Gamma-ray Burst 180728

(All information courtesy of the instrument teams.)

Previous IAU Circulars

• none

• GCN Circular #23056
  D. Svinkin, S. Golenetskii, R. Aptekar, D. Frederiks, A. Kozlova, and T. Cline on behalf of the Konus-Wind team,
  K. Hurley, on behalf of the IPN,
  A. Goldstein, M. S. Briggs, and C. Wilson-Hodge on behalf of the Fermi GBM team,
  A. von Kienlin, X. Zhang, A. Rau, V. Savchenko, E. Bozzo, and C. Ferrigno, on behalf of the INTEGRAL SPI-ACS GRB team,
  and
  S. Barthelmy, J. Cummings, H. Krimm, and D. Palmer, on behalf of the Swift-BAT team, report:
  The short-duration GRB 180728B was detected by Fermi (GBM; trigger 554505003), INTEGRAL (SPI-ACS), Konus-Wind, and Swift (BAT), at about 76199 s UT (21:09:59). The burst was outside the coded field of view of the BAT.
  We have triangulated it to a preliminary, 3 sigma error box whose coordinates are:

    ---------------------------------------------
     RA(2000), deg                 Dec(2000), deg
    ---------------------------------------------
    Center:
     222.078 (14h 48m 19s) +15.942 (+15d 56' 32")
    Corners: 
     221.253 (14h 45m 01s) +11.625 (+11d 37' 29")
     221.537 (14h 46m 09s) +11.383 (+11d 23' 00")
     222.836 (14h 51m 21s) +20.467 (+20d 28' 01")
     222.533 (14h 50m 08s) +20.757 (+20d 45' 26")
    ---------------------------------------------
  

  The error box area is 2.88 sq. deg, and its maximum dimension is 9.423 deg (the minimum one is 18.8 arcmin). The Sun distance was 88 deg.
  This box may be improved.
  A triangulation map is posted at < href="http://www.ioffe.ru/LEA/GRBs/GRB180728_T76197/IPN">http://www.ioffe.ru/LEA/GRBs/GRB180728_T76197/IPN
  The time history and spectrum will be given in forthcoming GCN Circulars.
• GCN Circular #23057
  R. Hamburg, P. Veres, and C. Meegan (UAH) report on behalf of the Fermi GBM Team:
  "At 21:09:58.91 UT on 28 July 2018, the Fermi Gamma-Ray Burst Monitor triggered and located GRB 180728B (trigger 554505003 / 180728882). which was also localized by IPN (GCN 23056).
  The angle from the Fermi LAT boresight at the GBM trigger time is 96 degrees.
  The GBM light curve shows a structured spike with a duration (T90) of about 0.6 s (50-300 keV). The time-averaged spectrum from T0-0.06 s to T0+0.38 s is best fit by a power law function with an exponential high-energy cutoff. The power law index is -0.18 +/- 0.15 and the cutoff energy, parameterized as Epeak, is 504 +/- 61 keV.
  The event fluence (10-1000 keV) in this time interval is (1.36 +/- 0.90)E-06 erg/cm^2. The 64-ms peak photon flux measured starting from T0+0.19 s in the 10-1000 keV band is 16.5 +/- 1.7 ph/s/cm^2.
  The spectral analysis results presented above are preliminary; final results will be published in the GBM GRB Catalog."
• GCN Circular #23060
  D. Svinkin, S. Golenetskii, R. Aptekar, D. Frederiks, M. Ulanov, A. Tsvetkova, A. Lysenko, A.Kozlova, and T. Cline on behalf of the Konus-Wind team, report:
  The short-duration GRB 180728B (IPN triangulation Svinkin et al., GCN Circ. 23056) triggered Konus-Wind at T0=76197.29 s UT (21:09:57.290).
  The burst light curve shows a multi-peaked structure which starts at ~T0-0.2 s and has a total duration of ~0.4 s. The emission is seen up to ~5 MeV.
  The Konus-Wind light curve of this GRB is available at http://www.ioffe.ru/LEA/GRBs/GRB180728_T76197/
  As observed by Konus-Wind, the burst had a fluence of 1.35(-0.22,+0.25)x10^-6 erg/cm2, and a 16-ms peak flux, measured from T0-0.004 s, of 9.59(-3.38,+3.55)x10^-6 erg/cm2/s (both in the 20 keV - 10 MeV energy range).
  The time-averaged spectrum of the burst (measured from T0 to T0+0.192 s) is best fit in the 20 keV - 10 MeV range by a power law with exponential cutoff model: dN/dE ~ (E^alpha)*exp(-E*(2+alpha)/Ep) with alpha = 0.25(-0.61,+0.88) and Ep = 404(-74,+118) keV (chi2 = 15/17 dof). Fitting by a GRB (Band) model yields the same alpha and Ep, and an upper limit on the high energy photon index: beta < -2.2 (chi2 = 15/16 dof).
  All the quoted errors are at the 90% confidence level. All the quoted values are preliminary.
• GCN Circular #23065
  V. Lipunov, E. Gorbovskoy, P.Balanutsa, N.Tiurina, D.Vlasenko, V.Kornilov, A.Kuznetsov, V.Chazov, I. Gorbunov, D.Zimnukhov, D.Kuvshinov, V.Vladimirov, Lomonosov Moscow State University,SAI
  D.Svinkin (Ioffe Institute, StPetersburg, Russia)
  D. Buckley, South African Astronomical Observatory (SAAO)
  R. Rebolo, M. Serra, N. Lodieu, G. Israelian, L. Suarez-Andres The Instituto de Astrofisica de Canarias (IAC)
  A. Tlatov, V.Senik, D. Dormidontov Kislovodsk Solar Station of the Pulkovo Observatory
  R. Podesta, F. Podesta, C. Lopez, C.Francile Observatorio Astronomico Felix Aguilar (OAFA)
  H.Levato, Instituto de Ciencias Astronomicas, de la Tierra y del Espacio (ICATE)
  O. Gres, N.M.Budnev , Yu.Ishmuhametova Irkutsk State University (ISU)
  A. Gabovich, V. Yurkov, Yu. Sergienko Blagoveschensk Educational State University (BSPU)
  MASTER-SAAO robotic telescope (MASTER-Net: http://observ.pereplet.ru) located in SAAO was starting survey on the IPN GRB180728B error-box (Svinkin et al., GCN Circ #23056; Hamburg et al., GCN Circ #23057) 14269 sec after notice time and 70698 sec after trigger time at 2018-07-29 16:48:15 UT. The 5-sigma upper limit on our first (180s exposure) set is about 18mag.
  The typical limit of coadded images is about 20 mag. We marginally found one candidate to uncataloged object source near PGC052927 galaxy:
  MASTER OT J144922.8+164418.2
  RA,DEC = 14h 49m 22.8s +16d 44' 18.2" error = 0.7 arcsec mag = 19.7; The offset from galaxy is 10.8W and 22.2N arcsec.
  ====================================================================
  The observations made on zenit distance = 50 degrees, galactic latitude b = 61 degree. The moon (97 % bright part) below the horizon (The altitude of the Moon is -8 deg. Observations started at twilight. The sun altitude is -11.1 deg. The object can be observed till sunrise at 2018-07-30 05:26:48.
  The covered map is available at http://master.sai.msu.ru/static//IPN/db/GRB180728.88/img/ligo_master_2018-07-30-16-09-11.eb.zoom.1.png
  We reobserved possible transient on the next night starting 2018-07-30 16:57:46 UT. We do not find the object brighter than 20.5 .
  
