GRB091020A

This page lists all entries on GRB091020A in GRBweb

Summary Fermi GBM IPN Swift GCN 10048 GCN 10050 GCN 10051 GCN 10052 GCN 10053 GCN 10054 GCN 10056 GCN 10058 GCN 10059 GCN 10060 GCN 10076 GCN 10080 GCN 10088 GCN 10090 GCN 10095 GCN 10231

Summary table
Variable Value Source
GRB_name_Fermi GRB091020900
T0 21:36:40.233 UTC Fermi_GBM
ra 175.7300° Swift
decl 50.9783° Swift
pos_error 6.47e-05° Swift
T90 24.256 s Fermi_GBM
T90_error 7.973 s Fermi_GBM
T90_start 21:36:40.233 UTC Fermi_GBM
fluence 8.35e-06 erg/cm² Fermi_GBM
fluence_error 1.50e-07 erg/cm² Fermi_GBM
redshift 1.7100
T100 38.367 s
GBM_located False
mjd 55124.900465659724 Fermi_GBM
Fermi GBM table
GRB_name_Fermi GRB091020900
trigger_name bn091020900
ra 175.7300°
decl 50.9800°
pos_error 4.22e+00°
datum 2009-10-20
t_trigger 21:36:43.817 UTC
T90 24.256 s
T90_error 7.973 s
T90_start 21:36:40.233 UTC
fluence 8.35e-06 erg/cm²
fluence_error 1.50e-07 erg/cm²
flux_1024 6.77e+00 erg/cm²/s
flux_1024_error 2.72e-01 erg/cm²/s
flux_1024_time 2.43e+00 erg/cm²/s
flux_64 1.03e+01 erg/cm²/s
flux_64_error 1.27e+00 erg/cm²/s
IPN table
GRB_name GRB091020A
ra 175.7167°
decl 50.9667°
pos_error 5.00e-02°
redshift 1.7100
Swift table
GRB_name GRB091020A
t_trigger 21:36:44 UTC
ra 175.7300°
decl 50.9783°
pos_error 6.47e-05°
T90 34.6 s
fluence 3.70e-06 erg/cm²
redshift 1.7100
GCN 10048 table
GRB_name GRB091020A
GCN_number 10048
Detection_method Swift Det
t_trigger 21:36:44 UTC
ra 175.7150°
decl 50.9720°
Circular_text TITLE: GCN CIRCULAR NUMBER: 10048 SUBJECT: GRB 091020: Swift detection of a burst with an optical afterglow DATE: 09/10/20 21:47:36 GMT FROM: David Palmer at LANL J. L. Racusin (NASA/GSFC/ORAU), S. D. Barthelmy (GSFC), A. P. Beardmore (U Leicester), D. N. Burrows (PSU), J. R. Cummings (NASA/UMBC), N. Gehrels (NASA/GSFC), C. Gronwall (PSU), S. T. Holland (CRESST/USRA/GSFC), E. A. Hoversten (PSU), J. A. Kennea (PSU), H. A. Krimm (CRESST/GSFC/USRA), N. P. M. Kuin (MSSL), W.B Landsman (GSFC), V. Mangano (INAF-IASFPA), F. E. Marshall (NASA/GSFC), P. T. O'Brien (U Leicester), K. L. Page (U Leicester), D. M. Palmer (LANL), P. Romano (INAF-IASFPA), A. Rowlinson (U Leicester), M. H. Siegel (PSU), E. Troja (NASA/GSFC/ORAU) and T. N. Ukwatta (GSFC/GWU) report on behalf of the Swift Team: At 21:36:44 UT, the Swift Burst Alert Telescope (BAT) triggered and located GRB 091020 (trigger=373458). Swift slewed immediately to the burst. The BAT on-board calculated location is RA, Dec 175.715, +50.972 which is RA(J2000) = 11h 42m 52s Dec(J2000) = +50d 58' 19" with an uncertainty of 3 arcmin (radius, 90% containment, including systematic uncertainty). The BAT light curve showed a bright peak with a second much smaller peak at T+30 s, for a total duration of about 45 sec. The peak count rate was ~5000 counts/sec (15-350 keV), at ~2 sec after the trigger. The XRT began observing the field at 21:38:05.5 UT, 80.8 seconds after the BAT trigger. XRT found a bright, fading, uncatalogued X-ray source located at RA, Dec 175.7284, +50.9788 which is equivalent to: RA(J2000) = 11h 42m 54.81s Dec(J2000) = +50d 58' 43.6" with an uncertainty of 5.0 arcseconds (radius, 90% containment). This location is 39 arcseconds from the BAT onboard position, within the BAT error circle. No event data are yet available to determine the column density using X-ray spectroscopy. The initial flux in the 2.5 s image was 3.01e-09 erg cm^-2 s^-1 (0.2-10 keV). UVOT took a finding chart exposure of 150 seconds with the White filter starting 89 seconds after the BAT trigger. There is a candidate afterglow in the rapidly available 2.7'x2.7' sub-image at RA(J2000) = 11:42:55.18 = 175.72993 DEC(J2000) = +50:58:41.9 = 50.97831 with a 90%-confidence error radius of about 0.74 arc sec. This position is 3.9 arc sec. from the center of the XRT error circle. The estimated magnitude is 15.73 with a 1-sigma error of about 0.14. No correction has been made for the expected extinction corresponding to E(B-V) of 0.02. Burst Advocate for this burst is J. L. Racusin (judith.racusin AT 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.)
