after the burst (Holland et al. #7362), and continued for 2100 secs. Our reanalysis of the stacked image show the detection of a possible optial transient within the error circle of the XRT position (Goad et al. #7366), and the reported Gemini-N i-band position (Tanvir et al.7369). The brightness of the OT, calibrated against USNO-B1 star at (09:06:31.6,+35:08,06.4), is I ~ 21.9 +- 0.3 mag with the error arising mostly from the uncertainty associated with the subtraction of the fringe pattern. Further deeper imaging is encouraged. We thank J. Seo and Yeon-Bom Jeon for their assistance with the BOAO observation. This message may be cited. //////////////////////////////////////////////////////////////////////// TITLE: GCN CIRCULAR NUMBER: 7379 SUBJECT: GRB080307, optical upper limit DATE: 08/03/10 06:59:51 GMT FROM: Hiroki Tanaka at U of Miyazaki H. Tanaka, R. Hara, K.Kono, N.Ohmori, H.hayasi, M.Yamauchi, E.Sonoda (University of Miyazaki) We have observed the field covering the error circle of GRB080307 (GCN 7366, M.R. Goad et al.) with the unfiltered CCD camera on the 30-cm telescope at University of Miyazaki. The observation was started 11:25:17 UT, but it was cloudy then,so we got first image at 13:44:43 UT, ~141 min after the Swift trigger time. We have compared our data of 30 sec exposures with the USNO-A2.0 catalog,there is no new source at the reported position (GCN 7369, N. R. Tanvir) the upper limits are as follows: -------------------------------------------------------------- Start(UT) End(UT) Num. of frames Limit (mag.) -------------------------------------------------------------- 14:01:59 14:02:29 1 ~16.36 14:01:59 17:26:12 20 ~16.99 --------------------------------------------------------------- //////////////////////////////////////////////////////////////////////// TITLE: GCN CIRCULAR NUMBER: 7400 SUBJECT: GRB080307: optical upper limit DATE: 08/03/10 19:17:24 GMT FROM: Alexei Pozanenko at IKI, Moscow G. Kornienko, A. Erofeeva (UAFO), A. Pozanenko (IKI) on behalf of larger GRB follow up collaboration report: We observed the error box of GRB080307 (Holland et al. GCN 7362) on March 05 with SR-22 telescope of UAFO observatory. A set of 20 unfiltered images of 60 s exposure was obtained starting (UT) 11:36:55, i.e. 13.5 minutes after burst onset. No new object is detected within enhanced XRT error circle (Goad et al. GCN 7366). Based on USNO-A2.0 (R) we estimated upper limit as following T0+ Exposure UL (mid) 23.5 m 10x60 s 18.8 The message may be cited. //////////////////////////////////////////////////////////////////////// TITLE: GCN CIRCULAR NUMBER: 7405 SUBJECT: GRB 080307: NIR upper limit DATE: 08/03/11 03:24:43 GMT FROM: Takeo Minezaki at U.of Tokyo/Astro T. Minezaki (IoA, Tokyo), P.A. Price (IfA, Hawaii), Y. Yoshii (IoA, Tokyo), L. Cowie (IfA, Hawaii) and Y. Kakazu (IfA, Hawaii) report: We observed the localisation of GRB 080307 with the MAGNUM telescope + MIP dual-beam imager. We do not find any afterglow in the RIYJHK images within the XRT error circle (GCN #7366), and at the Gemini-N i-band candidate position (GCN #7369). We estimated the upper limits in JHK based on flux calibration with a nearby 2MASS star as follows: Filter t - t_GRB (hour) Limit (mag) J +18.9 20.8 H +19.8 20.1 K +19.5 19.2 This message may be cited. //////////////////////////////////////////////////////////////////////// TITLE: GCN CIRCULAR NUMBER: 7408 SUBJECT: GRB 080307: GAO 150cm telescope Optical Observation DATE: 08/03/11 11:21:49 GMT FROM: Kenzo Kinugasa at Gunma Astro. Obs/Japan K. Kinugasa, S.Honda, O.Hashimoto, H.Taguchi (Gunma Astronomical Observatory) report: The field of GRB 080307 (Holland et al. GCN 7362) was observed with the 150 cm telescope of the Gunma Astronomical Observatory. Starting at 13:06 UT (1.67 hours after the burst), Rc, Ic, and V frames were acquired for 3 x 5-min, 6 x 5-min, and 2 x 5-min exposures, respectively. We do not identified the optical counterpart reported by Tanvir et al. (GCN 7369) to 3-sigma limiting magnitudes of Rc=21.5 and Ic=21.0 relative to USNO-B1.0 magnitudes.