NOTE THAT THIS FILE CONTAINS CIRCULARS FOR GRBs 050922 'A', 'B', and 'C'. //////////////////////////////////////////////////////////////////////// TITLE: GCN GRB OBSERVATION REPORT NUMBER: 4007 SUBJECT: Possible GRB 050922 detected by INTEGRAL DATE: 05/09/22 15:31:35 GMT FROM: Sandro Mereghetti at IASF/CNR D.Gotz, S.Mereghetti (IASF, Milano) S. Shaw, N. Mowlavi, M. Beck, J. Zurita Heras (ISDC, Versoix) and J. Borkowski (CAMK, Torun) on behalf of the IBAS Localization Team report: A possible GRB triggered IBAS at 13:43:18 UT with coordinates (J2000) R.A. = 271.1541 Dec. = -32.0235 with an uncertainty of 3.5 arcmin radius (90% c.l.). The trigger significance was below the threshold for automatic alert delivery. A preliminary analysis shows a spectrum consistent with an X-ray flash and a fluence (20-200 keV) is 1E-7 erg/cm^2. However, due to the position in the galactic bulge and the soft spectrum, we cannot exclude that the trigger is due to an uncatalogued Galactic source. This message can be cited. //////////////////////////////////////////////////////////////////////// TITLE: GCN GRB OBSERVATION REPORT NUMBER: 4008 SUBJECT: GRB050922B: Swift-BAT detection of a weak long burst DATE: 05/09/22 16:13:40 GMT FROM: Scott Barthelmy at NASA/GSFC J. Norris (GSFC), L. Barbier (GSFC), S. Barthelmy (GSFC), P. Boyd (GSFC), D. Burrows (PSU), J. Cummings (GSFC/NRC), N. Gehrels (GSFC), S.T. Holland (GSFC/USRA), J. Kennea (PSU), H. Krimm (GSFC/USRA), F. Marshall (GSFC), O. Godet (U. Leicester), D. Palmer (LANL), T. Sakamoto (GSFC) on behalf of the Swift team: At 15:02:00 UT, Swift-BAT triggered and located GRB050922B (trigger=156434). This was an image trigger with a 168-sec duration. The spacecraft slewed immediately after the end of the image trigger. The BAT on-board calculated location is RA,Dec 5.800d,-5.599d {00h 23m 12s,-05d 35' 55"} (J2000), with an uncertainty of 3 arcmin (radius, 90% containment, stat+sys). The TDRSS lightcurve does not show any significant emission, but these lightcurves are problematic for long image triggers. We will have to wait for the full Malindi data set (~8 hrs) to make a mask-tagged lightcurve. We note that this source is at a high galactic latitude of -67 degrees. We also note that the recent long-duration image trigger GRB 050904 was at high redshift. XRT began observing the field at 15:07:42, 342 seconds after the BAT trigger. Onboard centroiding found a bright fading uncatalogued X-ray source in the field of view at the following coordinates: RA(J2000): 0:23:13.3, Dec(J2000): -5:36:12.9. We estimate the uncertainty of this position to be 8 arcseconds (radius, 90% containment). This position is 26 arcseconds from the BAT position above. UVOT began observing at 343 sec after the trigger. The small UVOT TDRSS image does not overlap the BAT error circle. However, the full-field UVOT source list contains only catalogued sources, in particular no source is found inside the XRT error circle. At the present time it is not possible to determine a limiting magnitude for this field. The V-band extinction in this direction is A_V = 0.12 mag. //////////////////////////////////////////////////////////////////////// TITLE: GCN GRB OBSERVATION REPORT NUMBER: 4009 SUBJECT: GRB 050922B,optical observation DATE: 05/09/22 17:02:18 GMT FROM: Eri Sonoda at U of Miyazaki/Japan E.Sonoda,S.Maeno,Y.Tokunaga,M.Yamauchi (University of Miyazaki) "We have observed the field covering the error circle of GRB 050922(GCN4008;Swift-BAT Trigger time is 15:02:00 UT) with the unfiltered CCD camera on the 30-cm telescope at University of Miyazaki. The observation was started 15:28:46 UT on Sep.22. After co-adding a set of 6 images (15:28:46 - 15:37:46 UT) of 30 sec exposures, we have compared with the USNO A2.0 catalog. Preliminary analysis shows there is no new source brighter than 16.1 mag." //////////////////////////////////////////////////////////////////////// TITLE: GCN GRB OBSERVATION REPORT NUMBER: 4010 SUBJECT: GRB 050922B: ROTSE-III Optical Limits DATE: 05/09/22 17:20:37 GMT FROM: Brad Schaefer at LSU B. E. Schaefer (Louisiana State), R. Quimby (U Texas), S.A. Yost (U Mich), W. Rujopakarn (U Mich) report on behalf of the ROTSE collaboration: ROTSE-IIIa, located at Siding Spring Observatory, Australia, responded to GRB 050922B (Swift trigger 156434), producing images beginning 5.6 s after the GCN notice time. An automated response took the first image at 15:05:06.6 UT, 186.3 s after the burst, under excellent conditions. We took 10 5-sec, and 140 20-sec exposures. These unfiltered images are calibrated relative to USNO A2.0 (R). Comparison to the DSS (second epoch) reveals no new sources within the 3-sigma error circles for both the BAT and the XRT, for both single images and coadding into sets of 10. The field is not crowded but the gibbous moon was 57 degree away. Individual images have limiting magnitudes ranging from 15.4-16.5; we set the following specific limits. start UT end UT t_exp(s) mlim t_start-tGRB(s) Coadd? -------------------------------------------------------------------- 15:05:06.6 15:07:30.6 144 17.3 186.3 Y //////////////////////////////////////////////////////////////////////// TITLE: GCN GRB OBSERVATION REPORT NUMBER: 4011 SUBJECT: GRB 050922C: ROTSE-III Detection of Possible Counterpart DATE: 05/09/22 20:04:53 GMT FROM: Eli Rykoff at U of Michigan/ROTSE E.S. Rykoff (U Mich), S.A. Yost (U Mich), W. Rujopakarn (U Mich) report on behalf of the ROTSE collaboration: ROTSE-IIId, located at the Turkish National