GCN 10050 table
GRB_name GRB091020A
GCN_number 10050
Detection_method Swift-XRT Det
ra 175.7301°
decl 50.9784°
Circular_text TITLE: GCN CIRCULAR NUMBER: 10050 SUBJECT: GRB 091020: Enhanced Swift-XRT position DATE: 09/10/21 00:30:43 GMT FROM: Phil Evans at U of Leicester A.P. Beardmore, P.A. Evans, M.R. Goad and J.P. Osborne (U. Leicester) report on behalf of the Swift-XRT team. Using 1088 s of XRT Photon Counting mode data and 1 UVOT images for GRB 091020, 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 = 175.73005, +50.97839 which is equivalent to: RA (J2000): 11h 42m 55.21s Dec (J2000): +50d 58' 42.2" 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.
GCN 10051 table
GRB_name GRB091020A
GCN_number 10051
Detection_method Swift-BAT Det
ra 175.7270°
decl 50.9770°
Circular_text TITLE: GCN CIRCULAR NUMBER: 10051 SUBJECT: GRB 091020, Swift-BAT refined analysis DATE: 09/10/21 01:28:59 GMT FROM: Hans Krimm at NASA-GSFC D. M. Palmer (LANL), S. D. Barthelmy (GSFC), W. H. Baumgartner (GSFC/UMBC), J. R. Cummings (GSFC/UMBC), E. E. Fenimore (LANL), N. Gehrels (GSFC), H. A. Krimm (GSFC/USRA), C. B. Markwardt (GSFC/UMD), A. M. Parsons (GSFC), J. L. Racusin (NASA/GSFC/ORAU), T. Sakamoto (GSFC/UMBC), G. Sato (ISAS), M. Stamatikos (GSFC/ORAU), J. Tueller (GSFC), T. N. Ukwatta (GWU) (i.e. the Swift-BAT team): Using the data set from T-61 to T+242 sec from the recent telemetry downlink, we report further analysis of BAT GRB 091020 (trigger #373458) (Racusin, et al., GCN Circ. 10048). The BAT ground-calculated position is RA, Dec = 175.727, 50.977 deg which is RA(J2000) = 11h 42m 54.4s Dec(J2000) = +50d 58' 36.6" with an uncertainty of 1.0 arcmin, (radius, sys+stat, 90% containment). The partial coding was 43%. The mask-weighted light curve began with a small hump at T-10 sec, rising sharply to a peak at T+2 sec and decaying exponentially out to T+50 sec, with a much smaller peak superimposed at T+30 sec. T90 (15-350 keV) is 34.6 +- 2.7 sec (estimated error including systematics). The time-averaged spectrum from T-8.7 to T+38.3 sec is best fit by a simple power-law model. The power law index of the time-averaged spectrum is 1.53 +- 0.07. The fluence in the 15-150 keV band is 3.7 +- 0.1 x 10^-6 erg/cm2. The 1-sec peak photon flux measured from T+1.14 sec in the 15-150 keV band is 4.2 +- 0.3 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/373458/BA/
GCN 10052 table
GRB_name GRB091020A
GCN_number 10052
Detection_method Optical
