This file cotnains two GRBs: GRB 070810A and GRB 070810B //////////////////////////////////////////////////////////////////////// TITLE: GCN CIRCULAR NUMBER: 6733 SUBJECT: GRB 070810: Swift detection of a burst DATE: 07/08/10 02:53:00 GMT FROM: Scott Barthelmy at NASA/GSFC J. R. Cummings (NASA/UMBC), S. D. Barthelmy (GSFC), M. M. Chester (PSU), N. Gehrels (NASA/GSFC), S. T. Holland (CRESST/GSFC/USRA), J. A. Kennea (PSU), C. B. Markwardt (CRESST/GSFC/UMD), D. M. Palmer (LANL) and M. Stamatikos (NASA/ORAU) report on behalf of the Swift Team: At 02:11:52 UT, the Swift Burst Alert Telescope (BAT) triggered and located GRB 070810 (trigger=287364). Swift slewed immediately to the burst. The BAT on-board calculated location is RA, Dec 189.939, +10.744 which is RA(J2000) = 12h 39m 45s Dec(J2000) = +10d 44' 40" with an uncertainty of 3 arcmin (radius, 90% containment, including systematic uncertainty). The BAT light curve showed a single peak structure with a duration of about 20 sec. The peak count rate was ~2500 counts/sec (15-350 keV), at T+0 sec after the trigger. The XRT began taking data at 02:13:20 UT, 88 seconds after the BAT trigger. The XRT on-board centroid algorithm did not find a source in the image. Using prompt downlinked data, we find a fading, X-ray source located at RA, Dec 189.9629, 10.7513 which is RA(J2000) = 12 39 51.10 Dec(J2000) = +10 45 04.7 with an uncertainty of 3.9 arcsec (radius, 90% containment). This position is 89 arcminutes from the BAT position. UVOT took a finding chart exposure of 100 seconds with the White (160-650 nm) filter starting 92 seconds after the BAT trigger, and a finding chart exposure of a nominal 400 seconds starting 198 seconds. A possible candidate has been identified visually in the initial data products, but processing is still underway so no position or significance is available at this time. The 2.7' x 2.7' sub-image does not cover the XRT error circle; the 8' x 8' list of sources covers 100% of the XRT error circle. The typical 3-sigma upper limit has been about 18.5 mag. No BAT_Position Notice was distributed, because none was received from the TDRSS system. This burst occurred during a 24-sec gap in TDRSS coverage due to a hand-off from one TDRSS satellite to the next satellite, so none of the initial notices were available (BAT_Position, FOM, and SC_Slew). Burst Advocate for this burst is J. R. Cummings (jayc 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: 6734 SUBJECT: GRB 070810: ROTSE-III Detection of Optical Counterpart DATE: 07/08/10 03:12:03 GMT FROM: Heather Swan at U.of Michigan/ROTSE H. Swan (U Mich), B. E. Schaefer (Louisiana State), E.S. Rykoff (U Mich), report on behalf of the ROTSE collaboration: ROTSE-IIIb, located at McDonald Observatory, Texas, responded to GRB 070810 (Swift trigger 287364). The first image was at 02:34:02.5 UT, 1330.5 s after the burst. The unfiltered images are calibrated relative to USNO A2.0. We detect a 16.7 magnitude, fading source with coordinates: 12:39:51.48 +10:45:00.90 (J2000). The source is blended with a nearby USNO star visible in the DSS, and thus our initial positional uncertainty is ~3". start UT mag mlim(of image) ---------------------------------- 02:29:53.4 16.7 18.5 This source is not visible in DSS (second epoch), 2MASS or the MPChecker database. A jpeg image is available at http://www.rotse.net/images/gsb0174_3b01_img.jpg Continuing observations are in progress. //////////////////////////////////////////////////////////////////////// TITLE: GCN CIRCULAR NUMBER: 6735 SUBJECT: GRB 070810: Swift/UVOT Optical Counterpart DATE: 07/08/10 05:25:36 GMT FROM: Margaret Chester at PSU M.M. Chester (PSU), F.E. Marshall (NASA/GSFC), and J.R. Cummings (NASA/UMBC) report on behalf of the Swift UVOT team: The