//////////////////////////////////////////////////////////////////////// TITLE: GCN CIRCULAR NUMBER: 22589 SUBJECT: GRB 180404A: Swift detection of a burst with an optical afterglow DATE: 18/04/04 00:54:52 GMT FROM: David Palmer at LANL J.D. Gropp (PSU), D. N. Burrows (PSU), A. Deich (PSU), C. Gronwall (PSU), J. A. Kennea (PSU), A. Y. Lien (GSFC/UMBC), F. E. Marshall (NASA/GSFC), D. M. Palmer (LANL), T. Sakamoto (AGU) and M. H. Siegel (PSU) report on behalf of the Neil Gehrels Swift Observatory Team: At 00:45:35 UT, the Swift Burst Alert Telescope (BAT) triggered and located GRB 180404A (trigger=821881). Swift slewed immediately to the burst. The BAT on-board calculated location is RA, Dec 83.564, -37.170 which is RA(J2000) = 05h 34m 15s Dec(J2000) = -37d 10' 10" 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 50 sec. The peak count rate was ~1900 counts/sec (15-350 keV), at ~0 sec after the trigger. The XRT began observing the field at 00:47:02.1 UT, 86.5 seconds after the BAT trigger. Using promptly downlinked data we find an uncatalogued X-ray source located at RA, Dec 83.54900, -37.16824 which is equivalent to: RA(J2000) = 05h 34m 11.76s Dec(J2000) = -37d 10' 05.7" with an uncertainty of 4.2 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. We cannot determine whether the source is fading at the present time. No spectrum from the promptly downlinked event data is yet available to determine the column density. 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) = 05:34:11.63 = 83.54846 DEC(J2000) = -37:10:03.9 = -37.16774 with a 90%-confidence error radius of about 0.65 arc sec. This position is 2.3 arc sec. from the center of the XRT error circle. The estimated magnitude is 19.40 with a 1-sigma error of about 0.16. No correction has been made for the expected extinction corresponding to E(B-V) of 0.04. Burst Advocate for this burst is J.D. Gropp (jdg44 AT psu.edu). 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: 22591 SUBJECT: GRB 180404A: VLT/X-shooter redshift DATE: 18/04/04 03:15:44 GMT FROM: Daniele Malesani at Dark Cosmology Centre, Niels Bohr Inst J. Selsing (DARK/NBI), D. Malesani (DAWN/NBI and DARK/NBI), D.A. Kann (HETH/IAA-CSIC), N.R. Tanvir (Univ. Leicester) report on behalf of the Stargate consortium: We observed the optical counterpart of GRB 180404A (Gropp et al., GCN 22589) using the ESO Very Large Telescope (VLT) UT2 equipped with the X-shooter spectrograph. Observations were carried out in robotic "rapid response mode" (RRM), initiated automatically following the X-ray localization notice. In the 15-s r-band acquisition image, taken on 2018 Apr 4.0423 UT (15.3 min after the trigger), the afterglow is clearly detected, at coordinates (J2000): RA = 05:34:11.67 Dec = -37:10:04.1 We measure a magnitude R = 18.64 +- 0.1 (Vega), calibrated against nearby USNO stars, where the error is dominated by the calibration scatter. Several spectra were acquired. We report here on the exposure with mid epoch Apr 4.0495 UT (that is, 25.6 min after the GRB), with 600 s exposure time, and covering the wavelength range 3000-25000 AA. The afterglow continuum trace is clearly detected. Superposed on it, several absorption features are visible, which we identify as Al III, Fe II, Mg II, and Mg I, all at a common redshift redshift of z = 1.000. We acknowledge excellent support from the observing staff at Paranal, in particular Stephane Brillant, Luca Sbordone, Andrea Mehner, and Jose Velasquez. //////////////////////////////////////////////////////////////////////// TITLE: GCN CIRCULAR NUMBER: 22592 SUBJECT: GRB 180404A: Enhanced Swift-XRT position DATE: 18/04/04 04:57:12 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 646 s of XRT Photon Counting mode