Gamma-ray Burst 221115B

(All information courtesy of the instrument teams.)

Previous IAU Circulars

• none

• GCN Circular #32941
  James DeLaunay (UAlabama), Aaron Tohuvavohu (U Toronto), Gayathri Raman (PSU), Jamie A. Kennea (PSU), Tyler Parsotan (GSFC/UMBC) report:
  Swift/BAT did not localize GRB 221115B onboard (T0: 2022-11-15T09:46:15 UTC, CALET trig 1352540756).
  The CALET notice, distributed in near real-time, triggered the Swift Mission Operations Center operated Gamma-ray Urgent Archiver for Novel Opportunities (GUANO; Tohuvavohu et al. 2020, ApJ, 900, 1).
  Upon trigger by this notice, GUANO sent a command to the Swift Burst Alert Telescope (BAT) to save 200 seconds of BAT event-mode data from [-50,+150] seconds around the time of the burst. All the requested event mode data was delivered to the ground.
  The BAT likelihood search, NITRATES (DeLaunay + Tohuvavohu, arXiv:2111.01769), detects the burst in a 2.048 s analysis time bin with a sqrt(TS) of 27.7. The duration of the burst as seen by BAT is ~5 seconds.
  A confident arcminute localization is found with DeltaLLHPeak of 49.
  See Section 9.1 and Figure 17 in the NITRATES paper for brief descriptions and interpretations of sqrt(TS), DeltaLLHPeak, and DeltaLLHOut.
  The BAT position is RA, Dec = 54.788, -16.701 deg which is

     RA(J2000)  = 03h 39m 09.16s
     Dec(J2000) = -16d 42′ 03.5″
  

  with an estimated uncertainty of 3 arcmin.
  XRT and UVOT follow-up has been requested, but will be significantly delayed due to operational constraints. We encourage followup from other facilities.
  GUANO is a fully autonomous, extremely low latency, spacecraft commanding pipeline designed for targeted recovery of BAT event mode data around the times of compelling astrophysical events to enable more sensitive GRB searches.
  A live reporting of Swift/BAT event data recovered by GUANO can be found at: https://www.swift.psu.edu/guano/
• GCN Circular #32943
  S. de Wet (UCT), P.J. Groot (Radboud/UCT/SAAO) report on behalf of the MeerLICHT consortium:
  We observed the Swift/BAT-GUANO localisation of GRB 221115B (DeLaunay et al., GCN 32941) with the 0.6m wide-field MeerLICHT optical telescope situated in Sutherland, South Africa, obtaining 2x300s observations in the q-band (roughly g+r) fully encompassing the 3' error box. Observations began at 21:21:30 UT on 2022 November 16, 1.48 days post-trigger.
  Employing our transient detection pipeline along with an archival reference image, we detect no new transients within the GUANO error box down to a 5-sigma transient limiting magnitude of q > 20.80. Our new images had full-frame 5-sigma limiting magnitudes of q = 22.10 and q = 22.18, while our archival reference image had a limiting magnitude of q = 21.10. All magnitudes are in the AB system.
  MeerLICHT is built and run by a consortium consisting of Radboud University, the University of Cape Town, the South African Astronomical Observatory, the University of Oxford, the University of Manchester and the University of Amsterdam.
• GCN Circular #32945
  R. Strausbaugh (University of Minnesota), A. Cucchiara (NASA) report on behalf of a larger collaboration:
  We observed the GRB 221115B (DeLaunay et al., GCN 32941) field with the LCOGT 1-meter Sinistro instrument at the South African Astronomical Observatory site, on November 16, from 19:40 to 20:08 (corresponding to 34.15 to 34.62 hours from the GRB trigger time) with the SDSS r and i filters.
  We performed a series of 3x300s exposures in each band. We do not detect any fading uncatalogued sources in the BAT error region, in either band, consistent with other optical upper limits (de Wet et al., GCN 32943).
  The following upper limits are calculated using the Pan-STARRS catalog as reference:

  r > 22.4
  i > 21.5
  

  These magnitudes are not corrected for galactic extinction.
• GCN Circular #32948
  A. Yoshida, T. Sakamoto, S. Sugita (AGU), Y. Kawakubo (LSU), K. Yamaoka (Nagoya U), S. Nakahira (RIKEN), Y. Asaoka (ICRR), S. Torii, Y. Akaike, K. Kobayashi (Waseda U), Y. Shimizu, T. Tamura (Kanagawa U), N. Cannady (GSFC/UMBC), M. L. Cherry (LSU), S. Ricciarini (U of Florence), P. S. Marrocchesi (U of Siena) and the CALET collaboration:
  The long GRB 221115B (Swift/BAT-GUANO arcminute localization: DeLaunay et al., GCN Circ. 32941) triggered the CALET Gamma-ray Burst Monitor (CGBM) at 09:46:15.63 UTC on 15 November 2022 (http://cgbm.calet.jp/cgbm_trigger/flight/1352540756/index.html). The burst signal was seen by all CGBM detectors.
  The burst light curve shows two pulses. The first faint pulse is around T-12 s, and the second main pulse starts at T+0.0 sec, peaks at T+0.6, sec, and ends at T+2.4 sec. The T90 and T50 durations measured by the SGM data are 2.1 +/- 0.2 sec and 0.9 +/- 0.3 sec (40-1000 keV), respectively.
  The ground processed light curve is available at
  http://cgbm.calet.jp/cgbm_trigger/ground/1352540756/
  The CALET data used in this analysis are provided by the Waseda CALET Operation Center located at the Waseda University.