Swift/UVOT observed the field of GRB 070810 (Cummings et al., GCN Circ. 6733) beginning 02:13:24 UT, 92 seconds after the BAT trigger. We find an uncatalogued source inside the Swift/XRT error circle in the initial 2.7' x 2.7' subimage in the White filter at: RA(J2000) = 12:39:51.22 = 189.9634 DEC(J2000) = +10:45:04.3 = 10.7512 with a 1-sigma error radius of about 0.6 arc sec. This position is 1.9 arcsec from the center of the XRT error circle, and 5.0 arcsec from the position reported by ROTSE (Swan et al. GCN Circ. 6734). The counterpart is not blended in the Swift/UVOT images. The estimated magnitudes (1-sigma error is about 1 mag) are: Filter Tstart Exp Magnitude (s) (s) White 92 100 17.4 v 198 306 17.1 The values quoted above are not corrected for the expected Galactic extinction corresponding to a reddening of E_{B-V} = 0.02 mag in the direction of the burst (Schlegel et al. 1998). //////////////////////////////////////////////////////////////////////// TITLE: GCN CIRCULAR NUMBER: 6736 SUBJECT: GRB 070810: enhanced Swift-XRT position DATE: 07/08/10 08:28:14 GMT FROM: Phil Evans at U of Leicester P.A. Evans, M.R. Goad, J.P. Osborne and A.P. Beardmore (U. Leicester) report on behalf of the Swift-XRT team. Using 505 s of overlapping XRT Photon Counting mode and UVOT V-band data for GRB 070810, 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 = 189.96368, +10.75080 which is equivalent to: RA (J2000): 12d 39' 51.28" Dec (J2000): +10h 45m 02.9s 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, astro-ph/0708.0986 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: 6738 SUBJECT: GRB 070810: Swift-XRT Team Refined Analysis DATE: 07/08/10 10:01:17 GMT FROM: Kim Page at U.of Leicester K.L. Page, P.A. Evans (U. Leicester), M.M Chester (PSU) and J.R. Cummings (NASA/UMBC) report on behalf of the Swift-XRT team: We have analysed the first four orbits of Swift-XRT data obtained for GRB 070810 (Cummings et al., GCN Circ. 6733), totalling 7.9 ks of Photon Counting (PC) mode data. The enhanced XRT position was given by Evans et al. in GCN Circ. 6736, and is 1.7 arcsec from the fading UVOT source (Chester et al., GCN Circ. 6735). The X-ray light-curve is almost flat for the first orbit of PC data, with alpha = 0.30 +0.18/-0.20. About 1.1 ks after the trigger, the decay steepened to a slope of 1.1 +/- 0.2. Fitting the PC data from the second to fourth orbits (i.e. after the break; 3.8-17.8 ks after the trigger), the spectrum can be modelled by an absorbed power-law with Gamma = 2.3 +/- 0.3 and NH = (1.3 +/- 0.5)e21 cm^-2, in excess of the Galactic value of 1.75e20 cm^-2. The 0.3-10 keV observed (unabsorbed) flux during this time is 2.17e-12 (3.34e-12) erg cm^-2 s^-1. If the decay continues with a slope of alpha ~ 1.1, the predicted count rate at 24 hours is 4.1e-3 count s^-1. Using a flux conversion factor (determined from the post-break spectrum described above) of 1 count s^-1 ~ 4e-11 erg cm^-2 s^-1 (observed) and 5.8e-11 erg cm^-2 s^-1 (unabsorbed), this corresponds to an observed (unabsorbed) flux of 1.6e-13 (2.4e-13) erg cm^-2 s^-1. This circular is an official product of the Swift-XRT team. //////////////////////////////////////////////////////////////////////// TITLE: GCN CIRCULAR NUMBER: 6741 SUBJECT: GRB 070810: Keck redshift and photometry DATE: 07/08/10 13:47:14 GMT FROM: Christina Thoene at Niels Bohr Institute,DARK Cosmo Ctr C. C. Thoene (DARK, UC Berkeley), D. A. Perley (UCB), J. Cooke (UC Irvine), J. S. Bloom (UC Berkeley), H.