data and 1 UVOT images for GRB 180404A, 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 = 83.54906, -37.16807 which is equivalent to: RA (J2000): 05h 34m 11.77s Dec (J2000): -37d 10' 05.1" with an uncertainty of 2.0 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: 22593 SUBJECT: GRB 180404A: MASTER-OAFA OT observation DATE: 18/04/04 05:30:33 GMT FROM: Vladimir Lipunov at Moscow State U/Krylov Obs V. Lipunov, E. Gorbovskoy, V.Kornilov, N.Tyurina, A.Kuznetsov, V.Chazov, I. Gorbunov, D. Vlasenko, D.Kuvshinov, P.Balanutsa Lomonosov Moscow State University, Sternberg Astronomical Institute, Moscow State University R. Podesta, Carlos Lopez and F. Podesta Observatorio Astronomico Felix Aguilar (OAFA) Hugo Levato and Carlos Saffe Instituto de Ciencias Astronomicas, de la Tierra y del Espacio (ICATE) A. Tlatov, V.Senik, D. Dormidontov Kislovodsk Solar Station of the Pulkovo Observatory V. Yurkov, A. Gabovich, Yu. Sergienko Blagoveschensk Educational State University, Blagoveschensk O. Gres, N.M. Budnev, O. Chuvalaev, Yu.Ishmuhametova Irkutsk State University R. Rebolo, M. Serra, N. Lodieu, G. Israelian, L. Suarez-Andres The Instituto de Astrofisica de Canarias D. Buckley, S. Potter South African Astronomical Observatory MASTER-OAFA robotic telescope (MASTER-Net: http://observ.pereplet.ru) located in Argentina was pointed to the GRB180404A (Gropp et al. GCN 22589) 21 sec after notice time and 43 sec after trigger time at 2018-04-04 00:46:18 UT. On our first 10s exposure set we haven`t found optical transient with 17.4 5-sigma upper limit in SWIFT XRT error-box (ra=83.549 dec=-37.17 r=4.2"). MASTER auto-detection system detected OT with RA,Dec=5h 34m 11s.66, -37d 10m 03s.5 with unfiltered m_OT=19.8 on the summary image with 660s exposition started 2018-04-04 00:46:18.938UT, that was discovered by Swift (Gropp et al. GCN 22589) and confirmed by VLT (Selsing et al. GCN 22591) ==================================================================== The observations made on zenit distance = 42 degrees, galaxy latitude b = -30 degree. The moon (87 % bright part) below the horizon (The altitude of the Moon is -1 degree ). The sun altitude is -29.7 degree. The message may be cited. 1 //////////////////////////////////////////////////////////////////////// TITLE: GCN CIRCULAR NUMBER: 22599 SUBJECT: GRB 180404A: Swift-BAT refined analysis DATE: 18/04/04 14:33:36 GMT FROM: Takanori Sakamoto at AGU S. D. Barthelmy (GSFC), J. R. Cummings (CPI), J. D. Gropp (PSU), 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-239 to T+654 sec from the recent telemetry downlink, we report further analysis of BAT GRB 180404A (trigger #821881) (Gropp, et al., GCN Circ. 22589). The BAT ground-calculated position is RA, Dec = 83.540, -37.168 deg which is RA(J2000) = 05h 34m 09.5s Dec(J2000) = -37d 10' 05.0" with an uncertainty of 1.1 arcmin, (radius, sys+stat, 90% containment). The partial coding was 82%. The mask-weighted light curve shows a weak emission that starts at T-25 sec, followed by a bright peak which peaks at T+3 sec and ends at T+30 sec. T90 (15-350 keV) is 35.2 +- 5.3 sec (estimated error including systematics). The time-averaged spectrum from T-20.7 to T+24.2 sec is best fit by a simple power-law model. The power law index of the time-averaged spectrum is 1.95 +- 0.12. The fluence in the 15-150 keV band is 1.3 +- 0.1 x 10^-6 erg/cm2. The 1-sec peak photon flux measured from T+1.99 sec in the 15-150 keV band is 1.3 +- 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/821881/BA/ //////////////////////////////////////////////////////////////////////// TITLE: GCN CIRCULAR NUMBER: 22602 SUBJECT: GRB 180404A: Swift-XRT refined Analysis DATE: 18/04/05 00:55:03 GMT FROM: Phil Evans at U