Observatory at Bakirlitepe, Turkey, responded to GRB 050922C (Swift trigger 156467). The first image was at 19:58:42.8 UT, 172.4 s after the burst (6.8 s after the GCN notice time). The unfiltered images are calibrated relative to USNO A2.0. We detect a new object, not visible in the DSS (second epoch), with coordinates: 21:09:33.1 -08:45:29.8 (J2000) start UT mag mlim(of image) ---------------------------------- 19:58:42.8 14.7 16.1 Continuing observations are in progress. [GCN OPS NOTE(22sep05): Per author's request, the two instances of 'A' were changed to 'C'.] //////////////////////////////////////////////////////////////////////// TITLE: GCN GRB OBSERVATION REPORT NUMBER: 4012 SUBJECT: GRB 050922C: ROTSE-IIId Refined Analysis DATE: 05/09/22 20:31:39 GMT FROM: Eli Rykoff at U of Michigan/ROTSE E.S. Rykoff (U Mich), S.A. Yost (U Mich), W. Rujopakarn (U Mich), R. Quimby (U Texas), D. A. Smith (Guilford), F. Yuan (U Mich) report on behalf of the ROTSE collaboration: ROTSE-IIId, located at the Turkish National Observatory at Bakirlitepe, Turkey, responded to GRB 050922C (Swift trigger 156467). (Note that the burst designation in GCN 4011 is incorrect). We obtained 10 5-s images followed by 12 20-s images before precipitation ended observations. The object reported in GCN 4011 fades significantly from 172 s post-burst to 651 s post-burst as a simple power-law with index -1.0. At 640 s post-burst the counterpart was at 16.0+/-0.1 mag (unfiltered) relative to the USNO A2.0 R-band magnitudes. A finding chart can be found at: http://www.rotse.net/grb_reports/050922C_btab.html //////////////////////////////////////////////////////////////////////// TITLE: GCN GRB OBSERVATION REPORT NUMBER: 4013 SUBJECT: GRB 050922C: Swift detection of a bright burst DATE: 05/09/22 21:05:45 GMT FROM: Jay R. Cummings at NASA/GSFC/Swift J. Norris (GSFC), L. Barbier (GSFC), D. Burrows (PSU), A. Cucchiara (PSU), J. Cummings (GSFC/NRC), N. Gehrels (GSFC), M. Goad (U. Leicester), O. Godet (U. Leicester), S.T. Holland (GSFC/USRA), J. Kennea (PSU), F. Marshall (GSFC), D. Palmer (LANL), T. Sakamoto (GSFC/NRC), on behalf of the Swift team: At 19:55:50 UT Swift-BAT triggered and located GRB 050922C (Trigger=156467) and immediately slewed. The BAT on-board calculated position is RA,Dec= 317.391d, -8.772d {21h 09m 34s, -08d 46' 17"} (J2000) with an uncertainty of 3 arcmin (radius, 90% containment, stat+sys). The TDRSS light curve shows an intense GRB with a rising precursor starting at T-5 seconds, followed by 5-second long main peak surmounted by three spikes. The third and most intense spike has a maximum count rate at T+1 sec of 15,000 counts/sec (15-350 keV). XRT began observing the field at 19:57:38 UT, 108 seconds after the BAT trigger. XRT performed an onboard centroid and found a previously uncataloged fading source in the field of view at the following coordinates: RA(J2000): 21:09:33.4, Dec(J2000): -8:45:30.5, with an estimated uncertainty of 8 arcseconds radius (90% containment). This position is 49 arcseconds from the BAT position and within 4.5 arcsec of the optical transient reported by Rykoff et al. (GCN circ 4011 [mistitled]). UVOT began observing at 111 sec after the trigger. The small UVOT TDRSS image does not overlap the XRT error circle. However, the full-field UVOT source list contains a bright, uncataloged source within the XRT error circle. We estimate the V magnitude at 15.5 +- 0.5 uncorrected for extinction. The V-band extinction in this field is A_V = 0.34 mag. [GCN OPS NOTE(22sep05): Per author's request, the Subject-line was changed from "050822" to "050922".] //////////////////////////////////////////////////////////////////////// TITLE: GCN GRB OBSERVATION REPORT NUMBER: 4014 SUBJECT: GRB 050922A: Analysis of Swift/XRT TOO observation DATE: 05/09/22 21:56:40 GMT FROM: Jamie A. Kennea at PSU/Swift-XRT J. A. Kennea, D. N. Burrows (PSU) and N. Gehrels (GSFC) report on behalf of the Swift/XRT Team: Swift began a target of opportunity observation of the INTEGRAL discovered burst GRB 050922A (GCN 4007) at 15:21:21 UT on September 22nd, 2005. Analysis of ground processed XRT data reveals no point source inside the INTEGRAL error circle. We estimate a 90% confidence level upper limit on the X-ray flux from this burst of 3 x 10^-14 erg/s (0.5 - 10 keV). //////////////////////////////////////////////////////////////////////// TITLE: GCN GRB OBSERVATION REPORT NUMBER: 4015 SUBJECT: GRB 050922C: NOT optical observations DATE: 05/09/22 22:16:59 GMT FROM: Pall Jakobsson at Niels Bohr Inst Pall Jakobsson (DARK, NBI), Danka Paraficz, John Telting (NOT, La Palma), Johan P. U. Fynbo, Brian L. Jensen, Jens Hjorth and Jose Maria Castro Ceron (DARK, NBI) report: Using ALFOSC on the 2.56-meter Nordic Optical Telescope, we have obtained a 300 s R-band image of the GRB 050922C field (Swift trigger: 156467, GCN#4013 (Norris et al.)). Using a preliminary photometric zeropoint we estimate the following magnitude for the afterglow: R ~ 16.5 @ 1 hour post-burst. The coordinates are: (RA, Dec)(J2000.0) = (21:09:33.083, -08:45:30.2) with a 0.2" error in each coordiante. A finding chart of the field is available at: http://www.astro.ku.dk/~brian_j/grb/grb050922.830/ //////////////////////////////////////////////////////////////////////// TITLE: GCN GRB OBSERVATION REPORT NUMBER: 4016 SUBJECT: GRB 050922C: optical obserations DATE: 05/09/22 22:49:02 GMT FROM: Alexei Pozanenko at IKI, Moscow M. Andreev, A. Pozanenko on behalf of larger GRB follow up