//////////////////////////////////////////////////////////////////////// TITLE: GCN CIRCULAR NUMBER: 11047 SUBJECT: GRB 100805A: Swift detection of a burst with an optical counterpart DATE: 10/08/05 04:27:27 GMT FROM: David Palmer at LANL E. A. Hoversten (PSU), S. D. Barthelmy (GSFC), W. H. Baumgartner (GSFC/UMBC), J. M. Gelbord (PSU), C. Gronwall (PSU), S. T. Holland (CRESST/USRA/GSFC), D. M. Palmer (LANL), M. H. Siegel (PSU), M. C. Stroh (PSU) and T. N. Ukwatta (GSFC/GWU) report on behalf of the Swift Team: At 04:12:42 UT, the Swift Burst Alert Telescope (BAT) triggered and located GRB 100805A (trigger=430957). Swift slewed immediately to the burst. The BAT on-board calculated location is RA, Dec 299.874, +52.614 which is RA(J2000) = 19h 59m 30s Dec(J2000) = +52d 36' 52" with an uncertainty of 3 arcmin (radius, 90% containment, including systematic uncertainty). The BAT light curve shows a peak with a duration of about 20 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 04:14:48.7 UT, 126.4 seconds after the BAT trigger. Using promptly downlinked data we find a fading, uncatalogued X-ray source located at RA, Dec 299.87559, 52.62758 which is equivalent to: RA(J2000) = 19h 59m 30.14s Dec(J2000) = +52d 37' 39.3" with an uncertainty of 3.8 arcseconds (radius, 90% containment). This location is 47 arcseconds from the BAT onboard position, within the BAT error circle. This position may be improved as more data are received; the latest position is available at http://www.swift.ac.uk/sper. A power-law fit to a spectrum formed from promptly downlinked event data gives a column density consistent with the Galactic value of 1.69e+21 cm^-2 (Kalberla et al. 2005). UVOT took a finding chart exposure of 150 seconds with the White filter starting 129 seconds after the BAT trigger. There is a candidate afterglow in the rapidly available 2.7'x2.7' sub-image at RA(J2000) = 19:59:30.52 = 299.87716 DEC(J2000) = +52:37:40.3 = 52.62787 with a 90%-confidence error radius of about 0.62 arc sec. This position is 3.6 arc sec. from the center of the XRT error circle. The estimated magnitude is 18.00 with a 1-sigma error of about 0.14. No correction has been made for the expected extinction corresponding to E(B-V) of 0.19. Burst Advocate for this burst is E. A. Hoversten (hoversten AT astro.psu.edu). 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: 11048 SUBJECT: GRB 100805A: ROTSE-III Optical Limits DATE: 10/08/05 04:56:08 GMT FROM: Shashi Bhushan Pandey at ROTSE S. B. Pandey (U Mich) and W. Zheng (U Mich), report on behalf of the ROTSE collaboration: ROTSE-IIIb, located at McDonald Observatory, Texas, responded to GRB 100805A (Swift trigger 430957; Hoversten , E. A., GCN 11047), producing images beginning 6.2 s after the GCN notice time. An automated response took the first image at 04:13:39.2 UT, 50.9 s after the burst, under fair conditions. We took 10 5-sec, 10 20-sec and 10 60-sec exposures. These unfiltered images are calibrated relative to USNO A2.0 (R). Imaging is on going. Comparison to the DSS (second epoch) reveals no new sources within the 3-sigma Swift/BAT error circle or at the Swift/UVOT position, for both single images and coadding into sets of 10. Individual images have limiting magnitudes ranging from 16.1-17.3; we set the following specific limits. start UT end UT t_exp(s) mlim t_start-tGRB(s) Coadd? -------------------------------------------------------------------- 04:13:39.2 04:13:44.2 5 16.1 50.9 N 04:14:59.3 04:19:41.7 282 18.0 131.0 Y //////////////////////////////////////////////////////////////////////// TITLE: GCN CIRCULAR NUMBER: 11049 SUBJECT: GRB 100805A: Enhanced Swift-XRT position DATE: 10/08/05 04:57:18 GMT FROM: Michael Stroh at PSU/Swift M. C. Stroh and E. A. Hoversten (PSU) report on behalf of the Swift-XRT team: Using promptly downlinked data we find a fading, uncatalogued X-ray source with an enhanced position: RA,Dec = 299.8760, 52.6279 (degrees) which is equivalent to: RA (J2000.0) = 19 59 30.23 DEC (J2000.0) = +52 37 40.3 with an uncertainty of 2.3 arcsec (radius, 90% containment). This location is 48.4 arcseconds from the BAT onboard position, inside the BAT error circle. 