//////////////////////////////////////////////////////////////////////// TITLE: GCN CIRCULAR NUMBER: 16928 SUBJECT: GRB 141020A: Swift detection of a burst with an optical counterpart DATE: 14/10/20 08:01:15 GMT FROM: Hans Krimm at NASA-GSFC S. B. Cenko (GSFC), A. P. Beardmore (U Leicester), M. M. Chester (PSU), H. A. Krimm (CRESST/GSFC/USRA), P. T. O'Brien (U Leicester) and K. L. Page (U Leicester) report on behalf of the Swift Team: At 07:48:39 UT, the Swift Burst Alert Telescope (BAT) triggered and located GRB 141020A (trigger=615873). Swift slewed immediately to the burst. The BAT on-board calculated location is RA, Dec 225.009, +55.334 which is RA(J2000) = 15h 00m 02s Dec(J2000) = +55d 20' 02" with an uncertainty of 3 arcmin (radius, 90% containment, including systematic uncertainty). The BAT light curve showed a complex structure with a duration of about 30 sec. The peak count rate was ~1700 counts/sec (15-350 keV), at ~1 sec after the trigger. The XRT began observing the field at 07:50:06.5 UT, 87.3 seconds after the BAT trigger. Using promptly downlinked data we find an uncatalogued X-ray source located at RA, Dec 224.99514, 55.31391 which is equivalent to: RA(J2000) = 14h 59m 58.83s Dec(J2000) = +55d 18' 50.1" with an uncertainty of 3.7 arcseconds (radius, 90% containment). This location is 77 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. We cannot determine whether the source is fading at the present time. A power-law fit to a spectrum formed from promptly downlinked event data gives a column density consistent with the Galactic value of 1.25 x 10^20 cm^-2 (Willingale et al. 2013). UVOT took a finding chart exposure of 150 seconds with the White filter starting 91 seconds after the BAT trigger. There is a candidate afterglow in the rapidly available 2.7'x2.7' sub-image at RA(J2000) = 14:59:59.15 = 224.99647 DEC(J2000) = +55:18:46.8 = 55.31299 with a 90%-confidence error radius of about 0.75 arc sec. This position is 4.2 arc sec. from the center of the XRT error circle. The estimated magnitude is 17.73 with a 1-sigma error of about 0.14. No correction has been made for the expected extinction corresponding to E(B-V) of 0.01. Burst Advocate for this burst is S. B. Cenko (brad.cenko 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.) //////////////////////////////////////////////////////////////////////// TITLE: GCN CIRCULAR NUMBER: 16931 SUBJECT: GRB 141020A: Enhanced Swift-XRT position DATE: 14/10/20 14:13:36 GMT FROM: Phil Evans at U of Leicester J.P. Osborne, A.P. Beardmore, P.A. Evans and M.R. Goad (U. Leicester) report on behalf of the Swift-XRT team. Using 2694 s of XRT Photon Counting mode data and 3 UVOT images for GRB 141020A, 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 = 224.99618, +55.31341 which is equivalent to: RA (J2000): 14h 59m 59.08s Dec (J2000): +55d 18' 48.3" with an uncertainty of 1.6 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: 16932 SUBJECT: GRB 141020A: Swift/UVOT Detection DATE: 14/10/20 15:59:40 GMT FROM: Paul Kuin at MSSL N.P. M. Kuin (UCL-MSSL) and S. B. Cenko (GSFC) report on behalf of the Swift/UVOT team: The Swift/UVOT began settled observations of the field of GRB 141020A 92 s after the BAT trigger (Cenko et al., GCN Circ. 16928). A source consistent with the XRT position (Osborne et al. GCN Circ. 16931) is detected in the initial UVOT exposures. The preliminary UVOT position is: RA (J2000) = 14:59:59.15 = 224.99646 (deg.) Dec (J2000) = +55:18:46.7 = 55.31297 (deg.) with an estimated uncertainty of 0.43 arc sec. (radius, 90% confidence). Preliminary detections and 3-sigma upper limits using the UVOT photometric system (Breeveld et al. 2011, AIP Conf. Proc. 1358, 373) for the early exposures are: Filter T_start(s) T_stop(s) Exp(s) Mag white 92 241 147 18.02 +/- 0.04 v 634 1409 58 18.40 +/- 0.23 b 559 753 39 18.66 +/- 0.18 u 304 554 246 18.48 +/- 0.09 w1 683 6660 471 >20.9 m2 1238 6455 413 >21.1 w2 784 11546 1196 >21.8 The magnitudes in the table are not corrected for the Galactic extinction due to the reddening