• GCN Circular #23069
  D.Steeghs, J.Lyman (U. Warwick), G.Ramsay (Armagh O.), M.Dyer (U. Sheffield), K.Ulaczyk, A.Levan, R.Cutter (U. Warwick) K. Ackley, D.Galloway, E.Rol (Monash U.), V.Dhillon (U. Sheffield), P.O'Brien, R.Starling (U. Leicester), S.Poshyachinda (NARIT), D.Pollacco (U. Warwick), E.Thrane (Monash U.)
  report on behalf of the GOTO collaboration:
  In response to the short-duration GRB 180728B (GCN 23056, 23057, 23060), the Gravitational-wave Optical Transient Observer (GOTO) observed the IPN triangulation region as reported in Svinkin et al. (GCN 23056).
  Observations were spread over four telescope array pointings, beginning 2018-07-29T21:24 UT (24.25 hours after the burst) and employ sets of 3x120s exposures in our wide L filter(400-700nm). These fields were repeated on 2018-07-30 to permit difference imaging analysis. Conditions were affected by dust, typically achieved a 5 sigma limiting magnitude of V=19.8-20.1 on 2018-07-29 and V=20.4-20.6 on 2018-07-30.
  We made use of the GLADE galaxy catalog to pay particular attention to possible source candidates near galaxies within 200 Mpc. We find no significant sources that could be credibly associated with the GRB.
  Furthermore, we see no evidence for a source at the position reported in Lipunov et al. (GCN 23065), noting that our observations started 4.7 hours later than the MASTER observations and thus the source may have faded below our detection limit by then.
  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/
• GCN Circular #23379
  Authors: Michael W. Coughlin (Caltech), Tomás Ahumada (UMD), S. Bradley Cenko (NASA GSFC), Shaon Ghosh (UWM), Virginia Cunningham (UMD), Eric C. Bellm (UW), Mansi M. Kasliwal (Caltech) and Leo P. Singer (NASA GSFC) on behalf of the ZTF and GROWTH collaborations
  We observed the localization region of the short GRB 180728B (trigger 554505003) detected by the Gamma-Ray Burst Monitor (GBM) on the Fermi satellite with the Palomar 48-inch telescope equipped with the 47 square degree Zwicky Transient Facility (ZTF) camera. The observations taken during the night of July 29 did not cover the IPN updated localization of GRB 180628B available the next day. The IPN region was observed with ZTF beginning at 04:06 UT on 2018 July 30 (30:58 hours after the trigger time). The observations covered 334 square degrees, corresponding to ~ 76% of the probability enclosed in the localization region.
  The images were processed through the ZTF reduction and image subtraction pipelines at IPAC to search for potential counterparts. 7 high-significance transient and variable candidates were identified by our pipeline in the area observed, all of which had previous detections with ZTF in the days and weeks prior to the GRB trigger time (e.g., supernovae, active galactic nuclei). No viable optical counterparts were thus identified.
  The median 5-sigma upper limit for an isolated point source in our images was r > 18.7 and g > 20. mag for the observations made on July 30.
  ZTF is a project led by PI S. R. Kulkarni at Caltech (see ATEL #11266), and includes IPAC; WIS, Israel; OKC, Sweden; JSI/UMd, USA; UW, USA; DESY, Germany; NRC, Taiwan; UW Milwaukee, USA and LANL USA. ZTF acknowledges the generous support of the NSF under AST MSIP Grant No 1440341. Alert distribution service provided by DIRAC@UW. Alert filtering is being undertaken by the GROWTH marshal system, supported by NSF PIRE grant 1545949.