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) and Evans et al. (2009, MNRAS, 397, 1177). This circular was automatically generated, and is an official product of the Swift-XRT team. //////////////////////////////////////////////////////////////////////// TITLE: GCN CIRCULAR NUMBER: 11050 SUBJECT: GRB 100805A: P60 Optical Afterglow Candidate DATE: 10/08/05 04:59:00 GMT FROM: S. Bradley Cenko at Caltech S. B. Cenko (UC Berkeley) reports on behalf of a larger collaboration: We have imaged the field of GRB 100805A (Swift trigger #430957) with the robotic Palomar 60 inch telescope. Images were obtained in the Sloan r', i', and z' filters beginning at 04:15 UT on 5 August (~ 3 minutes after the Swift trigger time). At the edge of the XRT error circle we detect a bright point source not present in the Digital Sky Survey imaging of the field at coordinates (J2000.0): RA: 19:59:30.53 Dec: +52:37:40.0 Calibrating with respect to the USNO-B1 catalog, we measure a preliminary magnitude or R = 17.3. Observations to confirm the transient nature of this source are ongoing. //////////////////////////////////////////////////////////////////////// TITLE: GCN CIRCULAR NUMBER: 11051 SUBJECT: GRB 100805A: Further P60 Monitoring DATE: 10/08/05 05:18:42 GMT FROM: S. Bradley Cenko at Caltech S. B. Cenko (UC Berkeley) reports on behalf of a larger collaboration: We have continued to image the field of GRB 100805A with the automated Palomar 60 inch telescope (see GCN 11050). The object we identified as a candidate afterglow (first noted by Hoversten at al., GCN 11047) has faded significantly over the last hour, and we can therefore confirm this source is the optical afterglow of GRB 100805A. Using field stars from the USNO-B1 catalog for reference, we measure a magnitude of R = 19.5 at 04:56 UT on 5 August. Comparing with our previous measurement, we infer a power-law decay index of alpha ~ 0.8. //////////////////////////////////////////////////////////////////////// TITLE: GCN CIRCULAR NUMBER: 11052 SUBJECT: GRB 100805A: Liverpool Telescope afterglow observations DATE: 10/08/05 06:08:10 GMT FROM: Andreja Gomboc at LT,ARI,Liverpool JMU A. Gomboc (U. Ljubljana), C. Guidorzi (U. Ferrara), D. Kopac (U. Ljubljana) report on behalf of a larger collaboration: On 2010 August 05 at 04:14:32 UT the 2-m Liverpool Telescope automatically began observing the Swift GRB 100805A (Hoversten et al., GCN Circ. 11047) with Ringo 2 instrument, continuing with multi-filter (g', r', i') observations at 6.7 min after the GRB trigger. The LT-TRAP procedure automatically identified the optical afterglow at the UVOT position (Hoversten et al., GCN Circ. 11047, Cenko, GCN Circ. 11050) with the following magnitudes: ------------------------------------------------------------------------ T-t0 (s) Exp. (s) Filter Mag ------------------------------------------------------------------------ 400 10 r' 17.92 +- 0.07 421 10 r' 17.93 +- 0.07 726 10 r' 18.36 +- 0.10 3386 60 r' 19.79 +- 0.12 ------------------------------------------------ We confirm the power-law decay index of 0.8 found by P60 (Cenko, GCN Circ. 11051). Magnitudes were calibrated from nearby USNOB1.0 R2 stars. Observations are continuing. //////////////////////////////////////////////////////////////////////// TITLE: