//////////////////////////////////////////////////////////////////////// TITLE: GCN CIRCULAR NUMBER: 13831 SUBJECT: Swift Trigger 535026: Galactic Transient or possible GRB DATE: 12/10/01 18:54:05 GMT FROM: Jamie A. Kennea at PSU/Swift-XRT V. D'Elia (ASDC), D. N. Burrows (PSU), J. R. Cummings (NASA/UMBC), N. Gehrels (NASA/GSFC), S. T. Holland (STScI), J. A. Kennea (PSU), C. B. Markwardt (NASA/GSFC), F. E. Marshall (NASA/GSFC), K. L. Page (U Leicester), B. Sbarufatti (INAF-OAB/PSU), M. H. Siegel (PSU), E. Sonbas (NASA/GSFC/Adiyaman Univ.) and E. Troja (NASA/GSFC/UMCP) report on behalf of the Swift Team: At 18:23:02 UT, the Swift Burst Alert Telescope (BAT) triggered and located trigger 535026. Swift slewed immediately to the location. The BAT on-board calculated location is RA, Dec 276.033, -5.667 which is RA(J2000) = 18h 24m 08s Dec(J2000) = -05d 40' 00" with an uncertainty of 3 arcmin (radius, 90% containment, including systematic uncertainty). The BAT light curve showed a weak multi-peaked structure with a duration of about 25 sec. The peak count rate was ~1200 counts/sec (15-350 keV), at ~0 sec after the trigger. The XRT began observing the field at 18:25:03.7 UT, 121.5 seconds after the BAT trigger. Using promptly downlinked data we find a bright, fading, uncatalogued X-ray source with an enhanced position: RA, Dec 276.0325, -5.6654 which is equivalent to: RA(J2000) = 18h 24m 07.80s Dec(J2000) = -05d 39' 55.5" with an uncertainty of 2.7 arcseconds (radius, 90% containment). This location is 6.0 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 in excess of the Galactic value (4.53 x 10^21 cm^-2, Kalberla et al. 2005), with an excess column of 5.5 (+4.26/-3.49) x 10^21 cm^-2 (90% confidence). The initial flux in the 2.5 s image was 5.49e-10 erg cm^-2 s^-1 (0.2-10 keV). UVOT took a finding chart exposure of 250 seconds with the U filter starting 287 seconds after the BAT trigger. No credible afterglow candidate has been found in the initial data products. The 2.7'x2.7' sub-image covers 100% of the XRT error circle. The typical 3-sigma upper limit has been about 19.2 mag. The 8'x8' region for the list of sources generated on-board covers 100% of the XRT error circle. The list of sources is typically complete to about 18.0 mag. No correction has been made for the large, but uncertain extinction expected. The classification of this trigger is uncertain, but it's quite likely that it is a galactic transient. The duration (~20 sec) and low energy emission (<25 keV) are consistent with it being a thermonuclear X-ray burst from a neutron star. The location is 3.5 degrees from the galactic plane. Burst Advocate for this burst is V. D'Elia (delia AT asdc.asi.it). 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: 13832 SUBJECT: Swift Trigger 535026: ROTSE-III Optical Limits DATE: 12/10/01 19:02:26 GMT FROM: Weikang Zheng at U.of Michigan W. Zheng (U Mich), T. Guver (Sabanci U), report on behalf of the ROTSE collaboration: ROTSE-IIId, located at the Turkish National Observatory at Bakirlitepe, Turkey, responded to Swift trigger 535026 (D'Elia et al., GCN 12831), producing images beginning 8.0 s after the GCN notice time. An automated response took the first image at 18:24:26.0 UT, 83.7 s after the burst, under fair conditions. These observations were affected by proximity to the full moon. We took 10 5-sec, and 20 20-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 the XRT error circle. Individual images have limiting magnitudes ranging from 14.4-15.4; we set the following specific limits. start UT end UT t_exp(s) mlim t_start-tGRB(s) Coadd? -------------------------------------------------------------------- 18:24:26.0 18:24:31.0 5 14.4 83.7 N 18:24:39.5 18:24:44.5 5 14.4 97.2 N 18:24:53.0 18:24:58.0 5 14.7 110.8 N 18:24:26.0 18:26:32.4 50 15.6 83.7 Y 18:26:41.1 18:27:01.1 20 15.2 218.8 N 18:27:09.6 18:27:29.6 20 15.3 247.2 N 18:27:38.1 18:27:58.1 20 15.3 275.8 N //////////////////////////////////////////////////////////////////////// TITLE: GCN CIRCULAR NUMBER: 13833 SUBJECT: GRB 121001A: possible optical counterpart DATE: 12/10/01 20:32:27 GMT FROM: Alexei Pozanenko at IKI, Moscow M. Andreev, A. Sergeev (Terskol Branch of Institute of Astronomy), A. Pozanenko (IKI) on behalf of larger GRB follow up collaboration report: We observed field of the Swift GRB 121001A = Swift trigger 535026 (D'Elia et al. GCN 13831) with Zeiss-600 telescope of Mt.Terskol observatory in R filter starting on Oct. 01 (UT) 18:39:20. In a stacked image of first 13x60 exposures we detect optical source in coordinates (J2000) RA=18 24 07.8 Dec=-05 39 55.3 which is consistent with XRT error circle (GCN 13831). The optical source is absent in DSS2 plates. However at that time we cannot determine if the source is variable. Preliminary photometry of the source against nearby USNO B1.0 stars is 19.5R. Finding chart can be found at http://grb.rssi.ru/GRB121001A/GRB121001A_R_Z600_fc_1.png //////////////////////////////////////////////////////////////////////// TITLE: GCN CIRCULAR NUMBER: 13834 SUBJECT: GRB 121001A: MASTER optical observations DATE: 12/10/01 23:01:39 GMT FROM: Vladimir Lipunov at Moscow State U/Krylov Obs E. Gorbovskoy, V. Lipunov, V.Kornilov, D.Kuvshinov, A.Belinski, N.Tyurina, N.Shatskiy, P.Balanutsa, D.Zimnukhov, A.Kuznetsov, V.V.Chazov, A.Sankovich, D.Denisenko Moscow Lomonosov State University, Sternberg Astronomical Institute, K.Ivanov, S.Yazev, N.M.Budnev, O.Gres, O.Chuvalaev, V.A.Poleshchuk Irkutsk State University V.Yurkov, Yu.Sergienko, D.Varda, E.Sinyakov Blagoveschensk Educational State University, Blagoveschensk A. Tlatov, A.V. Parhomenko, D. Dormidontov, V.Sennik Kislovodsk Solar Station of the Pulkovo Observatory V.Krushinski, I.Zalozhnich, A. Popov, A. Bourdanov, A. Punanova Ural Federal University Hugo Levato and Carlos Saffe Instituto de Ciencias Astronomicas, de la Tierra y del Espacio (ICATE) Claudio Mallamaci, Carlos Lopez and Federico Podest Observatorio Astronomico Felix Aguilar (OAFA) MASTER II robotic telescope (MASTER-Net: http://observ.pereplet.ru) located in Kislovodsk was pointed to the Swift GRB121001A 43 s after notice time and 209 sec after GRB time at 2012-10-01 18:26:31 UT in a two polarizations. We haven`t found optical transient within SWIFT error-box (D'Elia et al. GCN 13831) on our first (20 s exposure) set. The 5-sigma upper limit has been about 15.8 mag Observations were carried out under the full moon and on high zenith distance (~70 deg). Also a high stars density complicates the analysis. The data reduction is continued. The message may be cited. //////////////////////////////////////////////////////////////////////// TITLE: GCN CIRCULAR NUMBER: 13835 SUBJECT: Swift Trigger 535026: Optical decay confirmation with IAC80 and BOOTES-2/TELMA. DATE: 12/10/02 00:35:53 GMT FROM: Javier Gorosabel at IAA-CSIC J.C. Tello (IAA-CSIC), R. Gimeno (IAC), J. Gorosabel (IAA-CSIC), M. Jelinek (IAA-CSIC), R. Sanchez-Ramirez (IAA-CSIC), A.J. Castro-Tirado (IAA-CSIC), report on behalf of a larger collaboration: "We observed the field of Swift trigger 535026 (D'Elia et al. GCN 13831) with the 82cm IAC80 telescope at the Observatorio del Teide, Tenerife, Spain. The observations were carried out in the I-band on 19:38--21:32 UT (starting 1.25 hours post burst) with a total exposure time of 18x240s. An optical source placed at RA(J2000)=18:24:07.88 DEC(J2000)=-05:39:55.0 (+/-0.9") shows a clear decay from I~19 to I~20 (Vega), against the USNO B1.0 catalogue. The coordinates of this source are consistent with the XRT error circle (GCN 13831) and the possible optical counterpart reported by Andreev et al. (GCN Circ. 13833). The object is also detected with the BOOTES-2/TELMA telescope at I~19.7 (Vega) at 20:49--21:52 UT Oct. 1." //////////////////////////////////////////////////////////////////////// TITLE: GCN CIRCULAR NUMBER: 13836 SUBJECT: Swift Trigger 535026 is GRB 121001A: Swift-BAT refined analysis DATE: 12/10/02 01:14:20 GMT FROM: Craig Markwardt at NASA/GSFC T. Sakamoto (AGU), S. D. Barthelmy (GSFC), W. H. Baumgartner (GSFC/UMBC), J. R. Cummings (GSFC/UMBC), V. D'Elia (ASDC), E. E. Fenimore (LANL), N. Gehrels (GSFC), H. A. Krimm (GSFC/USRA), C. B. Markwardt (GSFC), D. M. Palmer (LANL), G. Sato (ISAS), M. Stamatikos (OSU), J. Tueller (GSFC), T. N. Ukwatta (MSU) (i.e. the Swift-BAT team): Using the data set from T-60 to T+243 sec from the recent telemetry downlink, we report that Swift trigger #535026 (D'Elia, et al., GCN Circ. #13831) is consistent with being a GRB. We follow the designation of previous authors for the trigger as GRB 121001A (Zheng et al. GCN Circ. #13832; Andreev et al. GCN Circ. #13833; Gorbovskoy et al. GCN Circ. #13834). Based on the analysis below, the burst has strong emission up to 100 keV, and a FRED-like light curve profile with duration longer than 100sec. Neither of these is consistent with a neutron star thermonuclear X-ray burst (which would be blackbody emission with temperature kT ~ few keV). The soft emission we reported in GCN Circ. #535026 is associated with an X-ray burst from HETE J1900.1-2455, another active X-ray binary in the BAT field of view. Thus, we conclude that trigger #535026 is consistent with a GRB interpretation. We report further BAT analysis of GRB 121001A (trigger #535026). The BAT ground-calculated position is RA, Dec = 276.029, -5.667 deg which is RA(J2000) = 18h 24m 06.9s Dec(J2000) = -05d 40' 01.0" with an uncertainty of 2.4 arcmin, (radius, sys+stat, 90% containment). The partial coding was 100%. The light curve shows a FRED-like profile, starting near T-25sec, rising to maximum at T-15sec, and gradually decaying to background near T+130sec. T90 (15-350 keV) is 147 +- 24 sec (estimated error including systematics). The time-averaged spectrum from T-30 to T+143 sec is best fit by a simple power-law model. The power law index of the time-averaged spectrum is 1.34 +- 0.15. The fluence in the 15-150 keV band is 1.7 +- 0.2 x 10^-6 erg/cm2. The 1-sec peak photon flux measured from T+3.27 sec in the 15-150 keV band is 0.5 +- 0.1 ph/cm2/sec. All the quoted errors are at the 90% confidence level. The BAT results for this circular represent a limited time window. The results may be revised if additional downlinked data show more emission. The results of the batgrbproduct analysis are available at http://gcn.gsfc.nasa.gov/notices_s/535026/BA/ //////////////////////////////////////////////////////////////////////// TITLE: GCN CIRCULAR NUMBER: 13837 SUBJECT: GRB 121001A: Enhanced Swift-XRT Position DATE: 12/10/02 07:12:24 GMT FROM: Phil Evans at U of Leicester P.A. Evans (U. Leicester) reports on behalf of the Swift-XRT team: Using 2340 s of XRT Photon Counting mode data and 3 UVOT images of GRB 121001A (D'Elia et al., GCN Circ. 13831), 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 = 276.03227, -5.66587 which is equivalent to: RA (J2000): 18 24 07.74 Dec (J2000): -05 39 57.1 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 is an official product of the Swift-XRT team. //////////////////////////////////////////////////////////////////////// TITLE: GCN CIRCULAR NUMBER: 13838 SUBJECT: GRB 121001A: Swift-XRT refined Analysis DATE: 12/10/02 12:29:53 GMT FROM: Valerio D'Elia at ASDC V. D'Elia (ASDC) and P. Evans (U. Leicester) report on behalf of the Swift-XRT team: We have analysed 6.7 ks of XRT data for GRB 121001A (D'Elia et al. GCN Circ. 13831), from 111 s to 41.8 ks after the BAT trigger. The data comprise 93 s in Windowed Timing (WT) mode (the first 8 s were taken while Swift was slewing) with the remainder in Photon Counting (PC) mode. Using 2340 s of PC mode data and 3 UVOT images, we find an enhanced XRT position (using the XRT-UVOT alignment and matching UVOT field sources to the USNO-B1 catalogue): RA, Dec = 276.03227, -5.66587 which is equivalent to: RA (J2000): 18h 24m 07.74s Dec(J2000): -05d 39' 57.1" with an uncertainty of 1.8 arcsec (radius, 90% confidence). The light curve can be modelled with a power-law decay with a decay index of alpha=1.30 (+/-0.04). A spectrum