collaboration report: We observed the GRB 050922C field (Swift trigger: 156467, GCN4013 Norris et al.) in R-band with 60 cm telescope of Terskol observatory. We confirm the new OT found in by ROTSE-IIId (GCNs 4011, 4012, Rykoff et al.) OT is fading and preliminary photometry of the OT against of USNO A2.0 of the first image taken at (UT) 20:08:45 is R~16. The observation is continuing. //////////////////////////////////////////////////////////////////////// TITLE: GCN GRB OBSERVATION REPORT NUMBER: 4017 SUBJECT: GRB 050922C: Absorption redshift from the Nordic Optical Telescope DATE: 05/09/22 23:33:59 GMT FROM: Pall Jakobsson at Niels Bohr Inst Pall Jakobsson, Johan P. U. Fynbo, (DARK, NBI), Danka Paraficz, John Telting (NOT, La Palma), Brian L. Jensen, Jens Hjorth and Jose Maria Castro Ceron (DARK, NBI) report: Using ALFOSC on the Nordic Optical Telescope (NOT) we have obtained spectra of the afterglow of GRB 050922C (GCN#4013 Norris et al. [Swift], GCN#4012 Rykoff et al. [ROTSE-III], GCN#4015 Jakobsson et al. [NOT]) on 2005, Sep 22.9 UT. We find several absorption features, including strong Lyman-alpha, OI+SiII, CII, SiIV, CIV, AlII and AlIII, corresponding to a redshift of z = 2.17+-0.03 (based on a preliminary wavelength calibration). There is additional strong absorption, possibly corresponding to Lyman-alpha at z = 2.05+-0.03. //////////////////////////////////////////////////////////////////////// TITLE: GCN GRB OBSERVATION REPORT NUMBER: 4018 SUBJECT: GRB050922C: optical observations DATE: 05/09/22 23:50:07 GMT FROM: Eran Ofek at Tel Aviv U. E. O. Ofek, Y. M., Lipkin, J. Dann (Wise observatory, TAU) report: We have observed the Swift error box of GRB050922C (Norris et al. GCN 4013) using the Wise observatory 1m telescope starting at 2005, Sep 22nd, 22:10:56 UTC. We obtained a 210 sec unfiltered image (mid exposure time 0.0950 days after the Swift-BAT trigger) in which we detected the optical transient (OT) discovered by Rykoff et al. (GCN 4011). At that epoch, the OT magnitude was R~17.9, assuming R-mag=14.24 for the bright star 37 arcsec at PA=210deg from the OT. //////////////////////////////////////////////////////////////////////// TITLE: GCN GRB OBSERVATION REPORT NUMBER: 4019 SUBJECT: GRB 050922B: Swift-BAT refined analysis DATE: 05/09/23 00:03:15 GMT FROM: Takanori Sakamoto at NASA/GSFC D. Hullinger (UMD), L. Barbier (GSFC), S. Barthelmy (GSFC), J. Cummings (GSFC/NRC), E. Fenimore (LANL), F. Marshall (GSFC), N. Gehrels (GSFC), H. Krimm (GSFC/USRA), C. Markwardt (GSFC/UMD), D. Palmer (LANL), A. Parsons (GSFC), T. Sakamoto (GSFC/NRC), G. Sato (ISAS), A. Smale (NASA HQ), J. Tueller (GSFC) on behalf of the Swift-BAT team: Using the data set from T-120 to T+450 sec from the recent telemetry downlink, we report further analysis of Swift-BAT GRB 050922B (trigger #156434) (Norris, et al., GCN 4008). The refined BAT ground position is (RA,Dec) = 5.789, -5.602 {00:23:09,-05:36:08} [deg; J2000] +-2.3 arcmin, (radius, sys+stat, 90% containment). The partial coding was 12%. The light curve shows a broad peak from T+15 to T+65 and a second peak from T+80 to T+110. There is no extended emission T>120 sec. T90 (15-350 keV) is (80 +- 10) sec (estimated error including systematics). The power law index of the time-averaged spectrum is 1.89 +- 0.23. The fluence in the 15-150 keV band is (1.8 +- 0.3) x 10^-6 erg/cm2. The 1-sec peak photon flux measured from T0+98 sec in the 15-150 keV band is (1.1 +- 0.4) ph/cm2/sec. All the quoted errors are at the 90% confidence level. //////////////////////////////////////////////////////////////////////// TITLE: GCN GRB OBSERVATION REPORT NUMBER: 4020 SUBJECT: GRB 050922C: Swift-BAT refined analysis DATE: 05/09/23 00:37:09 GMT FROM: Takanori Sakamoto at NASA/GSFC H. Krimm (GSFC/USRA), L. Barbier (GSFC), S. Barthelmy (GSFC), J. Cannizzo (GSFC-UMBC), L. Cominsky (Sonoma State U.), J. Cummings (GSFC/NRC), E. Fenimore (LANL), N. Gehrels (GSFC), D. Hullinger (UMD), C. Markwardt (GSFC/UMD), D. Palmer (LANL), A. Parsons (GSFC), T. Sakamoto (GSFC/NRC), G. Sato (ISAS), J. Tueller (GSFC) on behalf of the Swift-BAT team: Using the data set from T-10 to T+60 sec from the recent telemetry downlink, we report further analysis of Swift-BAT GRB 050922C (trigger #156467) (Norris, et al., GCN 4013). The refined BAT ground position is (RA,Dec) = 317.381, -8.762 {21:09:32, -8:45:43} [deg; J2000] +- 1.0 arcmin, (radius, sys+stat, 90% containment). The partial coding was 53%. The light curve shows the intense broad peak starting from T-3 to T+3 with at least two sub-peaks on top. T90 (15-350 keV) is (5 +- 1) sec (estimated error including systematics). The power law index of the time-averaged spectrum is 1.33 +- 0.06. The fluence in the 15-150 keV band is (1.7 +- 0.1) x 10^-6 erg/cm2. The 1-sec peak photon flux measured from T-0.02 sec in the 15-150 keV band is (7.5 +- 0.3) ph/cm2/sec. All the quoted errors are at the 90% confidence level. //////////////////////////////////////////////////////////////////////// TITLE: GCN GRB OBSERVATION REPORT NUMBER: 4021 SUBJECT: HETE Fregate observations of GRB 050922C DATE: 05/09/23 01:18:28 GMT FROM: Roland Vanderspek at MIT HETE Fregate observations of GRB 050922C G. Crew, G. Ricker, J-L. Atteia, N. Kawai, D. Lamb, and S. Woosley, on behalf of the HETE Science Team; M. Arimoto, T. Donaghy, E. Fenimore, M. Galassi, C. Graziani, J. Kotoku, M. Maetou, M. Matsuoka, Y. Nakagawa, T. Sakamoto, R. Sato, Y. Shirasaki, M. Suzuki, T. Tamagawa, K. Tanaka, Y. Yamamoto, and A. Yoshida, on