GCN CIRCULAR NUMBER: 11053 SUBJECT: GRB 100805A: Enhanced Swift-XRT position DATE: 10/08/05 06:40:33 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 734 s of XRT Photon Counting mode data and 1 UVOT images for GRB 100805A, 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 = 299.87770, +52.62788 which is equivalent to: RA (J2000): 19h 59m 30.65s Dec (J2000): +52d 37' 40.4" 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) and Evans et al. (2009, MNRAS, 397, 1177). This circular was automatically generated, and is an official product of the Swift-XRT team. //////////////////////////////////////////////////////////////////////// TITLE: GCN CIRCULAR NUMBER: 11054 SUBJECT: GRB 100805A: I-band detection from 1.23m CAHA telescope. DATE: 10/08/05 06:46:49 GMT FROM: Javier Gorosabel at IAA-CSIC J. Gorosabel, V. Terron, M. Jelinek, A.J. Castro-Tirado (IAA-CSIC), report on behalf of a larger collaboration: "Following the detection of GRB 100805A by Swift (Hoversten et al. GCNC 11047) we carried out I-band observations with the 1.23m telescope at Observatory of Calar Alto. The first exposure started on Aug 5.1824 UT (~10 minutes post burst) with an integration time of 120s. The optical afterglow is well detected with a preliminary magnitude of I ~ 16.9, against USNO-B1.0 field stars." //////////////////////////////////////////////////////////////////////// TITLE: GCN CIRCULAR NUMBER: 11056 SUBJECT: GRB 100805A: GRAS 002 optical observations DATE: 10/08/05 08:40:39 GMT FROM: Veli-Pekka Hentunen at Taurus Hill Obs,A95 Markku Nissinen (Taurus Hill Observatory) and Veli-Pekka Hentunen (Taurus Hill Observatory) report: We used Global-rent-a-scope GRAS 002 Tak Mewlon 300 telescope with SBIG ST-8E CCD at RAS Observatory Mayhill H06 (New Mexico, USA) for follow-up observations of GRB 100805A (D. Palmer et al., GCN 11047). The observations were started on August 05, at 04:56 UTC (44 min after the burst) and stopped on August 05, at 06:29 UTC. Four luminance 600 seconds images and three optical R-band 600 seconds images were taken. We detected a very dim optical afterglow object at the position of RA 19h 59min 30s.64 and DEC +52o 37' 40".5 with respect to POSSII F/USNO-B1.0 (J2000) which is in good correlation with S.B. Cenko observations (GCN 11050). Upper limit for our luminance observations is >20.8 mag (LR) and R-band observations is >20.1 (R). Quoted upper limit has been derived using POSSII F and USNO-B1.0 field stars as reference. Filter Tmid(s) Exp(s) OA Mag USNO-B1.0 luminance 2949 600 19.6+/-0.5 (LR) luminance 3614 600 19.6+/-0.5 (LR) luminance 4276 600 19.8+/-0.5 (LR) luminance 8177 600 >20.8 optical R 5299 600 >20.1 optical R 5986 600 >20.1 optical R 7501 600 >20.1 URL-link to our luminance image: http://cutenews.kassiopeia.net/data/upimages/GRB100805A_web.jpg //////////////////////////////////////////////////////////////////////// TITLE: GCN CIRCULAR NUMBER: 11057 SUBJECT: GRB 100805A: Swift-XRT Refined Analysis DATE: 10/08/05 11:00:30 GMT FROM: Michael Stroh at PSU/Swift M. C. Stroh and E. A. Hoversten (PSU) report on behalf of the Swift-XRT team: We have analysed 3.3 ks of XRT data for GRB 100805A (Hoversten et al. GCN Circ. 11047), from 111 s to 6.7 ks after the BAT trigger. The data comprise 48 s in Windowed Timing (WT) mode (the first 8 s were taken while Swift was slewing) with the remainder in Photon Counting (PC) mode. The enhanced XRT position for this burst was given by Goad et al. (GCN. Circ 11049). The light curve can be modelled with an initial power-law decay with an index of alpha=3.6 (+0.5, -0.4), followed by a break at T+294 s to an alpha of 0.45 (+0.12, -0.23). A spectrum formed from