//////////////////////////////////////////////////////////////////////// TITLE: GCN CIRCULAR NUMBER: 21793 SUBJECT: GRB 170903A: Swift detection of a burst DATE: 17/09/03 13:00:50 GMT FROM: Kim Page at U.of Leicester C. B. Markwardt (NASA/GSFC), S. D. Barthelmy (GSFC), D. N. Burrows (PSU), J. R. Cummings (NASA/UMBC), J. A. Kennea (PSU), K. L. Page (U Leicester), J. L. Racusin (NASA/GSFC) and M. H. Siegel (PSU) report on behalf of the Swift Team: At 12:49:07 UT, the Swift Burst Alert Telescope (BAT) triggered and located GRB 170903A (trigger=770528). Swift did not slew due to an observing constraint. The BAT on-board calculated location is RA, Dec 254.512, +34.983, which is RA(J2000) = 16h 58m 03s Dec(J2000) = +34d 59' 01" with an uncertainty of 3 arcmin (radius, 90% containment, including systematic uncertainty). The BAT light curve shows a few peaks with a total duration of about 30 sec. The peak count rate was ~2000 counts/sec (15-350 keV), at ~4 sec after the trigger. Due to an observing constraint, Swift will not slew until T0+49.5 minutes. There will be no XRT or UVOT data until this time. Burst Advocate for this burst is C. B. Markwardt (Craig.Markwardt 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: 21794 SUBJECT: GRB 170903A: Swift-XRT observations DATE: 17/09/03 14:34:05 GMT FROM: Phil Evans at U of Leicester S. Campana (INAF-OAB), P.A. Evans (U. Leicester), J.P. Osborne (U. Leicester), D.N. Burrows (PSU), J.A. Kennea (PSU) and G. Tagliaferri (INAF-OAB) report on behalf of the Swift-XRT team: The XRT began observing the field of GRB 170903A at 13:41:04.6 UT, 3117.5 seconds after the BAT trigger. Using promptly downlinked data we find an uncatalogued X-ray source with an enhanced position: RA, Dec 254.5260, 34.9796 which is equivalent to: RA(J2000) = 16h 58m 06.23s Dec(J2000) = +34d 58' 46.6" with an uncertainty of 2.1 arcseconds (radius, 90% containment). This location is 43 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 (1.74 x 10^20 cm^-2, Willingale et al. 2013), with an excess column of 6.3 (+3.39/-2.89) x 10^21 cm^-2 (90% confidence). //////////////////////////////////////////////////////////////////////// TITLE: GCN CIRCULAR NUMBER: 21795 SUBJECT: GRB 170903A: Nanshan optical upper limit DATE: 17/09/03 15:01:49 GMT FROM: Dong Xu at NAOC/CAS H.X. Feng, D. Xu, Z.P. Zhu (NAOC), S.G. Ma, T.Z. Yang, J.H. Liu, P. Zong, H.B. Niu, J.Z. Liu, A. Esamdin, L. Ma (all XAO), Y.D. Hu (IAA-CSIC), Y. Qing (Geneva Observatory) report: We observed the field of GRB 170903A (Markwardt et al., GCN 21793) using the 1m telescope located at Nanshan, Xinjiang, China. We obtained 3x180s R-band frames, starting at 14:08:09 UT on 2017-09-03, i.e., 1.317 hr after the burst. No optical source is detected at the XRT position (Campana et al., GCN 21794) in the stacked image, down to a limiting magnitude of m(R)~21.3, calibrated with the nearby SDSS field. //////////////////////////////////////////////////////////////////////// TITLE: GCN CIRCULAR NUMBER: 21796 SUBJECT: GRB 170903A: Swift-BAT refined analysis DATE: 17/09/03 17:30:06 GMT FROM: Scott Barthelmy at NASA/GSFC S. D. Barthelmy (GSFC), J. R. Cummings (CPI), H. A. Krimm (NSF/USRA), A. Y. Lien (GSFC/UMBC), C. B. Markwardt (GSFC), D. M. Palmer (LANL), T. Sakamoto (AGU), M. Stamatikos (OSU), T. N. Ukwatta (LANL) (i.e. the Swift-BAT team): Using the data set from T-61 to T+242 sec from recent telemetry downlinks, we