behalf of the HETE WXM Team; N. Butler, J. Doty, G. Prigozhin, R. Vanderspek, J. Villasenor, J. G. Jernigan, A. Levine, G. Azzibrouck, J. Braga, R. Manchanda, and G. Pizzichini, on behalf of the HETE Operations and HETE Optical-SXC Teams; M. Boer, J-F Olive, J-P Dezalay, and K. Hurley, on behalf of the HETE FREGATE Team; report: The HETE Fregate instrument detected GRB 050922C (Swift trigger 156647; Norris et al, GCN 4013). The flight instruments did not trigger because they were processing another trigger (H3934) which occurred 204 seconds earlier. The burst was clearly detected in Fregate in the 7-30, 7-80, and 30-400 keV bands. The burst spectrum is best fit with a cutoff power law of photon index 0.83 (-0.26/+0.23) and Epeak of 130.5 keV (-26.8/50.9). The 2-30 keV fluence is 5.4e-7 erg/cm2; the 30-400 keV fluence is 2.6e-6 erg/cm2. The ratio of the 2-30 keV to 30-400 keV fluence is 0.2: thus, GRB 050922C is a classical GRB. Due to the hardness of the spectrum, we have not been able to determine the high-energy slope (beta) of the Band function for this burst. The determination of bolometric fluence is therefore subject to systematic uncertainty. Assuming z=2.17 (Jakobbson et al., GCN 4017) and assuming the above cutoff power-law applies in the source-frame energy range of 1-10000 keV, the lower bound on E_iso is E_iso=3.7E+52 erg. The upper bound, obtained assuming beta=-2.0, is E_iso=7.0E+52 erg. //////////////////////////////////////////////////////////////////////// TITLE: GCN GRB OBSERVATION REPORT NUMBER: 4022 SUBJECT: GRB 050922C: Swift XRT refined analysis DATE: 05/09/23 02:57:43 GMT FROM: Jamie A. Kennea at PSU/Swift-XRT J. A. Kennea, D. N. Burrows (PSU), M. Goad (U. Leicester), J. Norris and N. Gehrels (GSFC) report on behalf of the Swift/XRT Team: We report on detailed ground analysis of the first 2 orbits of data from X-ray afterglow of GRB050922C (GCN 4013) utilizing downlinked Swift/XRT data. We find a refined position for the XRT afterglow of: RA(J2000): 21:09:33.3, Dec(J2000): -8:45:27.5, with an estimated uncertainty of 6 arcseconds radius (90% containment). We note that this position is 4.6 arcseconds from the NOT optical afterglow position reported in GCN 4015. We have extracted a lightcurve of combined Window Timing and Photon Counting mode data from the first two orbits of XRT observations, covering 6500ks of time. The lightcurve of the afterglow is well described by a single powerlaw model with a slope of -1.14 +/- 0.02. The spectrum of the afterglow is well fit (reduced Chi^2 = 0.94 with 44 dof) by an absorbed power-law model with the following parameters: N_H = (6.5 +/- 2.7) x 10^20 cm^-2 Photon Index = 1.89 +/- 0.16 The absorption seen here is consistant with the expected Galactic absorption of 5.75 x 10^20 cm^-2. Utilizing this spectral model, we estimate the flux of this burst (corrected for absorption) to be: BAT Trigger +1 hour: 1.5 x 10^-11 erg/s/cm^2 (0.5 - 10 keV) BAT Trigger +1 day: 3.9 x 10^-13 erg/s/cm^2 (0.5 - 10 keV) Note that the latter flux estimate assumes that the lightcurve does not break. Observations of this burst by Swift are on-going. //////////////////////////////////////////////////////////////////////// TITLE: GCN GRB OBSERVATION REPORT NUMBER: 4023 SUBJECT: GRB050922C: Optical Observations DATE: 05/09/23 04:43:10 GMT FROM: Aaron Price at AAVSO D. T. Durig (Cordell-Lorenz Observatory - University of the South) and A. Price (AAVSO) report on behalf of the AAVSO International High Energy network on optical observations of GRB050922C. After glow reported by Rykoff et al (GCN #4011) was visible in 2 hours of exposures. The first three measurements are below and a link to the rest is in the full report at the bottom of the e-mail. Uncertainty is estimated at +/-0.2 mag. 09 23.03833 19.1 Rc 09 23.07725 19.5 Rc 09 23.10989 20.1 Rc The AAVSO would like to thank the Curry Foundation and NASA for their support of the AAVSO International High Energy Network. Name: Dr. Douglas T. Durig email: ddurig@sewanee.edu Observer: D. T. Durig, K. T. Crockett, L. R. Johnson Site: Cordell-Lorenz Observatory Location: Sewanee, TN, USA LatitudeLongitude: 35 12 N 85 55 W Elevation: 600 m Scope: SCT 0.30 m ScopeFocalRatio: f/5.9 1770 mm CCDVendor: SBIG ST-8E CCDDetector: KAF-1600E CCDSize: 1530x1020 binned 3x3 for 510x340 CCDPixelScale: 3.14 arc sec per pixel CCDFOV: 26.7x17.8 full, 13.3x8.9 cropped submitted Object: GRB050922C ObsDate: 2005 09 23 ObsMidPointTime: 01:51:14 UT TimePerFrame: 300 sec NumberOfFrames: best 24 out of 30 Filters: CR Processing: dark,flat, register,co-add, 1/2 frame crop Seeing: 5-6 arc sec LimitingMag: ~21.5 ??? Sky: clear, but very gusty winds afterglowmag: 19 fading to 20 over two hours time afterglowerr: 0.2 mag compstars: 94 UCAC, 188 B1.0 subframe Report: Full frame covers entire error box. After glow reported by Rykoff et al (GCN 4011) was visible in single 300 sec exposure but 6 frames were added to improved S/N for measurements. We measure a position of 21 09 33.10 -08 45 30.2 First three photometric measurements shown below. We have posted our first 2 hours of exposure at http://arthur.sewanee.edu/obsv/view.php comments: 09 23.03833 21 09 33.10 -08 45 30.2 19.1 R 09 23.07725 21 09 33.12 -08 45 30.4 19.5 R 09 23.10989 21 09 33.12 -08 45 30.7 20.1 R A FITS image has been uploaded to ftp://ftp.aavso.org/grb/Dr.DouglasT.Durig_GRB050922C_2453636.66853_.fits //////////////////////////////////////////////////////////////////////// TITLE: GCN GRB OBSERVATION REPORT