the PC mode data can be fitted with an absorbed power-law with a photon spectral index of 1.97 (+0.17, -0.10). The best-fitting absorption column is 1.7 (+0.5, -0.0) x 10^21 cm^-2, in excess of the Galactic value of 1.7 x 10^21 cm^-2 (Kalberla et al. 2005). The counts to observed (unabsorbed) 0.3-10 keV flux conversion factor deduced from this spectrum is 4.1 x 10^-11 (5.7 x 10^-11) erg cm^-2 count^-1. If the light curve continues to decay with a power-law decay index of 0.45, the count rate at T+24 hours will be 0.032 count s^-1, corresponding to an observed (unabsorbed) 0.3-10 keV flux of 1.3 x 10^-12 (1.8 x 10^-12) erg cm^-2 s^-1. The results of the XRT-team automatic analysis are available at http://www.swift.ac.uk/xrt_products/00430957. This circular is an official product of the Swift-XRT team. //////////////////////////////////////////////////////////////////////// TITLE: GCN CIRCULAR NUMBER: 11058 SUBJECT: GRB 100805A: Swift-BAT refined analysis DATE: 10/08/05 12:46:07 GMT FROM: Scott Barthelmy at NASA/GSFC S. D. Barthelmy (GSFC), W. H. Baumgartner (GSFC/UMBC), J. R. Cummings (GSFC/UMBC), N. Gehrels (GSFC), H. A. Krimm (GSFC/USRA), E. A. Hoversten (PSU), C. B. Markwardt (GSFC/UMD), D. M. Palmer (LANL), T. Sakamoto (GSFC/UMBC), M. Stamatikos (OSU), J. Tueller (GSFC), T. N. Ukwatta (GWU) (i.e. the Swift-BAT team): Using the data set from T-239 to T+963 sec from recent telemetry downlinks, we report further analysis of BAT GRB 100805A (trigger #430957) (Hoversten, et al., GCN Circ. 11047). The BAT ground-calculated position is RA, Dec = 299.846, 52.618 deg, which is RA(J2000) = 19h 59m 23.0s Dec(J2000) = +52d 37' 05.8" with an uncertainty of 2.0 arcmin, (radius, sys+stat, 90% containment). The partial coding was 39%. The mask-weighted light curve shows a few overlapping weak peaks starting at ~T-1 sec, peaking at ~T+2 sec, and ending at ~T+20 sec. There is a possible 3-sigma peak at ~T+60 sec. T90 (15-350 keV) is 15.0 +- 3.0 sec (estimated error including systematics). The time-averaged spectrum from T-1.4 to T+17.1 sec is best fit by a simple power-law model. The power law index of the time-averaged spectrum is 1.76 +- 0.23. The fluence in the 15-150 keV band is 5.1 +- 0.8 x 10^-7 erg/cm2. The 1-sec peak photon flux measured from T+1.97 sec in the 15-150 keV band is 0.7 +- 0.2 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/430957/BA/ //////////////////////////////////////////////////////////////////////// TITLE: GCN CIRCULAR NUMBER: 11060 SUBJECT: GRB 100805A: IAC80 BVR-band observations DATE: 10/08/05 14:05:26 GMT FROM: Javier Gorosabel at IAA-CSIC J. Gorosabel (IAA-CSIC), M. Chioare Diaz-Martin (IAC), R. Iglesias Marzoa (Univ. of La Laguna), M. Jelinek (IAA-CSIC), report on behalf of a larger collaboration: "We have acquired BVR-band images of the GRB 100805A (Hoversten et al. GCNC 11047) field with the 82-cm IAC80 telescope on the Observatory of Teide, Tenerife, Spain. The optical afterglow (Hoversten et al. GCNC 11047; Cenko et al. GCNC 11050, GCNC 11051; Gomboc et al. GCNC 11052; Gorosabel et al. GCNC 11054; Nissinen et al. GCNC 11056) is detected in the three optical bands with an approximate magnitude of R~19.3 on Aug. 5.2046 UT (mean observing time, ~42 minutes post burst). The calibration is based on USNO B1.0 field stars." //////////////////////////////////////////////////////////////////////// TITLE: GCN CIRCULAR NUMBER: 11062 SUBJECT: GRB 100805A: Swift/UVOT Observations of the Optical Afterglow DATE: 10/08/05 19:02:30 GMT FROM: Stephen Holland at USRA/NASA/GSFC/SSC S. T. Holland (CRESST/GSFC/USRA) and E. A. Hoversten (PSU) report on the behalf of the Swift UVOT team: The Swift/UVOT observed the field of GRB 100805A starting 