-W. Chen (Univ. Chicago) and E. Barton (UCI) report: We took 2x10min spectra of the afterglow of GRB 070810 (GCN 6734, Swan et al.; GCN 6735, Chester et al.) with Keck I + LRIS on Aug. 10, starting 05:46:32 UT (3.58h after the burst) in twilight. From a DLA and several absorption lines including Fe II, OI, SiII and CII, we infer a redshift of z=2.17 for that burst. In addition, we obtained 2x120 s imaging in R band and 2x150 s in g band, starting at 06:13:26 UT. Calibrating relative to five USNO-B1.0 stars, we measure a magnitude of R=20.45 +/- 0.5, dominated by the systematic uncertainty relative to the catalog. //////////////////////////////////////////////////////////////////////// TITLE: GCN CIRCULAR NUMBER: 6743 SUBJECT: GRB 070810B: Swift detection of a short burst DATE: 07/08/10 15:52:16 GMT FROM: David Palmer at LANL F. E. Marshall (NASA/GSFC), P. J. Brown (PSU), J. R. Cummings (NASA/UMBC), N. Gehrels (NASA/GSFC), O. Godet (U Leicester), C. Guidorzi (Univ Bicocca&INAF-OAB), S. T. Holland (CRESST/GSFC/USRA), J. A. Kennea (PSU), V. Mangano (INAF-IASFPA), C. B. Markwardt (CRESST/GSFC/UMD), J. P. Osborne (U Leicester), K. L. Page (U Leicester), D. M. Palmer (LANL), B. Sbarufatti (INAF-IASFPA), M. Stamatikos (NASA/ORAU), R. L. C. Starling (U Leicester), E. Troja (INAF-IASFPA), T. N. Ukwatta (GSFC/GWU) and D. E. Vanden Berk (PSU) report on behalf of the Swift Team: At 15:19:17 UT, the Swift Burst Alert Telescope (BAT) triggered and located GRB 070810B (trigger=287409). Swift slewed immediately to the burst. The BAT on-board calculated location is RA, Dec 8.940, +8.835 which is RA(J2000) = 00h 35m 46s Dec(J2000) = +08d 50' 07" with an uncertainty of 3 arcmin (radius, 90% containment, including systematic uncertainty). The BAT light curve showed a single short spike with a duration of < 0.2 sec. The peak count rate was ~4500 counts/sec (15-350 keV), at ~0 sec after the trigger. The lightcurves in different bands indicate an intermediate spectrum that is neither hard nor soft. The XRT began taking data at 15:20:19 UT, 62 seconds after the BAT trigger. The XRT on-board centroid algorithm did not find a source in the image and we do not detect a source in the initial SPER images. However, it is possible that the source is very faint or lies outside the SPER window. We await down-linked data to detect and determine a position for the source. UVOT took a finding chart exposure of 100 seconds with the White (160-650 nm) filter starting 65 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. The typical 3-sigma upper limit has been about 18.5 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 extinction corresponding to the expected reddening of E(B-V)=0.05. We note the presence of the bright extended galaxy 2MASX J00355339+0849273 (= LEDA 1354367) within the BAT error circle. Burst Advocate for this burst is F. E. Marshall (marshall 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: 6746 SUBJECT: GRB070810B: Optical observations with KANATA DATE: 07/08/10 17:34:52 GMT FROM: Makoto Uemura at Hiroshima U M. Uemura, A. Arai, O. Nagae, and T. Uehara (Hiroshima Univ.), report on behalf of the KANATA GRB team: We started optical imaging of the field of GRB070810B (GCN 6743) at 15:22:37 UT 10 Aug. using TRISPEC attached to the KANATA 1.5-m telescope at Higashi-Hiroshima Observatory, Japan. Exposure times are 30 sec for the first 10 frames, then changed to 123 sec for late frames. We have performed preliminary analysis for the first 30-min images. No new bright object was detected. There is no object showing significant fadings. Limit magnitudes are estimated from neighbour USNO A2.0 stars as follows: 10 Aug. UT limit mag. band 15:33:22 20.8 Rc 15:55:04 20.9 Rc We note that there is a possible minor planet at RA=00:35:59.3, Dec=+08:50:15 (time=15:33:22 UT). The object is about Rc=20.1, and moving northward during our observations. //////////////////////////////////////////////////////////////////////// TITLE: GCN CIRCULAR NUMBER: 6747 SUBJECT: GRB 070810B: Xinglong TNT optical Upper Limit