//////////////////////////////////////////////////////////////////////// TITLE: GCN CIRCULAR NUMBER: 6837 SUBJECT: GRB 071003: Swift detection of a bright burst DATE: 07/10/03 07:53:48 GMT FROM: David Palmer at LANL P. Schady (MSSL-UCL), P. A. Evans (U Leicester), N. Gehrels (NASA/GSFC), C. Guidorzi (Univ Bicocca&INAF-OAB), S. T. Holland (CRESST/USRA/GSFC), J. A. Kennea (PSU), C. B. Markwardt (CRESST/GSFC/UMD), P. T. O'Brien (U Leicester), K. L. Page (U Leicester), D. M. Palmer (LANL), G. Sato (GSFC/ISAS) and R. L. C. Starling (U Leicester) report on behalf of the Swift Team: At 07:40:55 UT, the Swift Burst Alert Telescope (BAT) triggered and located GRB 071003 (trigger=292934). The BAT on-board calculated location is RA, Dec 301.856, +10.960 which is RA(J2000) = 20h 07m 25s Dec(J2000) = +10d 57' 35" with an uncertainty of 3 arcmin (radius, 90% containment, including systematic uncertainty). The BAT light curve showed a multi-peaked structure with a duration of about 25 sec. The peak count rate was ~16000 counts/sec (15-350 keV), at ~0 sec after the trigger. Because Swift is in the process of returning to normal operations, automatic slewing to GRBs is currently disabled outside of business hours (US EDT). Therefore, there are no prompt XRT or UVOT observations of this burst. 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: 6838 SUBJECT: GRB 071003: KAIT optical afterglow observations DATE: 07/10/03 09:59:17 GMT FROM: Weidong Li at UC Berkeley KAIT/LOSS W. Li, University of California, Berkeley, on behalf of the KAIT GRB team, report: The robotic 0.76-m Katzman Automatic Imaging Telescope (KAIT) at Lick Observatory observed GRB 071003 detected with Swift (Trigger 292934; Schady et al. GCN 6837). The automatic sequence started at 07:41:37, 42 s after the burst. The BAT location has been monitored in V, I, and clear filters, with varying exposure times. Our image processing pipeline found a new object within the BAT error circle, with the following position: R. A. = 20:07:24.12 DEC. = +10:56:51.8 (J2000) The OA has magnitude of 12.8 (calibrated with USNO B1.0) in a 5s unfiltered exposure started at 07:41:37 UT, 42s after the BAT trigger. The new object is close to a bright foreground star. Further Analysis is ongoing. A finder chart can be found at http://astro.berkeley.edu/~weidong/grb071003.finder.gif This message may be cited. //////////////////////////////////////////////////////////////////////// TITLE: GCN CIRCULAR NUMBER: 6839 SUBJECT: GRB 071003: P60 Confirmation of Optical Afterglow DATE: 07/10/03 10:58:39 GMT FROM: S. Bradley Cenko at Caltech S. B. Cenko (Caltech) and D. B. Fox (Penn State) report on behalf of a larger collaboration: We have imaged the field of GRB071003 (Schady et al., GCN 6837) with the automated Palomar 60-inch telescope. Observations began approximately 3 minutes after the burst (~ 07:44 UT 10 October) and were taken at high airmass (~ 2.5). At the location of the optical afterglow candidate (Li, GCN 6838) we detect a fading source in the g, R, i', and z' filters. While photometry is complicated by the nearby bright star (Li, GCN 6838), we estimate a magnitude of R ~ 14.5 in our first 60 s image (photometric calibration was performed relative to several nearby objects from the USNO-B catalog). The corresponding decay index is ~ -1.0. //////////////////////////////////////////////////////////////////////// TITLE: GCN CIRCULAR NUMBER: 6840 SUBJECT: GRB 071003 Optical observations DATE: 07/10/03 