NUMBER: 4024 SUBJECT: GRB 050922B: optical limit DATE: 05/09/23 06:51:16 GMT FROM: Ken ichi Torii at RIKEN K. Torii (Osaka U.) reports: The error region of Swift GRB 050922B (Norris et al. GCN 4008) was observed by the 14 inch Automated Response Telescope. BVRcIc imaging started at 2005 September 22, 15:07:42 UT (342 s after the trigger) and 60 s integration was repeated. Due to low transparency and intermittent clouds, useful images were obtained after 15:16:47 UT. Preliminary analysis gives the following 3-sigma upper limits for an optical counterpart of the Swift XRT afterglow (GCN 4008). ------------------------------------------ StartUT Filter Limit Exposure ------------------------------------------ 15:17:55 Rc 15.5 60s 17:02:44 Ic 17.1 40x60s ------------------------------------------ //////////////////////////////////////////////////////////////////////// TITLE: GCN GRB OBSERVATION REPORT NUMBER: 4025 SUBJECT: INT 2.5m limit for GRB050922B DATE: 05/09/23 11:06:37 GMT FROM: Martin Jelinek at Inst.Astrophys.Andalucia,Granada S. Guziy, M. Jelinek, J. Gorosabel, A.J. Castro-Tirado, A. de Ugarte Postigo (IAA-CSIC Granada, Spain), Ernesto Rodriguez Flores (IGA, La Habana, Cuba) and K. Vijanen (IAC-CSIC La Laguna, Spain) report: "We have acquired r' image of the GRB 050922B XRT error box (Norris et al. GCN 4008) with INT 2.5m telescope at Observatorio del Roque de los Muchachos on La Palma starting on September 23.1943 UT (i.e. 0.5678d after the GRB) with 600s exposure. No sources brighter than r'=22.5 (3-sigma) are detected within the 8" radius of the XRT error circle" This message can be cited. //////////////////////////////////////////////////////////////////////// TITLE: GCN GRB OBSERVATION REPORT NUMBER: 4026 SUBJECT: GRB050922C: observation at MonteBoo DATE: 05/09/23 12:38:40 GMT FROM: Martin Jelinek at Inst.Astrophys.Andalucia,Granada T. Henych, M. Kocka, F. Hroch (MU Brno, Czech Republic), Martin Jelinek (IAA Granada, Spain) and Rene Hudec (ASU AV CR Ondrejov, Czech Republic) report: We have observed the optical transient of GRB050922C reported by Rykoff et al. (GCN 4011) for 1.2h with the mean time 0.100d after the GRB trigger (Norris et al., GCN 4013) with the 60cm telescope at MonteBoo Observatory equipped with an ST8 CCD. We have found the OT at roughly R=18 decaying with an index \alpha = -0.5 . This message may be cited. //////////////////////////////////////////////////////////////////////// TITLE: GCN GRB OBSERVATION REPORT NUMBER: 4028 SUBJECT: GRB050922B: Swift UVOT early upper limits. DATE: 05/09/23 15:09:06 GMT FROM: Massimiliano de Pasquale at MSSL-UCL M. De Pasquale (MSSL), J. Norris (GSFC), T. Kennedy (GSFC), K. Mason (PPARC), N. Gehrels (GSFC) on behalf of the Swift/UVOT team The Swift/UVOT began observing the field of GRB050922B at 15:07:42 UT, 342 seconds after the BAT trigger (Hullinger et al., GCN 4019). There is no detection of an optical counterpart in the first 100 sec exposure finding chart down to a 3 sigma upper limit of V=18.7. There is also no optical/UV counterpart detected in the summed images from all filters, down to the following 3 sigma magnitude upper limits: Filter T_range(sec) Exp(sec) 3sig UL V 342-5997 1158 20.1 B 489-1720 258 20.2 U 474-11434 720 20.5 UVW1 580-7616 873 20.3 UVM2 446-6904 1068 20.6 UVW2 503-1826 258 20.1 Where T_range is the time post-trigger over which the summed images were accumulated and Exp is the total exposure time. The magnitudes upper limits are not corrected for extinction. These magnitudes are based on preliminary zero- points, measured in orbit, and will require refinements with further calibrations. //////////////////////////////////////////////////////////////////////// TITLE: GCN GRB OBSERVATION REPORT NUMBER: 4029 SUBJECT: GRB 050922C: Refined redshift DATE: 05/09/23 15:39:42 GMT FROM: Pall Jakobsson at Niels Bohr Inst Páll Jakobsson, Johan P. U. Fynbo, (DARK, NBI), Danka Paraficz, John Telting (NOT, La Palma), Brian L. Jensen, Jens Hjorth and José María Castro Cerón (DARK, NBI) report: Using new wavelength calibration files, we have refined the GRB 050922C redshift obtained at the NOT (GCN 4017). Based on the detection of Lyman-alpha, OI+SiII, CII, SiIV, FeII, AlII, SiII* and SiII in absorption, we measure a redshift of z = 2.198+-0.001. There is additional strong absorption, possibly corresponding to Lyman-alpha at z = 2.07. //////////////////////////////////////////////////////////////////////// TITLE: GCN GRB OBSERVATION REPORT NUMBER: 4030 SUBJECT: Konus-Wind observation of GRB 050922C DATE: 05/09/23 16:05:24 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 GRB 050922C (Swift-BAT trigger #156467; Norris et al., GCN 4013, Krimm et al., GCN 4020) triggered Konus-Wind at T0=71754.480 s UT (19:55:54.480). As observed by Konus-Wind it had a duration of ~5 s, fluence (7.3 +/- 0.5)10-6 erg/cm2, peak flux on 128-ms time scale (4.5 +/- 0.7)10-6 erg/cm2/s (both in the 20 keV - 2 MeV energy range). The time-integrated spectrum of the GRB (from T0 to T0+8.448 s) is well fitted (in the 20 keV - 2 MeV range) by a power law model with photon index 1.55 +/- 0.07. The spectrum does not demonstrate an exponential cutoff with E0 ~100 keV reported by HETE Fregate (Crew et al., GCN 4021). Assuming z = 2.17 (Jakobsson et al., GCN 4017) and a standard cosmology model with H_0 = 70 km/s/Mpc, Omega_M = 0.3, Omega_\Lambda = 0.7, the isotropic energy release is E_iso ~8.1x10^52 erg, the maximum luminosity is (L_iso)_max ~1.6x10^53 