DATE: 07/08/10 18:21:53 GMT FROM: W.K. Zheng at NAOC gcncircL.P. Xin, M.Zhai, Y.L. Qiu, J.Y. Wei, J.Y. Hu, J.S. Deng, Y. Urata, and W.K. Zheng on behalf of EAFON report: We have imaged the field of GRB 070810B (Marshall et al., GCN 6743) with the Xinglong TNT 80cm telescope. Observation started from 15:24:17, 300s after the burst. A series of White and R band images were obtained. Preliminary analysis shows no new object was seen in our combined image within BAT error circle. The 3 sigam limit is ~20.5 in our co-added 20*20s White band image with mean time ~550s after the burst, and ~21.7 in co-added 11*360s R band image with mean time ~44 minutes after the burst derived from USNO-B1.0, Further analysis is on going. This message may be cited. //////////////////////////////////////////////////////////////////////// TITLE: GCN CIRCULAR NUMBER: 6748 SUBJECT: GRB 070810A: Swift-BAT refined analysis DATE: 07/08/10 19:13:07 GMT FROM: Jay R. Cummings at NASA/GSFC/Swift C. Markwardt (GSFC/UMD), L. Barbier (GSFC), S. D. Barthelmy (GSFC), J. Cummings (GSFC/UMBC), E. Fenimore (LANL), N. Gehrels (GSFC), H. Krimm (GSFC/USRA), D. Palmer (LANL), A. Parsons (GSFC), T. Sakamoto (GSFC/ORAU), G. Sato (GSFC/ISAS), M. Stamatikos (GSFC/ORAU), J. Tueller (GSFC), T. Ukwatta (GWU) Using the data set from T-240 to T+804 sec from the recent telemetry downlink, we report further analysis of BAT GRB 070810A (trigger #287364) (Cummings, et al., GCN Circ. 6733). The BAT ground-calculated position is RA, Dec = 189.947, 10.747 deg which is RA(J2000) = 12h 39m 47.2s Dec(J2000) = 10d 44' 48" with an uncertainty of 1.3 arcmin, (radius, sys+stat, 90% containment). This is 1.0 arcmin from the optical and refined XRT positions (Chester et al. GCN circ. 6735 and Evans et al. GCN circ. 6736). The partial coding was 53%. The mask-weighted light curve shows a single peak with softening spectral evolution. T90 (15-350 keV) is 11.0 +- 1 sec (estimated error including systematics). The time-averaged spectrum from T-3.1 to T+14.3 sec is best fit by a simple power-law model. The power law index of the time-averaged spectrum is 2.04 +- 0.14. The fluence in the 15-150 keV band is 6.9 +- 0.6 x 10^-07 erg/cm2. The 1-sec peak photon flux measured from T-0.11 sec in the 15-150 keV band is 1.9 +- 0.2 ph/cm2/sec. All the quoted errors are at the 90% confidence level. //////////////////////////////////////////////////////////////////////// TITLE: GCN CIRCULAR NUMBER: 6750 SUBJECT: Swift Alert 070810.8: MASTER optical observation DATE: 07/08/10 20:54:56 GMT FROM: Vladimir Lipunov at Moscow State U/Krylov Obs V. Lipunov, V.Kornilov, D.Kuvshinov, A.Belinski, E.Gorbovskoy, A.Krylov, N.Shatskiy, N.Tyurina,G.Borisov, A.Sankovich, V.Vladimirov, O.S.Shvartsman Sternberg Astronomical Institute, Moscow Union 'Optic' I.Zalozhnih Ural State University Sternberg Astronomical Institute, Moscow Union 'Optic' MASTER robotic system (http://observ.pereplet.ru) responded to GRB070810.8 (GRB_TIME is 2007-08-10 19:54:05.85). The first image was at 2007-08-10 19:56:11 UT, 125.15 after the GRB time The unfiltered image is calibrated relative to USNO A2.0 (0.8 R + 0.2 B). The robot not find OT-candidate in error box brighter then 14.8 (s/n=10). The JPG-image will be available at http://observ.pereplet.ru/images/GRB070810.8/img/i12.jpg The reduction is continuing. This work is supported by RFFI 04-02-16411 grant. This message can be cited. Mailto: lipunov@sai.msu.ru //////////////////////////////////////////////////////////////////////// TITLE: GCN CIRCULAR NUMBER: 6752 SUBJECT: GRB 070810: MASTER optical observation DATE: 07/08/10 22:33:24 GMT FROM: Vladimir Lipunov at Moscow State U/Krylov Obs V. Lipunov, V.Kornilov, D.Kuvshinov, A.Belinski, E.Gorbovskoy, A.Krylov, N.Shatskiy, N.Tyurina,G.Borisov, A.Sankovich, V.Vladimirov, O.S.Shvartsman