17:50:25 GMT FROM: Kuntal Mishra at ARIES,Nainital,India K. Misra, S. B. Pandey, Rupak Roy (ARIES, NainiTal, India) and Alberto J. Castro-Tirado (IAA, Granada) on behalf of larger Indian GRB collaboration The Swift GRB 071003 (Schady et al. GCN 6837) was observed using 1.04 m Sampurnanand Telescope. The optical afterglow candidate reported by Li (GCN 6838), Cenko & Fox (GCN 6839) is clearly seen in U and B band frames in 300 sec exposure each. The fading nature of the source is seen and U ~ 17 mag was measured around 7.5 hours after the burst. The contamination due to the nearby bright stars makes the photometry complicated. Multiband observations and detailed observations are underway. This message may be cited. //////////////////////////////////////////////////////////////////////// TITLE: GCN CIRCULAR NUMBER: 6841 SUBJECT: GRB 071003: MARGE Observations DATE: 07/10/03 22:02:30 GMT FROM: Heather Swan at U.of Michigan/ROTSE H. Swan (U Mich), I. Smith (Rice), W. Rujopakarn (Steward), F. Yuan (U Mich), S. Yost (College of St. Benedict), C. Akerlof (U Mich), M. Skinner (Boeing), R. Russell (Aerospace Corporation) report on behalf of the MARGE collaboration: The AEOS Burst Camera (ABC) on the AEOS telescope, located at the Maui Space Surveillance System on Haleakala, observed the fading counterpart to GRB071003 (Swift trigger 292934 (P. Schady et al. GCN 6837)). The images are unfiltered 10s exposures which started ~9 minutes after the trigger and ended ~ 3 hours later. We detect the OT first identified by W. Li (GCN 6838). A preliminary analysis gives a magnitude of approximately 16.04+/-0.01 at 7:40:55 UT. We calibrated the OT to the USNO-B1.0 R2 band magnitudes of several nearby stars. We find that the early ABC data fades as a power law decay with index ~1.9. We note that the lightcurve has a flatter decay index after about 2000 seconds. This may be partially due to contamination from the nearby 10.79 mag star that will be resolved by more careful analysis. It is possible that the OT is still visible (< 22nd mag). Further observations are planned. //////////////////////////////////////////////////////////////////////// TITLE: GCN CIRCULAR NUMBER: 6842 SUBJECT: GRB 071003, Swift-BAT refined analysis DATE: 07/10/03 22:22:49 GMT FROM: Scott Barthelmy at NASA/GSFC T. Ukwatta (GWU), L. Barbier (GSFC), S. D. Barthelmy (GSFC), J. Cummings (GSFC/UMBC), E. Fenimore (LANL), N. Gehrels (GSFC), H. Krimm (GSFC/USRA), C. Markwardt (GSFC/UMD), D. Palmer (LANL), A. Parsons (GSFC), T. Sakamoto (GSFC/UMBC), G. Sato (GSFC/ISAS), P. Schady (MSSL-UCL), M. Stamatikos (GSFC/ORAU), J. Tueller (GSFC) (i.e. the Swift-BAT team): Using the data set from T-239 to T+584 sec from recent telemetry downlinks, we report further analysis of BAT GRB 071003 (trigger #292934) (Schady, et al., GCN Circ. 6837). The BAT ground-calculated position is RA, Dec = 301.857, 10.954 deg which is RA(J2000) = 20h 07m 25.8s Dec(J2000) = 10d 57' 16" with an uncertainty of 1.0 arcmin, (radius, sys+stat, 90% containment). The partial coding was 34%. The mask-weighted light curve shows a strong first peak with multiple overlapping subpeaks starting at ~T-20sec, peaking at T+0 sec, and ending at ~T+55 sec. The second, much weaker peak starts at ~T+130 sec, peaks at ~T+145 sec, and ends at ~T+220 sec. T90 (15-350 keV) is 150 +- 10 sec (estimated error including systematics). The time-averaged spectrum from T-7.6 to T+167.4 sec is best fit by a simple power-law model. The power law index of