erg/s. //////////////////////////////////////////////////////////////////////// TITLE: GCN GRB OBSERVATION REPORT NUMBER: 4031 SUBJECT: GRB050922B: refined XRT analysis DATE: 05/09/23 16:39:11 GMT FROM: Olivier Godet at U.of Leicester O. Godet, K.L. Page, J. Kennea (PSU), J.P. Osborne (U. Leicester), D. N. Burrows (PSU), N. Gehrels (NASA/GSFC), K. Hurley (Berkeley), M. Chester (PSU) report on behalf of the Swift XRT team: We have analyzed the Swift XRT data of the burst GRB 050922B from the first 3 orbits (~4 ks). The refined coordinates are: RA(J2000) = 00h 23min 13.2s Dec(J2000) = -05d 36' 16.4" with an uncertainty of 7 arcseconds radius (90% containment). This position is consistent with that reported by Norris et al. (GCN 4008). Initial data show two flares peaking at ~370 s and ~846 s after the trigger (T0), followed by a steep temporal decline decay (power law decline index ~ 2.75+/-0.14). Later data from the second and third orbits show a shallow decline with an temporal index ~ 0.95 +/- 0.41. The X-ray spectrum after T0+5021 s is well fit by a power-law with Gamma = 1.9+0.3/-0.2 (90% confidence) and a Galactic absorbing column of 3.4e20 cm^-2. If the light-curve is still unbroken at T0+24 h, the predicted unabsorbed 0.3-10 keV flux is ~1.6e-13 erg cm^-2 s^-1. [GCN OPS NOTE(23sep05): Per author's request, J. Kennea as was added to the author list.] //////////////////////////////////////////////////////////////////////// TITLE: GCN GRB OBSERVATION REPORT NUMBER: 4032 SUBJECT: GRB050922C: TNG spectroscopic observations DATE: 05/09/23 17:37:41 GMT FROM: Silvia Piranomonte at OAR S. Piranomonte (INAF/OAR), A. Magazzu (TNG), G. Mainella (TNG), F. Fiore (INAF/OAR), S. Covino (INAF/OABr), D. Fugazza (INAF/OABr), A. Antonelli (INAF/OAR), G. Israel (INAF/OAR), G. Chincarini (Univ. Milano-Bicocca), D. Malesani (SISSA), , F. Mannucci (INAF/Arcetri), G. Tagliaferri (INAF/OABr), and L. Stella (INAF/OAR) on behalf of the CIBO collaboration, report: Starting on September 22 21:17:35 UT (about 82 min after the GRB trigger) we have obtained low resolution spectra of the optical afterglow of GRB050922C (Rykoff et al. GCN#4012). The observations consisted of 5 exposures for 300 sec each with DOLORES@TNG, using grism LR-B, with a 1" slit. This set-up provides a resolution of about 5 angstrom. At the time of the observations the afterglow magnitude varied between R~16.7 and R=17.7. A preliminary analysis of the data confirms a very rich spectrum (see Jakobsson et al. GCN#4017, GCN#4029). We detect strong Lyalpha, SiII1304, CII1334, SiIV1393, SiII1526, CIV1548,1550, AlII1670, SiII1808 absorption lines at z=2.198+/-0.001, We also confirm the strong Lyalpha absorption at z=2.07. A full analysis is underway. We thank the TNG staff for the excellent support in performing these observations. This message can be quoted. //////////////////////////////////////////////////////////////////////// TITLE: GCN GRB OBSERVATION REPORT NUMBER: 4033 SUBJECT: GRB 050922B: Correction to BAT refined analysis, longer burst DATE: 05/09/24 22:54:02 GMT FROM: Jay R. Cummings at NASA/GSFC/Swift J. Cummings (GSFC/NRC), L. Barbier (GSFC), S. Barthelmy (GSFC), E. Fenimore (LANL), N. Gehrels (GSFC), D. Hullinger (UMD), H. Krimm (GSFC/USRA), C. Markwardt (GSFC/UMD), D. Palmer (LANL), A. Parsons (GSFC), T. Sakamoto (GSFC/NRC), G. Sato (ISAS), J. Tueller (GSFC) on behalf of the Swift-BAT team: We report a correction to Hullinger et al. (GCN circ. 4019). There are two additional peaks in the interval T+260 to T+275 sec besides the broader, somewhat more intense peaks reported earlier. We had mistakenly stated that there was no emission after T+120. We have no mask-weighted data from T+300 to T+330 sec, but the raw rates show no peaks in this interval. There is no significant emission after T+330 sec; in particular, there does not seem to be any emission in the BAT energy range at the times of the Xray flares reported by Godet et al. (GCN circ. 4031). The two later peaks are softer, shorter, and sharper. The total fluence from T+0 to T+300 sec is (2.6 +- 0.4) x 10^-6 ergs/cm^2 in the 15-150 keV band. The power-law photon index for the total burst is 2.1 +- 0.2. T90 is 250 +- 20 sec. Errors are 90% confidence including systematics. //////////////////////////////////////////////////////////////////////// TITLE: GCN GRB OBSERVATION REPORT NUMBER: 4040 SUBJECT: GRB 050922C: break in the lightcurve DATE: 05/09/26 20:13:40 GMT FROM: Brian Lindgren Jensen at U.of Copenhagen Johan P. U. Fynbo, Brian L. Jensen, Páll Jakobsson, Jens Hjorth, Jesper Sollerman, José María Castro Cerón (DARK, NBI), Karianne Holhjem (NOT, La Palma), Ricardo Salinas (Universidad de Concepción, Chile) report: We have obtained further imaging of the afterglow of GRB 050922C (GCN 4011, 4012, 4013) using the ALFOSC at the Nordic Optical Telescope on La Palma and DFOSC at the Danish 1.5m telescope at La Silla, Chile. We find that the early decay slope of about 1 (GCN 4012) extends to less than a day post burst, after which the decay slope steepens to about alpha=1.7+-0.3. Further observations are planned. A preliminary lightcurve can be seen at: http://www.astro.ku.dk/~brian_j/grb/grb050922.830/ //////////////////////////////////////////////////////////////////////// TITLE: GCN GRB OBSERVATION REPORT NUMBER: 4041 SUBJECT: GRB050922C - Swift UVOT preliminary analysis DATE: 05/09/26 21:13:03 GMT FROM: Caryl Gronwall at PSU/Swift-UVOT S. D. Hunsberger (PSU), F. Marshall (GSFC), S. T. Holland (GSFC), P. Brown (PSU), A. Morgan (PSU), P. Roming (PSU), and A. Cucchiara (PSU) on behalf of the Swift/UVOT teams The UVOT began observing GRB050922C at 19:57:41UT, 111 seconds after the BAT trigger (Norris et al., GCN 4013). A fading optical counterpart is detected at 21:09:33.0 -08:45:30.1. The afterglow is apparent in the UBV filters and there is a marginal detection in UVW1 which is likely due to the redward edge of the filter response overlapping the U bandpass. The UVOT magnitudes listed below are not corrected for extinction. Tmid is the time since trigger of the midpoint of the exposure(s). Filter Tmid(s) Exp(s) Mag V 115.5 99.8 14.60 +- 0.10 V 374.5 9.8 15.49 +- 0.17 V 543.5 9.8 15.99 +- 0.21 V 712.5 9.8 16.01 +- 0.21 V 4543.5 899.8 17.62 +- 0.11 V 15962.5 899.8 18.89 +- 0.21 V 28443.5 899.8 19.95 is 3sigma upper limit B 261.5 9.8 15.88 +- 0.13 B 430.5 9.8 16.36 +- 0.15 B 598.5 9.8 16.45 +- 0.16 B 767.0 8.4 16.91 +- 0.20 B 11133.5 899.8 19.12 +- 0.11 B 22648.5 899.8 20.13 +- 0.21 B 39108.5 897.3 20.70 +- 0.38 B 50681.5 899.8 20.74 +- 0.39 U 246.5 9.8 15.09 +- 0.19 U 416.5 9.7 15.69 +- 0.20 U 584.5 9.8 15.84 +- 0.21 U 753.5 9.7 16.00 +- 0.21 U 10226.5 899.8 18.58 +- 0.18 U 21749.0 900.0 19.13 +- 0.20 U 34939.5 507.6 19.88 +- 0.31 U 46660.0 814.1 19.89 +- 0.26 UVW1 487.0 68.6 17.70 +- 0.29 (co-added 10s exposures) UVW1 6233.5 651.1 19.96 +- 0.41 UVW1 17730.0 806.0 20.18 is 3sigma upper limit UVM2 473.0 68.5 18.86 is 3sigma upper limit (co-added) UVM2 5450.5 899.8 20.48 is 3sigma upper limit UVW2 487.5 58.8 19.30 is 3sigma upper limit (co-added) UVW2 11969.5 753.2 20.62 is 3sigma upper limit Magnitudes are based on preliminary zeropoints, measured in orbit, and may require further refinement. //////////////////////////////////////////////////////////////////////// TITLE: GCN GRB OBSERVATION REPORT NUMBER: 4044 SUBJECT: GRB050922C: UVES/VLT high resolution spectroscopy DATE: 05/09/28 16:55:22 GMT FROM: Silvia Piranomonte at OAR V. D'Elia, S. Piranomonte, F. Fiore (INAF-OAR), S. Covino (INAF/OABr), L.A. Antonelli, G.L. Israel, L. Stella, L. Sbordone (INAF-OAR), D. Fugazza, G. Tagliaferri (INAF/OABr), D. Malesani (SISSA), G. Chincarini (Univ. Milano-Bicocca), on behalf of the MISTICI collaboration, report: "Starting on September 22, 2005 23:28:59 UT (~3.5 hours after the GRB trigger) we have obtained high resolution spectra (R~40,000, 7.5 km/s in the observer frame) of the optical afterglow of GRB050922C (Krimm et al., GCN 4020, Rykoff et al. GCN 4011) using UVES at VLT/Kueyen. The observations consisted of 2 exposures for a total of 6000 seconds net integration covering the full spectral range 3100-10000 Angstrom, under good seeing conditions. At the time of the observations the afterglow magnitude was R~19-19.5. The resulting continuum signal to noise per resolution element spans from 10 to 20 in the 4000-7000 Angstrom range. The afterglow is clearly detected down to ~3300 Angstrom. A preliminary analysis of the data shows a very rich spectrum. We find four main systems at z=2.199, 2.077, 2.008 and 1.9985 (the first 2 systems have been previously reported by Jakobsson et al., GCN 4029, and by Piranomonte et al., GCN 4032). The latter two systems are shifted by only 950 km/s (rest frame). The strongest absorption lines of the four systems are the following. z=2.199: Lyalpha, Lybeta, OVI1032,1038, SiII1190,1193, SiII1260, FeII1260, SiII*1264, SiII*1266, OI1302, SiII1304, OI*1304, OI*1306, SiII*1309, CII1334, CII*1335, SiIV1393,1402, SiII*1533, CIV1548,1550, FeII1608, FeII*1621, AlII1670, AlIII1862,1854, FeII2344,2374,2382,2586,2600, MgII2796,2803 z=2.077: Lyalpha, OI_1302, SiII1304, CII1334, SiIV1393,1402, CIV1548,1550, FeII1608, AlII1670, AlIII1854, FeII2344,2374,2382,2586,2600 z=2.008 Lyalpha, CIV1548,1550, SiIV1402,1393 z=1.9885 Lyalpha, CIV1548,1550, SiIV1402,1393 Therefore, fine-structure lines of CII*, SiII*, OI*, FeII*, witnessing a high density environment, are detected only for the highest redshift systems, likely associated with the GRB host galaxy. A full analysis is underway. We thank Paul Vreeswijk and Poshak Gandhi of the ESO staff for the excellent support in performing these observations in service mode." This message can be cited. //////////////////////////////////////////////////////////////////////// TITLE: GCN GRB OBSERVATION REPORT NUMBER: 4046 SUBJECT: GRB 050922C: further VLT observations DATE: 05/09/28 17:17:39 GMT FROM: Stefano Covino at Brera Astronomical Observatory S. Covino, S. Piranomonte, D. Fugazza, F. Fiore, D. Malesani, G. Tagliaferri, G. Chincarini, L. Stella on behalf of the MISTICI collaboration report: We are following the decay of the optical afterglow of GRB 050922C (Norris et al., GCN 4013) with the ESO VLT+FORS1. Multi-band BVR photometry was carried out on September 24 at 00:10 UT, about 1.2 days after the high-energy event. A preliminary calibration, based on Landolt standard stars, have been performed and the OT magnitude in the R band was: R = 21.57 +/- 0.05 confirming the break in the light curve reported by Fynbo et al. (GCN 4040). This message can be quoted. //////////////////////////////////////////////////////////////////////// TITLE: GCN GRB OBSERVATION REPORT NUMBER: 4047 SUBJECT: GRB050922B: optical limit DATE: 05/09/29 13:12:14 GMT FROM: Alexei Pozanenko at IKI, Moscow G. Kornienko (UAPhO), V.Rumyantsev (CrAO), A.Pozanenko (IKI) on behalf of larger GRB follow up collaboration report: We have observed the error box of the Swift GRB050922B (Norris et al. GCN 4008) with 0.4m telescope of Ussuriysk Astrophysical