Circular_text TITLE: GCN CIRCULAR NUMBER: 10052 SUBJECT: GRB 091020: MASTER optical transient polarimetry DATE: 09/10/21 05:15:37 GMT FROM: Vladimir Lipunov at Moscow State U/Krylov Obs E. Gorbovskoy,D.Kuvshinov, V. Lipunov, V.Kornilov, D.Kuvshinov, A.Belinski, A. Krylov, N.Shatskiy, N.Tyurina, P.Balanutsa, V.V.Chazov, Sternberg Astronomical Institute, Moscow State University A. Tlatov, A.V. Parkhomenko, D. Dormidontov Kislovodsk Solar Station of the Pulkovo Observatory V.Krushinski, I.Zalognikh, T.Kopytova, A. Popov Ural State University, Kourovka S.Yazev, K.Ivanov, N.M.Budnev Irkutsk State University V.Yurkov Blagoveschensk Educational State University, Blagoveschensk MASTER II robotic telescope (MASTER-Net: http://observ.pereplet.ru, 2x400 mm, 8 square degrees, 2x16Mpx Apogee CCD) located at Kislovodsk was pointed to the GRB 091020 (Racusin et al., GCN 10048) by internet 3422 s after the GRB time. The large delay was caused with technical problems on site. We see bright optical counterpart (~17.5 mag) on the firrst images at UVOT position. We have 130 images with 180 sec synchronous exposition each and 19.5 magnitude limit during ~4 hours in two polarization. The power low decay with alpha ~= 1.3 during 2.5 hours is observed. This is the preliminary result. The reduction is continued. The message may be cited. mailto: lipunov@sai.msu.ru
GCN 10053 table
GRB_name GRB091020A
GCN_number 10053
Detection_method Optical
Circular_text TITLE: GCN CIRCULAR NUMBER: 10053 SUBJECT: GRB 091020: NOT spectroscopic redshift DATE: 09/10/21 08:24:22 GMT FROM: Daniele Malesani at Dark Cosmology Centre, Niels Bohr Inst Dong Xu, Johan P.U. Fynbo (DARK/NBI), Nial R. Tanvir (Univ. Leicester), Jens Hjorth, Giorgos Leloudas, Daniele Malesani (DARK/NBI), Pall Jakobsson (Univ. Iceland), Paul A. Wilson (NOT and Univ. Oslo), Johannes Andersen (NBI and NOT), report on behalf of a larger collaboration: We observed the optical afterglow of GRB 091020 (Racusin et al., GCN 10048; Gorbovskoy et al., GCN 10052) with the Nordic Optical Telescope equipped with ALFOSC. We detect the afterglow with a magnitude R ~ 20, based on a nearby USNO star, with mean time Oct 21.220 UT (0.315 days after the GRB). We secured low-resolution spectroscopy (30 min exposure), covering the wavelength range 3500-9100 AA, starting on Oct. 21.231 UT. Wavelength calibration was carried out using archival frames. In a preliminary analysis we detect several absorption features, which we interpret as FeII 2344, 2374, 2382, Al III 1854, 1862, Mg II 2798 (Mg II 2803 is blended with the telluric A band), all at the common z = 1.71. There is flux in the spectrum down to ~3800 AA, setting a firm upper limit z < 2.13 to the GRB redshift.
