Gamma-ray Burst 170117A

(All information courtesy of the instrument teams.)

Previous IAU Circulars

• none

• GCN Circular #20481
  Swift Trigger #733426: possible detection of a burst or transient
  D. M. Palmer (LANL) reports on behalf of the Swift team:
  At 2017-01-17 03:37:48 UT, the Swift Burst Alert Telescope (BAT) took a series of waiting mode images that showed peaks of marginal significance, recognized in further ground analysis as a possible unknown source or GRB (Triggers #733426-#733430, GRB 170117A). The most significant image showed a peak at a BAT on-board calculated location RA, Dec 61.589, +21.743 which is

   
    RA(J2000) = 04h 06m 21s
    Dec(J2000) = +21d 44' 35"
  

  with an uncertainty of 3 arcmin (radius, 90% containment, including systematic uncertainty). The onboard images show a maximum flux level over the T+240 s to T+304 s time interval, while the maximum significance is found over the T+0 s to T+672 s image covering the entire pointing interval.
  Due to the marginal significance (maximum 6.5 sigma) of the image peak detection, the reality of this detection is uncertain. Its several-minute or longer duration is longer than usual for a GRB, but its distance from the Galactic plane (l,b ~ 172,-22) would e unusual for a Galactic transient. Therefore, both the reality and category of this source are uncertain.
  A Swift Target of Opportunity follow-up has been requested.
• GCN Circular #20481
  P. A. Evans (U. Leicester) reports on behalf of the Swift team:
  Swift has initiated a ToO observation of the Swift/BAT GRB 170117A. Automated analysis of the XRT data will be presented online at http://www.swift.ac.uk/ToO_GRBs/00020728
  Any uncatalogued X-ray sources detected in this analysis will be reported on this website and via GCN COUNTERPART notices. These are not necessarily related to the Swift/BAT event. Any X-ray source considered to be a probable afterglow candidate will be reported via a GCN Circular after manual consideration.
  Details of the XRT automated analysis methods are detailed in Evans et al. (2007, A&A, 469, 379; 2009, MNRAS, 397, 1177 and 2014, ApJS, 210, 8).
  This circular is an official product of the Swift-XRT team.
• GCN Circular #20482
  J.A. Kennea (PSU), B. Sbarufatti (INAF-OAB/PSU), D.N. Burrows (PSU), B. Mingo (U. Leicester), A.P. Beardmore (U. Leicester), V. D'Elia (ASDC), A. D'Ai (INAF-IASFPA), A. Melandri (INAF-OAB) and P.A. Evans (U. Leicester) report on behalf of the Swift-XRT team:
  Swift-XRT has performed follow-up observations of the Swift/BAT-detected burst GRB 170117A, collecting 2.9 ks of Photon Counting (PC) mode data between T0+86.3 ks and T0+116.0 ks.
  No X-ray sources have been detected consistent with being within 296 arcsec of the Swift/BAT position. The 3-sigma upper limit in the field ranges from ~0.003 to ~0.004 ct s^-1, corresponding to a 0.3-10 keV observed flux of 1.3e-13 to 1.8e-13 erg cm^-2 s^-1 (assuming a typical GRB spectrum).
  An uncatalogued was detected, however this was too far from the GRB position to be the afterglow.
  The results of the XRT-team automatic analysis of the XRT observations, including a position-specific upper limit calculator, are available at http://www.swift.ac.uk/ToO_GRBs/00020728.
  This circular is an official product of the Swift-XRT team.
• GCN Circular #20484
  A. A. Breeveld (UCL-MSSL) and A. Melandri (INAF-OAB) report on behalf of the Swift/UVOT team:
  The Swift/UVOT began settled observations of the field of GRB 170117A 86251 s after the BAT trigger (Palmer, GCN Circ. 20480). No optical afterglow consistent with the BAT position given in that circular is detected in the initial UVOT exposures. The preliminary 3-sigma upper limit using the UVOT photometric system (Breeveld et al. 2011, AIP Conf. Proc. 1358, 373) for the initial summed exposures is:

  Filter         T_start(s)   T_stop(s)      Exp(s)         Mag
  
  white            86251       116034         2654         >22.0
  

  The magnitudes in the table are not corrected for the Galactic extinction due to the reddening of E(B-V) = 0.35 in the direction of the burst (Schlegel et al. 1998).