of Leicester A. Tohuvavohu (PSU), S. J. LaPorte (PSU), K.L. Page (U. Leicester), A.P. Beardmore (U. Leicester), P.A. Evans (U. Leicester), A. Melandri (INAF-OAB), P. D'Avanzo (INAF-OAB), V. D'Elia (ASDC), J.A. Kennea (PSU) and J.D. Gropp report on behalf of the Swift-XRT team: We have analysed 3.9 ks of XRT data for GRB 180404A (Gropp et al. GCN Circ. 22589), from 90 s to 52.0 ks after the BAT trigger. The data comprise 26 s in Windowed Timing (WT) mode with the remainder in Photon Counting (PC) mode. The enhanced XRT position for this burst was given by Osborne et al. (GCN Circ. 22592). The light curve can be modelled with a power-law decay with a decay index of alpha=0.5 (+nan, -nan). A spectrum formed from the PC mode data can be fitted with an absorbed power-law with a photon spectral index of 1.62 (+0.27, -0.22). The best-fitting absorption column is consistent with the Galactic value of 3.1 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 4.1 x 10^-11 (4.2 x 10^-11) erg cm^-2 count^-1. A summary of the PC-mode spectrum is thus: Total column: 3.1 (+/-5.1) x 10^20 cm^-2 Galactic foreground: 3.1 x 10^20 cm^-2 Excess significance: <1.6 sigma Photon index: 1.62 (+0.27, -0.22) If the light curve continues to decay with a power-law decay index of 0.5, the count rate at T+24 hours will be 0.011 count s^-1, corresponding to an observed (unabsorbed) 0.3-10 keV flux of 4.3 x 10^-13 (4.5 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/00821881. This circular is an official product of the Swift-XRT team. //////////////////////////////////////////////////////////////////////// TITLE: GCN CIRCULAR NUMBER: 22603 SUBJECT: GRB 180404A: LCO FTS observations DATE: 18/04/05 09:36:04 GMT FROM: Cristiano Guidorzi at Ferrara U,Italy C. Guidorzi, R. Martone (U. Ferrara), S. Kobayashi (LJMU), C.G. Mundell (U. Bath), A. Gomboc (U. Nova Gorica), I.A. Steele (LJMU) on behalf of a large collaboration report: We began observing Swift GRB180404A (Gropp et al. GCN 22589) on April 4, 09:30 UT (0.36 days post burst) with the LCO 2-m Faulkes Telescope South unit in Siding Springs in the SDSS-R filter. We marginally detect the optical afterglow (Gropp et al.; Selsing et al. GCN 22591) with the following magnitude: Mid time since GRB     Exp        Filter         Magnitude (days)                 (s) ------------------------------------------------------------- 0.37                   5x120      SDSS-R         21.3 +- 0.3 ------------------------------------------------------------- as calibrated against nearby USNO UCAC4 objects. //////////////////////////////////////////////////////////////////////// TITLE: GCN CIRCULAR NUMBER: 22605 SUBJECT: GRB 180404A: Swift/UVOT Detection DATE: 18/04/05 17:04:53 GMT FROM: Mike Siegel at PSU/Swift MOC M. H. Siegel (PSU) and J. D. Gropp (PSU) report on behalf of the Swift/UVOT team: The Swift/UVOT began settled observations of the field of GRB 180404A 90 s after the BAT trigger (Gropp et al., GCN Circ. 22589). A source consistent with the XRT position (Osborne et al. GCN Circ. 22592) is detected in the initial UVOT exposures. The preliminary UVOT position is: RA (J2000) = 05:34:11.64 = 83.54850 (deg.) Dec (J2000) = -37:10:03.9 = -37.16774 (deg.) with an estimated uncertainty of 0.50 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 (fc) 90 240 147 19.47 +/- 0.09 white 90 770 180 19.34 +/ -0.10 white 45830 52026 1028 >21.66 v 632 5179 99 >18.9 b 558 750 39 >19.4 u (fc) 302 552 246 18.95 +/- 0.12 u 303 726 265 18.95 +/ -0.14 w1 682 701 19 >17.8 m2 656 676 19 >17.4 w2 607 5094 216 19.45 +/- 0.28 The magnitudes in the table are not corrected for the Galactic extinction due to the reddening of E(B-V) = 0.04 in the direction of the burst (Schlegel et al. 1998).