GCN 10054 table
GRB_name GRB091020A
GCN_number 10054
Detection_method Swift-UVOT Det
ra 175.7300°
decl 50.9783°
redshift 1.7000
Circular_text TITLE: GCN CIRCULAR NUMBER: 10054 SUBJECT: GRB091020 Swift/UVOT observations DATE: 09/10/21 11:18:58 GMT FROM: Samantha Oates at MSSL S. R. Oates (MSSL-UCL) and J. L. Racusin (NASA/GSFC/ORAU) report on behalf of the Swift/UVOT team: The Swift/UVOT began observerving the field of GRB 091020 89 s after the BAT trigger (Racusin et al., GCN Circ. 10048). We detect the optical afterglow in all filters at the refined UVOT position RA, Dec 175.730, +50.97833, which is RA (J2000) 11:42:55.20 Dec (J2000) 50:58:42.0 with an estimated uncertainty of 0.5 arcsec (radius, 90% confidence). This position is consistent with the enhanced XRT position (Beardmore et al., GCN 10050). The detection in the white, v, b and u filters and the weak detection in the uvw1 filter is consistent with a redshift z~1.7, which is consistent with redshift reported by NOT (Xu, et al., GCN 10053). Preliminary magnitudes and 3 sigma upper limits are reported below. Filter T_start(s) T_stop(s) Exposure(s) Mag Err ------------------------------------------------------------------------ white 89 239 147 15.73 +/- 0.01 white 874 1024 147 17.27 +/- 0.03 v 799 819 19 16.40 +/- 0.15 b 1153 1173 19 17.27 +/- 0.15 u 707 727 19 17.06 +/- 0.16 uvw1 683 6929 490 20.29 +/- 0.35 uvm2 657 6723 490 > 20.29 uvw2 608 6314 303 > 20.27 ------------------------------------------------------------------------- The above magnitudes are not corrected for the Galactic extinction corresponding to a reddening of E_{B-V} = 0.02 mag (Schlegel et al., 1998, ApJS, 500, 525). The photometry is on the UVOT photometric system described in Poole et al. (2008, MNRAS, 383,627).
GCN 10056 table
GRB_name GRB091020A
GCN_number 10056
Detection_method Swift-XRT Other
redshift 1.7100
Circular_text TITLE: GCN CIRCULAR NUMBER: 10056 SUBJECT: GRB 091020: Swift-XRT refined analysis DATE: 09/10/21 14:08:47 GMT FROM: Andy Beardmore at U Leicester A. P. Beardmore, P. A. Evans (U. Leicester) and J. L. Racusin (NASA/GSFC/ORAU) report on behalf of the Swift-XRT team: We have analysed 13 ks of Swift-XRT data for GRB 091020 (Racusin et al., GCN Circ. 10048), from 87 s to 29.6 ks after the BAT trigger (#373458). The data comprise 350 s in Windowed Timing (WT) mode with the remainder in Photon Counting (PC) mode. The enhanced XRT position for this burst was given by Beardmore et al. (GCN. Circ 10050). The light curve shows an initial steep decay with an index of 3.7 +/-0.6, breaking at T+130 s to a shallower decay of slope 0.90 +/- 0.03, with a small flare superimposed at T+190s. A further break to a decay slope of 1.39 +/- 0.1 is apparent at T+6.6 ks. The WT mode spectrum, from 87 s to 434 s after the trigger, can be fit by an absorbed power-law with a photon index of 1.99 +/- 0.07. The best-fitting absorption column is (6.08 +1.04 -0.99) x 10^21 cm^-2, at a redshift of 1.71 (Xu et al., GCN Circ 10053), in addition to the Galactic value of 1.4 x 10^20 cm^-2 (Kalberla et al. 2005). The PC mode spectrum from 436 s to 7.3 ks (with an exposure time of 3.5 ks) has a photon index of (2.15 +0.12 -0.11) and a best-fitting intrinsic absorption column of (5.1 +1.6 -1.5) x 10^21 cm^-2. The counts to observed (unabsorbed) 0.3-10 keV flux conversion factor deduced from this spectrum is 3.4 x 10^-11 (4.4 x 10^-11) erg cm^-2 count^-1. If the light curve continues to decay at the same rate, the count rate at T+24 hours will be 0.015 count s^-1, which corresponds to an observed (unabsorbed) 0.3-10 keV flux of 4.8 x 10^-13 (6.3 x 10^-13) erg cm^-2 s^-1. The results of the XRT-team automatic analysis are available at http://www.swift.ac.uk/xrt_products/00373458. This circular is an official product of the Swift-XRT team.
GCN 10058 table
GRB_name GRB091020A
GCN_number 10058
Detection_method Other
Circular_text TITLE: GCN CIRCULAR NUMBER: 10058 SUBJECT: GRB 091020: Lick observations DATE: 09/10/21 14:24:31 GMT FROM: Daniel Perley at U.C. Berkeley D. A. Perley (UC Berkeley) reports: I observed the location of GRB 091020 (Racusin et al, GCN 10048) starting at UT 2009-10-21 12:30 using the Nickel 40-inch telescope at Lick Observatory. A series of nine exposures in R-band were acquired, followed by five exposures in I-band and an additional sequence in R-band during morning twilight. All exposures except for the first were of 180 seconds duration. The afterglow is marginally detected in individual frames and well-detected in a combined stack. Calibrating relative to five nearby SDSS standard stars transformed to R-band using the transformation equation of Lupton (2005), the estimated magnitude of the afterglow in the first R-band stack is: R = 20.91 +/- 0.13 mag (t_mid = 15.17 hr) Additional follow-up is planned if weather permits.