112 s after the BAT trigger (Hoversten, et al., 2010, GCN Circ. 11047). Settled observations started at 130 s. We detect the optical afterglow (Hoversten, et al., 2010, GCN Circ, 11047) in all filters except uvw2. The refined UVOT position is RA (J2000) = 19:59:30.51 = 299.87713 (deg) Dec (J2000) = +52:37:40.1 = +52.62783 (deg) with an estimated uncertainty of 0.43 arcsec (radius, 90% confidence, statistical + systematic). This is 1.31 arcsec west of the UVOT-enhanced XRT position (Goad, et al., 2010, GCN Circ. 11053). Preliminary magnitudes, and 3-sigma upper limits for detecting a source in the finding charts and in the co-added images, are Filter T_start T_stop Exp(s) Mag Err ----------------------------------------------------------- white (fc) 130 280 147 18.10 0.08 u (fc) 288 538 246 18.32 0.11 v 619 5984 432 19.80 0.23 b 544 10,831 1213 21.22 0.20 u 288 6600 659 18.55 0.09 uvw1 668 6395 432 20.78 0.39 uvm2 643 6189 432 20.68 0.45 uvw2 594 12,479 1149 >21.6 3-sigma UL white 130 11,744 1319 19.42 0.07 ----------------------------------------------------------- The quoted magnitudes and upper limits have not been corrected for the expected Galactic extinction along the line of sight corresponding to a reddening of E_{B-V} = 0.19 mag (Schlegel, et al., 1998, ApJS, 500, 525). All photometry is on the UVOT photometry system described in Poole et al. (2008, MNRAS, 383, 627). The non-detection in the UVOT uvw2 filter, and the observed UVOT spectral energy distribution at 4895 s, is consistent with GRB 100805A having a redshift of approximately z = 1.3, although we can not rule out the non-detection in uvw2 being due to extinction in the host galaxy. The white light curve exhibits a power-law decay with an index of alpha = -0.71 +/- 0.03, consistent with what was observed by Cenko, et al. (2010, GCN Circ. 11051). //////////////////////////////////////////////////////////////////////// TITLE: GCN CIRCULAR NUMBER: 11063 SUBJECT: GRB 100805A: ROTSE-III Optical detection DATE: 10/08/05 20:48:46 GMT FROM: Shashi Bhushan Pandey at ROTSE S. B. Pandey and W. Zheng (U Mich), report on behalf of the ROTSE collaboration: Further analysis of GRB 100805A data taken from ROTSE-IIIb clearly detects the optical afterglow candidate (Hoversten E. A. et al., GCN 11047) in the images taken ~50.9 s after the burst (Pandey S. B. & Zheng W., GCN 11048). In the consecutive images taken by ROTSE, the optical afterglow show a temporal decay nature very similar to those reported by Cenko S. B. (GCN 11051) and Holland S. T. et al (GCN 11062). The optical afterglow detection by ROTSE was not reported in the previous circular (GCN 11048) due to a problem in the online data processing. //////////////////////////////////////////////////////////////////////// TITLE: GCN CIRCULAR NUMBER: 11064 SUBJECT: GRB 100805A: Early RAPTOR Observations DATE: 10/08/05 21:09:45 GMT FROM: James Wren at LANL J. Wren, W.T. Vestrand, P.R. Wozniak, H. Davis, of Los Alamos National Laboratory report: The RAPTOR telescope system responded to Swift trigger 430957 (Hoversten et al., GCN 11047) under fair observing conditions. Our narrow-field instruments began observing the location at 04:13:44.3 UTC, 62.2 seconds after the initial BAT trigger. At 100 seconds after the trigger, we estimate the counterpart to have magnitude R~16.7 +/- 0.3. The object fades steadily reaching R~17.4 +/- 0.3 at 200 seconds after the trigger. It appears to remain near this level for the next 150 seconds or so before resuming the fading behavior. Our unfiltered images were calibrated against the USNO-B1 R-band. Further analysis is ongoing. //////////////////////////////////////////////////////////////////////// TITLE: GCN