of E(B-V) = 0.01 in the direction of the burst (Schlegel et al. 1998). //////////////////////////////////////////////////////////////////////// TITLE: GCN CIRCULAR NUMBER: 16933 SUBJECT: GRB 141020A: 1.4 GHZ observation DATE: 14/10/20 17:19:46 GMT FROM: Dirk Grupe at Swift-XRT D. Grupe and B. Malphrus (Space Science Center, Morehead State University) report: We observed the UVOT position of GRB 141020A (Cenko et al., GCN Circ. 16928) with the 21m Morehead State University 21m Space Tracking Antenna at 1.4 GHz at 2014-10-20 13:20 UT, 5.5 hours after the burst. We did not detect any source at the position of the burst. The minimal detactable flux density of the MSU 21m telescope is 2 Jy. //////////////////////////////////////////////////////////////////////// TITLE: GCN CIRCULAR NUMBER: 16934 SUBJECT: GRB 141020A: Swift-XRT refined Analysis DATE: 14/10/20 20:01:05 GMT FROM: Phil Evans at U of Leicester C. Pagani (U. Leicester), B. Sbarufatti (INAF-OAB/PSU), P. D'Avanzo (INAF-OAB), V. D'Elia (ASDC), V. Mangano (PSU), M.C. Stroh (PSU), D.N. Burrows (PSU), A.P. Beardmore (U. Leicester), P.A. Evans (U. Leicester) and S.B. Cenko report on behalf of the Swift-XRT team: We have analysed 9.8 ks of XRT data for GRB 141020A (Cenko et al. GCN Circ. 16928), from 72 s to 23.9 ks after the BAT trigger. The data comprise 6 s in Windowed Timing (WT) mode (taken while Swift was slewing), with the remainder in Photon Counting (PC) mode. The enhanced XRT position for this burst was given by Osborne et al. (GCN Circ. 16931). The late-time light curve (from T0+4.8 ks) can be modelled with a power-law decay with a decay index of alpha=1.10 (+0.24, -0.22). A spectrum formed from the PC mode data can be fitted with an absorbed power-law with a photon spectral index of 1.80 (+0.16, -0.13). The best-fitting absorption column is 2.3 (+3.6, -1.0) x 10^20 cm^-2, consistent with the Galactic value of 1.2 x 10^20 cm^-2 (Willingale et al. 2013). The counts to observed (unabsorbed) 0.3-10 keV flux conversion factor deduced from this spectrum is 3.5 x 10^-11 (3.7 x 10^-11) erg cm^-2 count^-1. A summary of the PC-mode spectrum is thus: Total column: 2.3 (+3.6, -1.0) x 10^20 cm^-2 Galactic foreground: 1.2 x 10^20 cm^-2 Excess significance: <1.6 sigma Photon index: 1.80 (+0.16, -0.13) If the light curve continues to decay with a power-law decay index of 1.10, the count rate at T+24 hours will be 3.1 x 10^-3 count s^-1, corresponding to an observed (unabsorbed) 0.3-10 keV flux of 1.1 x 10^-13 (1.1 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/00615873. This circular is an official product of the Swift-XRT team. //////////////////////////////////////////////////////////////////////// TITLE: GCN CIRCULAR NUMBER: 16935 SUBJECT: GRB 141020A: Swift-BAT refined analysis DATE: 14/10/20 21:06:53 GMT FROM: Hans Krimm at NASA-GSFC D. M. Palmer (LANL), S. D. Barthelmy (GSFC), W. H. Baumgartner (GSFC/UMBC), S. B. Cenko (GSFC), J. R. Cummings (GSFC/UMBC), N. Gehrels (GSFC), H. A. Krimm (GSFC/USRA), A. Y. Lien (GSFC/UMBC), C. B. Markwardt (GSFC), T. Sakamoto (AGU), M. Stamatikos (OSU), J. Tueller (GSFC), T. N. Ukwatta (LANL) (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 141020A (trigger #615873) (Cenko, et al., GCN Circ. 16928). The BAT ground-calculated position is RA, Dec = 225.054, 55.328 deg which is RA(J2000) = 15h 00m 12.9s Dec(J2000) = +55d 19' 42.3" with an uncertainty of 1.7 arcmin, (radius, sys+stat, 90% containment). The partial coding was 67%. The mask-weighted light curve shows a broad structure with multiple peaks superimposed starting at T-8 sec and continuing until T+13 sec. T90 (15-350 keV) is 15.55 +- 2.05 sec (estimated error including systematics). The time-averaged spectrum from T-5.66 to T+11.30 sec is best fit by a simple power-law model. The power law index of the time-averaged spectrum is 1.74 +- 0.18. The fluence in the 15-150 keV band is 4.6 +- 0.6 x 10^-7 erg/cm2. The 1-sec peak photon flux measured from T-0.20 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/615873/BA/ //////////////////////////////////////////////////////////////////////// TITLE: GCN CIRCULAR NUMBER: 16943 SUBJECT: GRB 141020A: Mondy optical observations DATE: 14/10/22 18:36:37 GMT FROM: Alexei Pozanenko at IKI E. Mazaeva (IKI), E. Klunko (ISTP), A. Volnova (IKI), M. Eselevich (ISTP), I. Korobtsev (ISTP), A. Pozanenko (IKI) report on behalf of larger GRB follow-up collaboration: We observed the field of the Swift GRB 141020A (Cenko et al., GCN 16928) with with AZT-33IK telescope of Sayan observatory (Mondy). We obtained several images on Oct. 20 starting on (UT) 13:28:20. At the position reported in (Kuin et al., GCN 16932) we clearly detect the afterglow of GRB 141020A (Cenko et al., GCN 16928; Kuin et al., GCN 16932). Preliminary photometry is following: date UT start t-T0 Filter Exp. OT OT_err (mid, days) (s) 2014-10-20 13:28:20 10.2672 R 45*120 22.0 0.3 The photometry is based on SDSS stars SDSS R_Lupton J150002.80+552112.7 16.749 J150012.34+552137.2 17.210 J150017.07+551830.3 18.482 J150000.59+552221.9 17.001 The finding chart can be found in http://grb.rssi.ru/GRB141020A/GRB141020A_R_AZT33IK_fc.png //////////////////////////////////////////////////////////////////////// TITLE: GCN CIRCULAR NUMBER: 16947 SUBJECT: GRB 141020A: Khureltogot optical upper limit DATE: 14/10/25 00:46:27 GMT FROM: Alexei Pozanenko at IKI E. Mazaeva (IKI), S. Schmalz (AIP), N. Tungalag (Research Center of Astronomy and Geophysics MAS), A. Volnova (IKI), I.Molotov (KIAM), A. Pozanenko (IKI) report on behalf of larger GRB follow-up collaboration: We observed the field of the Swift GRB 141020A (Cenko et al., GCN 16928) with ORI-40 telescope of Khureltogot observatory. We obtained several unfiltered images on Oct. 20 starting on (UT) 12:09:56. At the position reported in (Kuin et al., GCN 16932) we do not detect the afterglow of GRB 141020A (Cenko et al., GCN 16928; Kuin et al., GCN 16932; Mazaeva et al., GCN 16943). Preliminary photometry is following: date UT start t-T0 Filter Exp. OT UL(3sigma) (mid, days) (s) 2014-10-20 12:09:56 0.2037 clear 60*60 n/d 19.8 The photometry is based on SDSS stars reported in GCN 16943. //////////////////////////////////////////////////////////////////////// TITLE: GCN CIRCULAR NUMBER: 16948 SUBJECT: GRB 141020A: AAO optical upper limit DATE: 14/10/25 00:48:28 GMT FROM: Alexei Pozanenko at IKI E. Mazaeva (IKI), R. Inasaridze (AAO), A. Volnova (IKI), Molotov (KIAM), A. Pozanenko (IKI) report on behalf of larger GRB follow-up collaboration: We observed the field of the Swift GRB 141020A (Cenko et al., GCN 16928) with AS-32 (0.7m) telescope of Abastumani Observatory. We obtained several unfiltered images on Oct. 20 starting on (UT) 15:41:01. At the position reported in (Kuin et al., GCN 16932) we do not detect the afterglow of GRB 141020A (Cenko et al., GCN 16928; Kuin et al., GCN 16932; Mazaeva et al., GCN 16943). Preliminary photometry is following: date UT start t-T0 Filter Exp. OT UL(3sigma) (mid, days) (s) 2014-10-20 15:41:01 0.3630 clear 38*120 n/d 21.4 The photometry is based on SDSS stars reported in GCN 16943. //////////////////////////////////////////////////////////////////////// TITLE: GCN CIRCULAR NUMBER: 16976 SUBJECT: GRB 141020A: Continued Mondy Observations, optical upper limit DATE: 14/10/29 00:06:16 GMT FROM: Alexei Pozanenko at IKI, Moscow E. Mazaeva (IKI), E. Klunko (ISTP), A. Volnova (IKI), M. Eselevich (ISTP), I. Korobtsev (ISTP), A. Pozanenko (IKI) report on behalf of larger GRB follow-up collaboration: We observed the field of the Swift GRB 141020A (Cenko et al., GCN 16928) with with AZT-33IK telescope of Sayan observatory (Mondy). We obtained several images on Oct. 23 starting on (UT) 14:25:05. At the position of optical afterglow (Cenko et al., GCN 16928; Kuin et al., GCN 16932; Mazaeva et al., GCN 16943) we do not detect any object down to R=23.0. Preliminary photometry is following: date UT start t-T0 Filter Exp. OT OT_UL (3 sigma) (mid, days) (s) 2014-10-23 14:25:05 3.3309 R 80*120 n/d 23.0 The photometry is based on SDSS stars reported in GCN 16943.