GCN 10059 table
GRB_name GRB091020A
GCN_number 10059
Detection_method correction
Circular_text TITLE: GCN CIRCULAR NUMBER: 10059 SUBJECT: Konus-Wind observations of GRB 091020 (correction to GCN 10057) DATE: 09/10/21 14:24:40 GMT FROM: Dmitry Frederiks at Ioffe Institute Dmitry Frederiks reports: I made a mistake in the subject line of GCN 10057: it should be "Konus-Wind observations of GRB 091020" instead of "Konus-Wind observations of GRB 091010". I apologize for the confusion.
GCN 10060 table
GRB_name GRB091020A
GCN_number 10060
Detection_method Other
Circular_text TITLE: GCN CIRCULAR NUMBER: 10060 SUBJECT: GRB 091020: Additional Lick observations DATE: 09/10/22 14:22:00 GMT FROM: Daniel Perley at U.C. Berkeley D. A. Perley (UC Berkeley) reports: Further to observations the previous night (GCN 10058), I re-observed the afterglow of GRB 091020 between UT 2009-10-22 12:23 and 13:25 using the Nickel 40-inch telescope at Lick Observatory in a series of seventeen 180 second exposures (51 minutes total integration) in R-band. The afterglow is detected in in the combined stack of all frames. Calibrating relative to the same SDSS standard stars as in GCN 10058, the estimated magnitude of the afterglow at this time is: R = 21.81 +/- 0.23 mag (t_mid = 39.29 hr) The implied average decay index over the 24 hours since the previous observation is alpha=0.87.
GCN 10076 table
GRB_name GRB091020A
GCN_number 10076
Detection_method Swift Other
Circular_text TITLE: GCN CIRCULAR NUMBER: 10076 SUBJECT: GRB 091020: Early TLS Multicolor detections, red afterglow DATE: 09/10/25 05:58:15 GMT FROM: Alexander Kann at TLS Tautenburg D. A. Kann, U. Laux, M. Roeder & H. Meusinger (TLS Tautenburg) report: We observed the afterglow of the Swift GRB 091020 (Racusin et al., GCN 10048) with the 1.34m Schmidt telescope of the Thueringer Landessternwarte Tautenburg, Germany, as soon as it had risen to an airmass of 2.2, starting 0.167 days after the GRB. We obtained 3 x 300 sec images in Z, Ic, Rc, V and B each. We detect the afterglow in all single images. As a comparison star, we use the SDSS star at: RA (J2000) = 11:42:49.2 (175.7050129) Dec. (J2000) = +51:00:52.42 (+51.01456163) For this star, using the transformation equations of Lupton (2005) (taking the mean of the two transformation equations each), and transforming the z' value to Vega mags following Fukugita (1995), we derive the magnitudes: B = 19.109 V = 17.740 Rc = 16.759 Ic = 15.927 Z = 15.563 We derive the following afterglow magnitudes: dt Filter mag dmag ____________________________________ 0.166947 Z 18.17 0.13 0.170987 Z 18.10 0.13 0.175038 Z 18.16 0.13 0.179181 Ic 18.45 0.06 0.183221 Ic 18.30 0.05 0.187260 Ic 18.32 0.05 0.191404 Rc 19.43 0.04 0.195444 Rc 19.40 0.04 0.199483 Rc 19.40 0.04 0.203627 V 19.90 0.10 0.207666 V 20.00 0.10 0.211706 V 20.06 0.10 0.215849 B 20.78 0.10 0.219889 B 20.71 0.08 0.223928 B 20.72 0.08 Using further reported magnitudes (Oates et al., GCN 10054; Gorbovskoy et al., GCN 10052, Xu et al., GCN 10053, Perley, GCN 10058, GCN 10060), we find that the Rc band light curve is very well described by a single power-law decay with alpha = 1.12 +/- 0.06, B and V light curves agree with an achromatic light curve evolution. We find a red afterglow with spectral slope beta ~ 2, and note that the Ic - Z color is very blue, this may be due to a filter mismatch between the SDSS z' filter and our Z filter. This message may be cited.