formed from the PC mode data can be fitted with an absorbed power-law with a photon spectral index of 1.28 (+0.25, -0.24). The best-fitting absorption column is 7.6 (+2.4, -2.0) x 10^21 cm^-2, in excess of the Galactic value of 4.5 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 7.6 x 10^-11 (9.9 x 10^-11) erg cm^-2 count^-1. A summary of the PC-mode spectrum is thus: Total column: 7.6 (+2.4, -2.0) x 10^21 cm^-2 Galactic foreground: 4.5 x 10^21 cm^-2 Excess significance: 2.5 sigma Photon index: 1.28 (+0.25, -0.24) If the light curve continues to decay with a power-law decay index of 1.30, the count rate at T+24 hours will be 2.1 x 10^-3 count s^-1, corresponding to an observed (unabsorbed) 0.3-10 keV flux of 1.6 x 10^-13 (2.1 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/00535026. This circular is an official product of the Swift-XRT team. //////////////////////////////////////////////////////////////////////// TITLE: GCN CIRCULAR NUMBER: 13839 SUBJECT: GRB 121001A: Swift/UVOT Upper Limits DATE: 12/10/02 17:12:45 GMT FROM: Frank Marshall at GSFC F. E. Marshall (NASA/GSFC) and V. D'Elia (ASDC) report on behalf of the Swift/UVOT team: The Swift/UVOT began settled observations of the field of GRB 121001A 130 s after the BAT trigger (D'Elia et al., GCN Circ. 13831). No optical afterglow consistent with the optical position (Tello et al. GCN Circ. 13835) is detected in the initial UVOT exposures. Preliminary 3-sigma upper limits using the UVOT photometric system (Breeveld et al. 2011, AIP Conf. Proc. 1358, 373) for the first finding chart (FC) exposures and subsequent exposures are: Filter T_start(s) T_stop(s) Exp(s) Mag white_FC 130 280 147 >21.0 u_FC 288 538 246 >20.0 white 130 7415 824 >22.4 v 618 6390 352 >20.2 b 544 7210 526 >21.2 u 288 7005 756 >20.7 w1 668 6800 529 >20.4 w2 767 7608 439 >21.1 The magnitudes in the table are not corrected for the Galactic extinction due to the reddening of E(B-V) = 1.36 in the direction of the burst (Schlegel et al. 1998). //////////////////////////////////////////////////////////////////////// TITLE: GCN CIRCULAR NUMBER: 13840 SUBJECT: GRB 121001A: GROND Afterglow Confirmation DATE: 12/10/02 23:46:14 GMT FROM: Alexander Kann at TLS Tautenburg S. Schmidl (TLS Tautenburg), D. A. Kann (MPE Garching), S. Klose (TLS Tautenburg), and J.Greiner (MPE Garching) report on behalf of the GROND team: We observed the field of GRB 121001A (Swift trigger 535026, D'Elia et al., GCN # 13831) simultaneously in g'r'i'z'JHK with GROND (Greiner et al. 2008, PASP 120, 405) mounted at the 2.2 m MPG/ESO telescope at La Silla Observatory (Chile). Observations started on October 01, 2012, at 23:37 UT, 5.23 hr after the GRB trigger. They were performed at an average seeing of 2".7 (in r') and at an average airmass of 1.2. We found a source in the z', J, H and K bands at coordinates (J2000): RA = 18:24:07.84 Dec. = -05:39:55.30 with an error of 0".3 in each coordinate. This is consistent with the afterglow positions reported by Andreev et al. (GCN # 13833) and Tello et al. (GCN # 13835), but slightly outside the refined XRT position reported by Evans et al. (GCN # 18837). Based on 1380 s of total exposures in g'r'i'z' (mean time 0.2415 days after the trigger) and 1920 s in JHK (mean time 0.2363 days after the trigger) we estimate preliminary AB magnitudes (upper limits are 3 sigma) of g' > 23.6, r' > 22.9, i' > 22.2, z' = 21.7 +/- 0.2, J = 19.5 +/- 0.4, H = 18.4 +/- 0.1 and K = 17.94 +/- 0.06. Given magnitudes are calibrated against GROND zeropoints in the optical as well as 2MASS field stars in the NIR and are not corrected for the high Galactic foreground reddening of E_(B-V) ~ 1.3 mag (Schlegel et al. 1998). Our r'- and i'-band non-detections vs. the detections reported by Andreev et al. (GCN # 13833) and Tello et al. (GCN # 13835) confirm that this is the afterglow of GRB 121001A. Furthermore, the bright source we detect in K is not detected in 2MASS, while nearby sources of similar magnitude are clearly visible in 2MASS.