//////////////////////////////////////////////////////////////////////// TITLE: GCN CIRCULAR NUMBER: 22909 SUBJECT: GRB 180706A: Swift detection of a burst with optical counterpart DATE: 18/07/06 08:43:15 GMT FROM: Scott Barthelmy at NASA/GSFC M. Stamatikos (OSU/NASA/GSFC), S. D. Barthelmy (GSFC), A. P. Beardmore (U Leicester), A. D'Ai (INAF-IASFPA), V. D'Elia (ASDC), P. A. Evans (U Leicester), J.D. Gropp (PSU), J. A. Kennea (PSU) and K. L. Page (U Leicester) report on behalf of the Neil Gehrels Swift Observatory Team: At 08:24:40 UT, the Swift Burst Alert Telescope (BAT) triggered and located GRB 180706A (trigger=846395). Swift slewed immediately to the burst. The BAT on-board calculated location is RA, Dec 181.665, +66.035, which is RA(J2000) = 12h 06m 40s Dec(J2000) = +66d 02' 05" with an uncertainty of 3 arcmin (radius, 90% containment, including systematic uncertainty). The BAT light curve shows two main peaks with a total duration of about 40 sec. The peak count rate was ~4000 counts/sec (15-350 keV), at ~28 sec after the trigger. The XRT began observing the field at 08:26:08.0 UT, 87.7 seconds after the BAT trigger. Using promptly downlinked data we find a bright, uncatalogued X-ray source with an enhanced position: RA, Dec 181.6428, 66.0366 which is equivalent to: RA(J2000) = 12h 06m 34.28s Dec(J2000) = +66d 02' 11.6" with an uncertainty of 2.4 arcseconds (radius, 90% containment). This location is 32 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 1.44 x 10^20 cm^-2 (Willingale et al. 2013). The initial flux in the 2.5 s image was 7.91e-10 erg cm^-2 s^-1 (0.2-10 keV). UVOT took a finding chart exposure of 250 seconds with the U filter starting 307 seconds after the BAT trigger. There is a candidate afterglow in the rapidly available 2.7'x2.7' sub-image at RA(J2000) = 12:06:34.34 = 181.64308 DEC(J2000) = +66:02:13.6 = 66.03712 with a 90%-confidence error radius of about 0.77 arc sec. This position is 2.9 arc sec. from the center of the XRT error circle. The estimated magnitude is 17.74 with a 1-sigma error of about 0.15. No correction has been made for the expected extinction corresponding to E(B-V) of 0.02. Burst Advocate for this burst is M. Stamatikos (Michael.Stamatikos-1 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: 22910 SUBJECT: GRB 180706A: COATLI Optical Detection DATE: 18/07/06 09:02:57 GMT FROM: Alan M. Watson at Instituto de Astronomia UNAM Alan M. Watson (UNAM), Nat Butler (ASU), Rosa L. Becerra (UNAM), Carlos Román-Zúñiga (UNAM), and William H. Lee (UNAM) report: We observed the field of the GRB 180706A (Stamatikos et al., GCN Circ. 22909) with the COATLI 50-cm telescope and interim imager (Watson et al. 2016, Proc. SPIE, 9908, 50) at the Observatorio Astronómico Nacional on the Sierra de San Pedro Mártir from 2018-07-06 08:25:26.83 (29.5 seconds after alert and 46.4 seconds after trigger) to 08:50:34, obtaining 795 seconds of exposure in the w filter. We detect an uncatalogued source in the XRT error region with a preliminary magnitude of w = 18.73 +/- 0.08 This magnitude is calibrated against the USNO-B1 catalog (adjusted to an approximate AB system) and is not corrected for Galactic extinction in the direction of the GRB. At the moment we have no information on fading. Further observations are planned. We thank the COATLI technical team (Fernando Ángeles, Oscar Chapa, Salvador Cuevas, Alejandro Farah, Jorge Fuentes, Rosalía Langarica, Fernando Quirós, and Carlos Tejada) and the staff of the Observatorio Astronómico Nacional. //////////////////////////////////////////////////////////////////////// TITLE: GCN CIRCULAR NUMBER: 22916 SUBJECT: GRB 180706A: Enhanced Swift-XRT position DATE: 18/07/06 14:46:59 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 1356 s of XRT Photon Counting mode data and 1 UVOT images for GRB 180706A, 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 = 181.64259, +66.03714 which is equivalent to: RA (J2000): 12h 06m 34.22s Dec (J2000): +66d 02' 13.7" with an uncertainty of 1.7 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: 22917 SUBJECT: GRB 180706A: Swift-XRT refined Analysis DATE: 18/07/06 15:38:54 GMT FROM: Phil Evans at U of Leicester A. D'Ai (INAF-IASFPA), A. Melandri (INAF-OAB), P. D'Avanzo (INAF-OAB), B. Sbarufatti (INAF-OAB/PSU), D.N. Burrows (PSU), A. Tohuvavohu (PSU), J.P. Osborne (U. Leicester), K.L. Page (U. Leicester), A.P. Beardmore (U. Leicester) and M. Stamatikos report on behalf of the Swift-XRT team: We have analysed 6.1 ks of XRT data for GRB 180706A (Stamatikos et al. GCN Circ. 22909), from 77 s to 17.9 ks after the BAT trigger. The data comprise 169 s in Windowed Timing (WT) mode (the first 9 s were 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. 