Sternberg Astronomical Institute, Moscow Union 'Optic' I.Zalozhnih Ural State University Sternberg Astronomical Institute, Moscow Union 'Optic' MASTER robotic system (http://observ.pereplet.ru) responded to GRB070810.8 (GRB_TIME is 2007-08-10 19:54:05.85). The first image was at 2007-08-10 19:56:11 UT, 125.15 after the GRB time The unfiltered image is calibrated relative to USNO A2.0 (0.8 R + 0.2 B). The robot not find OT-candidate in error box brighter then 14.8 (s/n=10). The JPG-image will be available at http://observ.pereplet.ru/images/GRB070810.8/img/i12.jpg The reduction is continuing. This work is supported by RFFI 04-02-16411 grant. This message can be cited. Mailto: lipunov@sai.msu.ru //////////////////////////////////////////////////////////////////////// TITLE: GCN CIRCULAR NUMBER: 6753 SUBJECT: GRB 070810B, Swift-BAT refined analysis DATE: 07/08/11 00:19:40 GMT FROM: Craig Markwardt at NASA/GSFC/UMD T. Sakamoto (GSFC/ORAU), 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), F. E. Marshall (GSFC), D. Palmer (LANL), A. Parsons (GSFC), G. Sato (GSFC/ISAS), 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+303 sec from recent telemetry downlinks, we report further analysis of BAT GRB 070810B (trigger #287409) (Marshall, et al., GCN Circ. 6743). The BAT ground-calculated position is RA, Dec = 8.952, 8.822 deg which is RA(J2000) = 0h 35m 48.4s Dec(J2000) = 8d 49' 18" with an uncertainty of 2.5 arcmin, (radius, sys+stat, 90% containment). The partial coding was 100%. The light curve is a single FRED-like peak starting at T+0, and ending at T+0.12 sec. T90 (15-350 keV) is 80 +- 10 msec (estimated error including systematics). The time-averaged spectrum from T+0.008 to T+0.092 sec is best fit by a simple power-law model. The power law index of the time-averaged spectrum is 1.44 +- 0.37. The fluence in the 15-150 keV band is 1.2 +- 0.3 x 10^-8 erg/cm2. The 1-sec peak photon flux measured from T-0.45 sec in the 15-150 keV band is 1.8 +- 0.4 ph/cm2/sec. All the quoted errors are at the 90% confidence level. //////////////////////////////////////////////////////////////////////// TITLE: GCN CIRCULAR NUMBER: 6754 SUBJECT: GRB 070810B: XRT refined analysis DATE: 07/08/11 01:59:15 GMT FROM: Rhaana Starling at U of Leicester R. Starling (U. Leicester), C. Markwardt (CRESST/GSFC/UMD) and F.E. Marshall (NASA/GSFC) report, on behalf of the Swift XRT team: We have analysed 7.2 ks of Swift XRT photon counting mode data, beginning 70 s and ending 13.8 ks after the BAT trigger, for the short GRB 070810B (trigger=287409; Marshall et al., GCN Circ. 6743). We do not detect any X-ray sources at 3-sigma significance or greater within the refined BAT error circle (Sakamoto et al., GCN Circ. 6753). Two low significance (2-sigma) possible sources are found within the BAT refined error circle at the following positions: Source 1 RA (J2000) = 00h 35m 51.2s Dec (J2000) = +08d 51' 21.3'' Source 2 RA (J2000) = 00h 35m 50.0s Dec (J2000) = +08d 48' 45.0'' Using the Bayesian method we find that both sources have between 4 and 26 counts at the 99% confidence level. It is not possible to determine at this stage whether or not either of these sources are fading. We note that Source 2 lies 1.1 arcmin from the galaxy 2MASX J00355339+0849273 (= LEDA 1354367; RA, Dec (J2000) = 00h 35m 53.39s, +08d 49' 27.3''), which has angular diameter approximately 0.7 x 0.3 arcmin. This is an official product of the Swift XRT team. //////////////////////////////////////////////////////////////////////// TITLE: GCN CIRCULAR NUMBER: 6755 SUBJECT: GRB070810B: Swift/UVOT Upper Limits DATE: 07/08/11 19:32:53 GMT FROM: Peter Brown at PSU P.J. Brown and F.E. Marshall (NASA/GSFC) report on behalf of the