the time-averaged spectrum is 1.36 +- 0.07. The fluence in the 15-150 keV band is 8.3 +- 0.3 x 10^-6 erg/cm2. The 1-sec peak photon flux measured from T+0.37 sec in the 15-150 keV band is 6.3 +- 0.4 ph/cm2/sec. All the quoted errors are at the 90% confidence level. //////////////////////////////////////////////////////////////////////// TITLE: GCN CIRCULAR NUMBER: 6843 SUBJECT: GRB 071003: Keck HIRES spectroscopy DATE: 07/10/03 23:12:24 GMT FROM: Daniel Perley at U.C. Berkeley D. A. Perley (UCB), J. X. Prochaska (UCSC), J. S. Bloom (UCB), and G. Smith (UCO/Lick) report on behalf of the GRAASP collaboration: We observed GRB 071003 (Schady et al., GCN 6837) with Keck/HIRESr starting at UT 10:24 for one exposure of 1700s. The data were acquired through very high airmass and have a low S/N ratio (~1 per 1.3 km/s pixel at 5000A). We identify no obvious absorption features in either the 2D image nor 1D spectrum. Allowing for the following priors, we place the following upper limits on the GRB redshift: 1. Assuming the GRB host galaxy would emit no flux below the Lyman limit, we infer z_GRB < 3.4 2. Assuming the GRB host galaxy would imprint a damped Lya profile on the spectrum, we infer z_GRB < 2.5 3. Assuming the GRB host galaxy would imprint a strong MgII absorber on the spectrum (EW > 1A), we infer z_GRB < 1. Given these constraints and the U-band detection from Mishra et al. (GCN 6840), it is possible that this GRB is at low redshift. We encourage follow-up observations to search for, or place limits on, a low-redshift host galaxy or associated supernova. //////////////////////////////////////////////////////////////////////// TITLE: GCN CIRCULAR NUMBER: 6844 SUBJECT: GRB 071003: OA power-law decay indices from KAIT DATE: 07/10/03 23:14:54 GMT FROM: Weidong Li at UC Berkeley KAIT/LOSS W. Li, R. Chornock, A. V. Filippenko, D. A. Perley, J. S. Bloom (University of California, Berkeley), on behalf of the KAIT GRB team, report: We have analyzed the KAIT observations of the GRB 071003 optical afterglow (OA) reported by Li (GCN 6838) and confirmed by Cenko and Fox (GCN 6839). Our preliminary unfiltered light curve, calibrated with USNO B1.0, shows two potential breaks for the OA in the first 10 minutes after the burst. We measured a steep power law index of -1.52 +/- 0.06 between t = 0.7 min and 1.2 min after the burst (from 5 x 5s images), possibly signaling the detection of the optical reverse shock emission from the GRB. A shallower power law index of -0.89 +/- 0.03 is measured between t = 1.2 min and 4.3 min (from 3 images), suggesting a break in the light curve between t = 1.2 min to 2.8 min. The second potential break occurred at about 4 minutes after the burst, with the power law decay index measured as -1.85 +/- 0.10 from 3 images observed between t = 4.3 min to 7.4 min. We note this power law decay index is consistent with the value reported by Swan et al. (GCN 6841) at later times. Our observations ended at about 27 minutes after the burst due to physical limits of KAIT. The analysis of all the data is still ongoing. The overall behavior of the OA of GRB 071003 OA is similar to that of GRB 061126 (Perley et al., astro-ph/0703538), but with the breaks occurring at an earlier stage of the evolution. We expect contamination from the nearby bright star as discussed by Li (GCN 6838), Cenko and Fox (GCN 6839), and Misra et al. (GCN 6840) to slightly affect the above power indices, but not the overall photometric behavior. Some selected