CIRCULAR NUMBER: 11065 SUBJECT: GRB 100805A: Xinglong TNT optical observation DATE: 10/08/06 05:36:45 GMT FROM: L.P. Xin at NAOC L.P. Xin, Z. X. Ling, Y.L. Qiu, J.Y. Wei, J. Wang, J.S. Deng, C. Wu, X. H. Han, J.Y. Hu on behalf of EAFON report: We began to observe GRB100805A (Hoversten E. A. et al., GCN 11047 ) with Xinglong TNT telescope at 12:29:52 (UT), 8.28h after the burst. Nine R band images were obtained. The exposure time for each frame is 600 sec. The afterglow (Hoversten E. A. et al., GCN 11047) with a brightness of 21.3+/-0.2 mag was detected with the combined 9*600s white-band data at the mean time of 8.95h after the burst. The reference star is a nearby USNO-B1.0 star with a coordinates of 19:59:33.3, +52:37:54.0, and a brightness of R2=17.41 mag. Combining TNT data and other data reported in the previous GCN circulars (Cenko, GCN 11050, GCN 11051;Gomboc et al. GCN11052; Nissinen et al. GCN 11056; Gorosabel et al. GCN 11060; Wren et al. GCN 11064 ), we infer that the brightness of OT was decaying with a power-law decay index of alpha~0.73 from 100sec to 8.9h after the burst, consistent with the reports of Cenko, GCN Circ. 11051 and Gomboc et al. GCN 10052. 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: 11066 SUBJECT: GRB 100805A: IAC80 and 1.5m OSN optical observations DATE: 10/08/06 17:24:14 GMT FROM: Javier Gorosabel at IAA-CSIC J. Gorosabel (IAA-CSIC, Granada), M. Chioare Diaz-Martin (IAC, Obs. del Teide, Tenerife), R. Iglesias Marzoa (Univ. of La Laguna, Tenerife), A. Sota (IAA-CSIC, Granada), A.J. Castro-Tirado (IAA-CSIC, Granada), J.M. Castro Cerón (ESAC, Madrid), report on behalf of a larger collaboration: "We observed the field of GRB 100805A (Hoversten et al., GCNC 11047) with the 0.82m IAC80 (Obs. of Teide, Tenerife, Spain) and 1.5m OSN (Obs. of Sierra Nevada, Granada, Spain) telescopes in VRI-bands. The observations were carried out on Aug 6.0515-6.1393 UT (IAC80) and Aug 6.1608-6.1875 UT (1.5m OSN), respectively. The optical afterglow is marginally detected in our images with a preliminary magnitude of R~21.5, calibrated against USNO-B1.0 field stars." //////////////////////////////////////////////////////////////////////// TITLE: GCN CIRCULAR NUMBER: 11071 SUBJECT: GRB 100805A: SAO RAS optical observations DATE: 10/08/07 13:47:19 GMT FROM: Vladimir Sokolov at SAO RAS A. S. Moskvitin, T. A. Fatkhullin, V. V. Sokolov, T. N. Sokolova & V. N. Komarova (SAO RAS, Niznijh Arkhyz, Russia), report: We observed the field of the GRB100805A (Hoversten E. A. et al., GCN 11047) with the Zeiss-1000 telescope of SAO RAS, Russia. The observations were carried out in the BVRc bands on Aug. 5.843-6.033 UT. Assuming the magnitudes of the reference USNO-B1.0 star (L.P. Xin et al., GCN 11065) as B = 18.94 and R = 17.41 we estimated the brightness of the GRB100805A optical transient as: B = 22.85 +/- 0.11 R = 21.43 +/- 0.10 Errors are formal and do not include ones of USNO-B1.0 to Johnson-Cousins photometric system transformation. This message may be cited. //////////////////////////////////////////////////////////////////////// TITLE: GCN CIRCULAR NUMBER: 11076 SUBJECT: GRB 100805A: 2-nd epoch of SAO RAS optical observations DATE: 10/08/08 15:40:35 GMT FROM: Vladimir Sokolov at SAO RAS A. S. Moskvitin, T. A. Fatkhullin, V. V. Sokolov, T. N. Sokolova & V. N. Komarova (SAO RAS, Niznijh Arkhyz, Russia), report: We observed the field of the GRB100805A (Hoversten E. A. et al., GCN 11047) once again with the Zeiss-1000 telescope of SAO RAS, Russia. The observations were carried out in the Rc band on Aug. 7.832 - 7.918 UT. At the position of the OT we detected a faint object with R = 23.3 +/- 0.2. We assume the magnitude of the reference USNO-B1.0 