Swift/UVOT team: The Swift/UVOT observed the field of GRB 070810B (trigger #287409) starting 65 s after the BAT trigger (Marshall et al., GCN Circ. 6743). We do not find any new source in the UVOT observations inside the refined BAT error circle (Sakamoto et al., GCN Circ. 6753) including the two low significance XRT sources (Starling et al., GCN Circ. 6754). The galaxy 2MASX J00355339+0849273 (= LEDA 1354367) is visible in all filters except uvm2, but does not show signs of variability. The 3-sigma upper limits for detecting a source in the first finding chart (FC) exposure and co-added frames are: Filter T_start(s) T_stop(s) Exp(s) Mag (3-sigma UL) white (FC) 66 165 98 >20.5 white 66 13134 1345 >22.0 v 172 7372 1296 >20.4 b 653 12222 1299 >21.2 u 628 7987 549 >20.3 uvw1 604 7782 549 >20.5 uvm2 579 7577 549 >20.4 uvw2 683 13859 1237 >21.1 The values quoted above are not corrected for the expected Galactic extinction corresponding to a reddening of E(B-V) = 0.053 mag towards the direction of the burst (Schlegel et al. 1998). //////////////////////////////////////////////////////////////////////// TITLE: GCN CIRCULAR NUMBER: 6756 SUBJECT: GRB 070810B: Keck spectroscopy of possible host galaxies DATE: 07/08/12 03:25:02 GMT FROM: Christina Thoene at Niels Bohr Institute,DARK Cosmo Ctr Christina C. Thoene (DARK, UC Berkeley), Joshua S. Bloom, Nathaniel R. Butler (UCB) and Peter Nugent (LBL) report: We obtained spectra of several sources around the reported XRT positions of GRB70810B (GCN 6754 , Starling et al.) on Aug. 11, 12:30 UT, using Keck I + LRIS. No new source is seen in imaging of the field at the same time. At the position of source 1 ("S1") from Starling et al., there is no optical counterpart visible. From further analysis of the X-ray data, we detect another weak X-ray source at RA 00:35:46.892, DEC 08:51:05.96 ("S3") which includes a weak optical source. Within the BAT error circle, there is an early type galaxy (LEDA 1354367) as noted first in Marshall et. al, GCN 6743, for which we determined a redshift of z=0.0385 derived from Ca H&K absorption lines. Around source 2 ("S2"), there are four galaxies of which two show strong emission lines leading to a redshifts around z=0.49 from OII, OIII and the Balmer series. The two other galaxies have marginal detections of emission lines at the same redshift and these galaxies might therefore be part of a cluster or even interacting. An image indicating the different XRT positions and galaxies observed can be found at: http://lyra.berkeley.edu/~cthoene/GRBs/GRB070810B.png CT wants to thank Keck support astronomer Greg Wirth and his wife for excellent dinner support during the observations. Tusend tak! //////////////////////////////////////////////////////////////////////// TITLE: GCN CIRCULAR NUMBER: 6757 SUBJECT: GRB 070810A: Continued Keck Imaging DATE: 07/08/12 05:08:12 GMT FROM: Daniel Perley at U.C. Berkeley D. A. Perley, J. S. Bloom (UC Berkeley), and C. C. Thoene (DARK, UCB) report: Beginning at 06:48:00 UT (2007-08-11) we began a second series of imaging exposures on the field of GRB 070810A (GCN 7433) using the Keck I telescope (+LRIS). We acquired a total of 390s in R band and 480s in g band through high airmass. The optical afterglow (GCN 6734) is still detected, but has faded significantly since our previous imaging epoch (GCN 6741) and appears marginally extended. Aperture photometry of the source indicates that it has has faded by 3.2 +/- 0.1 magnitudes since the observations the first night, corresponding to a decay index of alpha >= 1.5 between 4 hours and 28.6 hours including a possible contribution from a host galaxy or other extended source. Using the same calibration system as in our previous circular, we estimate a preliminary magnitude of