KAIT unfiltered photometry: t_start(s) Exptime(s) Mag Mag(err) 42 5.000 12.83 0.02 67 5.000 13.56 0.03 249 20.000 14.82 0.03 431 20.000 15.89 0.06 This message may be cited. //////////////////////////////////////////////////////////////////////// TITLE: GCN CIRCULAR NUMBER: 6845 SUBJECT: GRB 071003: Swift XRT position DATE: 07/10/03 23:15:38 GMT FROM: Rhaana Starling at U of Leicester R. Starling (U. Leicester) and P. Schady (MSSL/UCL) report on behalf of the Swift team: Swift XRT observed the GRB 071003 (trigger=292934, Schady et al., GCN Circ. 6837) beginning 22 ks after the BAT trigger. In 2650 s of Photon Counting mode data spanning 22--25 ks after the trigger a bright X-ray source (approximate count rate 0.1 count/s) is detected at the position RA,Dec = 301.85102, +10.94688 deg, equivalent to: RA(J2000) = 20h 07m 24.25s Dec(J2000)= +10d 56' 48.8" with an error of radius 5.7 arcseconds (90%, including boresight uncertainties). This is 35.5 arcseconds from the BAT refined position (Ukwatta et al., GCN Circ. 6842) and 3.6 arcseconds from the optical afterglow position (Li, GCN Circ. 6838). Further analysis will be reported in a subsequent circular. This is an official product of the Swift XRT team. //////////////////////////////////////////////////////////////////////// TITLE: GCN CIRCULAR NUMBER: 6846 SUBJECT: GRB 071003 : Lulin R-band observations DATE: 07/10/04 01:07:53 GMT FROM: Yuji Urata at Saitama U C.Y. Shih, Y.H. Lee, Y. Urata and K.Y. Huang on behalf of the EAFON team "We have performed R-band observations for GRB 071003 field (Schady et al., GCN 6837; Li GCN 6838) using Lulin 1-m telescope at 11:41:44 UT (about 4 hours after the burst). There is no optical afterglow emission in our combined image with R<21.5 (3-sigma limit) derived from USNO-B1.0 red stars." //////////////////////////////////////////////////////////////////////// TITLE: GCN CIRCULAR NUMBER: 6847 SUBJECT: GRB 071003: Possible rebrightening DATE: 07/10/04 08:33:56 GMT FROM: Daniel Perley at U.C. Berkeley D. A. Perley, W. Li, J. S. Bloom (UC Berkeley), C. Fassnacht (UC Davis), and P. Nugent (LBL) report: On the night of 2007-10-04 (UT) we imaged the field of GRB 071003 with Keck I + LRIS, in g+R filters simultaneously for 3 exposures of 300 seconds, starting at 04:49 UT. We detect at the position reported by Li (GCN 6838) a bright source with an estimated magnitude of R~20, though photometry is complicated by the presence of the nearby 11th magnitude star. The position is consistent within 0.3" of the KAIT detection, strongly suggesting that this is the same source. Given the rapid fading noted in earlier circulars (GCN 6841, GCN 6844) and the limit of R > 21 reported by Shih et al. (GCN 6848) this may suggest that the optical afterglow is rebrightening, either due to a late-time flare or a rising low-redshift supernova. We also note what appears to be a faint, extended object approximately 2" to the southwest of the afterglow (towards the bright star), which may be the host galaxy of this burst. Further analysis is in progress. Additional observations are strongly encouraged to further examine the nature of this transient. //////////////////////////////////////////////////////////////////////// TITLE: GCN CIRCULAR NUMBER: 6848 SUBJECT: GRB071003: Faulkes Telescope North observations DATE: 07/10/04 10:15:37 GMT FROM: Cristiano Guidorzi at INAF-OAB C. Guidorzi (U. Bicocca & INAF-OAB), D.F. Bersier, R.J. Smith, C.J. Mottram, M.F. Bode, D. Carter, S. Kobayashi, A. Melandri, C.G. Mundell, I.A. Steele (Liverpool JMU), A. Gomboc (U. Ljubljana), P. O'Brien, E. Rol, N. Bannister (U. Leicester) report: The 2-m Faulkes Telescope North robotically followed up GRB071003 (Schady et al., GCN Circ. 6837) beginning 189 s after the GRB trigger time (UT 07:40:55). We clearly detect the afterglow (Li et al., GCN Circ. 6838). We measure the following magnitudes in the R filter: Start Time from trigger (s) Exp(s) mag R ---------------------------------------------------- 189 10 14.72 +/- 0.01 210 10 14.81 +/- 0.01 229 10 14.90 +/- 0.01 ---------------------------------------------------- Magnitudes are calibrated with respect to several nearby USNO-B1 objects. //////////////////////////////////////////////////////////////////////// TITLE: GCN CIRCULAR NUMBER: 6849 SUBJECT: Konus-Wind observation of GRB 071003 DATE: 07/10/04 11:50:07 GMT FROM: Valentin Pal'shin at Ioffe Inst S. Golenetskii, R.Aptekar, E. Mazets, V. Pal'shin, D. Frederiks, and T. Cline on behalf of the Konus-Wind team report: The long GRB 071003 (Swift-BAT trigger #292934: Schady et al., GCN 6837; Ukwatta et al., GCN 6842) triggered Konus-Wind at T0=27655.120 s UT (07:40:55.120). The burst light curve shows a multipeaked structure with a duration of ~30 s. There is a hint of the weak extended emission reported by BAT (Ukwatta et al., GCN 6842) in the Konus-Wind data. As observed by Konus-Wind the burst had a fluence of 5.32(-0.67, +0.30)x10^-5 erg/cm2, and a 64-ms peak flux measured from T0+2.464 s of 1.22(-0.22, +0.19)x10^-5 erg/cm2/s (both in the 20 keV - 4 MeV energy range). The time-integrated spectrum of the burst (from T0 to T0+30.720 s) is well fitted (in the 20 keV - 4 MeV range) by a power law with exponential cutoff model: dN/dE ~ E^(-alpha)*exp(-E*(2-alpha)/Ep) with alpha = 0.97 +/- 0.07 and Ep = 799(-100, +124) keV (chi2 = 74.2/74 dof). The spectrum of the most intense part (from T0 to T0+14.336 s) is well fitted (in the same range) by a power law with exponential cutoff model with alpha = 0.76 (-0.07, +0.06) and Ep = 780(-70, +81) keV (chi2 = 75.6/74 dof). All the quoted errors are at the 90% confidence level. The Konus-Wind light curve of this GRB is available at http://www.ioffe.rssi.ru/LEA/GRBs/GRB071003_T27655/ //////////////////////////////////////////////////////////////////////// TITLE: GCN CIRCULAR NUMBER: 6850 SUBJECT: GRB 071003: Keck spectroscopy DATE: 07/10/04 13:11:24 GMT FROM: Daniel Perley at U.C. Berkeley D. A. Perley, R. Chornock, J. S. Bloom (UC Berkeley), C. Fassnacht, and M. W. Auger (UC Davis) report on behalf of GRAASP: We obtained spectroscopic follow-up of the bright transient associated with GRB 071003 (Schady et al., GCN 6837; Li, GCN 6838) starting at 07:51 UT on the night of 2007-10-04 using Keck I + LRIS (range 3300-8630 Angstroms). Two 10-minute exposures were acquired. The source is well-detected and a preliminary reduction reveals a smooth spectrum consistent with a GRB afterglow with multiple absorption-line systems. We identify a pair of absorption features at 5870 and 5886 Angstroms with the Mg II 2796, 2803 Angstrom doublet at a redshift of 1.100. Other absorption features are consistent with Fe II 2382, 2586, and 2599 Angstroms at this redshift. This absorption system sets a lower limit on the redshift of the GRB of z=1.100. In addition, numerous lines (e.g., Mg II 2796, 2803 Angstroms, Mg I 2852 Angstroms, and Fe II 2599 Angstroms) are present from an intervening absorption system at