Observatory (UAPhO) in R-band starting on Sep. 22 15:22 (UT). No new source was found in the GRB error box. Upper limit of a stacked image (10x60 s) calibrated against of USNO-A2.0 (R) is following: Mid time, Exposure, Filter, Limiting mag. (UT) (s) Sep.22 15:37 10x60 R 16.0 The message may be cited. //////////////////////////////////////////////////////////////////////// TITLE: GCN GRB OBSERVATION REPORT NUMBER: 4048 SUBJECT: GRB050922C: optical observation DATE: 05/09/29 13:12:57 GMT FROM: Alexei Pozanenko at IKI, Moscow M. Andreev (Institute of Astronomy), A. Pozanenko, V. Loznikov (IKI) and V.Rumyantsev (CrAO), on behalf of larger GRB follow up collaboration report: We observed OT (GCNs 4011, 4012, Rykoff et al.) of GRB050922C (GCN4013 Norris et al.) in R-band with 60 cm telescope of Peak Terskol observatory starting Sep. 22 (UT) 20:08:45 (Andreev et al. GCN4016). 61 images of 60 s exposure were taken between (UT) 20:08:45 and 21:18:20. The photometry calibration was done against USNO-A2.0. Light curve of OT may be approximated with two power laws: index alpha = -0.67 (0.02) between T0+ 0.00862d and T0+ 0.04338d, alpha = -1.24 (0.15) starting on T0+ 0.04338d with a break at ~T0+1h. Preliminary light curve can be found in http://grb.rssi.ru/GRB050922c/ The message may be cited. //////////////////////////////////////////////////////////////////////// TITLE: GCN GRB OBSERVATION REPORT NUMBER: 4095 SUBJECT: Photometric calibration of Swift/UVOT and Re-analysis of Swift/UVOT GRB 050922C data DATE: 05/10/14 19:23:02 GMT FROM: Weidong Li at UC Berkeley KAIT/LOSS W. Li, S. Jha, A. V. Filippenko, J. S. Bloom, D. Pooley, R. J. Foley, and D. A. Perley (University of California, Berkeley) report: We would like to alert the community to the photometric calibration of Swift/UVOT, for the U, B, and V filters, in an accepted paper scheduled to be published in PASP in Jan. 2006 (available as astro-ph/0505504, and significantly updated from its original version). A simple, yet detailed, step-by-step recipe for photometry is provided in Section 3.6 of the paper. In particular, we have determined optimal aperture and sky regions, and measured precise (+/- 0.01 mag) photometric zeropoints for the U, B, and V filters, based on hundreds of observations of Landolt and secondary standard stars. We also introduce a theoretically motivated single parameter (m_infinity) to correct for coincidence loss; this parameter is determined for all three filters to +/- 0.02 mag. With these calibration results, we have re-analyzed the Swift/UVOT UBV data on GRB 050922C, tabulated below. The preliminary analysis by Hunsberger et al. (GCN 4041), based on the preliminary in-orbit zeropoints, is listed for comparison whenever possible: Filter Tmid(s) Exp(s) Mag Mag(err) GCN 4041 V 160.5 99.8 14.68 +- 0.03 14.60 +- 0.10 V 289.9 9.8 15.29 +- 0.12 V 374.5 9.8 15.46 +- 0.13 15.49 +- 0.17 V 458.9 9.8 16.00 +- 0.16 V 543.5 9.8 15.94 +- 0.16 15.99 +- 0.21 V 627.9 9.8 15.89 +- 0.15 V 712.5 9.8 16.04 +- 0.17 16.01 +- 0.21 V 4543.5 899.8 17.68 +- 0.04 17.62 +- 0.11 V 15962.5 899.8 18.99 +- 0.10 18.89 +- 0.21 V 28443.5 899.8 20.26 +- 0.24 >19.95 (3sigma upper limit) V 40821.5 721.3 20.09 +- 0.22 V 52450.0 805.9 20.82 +- 0.38 V 64023.0 806.7 20.47 +- 0.29 B 261.5 9.8 15.88 +- 0.09 15.88 +- 0.13 B 345.5 9.8 16.02 +- 0.10 B 430.5 9.8 16.23 +- 0.10 16.36 +- 0.15 B 514.5 9.8 16.31 +- 0.11 B 598.5 9.8 16.46 +- 0.12 16.45 +- 0.16 B 683.5 9.8 16.64 +- 0.13 B 767.0 8.4 16.72 +- 0.14 16.91 +- 0.20 B 11133.5 899.8 19.15 +- 0.05 19.12 +- 0.11 B 22648.5 899.8 20.20 +- 0.10 20.13 +- 0.21 B 39108.5 897.3 21.14 +- 0.25 20.70 +- 0.38 B 50681.5 899.8 21.24 +- 0.26 20.74 +- 0.39 B 62254.5 899.8 20.81 +- 0.20 U 246.5 9.8 15.34 +- 0.10 15.09 +- 0.19 U 331.5 9.8 15.29 +- 0.09 U 416.5 9.7 15.80 +- 0.12 15.69 +- 0.20 U 500.5 9.8 15.97 +- 0.13 U 584.5 9.8 15.92 +- 0.12 15.84 +- 0.21 U 669.5 9.8 15.94 +- 0.12 U 753.5 9.7 15.99 +- 0.13 16.00 +- 0.21 U 10226.5 899.8 18.55 +- 0.05 18.58 +- 0.18 U 21749.0 900.0 19.48 +- 0.08 19.13 +- 0.20 U 34939.5 507.6 20.17 +- 0.17 19.88 +- 0.31 U 46660.0 814.1 20.38 +- 0.15 19.89 +- 0.26 U 58236.5 807.0 20.78 +- 0.20 U 69598.0 348.5 20.63 +- 0.27 Note the significantly improved photometric precision, especially for the long-exposure observations. Our re-analyzed UVOT photometry for GRB 050922C confirms the break in the light curve reported by Fynbo et al. (GCN 4040), Covino et al. (GCN 4046), and Andreev et al. (GCN 4048). A single power-law fit to the UVOT UBV data yields a decline index of -0.87, but the fit is relatively poor (reduced chi^2 about 3.0). Using a broken power-law fit (with parameters as in Li et al. 2003, PASP, 115, 844), we find t(break) = 2.7 +- 0.7 hours, alpha1 = -0.82 +- 0.06, alpha2 = -1.16 +- 0.14, and s = 30.5 +- 5.0, with a reduced chi^2 = 1.21. This fit can be seen at http://astron.berkeley.edu/~weidong/grb050922c.lc1.gif . If we instead force the break to be smoother (s = 1; e.g., Stanek et al., 1999, ApJ, 522, L39), we derive t(break) = 4.3 +- 0.6 h, alpha1 = -0.71 +- 0.08, and alpha2 = -1.37 +- 0.16, with a reduced chi^2 = 1.46. This fit is shown at http://astron.berkeley.edu/~weidong/grb050922c.lc2.gif . In contrast, the UBV photometry reported in GCN 4041 can accommodate a single power-law fit with a decline index of -0.84 (reduced chi^2 = 0.58). We urge the community to make use of the calibration and photometric recipe in astro-ph/0505504 for Swfit/UVOT U, B, and V data until even better calibration results are available.