R=23.7. //////////////////////////////////////////////////////////////////////// TITLE: GCN CIRCULAR NUMBER: 6758 SUBJECT: GRB 070810B : Faulkes Telescope South Observations DATE: 07/08/12 18:59:35 GMT FROM: Cristiano Guidorzi at INAF-OAB C. Guidorzi (U. Bicocca/INAF-OAB), R.J. Smith, A. Melandri, I.A. Steele, C.G. Mundell, M.J. Burgdorf, C.J. Mottram, M.F. Bode, S.N. Fraser, S. Kobayashi, D.F. Bersier (Liverpool JMU), A. Gomboc (Ljubljana), P. O'Brien, E. Rol, N. Bannister, N. Tanvir (U. Leicester) report on behalf of larger GRB collaboration: On 2007 Aug 10 at 15:22:06 UT the 2-m Faulkes Telescope South automatically observed the field of GRB 070810B (trigger 287409, Marshall et al., GCN Circ. 6743). In our coadded frames we do not detect anything corresponding to XRT sources 1 or 2 (Starling et al., GCN Circ. 6754) down to the limiting magnitudes reported below. Filter Tstart(min) Tstop(min) Exposure(s) M_lim ------------------------------------------------------- R 2.80 64.3 840 21.2 i' 6.22 54.9 520 21.5 ------------------------------------------------------- Magnitudes are calibrated with respect to USNOB1 R2 in the R filter. For the SDSS-i' filter we calibrated with the i' magnitudes derived for USNOB1 field stars by converting from the (R2,I) magnitudes. //////////////////////////////////////////////////////////////////////// TITLE: GCN CIRCULAR NUMBER: 6761 SUBJECT: GRB 070810A: ROTSE-III Refined Analysis DATE: 07/08/17 00:24:27 GMT FROM: Fang Yuan at ROTSE F. Yuan, E.S. Rykoff (U Mich), report on behalf of the ROTSE collaboration: ROTSE-IIIb, located at McDonald Observatory, Texas, responded to GRB 070810A (Swift trigger 287364; Cummings, et al., GCN 6733), and detected the optical counterpart (Swan, et al., GCN 6734). The initial aperture photometry reported in GCN 6734 was biased due to contamination from the nearby star. With a reference image taken 6 days after the burst, we were able to subtract the nearby star and obtain better estimate of the OT brightness with PSF fitting. Our refined analysis shows the OT at 18.0 ± 0.2 mag (unfiltered images, calibrated relative to USNO-B1.0 R) between 1607s and 2290s after the burst. start UT end UT mag ------------------------------------- 02:38:39.5 02:50:02.3 18.0+/-0.2 03:13:15.7 03:24:39.0 18.5+/-0.2 The OT faded with a decay index 0.7 ±0.2 in the next 40 minutes before dropping below our detection threshold. This decay index is significantly shallower than seen at later time in Keck photometry (Perley, et al., GCN 6757), implying a light curve break between 1.2 hr and 4 hr after the burst. //////////////////////////////////////////////////////////////////////// TITLE: GCN CIRCULAR NUMBER: 6762 SUBJECT: GRB070810b: optical candidate DATE: 07/08/21 17:05:01 GMT FROM: Alexei Pozanenko at IKI, Moscow V. Rumyantsev (CrAO) , V.Biryukov (SAI, MSU and CrAO), A. Pozanenko (IKI) report on behalf of larger GRB follow-up collaboration: We observed the error box of short GRB070810b (Marshall et al., GCN 6743) with Shajn 2.6m telescope of CrAO on Aug. 10. Series of images were obtained between (UT) 2007-08-10 22:05:23 and 2007-08-10 23:25:50 in R filter. The combined image of a total exposure of 4260 s (71x60 s) covers entire of the error box of GRB 070810b and can be found at http://grb.rssi.ru/GRB070810b/GRB070810b_ZTSh.gif. The limiting magnitude (3 sigma) calibrated against USNO-A2.0 of the combined image is 24.8 mag. We investigate the S1, S2 XRT positions of GRB70810b (GCN 6754 , Starling et al.) and S3 position (Thoene et al., GCN 6756). There is marginally detected object in a place of the source S1 (see http://grb.rssi.ru/GRB070810b/GRB070810b_s1_ZTSh.gif). Both optical sources around S3 (RA = 00:35:46.892 Dec = +08:51:05.96) are presented in our and