22916). The late-time light curve (from T0+5.5 ks) can be modelled with a power-law decay with a decay index of alpha=0.58 (+0.21, -0.22). A spectrum formed from the WT mode data can be fitted with an absorbed power-law with a photon spectral index of 3.11 (+/-0.09). The best-fitting absorption column is 1.65 (+/-0.18) x 10^21 cm^-2, in excess of the Galactic value of 1.4 x 10^20 cm^-2 (Willingale et al. 2013). The PC mode spectrum has a photon index of 2.16 (+0.17, -0.16) and a best-fitting absorption column of 6.7 (+3.7, -3.3) x 10^20 cm^-2. The counts to observed (unabsorbed) 0.3-10 keV flux conversion factor deduced from this spectrum is 3.0 x 10^-11 (3.6 x 10^-11) erg cm^-2 count^-1. A summary of the PC-mode spectrum is thus: Total column: 6.7 (+3.7, -3.3) x 10^20 cm^-2 Galactic foreground: 1.4 x 10^20 cm^-2 Excess significance: 2.6 sigma Photon index: 2.16 (+0.17, -0.16) If the light curve continues to decay with a power-law decay index of 0.58, the count rate at T+24 hours will be 0.026 count s^-1, corresponding to an observed (unabsorbed) 0.3-10 keV flux of 7.7 x 10^-13 (9.3 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/00846395. This circular is an official product of the Swift-XRT team. //////////////////////////////////////////////////////////////////////// TITLE: GCN CIRCULAR NUMBER: 22919 SUBJECT: GRB 180706A: Fermi GBM observation DATE: 18/07/06 17:06:31 GMT FROM: Elisabetta Bissaldi at INFN,Bari E. Bissaldi (Politecnico & INFN Bari) reports on behalf of the Fermi GBM Team: "At 08:25:09.03 UT on 06 July 2018, the Fermi Gamma-Ray Burst Monitor triggered and located GRB 180706A (trigger 552558314 / 180706351), which was also detected by the Swift/BAT (Stamatikos et al. 2018, GCN 22909). The GBM on-ground location is consistent with the Swift position. The angle from the Fermi LAT boresight at the GBM trigger time is 60 degrees. The GBM light curve consists of multiple peaks with a duration (T90) of about 38 s (50-300 keV). The time-averaged spectrum from T0-30 s to T0+10 s is adequately fit by a power law function with an exponential high-energy cutoff. The power law index is -0.98 +/- 0.13 and the cutoff energy, parameterized as Epeak, is 53 +/- 4 keV. The event fluence (10-1000 keV) in this time interval is (3.3 +/- 0.2)E-06 erg/cm^2. The 1-sec peak photon flux measured starting from T0-2 s in the 10-1000 keV band is 4.9 +/- 0.3 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: 22921 SUBJECT: GRB 180706A: Swift-BAT refined analysis DATE: 18/07/06 18:11:57 GMT FROM: Amy Lien at GSFC T. Sakamoto (AGU), 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), M. Stamatikos (OSU), T. N. Ukwatta (LANL) (i.e. the Swift-BAT team): Using the data set from T-240 to T+962 sec from the recent telemetry downlink, we report further analysis of BAT GRB 180706A (trigger #846395) (Stamatikos et al., GCN Circ. 22909). The BAT ground-calculated position is RA, Dec = 181.687, 66.044 deg which is RA(J2000) = 12h 06m 45.0s Dec(J2000) = +66d 02' 40.1" with an uncertainty of 1.1 arcmin, (radius, sys+stat, 90% containment). The partial coding was 86%. The mask-weighted light curve shows a double-peaked structure that starts at ~T-20 s and ends at ~T+50 s. The smaller peak occurs at ~T+2 s, and the larger peak happens at ~T+28 s. T90 (15-350 keV) is 42.7 +- 8.7 sec (estimated error including systematics). The time-averaged spectrum from T-18.77 to T+50.99 sec is best fit by a simple power-law model. The power law index of the time-averaged spectrum is 1.90 +- 0.08. The fluence in the 15-150 keV band is 2.4 +- 0.1 x 10^-6 erg/cm2. The 1-sec peak photon flux measured from T+27.82 sec in the 15-150 keV band is 3.2 +- 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/846395/BA/ //////////////////////////////////////////////////////////////////////// TITLE: GCN CIRCULAR NUMBER: 22922 SUBJECT: GRB 180706A: Swift/UVOT Detection DATE: 18/07/06 18:42:37 GMT FROM: Samantha Oates at MSSL S. R. Oates (U.Warwick) and M. Stamatikos (OSU/NASA/GSFC) report on behalf of the Swift/UVOT team: The Swift/UVOT began settled observations of the field of GRB 180706A 95 s after the BAT trigger (Stamatikos et al., GCN Circ. 22909). A source consistent with the XRT position (Osborne et al. GCN Circ. 22916) and the COATLI optical detection (Watson et al. GCN Circ. 22910) is detected in the initial UVOT exposures. 