GCN 10080 table
GRB_name GRB091020A
GCN_number 10080
Detection_method Optical
Circular_text TITLE: GCN CIRCULAR NUMBER: 10080 SUBJECT: GRB 091020 : Xinglong TNT upper limit DATE: 09/10/26 12:31:47 GMT FROM: L.P. Xin at NAOC L.P. Xin, X.F. Wang, J. Wang, Y.L. Qiu, J.Y. Wei, W.K. Zheng, J.S. Deng, and C. Wu, J.Y. Hu on behalf of EAFON report: We observed the optical afterglow of GRB 091020 (e.g. Racusin et al., GCN 10048; Gorbovskoy et al., GCN 10052; Perley GCN 10060) with Xinglong TNT telescope from Oct. 22, 20:27:52(UT),1.952 days after the burst. The optical afterglow (Gorbovskoy et al., GCN 10052; Perley GCN 10060) was not detected in our combined image with a duration of 7*600 sec. The upper limit is estimated to be R~21.4 mag from USNO-B1.0 R2 magnitude, at the mean time of 1.974 days since the trigger. This message may be cited. For more information about Xinglong GRBs Follow-up observations, please visit the web-site: http://www.xinglong-naoc.org/grb/
GCN 10088 table
GRB_name GRB091020A
GCN_number 10088
Detection_method Swift Other
ra 175.7303°
decl 50.9782°
Circular_text TITLE: GCN CIRCULAR NUMBER: 10088 SUBJECT: Radio afterglow detection from GRB 091020 DATE: 09/10/26 23:00:25 GMT FROM: Dale A. Frail at NRAO Dale A. Frail (NRAO), Poonam Chandra (RMC), and Tanay Singh report on behalf of a larger collaboration: "We used the Very Large Array (VLA) to observe the field of view towards the Swift burst GRB 091020A (GCN 10048, 10050, 10051) at a frequency of 8.46 GHz. Data has been taken at 6 different epochs: October 21.66, 22.54, 22.77, 22.99, 24.60 and 26.71 UT. The average flux density of the source during the first 4 epochs was 108 +/- 25 uJy. The source has since increased in flux, rising to 230 +/- 42 uJy on Oct 24.60 UT and 436 +/- 42 uJy on Oct. 26.71 UT. Our current best-fit position is (J2000) R.A.=11:42:55.268, Dec.=+50:58:41.36 with a conservative error of +/-0.6". Further observations are planned. The National Radio Astronomy Observatory is a facility of the National Science Foundation operated under cooperative agreement by Associated Universities, Inc."
GCN 10090 table
GRB_name GRB091020A
GCN_number 10090
Detection_method Swift Other
Circular_text TITLE: GCN CIRCULAR NUMBER: 10090 SUBJECT: GRB 091020: Late TLS detection DATE: 09/10/27 02:31:21 GMT FROM: Alexander Kann at TLS Tautenburg D. A. Kann, U. Laux, M. Roeder & H. Meusinger (TLS Tautenburg) report: We observed again the afterglow of the Swift GRB 091020 (Racusin et al., GCN 10048) with the 1.34m Schmidt telescope of the Thueringer Landessternwarte Tautenburg, Germany, on the 26th of October, 5.2 days after the GRB. We obtained 11 x 600 sec images in Rc before clouds shut us down again. At the position of the afterglow, we detect a faint source in the stacked image. We derive the following afterglow magnitudes using the same comparison star as Kann et al., GCN 10076: dt Filter mag dmag ____________________________________ 5.213357 Rc 23.62 0.31 Kann et al., GCN 10076, found a single power-law decay with alpha = 1.12 +/- 0.06. Compared to the extrapolation of this fit, there is no significant evidence for a break yet. No further observations are possible due to an instrument change. This message may be cited.