z=0.372. No strong supernova features or host-galaxy emission lines are seen in the spectrum. This suggests that the transient is a GRB afterglow undergoing a bright late-time optical flare, similar to the afterglow of GRB 070311 (e.g. Halpern & Armstrong, GCN 6203; Guidorzi et al., astroph/0708.1383), rather than a supernova. That flare peaked at R~22 approximately two days after the burst. Improved photometry of the optical transient associated with GRB 071003 gives a magnitude of R = 19.1 +/- 0.3 at 04:49 UT (0.88 days after the trigger) and further rebrightening appears possible. Further monitoring is strongly encouraged. //////////////////////////////////////////////////////////////////////// TITLE: GCN CIRCULAR NUMBER: 6851 SUBJECT: GRB 071003: VLT spectroscopy DATE: 07/10/05 17:30:14 GMT FROM: Paolo D'Avanzo at INAF-OAB D. Fugazza (INAF-OABr), F. Fiore, V. D'Elia (INAF-OAR), P. D'Avanzo (INAF-OABr), S. Piranomonte, L.A. Antonelli (INAF-OAR), G. Chincarini (Univ. Bicocca), S. Covino, G. Tagliaferri (INAF-OABr), M. Della Valle (INAF-OAA), A. Fernandez Soto (Univ. Valencia) report on behalf of the MISTICI collaboration: We observed the optical afterglow of GRB 071003 (Schady et al., GCN 6837; Li et al. GCN 6838; Cenko et al. GCN 6839) with the ESO-Very Large Telescope equipped with the FORS2 camera in spectroscopic mode. We took a 1800s spectrum with the grism 600B (with a resolution of R = 780) on Oct 04.055 UT (~ 0.735 days after the burst), under good seeing conditions (1.0"). The detection of a MgII system at z=1.100 (Perley et al. GCN 6850), cannot be confirmed by our data, because the 2803 AA component of the MgII doublet is contamined by the NaI 5891 and 5897 AA doublet of the nearby bright star. We also find significant lines at 5417 and 5430 AA, which we interpret as the MgII absorption doublet at 2797 and 2803 AA at z=0.937. FeII 2382 is also detected at the same redshift. In addition, we find two more significant absorption lines (5417 and 5446 AA), that can be identified as Ca H and K at z=0.372. Alternatively, the 5446 AA line can be interpreted as the 2803 AA component of the MgII doublet at z=0.942, with the 2797 AA component sharing the absorption feature at 5430 AA with the MgII 2803 of the system at z=0.937. This can be another line-locking example like that of the CIV system of GRB 021004 at z=2.3 (Fiore et al. 2005, ApJ, 624, 853; Starling et al. 2005, MNRAS, 360, 305 ). Finally, we find another MgII doublet at ~4000 AA (z=0.370), not consistent with the Ca system at z=0.372. No emission lines are visible. In summary our analysis of the FORS2 spectrum puts a lower limit on the redshift of GRB 071003 to z=0.937. We thank VLT staff for performing the observations, in particular Thomas Szeifert and Alain Smette. //////////////////////////////////////////////////////////////////////// TITLE: GCN CIRCULAR NUMBER: 6853 SUBJECT: Radio detection of GRB 071003 with the VLA DATE: 07/10/05 20:13:04 GMT FROM: Poonam Chandra at U Virginia/NRAO P. Chandra (UVA/NRAO) and D. A. Frail (NRAO) report on behalf of the Caltech-NRAO-Carnegie GRB Collaboration: "We observed the field centered on the BAT position of the Swift burst GRB 070923 (GCN#6837) using the VLA at a frequency of 8.46 GHz and starting at 1.85 UT on Oct 5, 2007. We detect the radio afterglow at KAIT optical position (GCN#6838) with flux density of 393 +/- 55 uJy. Further observations are planned. The National Radio Astronomy Observatory is a facility of the