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 (FC) 95 245 147 19.88 +/- 0.34 white 587 607 20 18.11 +/- 0.21 v 637 1582 117 >18.5 b 563 756 39 18.34 +/- 0.30 u 308 557 246 17.90 +/- 0.12 w1 686 1459 78 18.44 +/- 0.33 m2 661 1606 117 >18.8 w2 613 1558 117 >19.1 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: 22923 SUBJECT: GRB 180706A: TSHAO optical observations DATE: 18/07/06 21:15:30 GMT FROM: Alexei Pozanenko at IKI, Moscow A. Volnova (IKI), I. Reva (FAPHI), E. Mazaeva (IKI), A. Pozanenko (IKI), A. Kusakin (FAPHI), M. Krugov (FAPHI) report on behalf of larger GRB follow-up collaboration: We observed the field of GRB 180706A (Stamatikos et al., GCN 22909) with Zeiss-1000 telescope of Tien Shan Astronomical Observatory starting on July 06 (UT) 16:18:35. We obtained several images in R-filter. The optical afterglow (Stamatikos et al., GCN 22909; Watson et al., GCN 22910) is clearly detected in a combined image. Preliminary photometry of the afterglow is following. Date UT start t-T0 Filter Exp. OT Err. UL (mid, days) (s) 2018-07-06 16:18:35 0.35345 R 29*120 20.65 0.09 22.2 The photometry is based on several SDSS-DR12 stars. Ref.stars SDSS-DR12_id R(Lupton) J120642.39+660133.6 18.5600.025 J120649.22+660218.2 17.5190.018 J120653.24+660249.5 17.9870.017 //////////////////////////////////////////////////////////////////////// TITLE: GCN CIRCULAR NUMBER: 22924 SUBJECT: GRB 180706A: GOTO optical limits DATE: 18/07/06 23:16:00 GMT FROM: Danny Steeghs at U.of Warwick/GOTO K.Ulaczyk, D.Steeghs (U. Warwick), G.Ramsay (Armagh O.), M.Dyer (U. Sheffield), B.Gompertz, J.Lyman, A.Levan, R.Cutter (U. Warwick) K. Ackley, D.Galloway, E.Rol (Monash U.), V.Dhillon (U. Sheffield), P.O'Brien, N.Tanvir (U. Leicester), S.Poshyachinda (NARIT), D.Pollacco (U. Warwick), E.Thrane (Monash U.) report on behalf of the GOTO collaboration: In response to GRB 180706A (GCN 22909, 22910, 22916, 22917, 22919, 22921), the Gravitational-wave Optical Transient Observer (GOTO) observed the field near the XRT position as reported by Osborne et al. (GCN 22916). Observations started at 2018-07-06T21:26:42 UT (13 hours after the burst) and ended at 2018-07-06T23:49:54 and consisted of a set of 12x120s exposures in our wide L filter(400-700nm). We did not detect a significant source corresponding to the reported optical counterpart. A stacked image was used to derive a 5-sigma upper limit of V>21.6, after astrometric and photometric (APASS V) calibrations. This is consistent with the photometric evolution between the early optical detections (GCN 22910, 22922) and the TSHAO magnitude reported in Volnova et al. (GCN 22923). GOTO is operated at the La Palma observing facilities of the University of Warwick on behalf of a consortium including the University of Warwick, Monash University, Armagh Observatory, the University of Leicester, the University of Sheffield, the National Astronomical Research Institute of Thailand (NARIT) and the Instituto de Astrofisica de Canarias (IAC) https://goto-observatory.org/ //////////////////////////////////////////////////////////////////////// TITLE: GCN CIRCULAR NUMBER: 22989 SUBJECT: GRB 180706A: OSN detection DATE: 18/07/21 05:26:20 GMT FROM: Alexander Kann at IAA-CSIC D. A. Kann, L. Izzo (both HETH/IAA-CSIC) and A. Sota (IAA-CSIC) report on behalf of HETH: We observed the position of the Swift GRB 180706A (Stamatikos et al., GCN #22909) with the T150 telescope of the Observatorio Sierra Nevada (OSN) near Granada, Spain. We obtained 6 x 300 s Ic images (mean time after trigger 0.546615 days) and further 5 x 300 s Ic images a night later (mean time after trigger 1.57231 days). The afterglow (Stamatikos et al., GCN #22909; Watson et al., GCN #22910; Oates et al., GCN #22922; Volnova et al., GCN #22923) is clearly detected in the first night, and we derive Ic = 20.56 +/- 0.06 mag. It is not detected anymore in the second night to a limit of Ic > 22.5. The detection magnitude is in good agreement with the earlier measurement of Volnova et al. when typical Rc-Ic colors of GRBs are taken into account. The lead author is sorry for the long vacation this data took.