GCN 10095 table
GRB_name GRB091020A
GCN_number 10095
Detection_method Fermi GBM Det
t_trigger 21:36:43.820 UTC
Circular_text TITLE: GCN CIRCULAR NUMBER: 10095 SUBJECT: GRB 091020: Fermi GBM observation DATE: 09/10/28 14:27:17 GMT FROM: Vandiver Chaplin at UAH/Fermi-GBM V.Chaplin (UAH) reports on behalf of the Fermi GBM Team: "At 21:36:43.82 UT on 20 October 2009, the Fermi Gamma-Ray Burst Monitor triggered on GRB 091020 (trigger 277767405 / 091020900), which was also detected by the Swift-BAT (Racusin et al., GCN 10048). The angle from the Fermi LAT boresight of the Swift-XRT position (Beardmore et al., GCN 10050) is 118 degrees. The GBM light curve consists of a single pulse with a duration (T90) of about 37 s (8-1000 keV). The time-averaged spectrum from T0-7.7 s to T0+21 s is best fit by a Band function with Epeak = 47.9 +/- 7.1 keV, alpha = 0.2 +/- 0.4, and beta = -1.7 +/- .02. The event fluence (8-1000 keV) in this time interval is (1.0 +/- 0.2)E-05 erg/cm^2. The 1-sec peak photon flux measured starting from T0+1.5 s in the 8-1000 keV band is 7.4 +/- 0.5 ph/s/cm^2. The spectral analysis results presented above are preliminary; final results will be published in the GBM GRB Catalog."
GCN 10231 table
GRB_name GRB091020A
GCN_number 10231
Detection_method Optical
Circular_text TITLE: GCN CIRCULAR NUMBER: 10231 SUBJECT: GRB 091020: MASTER-Net optical polarization observations DATE: 09/12/02 19:15:38 GMT FROM: Vladimir Lipunov at Moscow State U/Krylov Obs E. Gorbovskoy, V. Lipunov, V.Kornilov, A.Belinski, N.Shatskiy, N.Tyurina, D.Kuvshinov, P.Balanutsa, V.V.Chazov, P.V.Kortunov, A.Kuznetsov, D.Zemnukhov, M. Kornilov Sternberg Astronomical Institute, Moscow State University V.Krushinski, I.Zalozhnih, T.Kopytova Ural State University, Kourovka A. Tlatov, A.V. Parhomenko, D. Dormidontov Kislovodsk Solar Station of the Pulkovo Observatory K.Ivanov, S.Yazev, N.M.Budnev, E.Konstantinov, V.Lenok Irkutsk State University S.Sergienko, V.Yurkov Blagoveschensk Educational State University, Blagoveschensk MASTER II robotic telescope (MASTER-Net: http://observ.pereplet.ru, 2x400 mm, 2x 4 square degrees, 2x16Mpx Apogee CCD) located at Kislovodsk was pointed to the GRB 091020 (Racusin et al., GCN 10048) by internet 3422 s after the GRB time. The large delay was caused with technical problems on site (Gorbovskoy et al., GCN 10052). The first 7 images was taken in R-band. The exposure each images is 180s. West-telescope GRB Time OT Mag Error 1.02097639 17.93 0.22 1.07643278 17.43 0.09 1.13188834 17.78 0.14 1.18734417 18.03 0.19 1.24280056 17.87 0.15 1.29825584 17.58 0.10 1.35371584 17.94 0.12 The result of the unfiltred polarization combined images is: West-telescope GRB Time OT Mag Error (Hours) 1.604558 18.65 0.10 1.983004 18.91 0.08 2.285582 19.04 0.08 2.562864 19.28 0.11 2.84015 19.36 0.09 3.117435 19.32 0.08 3.394721 19.35 0.06 3.672004 19.23 0.10 3.949285 20.07 0.16 4.226602 20.67 0.28 4.503883 20.07 0.22 East-telescope GRB Time GRB Error (Hours) 1.604718 18.60 0.06 1.983232 18.46 0.06 2.285826 19.14 0.09 2.563109 19.11 0.09 2.84039 19.56 0.10 3.117671 19.38 0.09 3.394954 19.70 0.17 3.672234 19.53 0.11 3.949516 19.92 0.16 4.226796 20.03 0.19 4.50408 19.99 0.16 Using all our polarizated magnitudes we find that the light curve is very well described by a single power-law decay with alpha = 1.2 +/- 0.1, that is in good agreement with the following observations (Kann et al., GCN 10076) The light curve of our observations is available at http://observ.pereplet.ru/images/GRB091020/grb.html . The message may be cited. mailto: lipunov@sai.msu.ru