star (L. P. Xin et al., GCN 11065; A. S. Moskvitin et al., GCN 11071) as R = 17.41. Error are formal and do not include one of USNO-B1.0 to Johnson-Cousins photometric system transformation. This message may be cited. //////////////////////////////////////////////////////////////////////// TITLE: GCN CIRCULAR NUMBER: 11077 SUBJECT: GRB 100805A: optical observation in CrAO DATE: 10/08/09 11:35:24 GMT FROM: Alexei Pozanenko at IKI, Moscow V. Rumyantsev (CrAO), A. Pozanenko (IKI) report on behalf of larger GRB follow-up collaboration: We observed the field of the Swift GRB 100805A (Hoversten et al., GCN 11047) with Shajn telescope of CrAO in filter R between (UT) July, 07 18:57:40 - 20:10:19 under good weather conditions and mean seeing of about 1.7". Within enhanced Swift-XRT position (Goad et al., GCN 11053) we do not detect the afterglow (Cenko, GCN 11050). However we detect the object in coordinates (J2000) RA: 19 59 30.11 Dec: +52 37 37.79. The object is 5.6" away from the center of enhanced XRT position (Goad et al., GCN 11053) and about 4.5" from afterglow position (Cenko, GCN 11050; Holland et al, GCN 11062). The object could be a host galaxy of GRB 100805A. The photometry is based on USNO-B1.0 star 1426-0390273 (J2000) RA= 19 59 29.55 +52 37 19.6 Dec= +52 37 19.6 and assuming R=17.59 is following: T0+ Filter, Exposure, Obj. mag., Upper Limit (mid, d) (s) 2.6401 R 68x60 22.5 +/- 0.1 24.0 The combined images can be found http://grb.rssi.ru/GRB100805A/GRB100805a_100807_R_ZTSh.gif Our observation and photometry is in some contradiction with observation reported in GCN 11076 (Moskvitin et al.) //////////////////////////////////////////////////////////////////////// TITLE: GCN CIRCULAR NUMBER: 11079 SUBJECT: GRB 100805A: the 3-rd epoch of SAO RAS optical observations DATE: 10/08/11 11:37:35 GMT FROM: Vladimir Sokolov at SAO RAS A. S. Moskvitin, T. A. Fatkhullin, V. V. Sokolov, T. N. Sokolova & V. N. Komarova (SAO RAS, Niznijh Arkhyz, Russia), report: We performed the third epoch of observations of the GRB 100805A (Hoversten E. A. et al., GCN 11047) field with the Zeiss-1000 telescope of SAO RAS, Russia. The observations were carried out in the Rc band on Aug. 9.882 - 10.043 UT under good weather conditions and the seeing 1".7. At the position of OT we detected an object with R = 23.54 +/- 0.22. We assume the magnitude of the reference USNO-B1.0 star (L. P. Xin et al., GCN 11065; A. S. Moskvitin et al., GCN 11071, A. S. Moskvitin et al., GCN 11076) as R = 17.41. Also we estimate the magnitude of the source reported by V. Rumyantsev and A. Pozanenko (GCN 11077) as R = 22.31 +/- 0.08 according to their standard star with R=17.59. All errors are formal and they do not include errors of the USNO-B1.0 to Johnson-Cousins photometric system transformation. Images from all 3 epochs with the marked OT and nearby object (GCN 11077) can be found in ftp://ftp.sao.ru/pub/grb/GRB100805A/GRB100805A_Zeiss1000.jpeg This message may be cited. //////////////////////////////////////////////////////////////////////// TITLE: GCN CIRCULAR NUMBER: 11081 SUBJECT: GRB 100805A: Swift/UVOT Observations of a Possible Late-Time Brightening DATE: 10/08/11 19:48:49 GMT FROM: Stephen Holland at USRA/NASA/GSFC/SSC S. T. Holland (CRESST/USRA/GSFC) and E. A. Hoversten (PSU) report on the behalf of the Swift UVOT team: Swift/UVOT observations of the optical afterglow of GRB 100805A (Hoversten, et al., 2010, GCN Circ, 11047) suggest that the afterglow may have brightened in the UVOT white band between approximately 1 day and 6 days after the BAT trigger. This may indicate the presence of a supernova component in the light curve. Our analysis is complicated by the presence of several