report further analysis of BAT GRB 170903A (trigger #770528) (Markwardt, et al., GCN Circ. 21793). The BAT ground-calculated position is RA, Dec = 254.532, 34.985 deg, which is RA(J2000) = 16h 58m 07.7s Dec(J2000) = +34d 59' 07.5" with an uncertainty of 1.3 arcmin, (radius, sys+stat, 90% containment). The partial coding was 30%. The mask-weighted light curve shows two slightly overlapping peaks starting at ~T-5 sec, with a maximum at ~T+1 sec, and returning to baseline at ~T+70 sec. T90 (15-350 keV) is 29.2 +- 4.4 sec (estimated error including systematics). The time-averaged spectrum from T-10.00 to T+25.70 sec is best fit by a simple power-law model. The power law index of the time-averaged spectrum is 1.94 +- 0.12. The fluence in the 15-150 keV band is 2.4 +- 0.2 x 10^-6 erg/cm2. The 1-sec peak photon flux measured from T+0.58 sec in the 15-150 keV band is 3.9 +- 0.5 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/770528/BA/ //////////////////////////////////////////////////////////////////////// TITLE: GCN CIRCULAR NUMBER: 21797 SUBJECT: GRB 170903A: Enhanced Swift-XRT position DATE: 17/09/03 19:49:46 GMT FROM: Phil Evans at U of Leicester M.R. Goad, J.P. Osborne, A.P. Beardmore and P.A. Evans (U. Leicester) report on behalf of the Swift-XRT team. Using 1379 s of XRT Photon Counting mode data and 2 UVOT images for GRB 170903A, 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 = 254.52613, +34.97887 which is equivalent to: RA (J2000): 16h 58m 6.27s Dec (J2000): +34d 58' 43.9" with an uncertainty of 1.9 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: 21799 SUBJECT: GRB 170903A: Host galaxy redshift from OSIRIS/GTC DATE: 17/09/03 23:16:16 GMT FROM: Antonio de Ugarte Postigo at IAA-CSIC A. de Ugarte Postigo (HETH/IAA-CSIC, DARK/NBI), L. Izzo (HETH/IAA-CSIC) C.C. Thoene (HETH/IAA-CSIC), D.A. Kann (HETH/IAA-CSIC), K.E. Heintz (DARK/NBI), N. Castro-Rodriguez (GRANTECAN, IAC, ULL), A. Marante (GRANTECAN) report on behalf of a larger collaboration: We have observed the field of GRB 170903A (Markwardt et al., GCN 21793) with OSIRIS at the 10.4m GTC telescope. Observations started at 20:49 UT (8.0 hrs after the burst). Observations consisted of an acquisition image in i-band and 3x900s spectra with the R1000B grism, which covers the range between 3700 and 7880 AA. The acquisition image shows a single source within the refined XRT error box (Goad et al., GCN 21797), with an i-band magnitude (AB) of 23.17 +/- 0.15. The object appears unresolved at a seeing of 0.6”. Spectroscopy of it shows a weak trace covering the complete range above 4000 AA and a single, very prominent emission feature. Due to the strength of this feature and the non-detection of any other features in the spectral range, we identify it as the unresolved [OII] 3727/3729 doublet at a redshift of 0.886, which we propose as the redshift of the host galaxy and hence of the GRB. //////////////////////////////////////////////////////////////////////// TITLE: GCN CIRCULAR NUMBER: 21800 SUBJECT: GRB 170903A: Swift-XRT refined Analysis DATE: 17/09/03 23:24:17 GMT FROM: Phil Evans at U of Leicester P. D'Avanzo (INAF-OAB), V. D'Elia (ASDC), A. D'Ai (INAF-IASFPA), B. Sbarufatti (INAF-OAB/PSU), D.N. Burrows (PSU), A. Tohuvavohu (PSU), S.L. Gibson (U. Leicester), J.P. Osborne (U. Leicester), K.L. Page (U. Leicester) and C.B. Markwardt report on behalf of the Swift-XRT team: We have analysed 7.0 