National Science Foundation operated under cooperative agreement by Associated Universities, Inc." //////////////////////////////////////////////////////////////////////// TITLE: GCN CIRCULAR NUMBER: 6855 SUBJECT: GRB 071003: XRT refined analysis DATE: 07/10/06 16:01:59 GMT FROM: Rhaana Starling at U of Leicester R. Starling, P.A. Evans, K.L. Page, A.P. Beardmore (U. Leicester) and P. Schady (MSSL/UCL) report on behalf of the Swift team: We report on Swift XRT observations of the GRB 071003 (trigger=292934, Schady et al., GCN Circ. 6837) beginning 22.3 ks and ending 244 ks after the BAT trigger, totalling 29.6 ks of photon counting mode data. We refine the position given in Starling and Schady, GCN Circ. 6845, to RA,Dec(J2000) = 301.85090, 10.947225 deg, equivalent to: RA(J2000) = 20h 07m 24.22s Dec(J2000)= +10d 56' 50.0" with an error of radius 5.5 arcseconds (90%, including boresight uncertainties). This is 1.3 arcseconds away from the initial XRT position and 2.3 arcseconds from the optical transient (Li, GCN Circ. 6838). The light curve is best fit with a broken power law with initial decay slope of alpha_1 = 1.0(+0.2/-0.4), T_bk = 3.9(+0.8/-0.4)E4 s and alpha_2 = 1.8(+/-0.4). The spectrum can be modelled with a power law of photon index Gamma = 2.1(+/-0.2) with fixed Galactic absorption of nH = 1.4E21 cm^-2 and allowing for intrinsic absorption at z = 1.1 (lower limit from Perley et al., GCN Circ. 6850) which we find is consistent with zero. The mean observed (unabsorbed) 0.3-10 keV flux is 7E-13 (1E-12) erg/cm^2/s. The count to flux conversion from these data is approximately 1 ct/s = 4.7E-11 erg/cm^2/s. This is an official product of the Swift XRT team. //////////////////////////////////////////////////////////////////////// TITLE: GCN CIRCULAR NUMBER: 7010 SUBJECT: GRB 071003: Infrared Photometry with Keck Adaptive Optics DATE: 07/10/26 22:51:07 GMT FROM: Daniel Perley at U.C. Berkeley L. K. Pollack (UC Santa Cruz), M. A. van Dam (WM Keck Observatory), D. Le Mignant (WM Keck Observatory, UC Santa Cruz), E. M. Johansson (WM Keck Observatory), D. A. Perley (UC Berkeley), and J. S. Bloom (UC Berkeley) report: On October 19 at UT 05:14:04 we observed the afterglow of GRB 071003 (Schady et al., GCN 6837; Li, GCN 6838; Cenko et al. GCN 6839) with the NIRC2 narrow-field camera (0.01 arcsec/pixel) on Keck II using natural guide star adaptive optics (NGS AO). We took 15 exposures, each of 60 seconds and 2 coadds, resulting in a total integration time of 30 minutes. The natural guide star is located 6.5 arcseconds west of the afterglow position, and has R=11 mag. The K=12.011 +/- 0.024 mag 2MASS star located 7.8 arcseconds east of the afterglow position was used as a photometric calibrator. Assuming no changes in the AO-corrected PSF over these distances, we measure the afterglow to have K' = 21.58 +/- 0.03. We find no host galaxy at the position of the afterglow. We detect the galaxy previously reported by Perley et al. (GCN 6874) at a position 2.07 arcseconds southwest of the afterglow position. Photometry on this extended object is difficult in the presence of the bright nearby star; however, we measure the galaxy to have an approximate brightness of K'=19.1 +/- 0.1 mags within an aperture of a 0.5 arcsecond radius. An image of the observations has been posted to: http://www.ucolick.org/~pollack/071003.jpg . We thank the Keck staff for performing these observations. In particular, we would like to acknowledge the help of Al Conrad.