Keck's images, see http://grb.rssi.ru/GRB070810b/GRB070810b_s3_ZTSh.gif. Comparison of objects around source S2 ( RA = 00h 35m 50.0s Dec = +08d 48' 45.0'' ) in our image ( see http://grb.rssi.ru/GRB070810b/GRB070810b_s2_ZTSh.gif) with the image obtained on Aug. 11 (Thoene et al., GCN 6756) reveals a source between two nearby galaxies. We consider this source as a candidate of the optical counterpart of GRB070810b and a redshift z~0.49 obtained for the galaxies (Thoene et al., CN 6756) is quite natural for short GRB detected by Swift. However more detailed comparison of the images (Keck I and ZTSh) and additional observations are necessary to secure the nature of the candidate. The massage can be cited. //////////////////////////////////////////////////////////////////////// TITLE: GCN CIRCULAR NUMBER: 6771 SUBJECT: GRB 070810b: Image Subtraction of Multiple Keck Observations DATE: 07/09/01 04:05:55 GMT FROM: Daniel Kocevski at UC Berkeley D. Kocevski, J.S. Bloom, C. C. Thoene, and J. Prochaska report: We performed image subtraction between multiple R-band observations of the error box of short burst GRB070810b (Marshall et al., GCN 6743) with the Keck I telescope (+LRIS). The first epoch of observations began at (UT) 2007-08-11 14:45:00 followed by a second epoch six nights later at (UT) 2007-08-17 12:02:00, with equivalent exposures of 630 and 900 seconds respectively. Image subtraction using the public POIS-IPP package(*) software shows no variable sources associated with the S1, S2 XRT positions (GCN 6754 , Starling et al.) or the S3 position (Thoene et al., GCN 6756) nor any significant residual sources within the BAT error circle down to a limiting magnitude of ~25.5 mag in R band. The potential candidate afterglow close to S2, reported by Pozanenko et al. can be resolved as two objects in our images, which show no sign of variability between the two epochs. * See http://pan-starrs.ifa.hawaii.edu/project/IPP/software/ //////////////////////////////////////////////////////////////////////// TITLE: GCN CIRCULAR NUMBER: 6852 SUBJECT: GRB 070810B: further XRT analysis DATE: 07/10/05 18:33:55 GMT FROM: Rhaana Starling at U of Leicester R. Starling, J.P. Osborne, K.L. Page (U. Leicester) and F.E. Marshall (NASA/GSFC) report, on behalf of the Swift XRT team: Previously, Swift XRT data for the short GRB 070810B (trigger=287409; Marshall et al., GCN Circ. 6743) up to 13.8 ks after the BAT trigger showed two possible sources within the BAT refined error circle, detected at 2-sigma significance in 7.2 ks and termed S1 and S2 (Starling et al., GCN Circ. 6754). We have analysed a further 12.6 ks of Swift XRT photon counting mode data beginning 42 days and ending 54 days after the burst, in order to assess the variability of the two possible afterglow candidates. In this second epoch of data we detect one X-ray source at 4-sigma significance within the refined BAT error circle (Sakamoto et al., GCN Circ. 6753), corresponding to the source S2 described in GCN Circ. 6754. Using Bayesian analysis we find that S2 has between 20 and 54 counts at the 99% confidence level or 1.6e-3 to 4.3e-3 count/s, consistent with the first epoch limits of 5.6e-4 to 3.6e-3 count/s. This suggests that S2 is a persistent faint source, and not the afterglow of GRB 070810B. The possible source S1 (GCN Circ. 6754), detected only at the 2-sigma level in the intial epoch observations, is not detected in the second epoch observations, providing an upper limit on the count rate of 6.7e-4 count/s at 99% confidence based on the background count rate. This is above the 3-sigma lower limit on the source count rate at epoch 1 of 5.6e-4 count/s, hence we cannot determine whether or not this source has faded. This is an official product of the Swift XRT team.