ks of XRT data for GRB 170903A (Markwardt et al. GCN Circ. 21793), from 3.4 ks to 32.1 ks after the BAT trigger. The data are entirely in Photon Counting (PC) mode. The enhanced XRT position for this burst was given by Goad et al. (GCN Circ. 21797). The light curve can be modelled with a power-law decay with a decay index of alpha=0.41 (+/-0.08). A spectrum formed from the PC mode data can be fitted with an absorbed power-law with a photon spectral index of 2.22 (+0.19, -0.18). The best-fitting absorption column is 5.6 (+1.1, -1.0) x 10^21 cm^-2, in excess of the Galactic value of 1.7 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 3.7 x 10^-11 (7.2 x 10^-11) erg cm^-2 count^-1. A summary of the PC-mode spectrum is thus: Total column: 5.6 (+1.1, -1.0) x 10^21 cm^-2 Galactic foreground: 1.7 x 10^20 cm^-2 Excess significance: 9.3 sigma Photon index: 2.22 (+0.19, -0.18) If the light curve continues to decay with a power-law decay index of 0.41, the count rate at T+24 hours will be 0.048 count s^-1, corresponding to an observed (unabsorbed) 0.3-10 keV flux of 1.8 x 10^-12 (3.5 x 10^-12) erg cm^-2 s^-1. The results of the XRT-team automatic analysis are available at http://www.swift.ac.uk/xrt_products/00770528. This circular is an official product of the Swift-XRT team. //////////////////////////////////////////////////////////////////////// TITLE: GCN CIRCULAR NUMBER: 21801 SUBJECT: GRB 170903A: MITSuME Okayama upper limits DATE: 17/09/04 00:19:21 GMT FROM: Daisuke Kuroda at OAO/NAOJ D. Kuroda, K. Yanagisawa, Y. Shimizu, H. Toda (OAO, NAOJ), S. Nagayama (NAOJ), M. Yoshida (Hiroshima), K. Ohta (Kyoto) and N. Kawai(Tokyo Tech) report on behalf of MITSuME and OISTER collaboration: We observed the field of GRB 170903A (Markwardt et al., GCNC 21793) with the optical three color (g', Rc and Ic) CCD camera attached to the MITSuME 50cm telescope of Okayama Astrophysical Observatory. The observation started on 2017-09-03 12:49:43 UT (~35 sec after the burst). We did not find any new point source within the enhanced XRT error circle (Goad et al., GCNC 21797) in all the three bands. Three sigma upper limits of the OT are listed below. We used SDSS-DR8 catalog for flux calibration. #T0+[day] MID-UT T-EXP[sec] g' Rc Ic ----------------------------------------------------- 0.03712 13:42:34 5280.0 >19.4 >19.5 >18.7 ----------------------------------------------------- T0+ : Elapsed time after the burst [day] T-EXP: Total Exposure time [sec] //////////////////////////////////////////////////////////////////////// TITLE: GCN CIRCULAR NUMBER: 21805 SUBJECT: GRB 170903A: UAFO /ISON optical upper limit DATE: 17/09/04 11:01:47 GMT FROM: Alexei Pozanenko at IKI, Moscow E. Mazaeva (IKI), E. Chornaya (UAFO), A. Pozanenko (IKI), A. Volnova (IKI), A. Matkin (UAFO), I. Molotov (KIAM) report on behalf of larger GRB follow-up collaboration: We observed the field of Swift GRB 170903A (Markwardt et al., GCN 21793) with SANTEL-650 (0.65m) telescope of UAFO/ISON-Ussuriysk observatory. We obtained several unfiltered images starting on Sep. 03 (UT) 13:20:15. Within enhanced XRT position (Goad et al., GCN 21797) we do not detect any source. Preliminary photometry of a combined image is following Date UT start t-T0 Filter Exp. OT Err. UL (mid, days) (s) 2017-09-03 13:20:15 0.04847 CR 120*30 n/d n/d 20.4 Photometry is based on nearby SDSS DR9 stars SDSS_DR9_id R(Lupton) J165744.06+345751.4 16.01 