bright stars near the optical afterglow. Further observations are needed to confirm that this possible brightening is real. Follow-up observations of this source are strongly encouraged. //////////////////////////////////////////////////////////////////////// TITLE: GCN CIRCULAR NUMBER: 11083 SUBJECT: GRB 100805A: optical observation in CrAO (correction to the GCN 11077 and second epoch) DATE: 10/08/12 20:25:38 GMT FROM: Alexei Pozanenko at IKI, Moscow V. Rumyantsev (CrAO), A. Pozanenko (IKI) report on behalf of larger GRB follow-up collaboration: We observed the field of the Swift GRB 100805A (Hoversten et al., GCN 11047) with Shajn telescope of CrAO in filter R in two epochs Aug. 07 and Aug 08. After revision of our first epoch observation reported in GCN 11077 (Rumyantsev et al.) we do find the afterglow (Cenko, GCN 11050). Our photometry (see below) is compatible with photometry reported for approximately the same epoch observation (Moskvitin et al. GCN 11076). We thank to C.Guidorzi for mention of inconsistency of our results reported in GCN 11077. Coordinates of the afterglow is following Aug. 07 (J2000) RA: 19 59 30.49 Dec: +52 37 40.3 Aug. 08 (J2000) RA: 19 59 30.47 Dec: +52 37 39.6 The coordinates are compatible within error bars with afterglow coordinates (Cenko, GCN 11050; Holland et al, GCN 11062). The photometry is based on USNO-B1.0 star 1426-0390273 (J2000) RA= 19 59 29.55 +52 37 19.6 Dec= +52 37 19.6 and assuming R=17.59 is following: T0+ Filter, Exposure, OT. mag., Upper Limit (mid, d) (s) 2.6401 R 68x60 23.6 +/- 0.25 24.0 3.6417 R 101x60 23.3 +/- 0.15 24.3 The combined images can be found http://grb.rssi.ru/GRB100805A/GRB100805a_100808_R_ZTSh.gif Taken together late time photometry above and (Moskvitin et al., GCN 11076; Moskvitin et al., GCN 11079) one can suggest flattening of the light curve in R-filter in 2.5 - 4.5 days after burst trigger. However some re-brightening suggested by Holland & Hoversten (GCN 11081) could not be excluded in this period too. //////////////////////////////////////////////////////////////////////// TITLE: GCN CIRCULAR NUMBER: 11084 SUBJECT: GRB 100805A: the 4-th epoch of SAO RAS optical observations DATE: 10/08/13 15:30:09 GMT FROM: Vladimir Sokolov at SAO RAS A. S. Moskvitin, T. A. Fatkhullin, V. V. Sokolov, T. N. Sokolova & V. N. Komarova (SAO RAS, Niznijh Arkhyz, Russia), report: We performed further observations of the GRB100805A (Hoversten E. A. et al., GCN 11047) field with the Zeiss-1000 telescope of SAO RAS, Russia. The observations were carried out in the Rc band on Aug. 12.821 - 13.046 UT under good transparency and seeing of 2".5. Total integration time is 15600 sec. We do not detect any objects at the position of the OT up to limiting magnitude R = 24.2 (3-sigma limit for stellar-like object). We assumed the magnitude of the reference USNO-B1.0 star (L. P. Xin et al., GCN 11065; A. S. Moskvitin et al., GCN 11071, A. S. Moskvitin et al., GCN 11076, A. S. Moskvitin et al., GCN 11079) as R = 17.41. Also we confirm the magnitude of the source reported by V. Rumyantsev and A. Pozanenko (GCN 11077) as R = 22.47 +/- 0.06 according to their standard star with R=17.59. All errors are formal and they do not include errors of the USNO-B1.0 to Johnson-Cousins photometric system transformation. Combining all data in the R-band we found that late-time light curve (T-T_0 > 2.3 days) behaviour follows the one of the early stage (F ~ t^-0.77, t < 3000 sec). Thus one can conclude that possible re-brightening (Holland & Hoversten (GCN 11081)) occurred within ~0.3-2.3 days after the burst. The R-band light curve can be found at ftp://ftp.sao.ru/pub/grb/GRB100805A/GRB100805A_lc_R.jpeg This message may be cited.