J165803.01+345725.1 16.56 J165808.53+350159.7 15.58 J165749.08+345655.1 16.66 J165805.88+345230.1 16.24 //////////////////////////////////////////////////////////////////////// TITLE: GCN CIRCULAR NUMBER: 21806 SUBJECT: GRB 170903A: Swift/UVOT Upper Limits DATE: 17/09/04 11:02:08 GMT FROM: Alice Breeveld at MSSL-UCL A. A. Breeveld (UCL-MSSL) and C. B. Markwardt (NASA/GSFC) report on behalf of the Swift/UVOT team: The Swift/UVOT began settled observations of the field of GRB 170903A 3484 s after the BAT trigger (Markwardt et al., GCN Circ. 21793). No optical afterglow consistent with the XRT position (Goad et al. GCN Circ. 21797) 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) exposure and subsequent exposures are: Filter T_start(s) T_stop(s) Exp(s) Mag white_FC 3484 3634 147 >20.7 white 3484 4865 344 >21.6 v 3640 5275 393 >19.7 b 4460 4660 197 >20.5 u 4255 4455 197 >21.0 w1 4050 9664 362 >20.7 m2 3845 5482 393 >20.4 w2 4871 5071 197 >21.8 The magnitudes in the table are not corrected for the Galactic extinction due to the reddening of E(B-V) = 0.02 in the direction of the burst (Schlegel et al. 1998). //////////////////////////////////////////////////////////////////////// TITLE: GCN CIRCULAR NUMBER: 21812 SUBJECT: GRB 170903A: Fermi GBM observation DATE: 17/09/04 19:48:16 GMT FROM: Bill Paciesas at UAH F. Berlato (MPE) and C. Meegan (UAH) report on behalf of the Fermi GBM Team: "At 12:49:07.79 UT on 3 September 2017, the Fermi Gamma-Ray Burst Monitor triggered and located GRB 170903A (trigger 526135752 / 170903534), which was also detected by the Swift/BAT (Markwardt et al., GCN 21793). The GBM on-ground localization is consistent with the Swift location. The angle from the Fermi LAT boresight at the GBM trigger time is 93 degrees. The GBM light curve shows two pulses with a duration (T90) of about 25 s (50-300 keV). The time-averaged spectrum from T0-1.5 s to T0+25.5 s is adequately fit by a Comptonized model, with index -1.56 +/- 0.10 and Epeak 124 +/- 33 keV . The event fluence (10-1000 keV) in the time interval is (4.34 +/- 0.54)E-06 erg/cm^2. The 1-sec peak photon flux (10-1000 keV) measured starting from T0-1.5 s is (5.80 +/- 0.36) ph/s/cm^2. The spectral analysis results presented above are preliminary; final results will be published in the GBM GRB Catalog." //////////////////////////////////////////////////////////////////////// TITLE: GCN CIRCULAR NUMBER: 21950 SUBJECT: GRB 170903A: 15 GHz upper limits from AMI DATE: 17/10/01 20:12:06 GMT FROM: Kunal Mooley at Oxford U K. P. Mooley (Hintze Fellow, Oxford), T. D. Staley, R. P. Fender (Oxford), G. E. Anderson (Curtin), T. Cantwell (Manchester), D. Titterington, S. H. Carey, J. Hickish, Y. C. Perrott, N. Razavi-Ghods, P. Scott (Cambridge), K. Grainge, A. Scaife (Manchester) The AMI Large Array robotically triggered on the Swift alert for GRB 170903A (Markwardt et al., GCN 21793) as part of the 4pisky program, and subsequent follow up observations were obtained up to 10 days post-burst. Our observations at 15 GHz on 2017 Sep 03.57, Sep 04.79, Sep 06.82, Sep 12.66 (UT) do not reveal any radio source at the XRT location (Goad et al., GCN 21797), with 3sigma upper limits of 225 uJy, 120 uJy, 126 uJy, 99 uJy respectively. We thank the AMI staff for scheduling these observations. The AMI-GRB database is a log of all GRB follow up observations with the AMI, and is available at http://4pisky.org/ami-grb/.