Gamma-ray Burst 230616A

(All information courtesy of the instrument teams.)

Previous IAU Circulars

none

Results of Observations

GCN Circular #33982
Aaron Tohuvavohu (U Toronto), James DeLaunay (U Alabama), Samuele Ronchini (PSU), Gayathri Raman (PSU), Jamie A. Kennea (PSU) report:
Swift/BAT did not localize GRB 230616A onboard (T0: 2023-06-16T20:37:56.8 UTC, INTEGRAL trig 10287)
The INTEGRAL 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 90 seconds of BAT event-mode data from [-45,+45] 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 2022, ApJ, 941, 169), detects the burst with a sqrt(TS) of 29.2 in a 0.128 s analysis time bin.
NITRATES results are consistent with a burst coming from outside the FOV, with DeltaLLHOut of -1.
See Section 9.1 and Figures 10 and 17 in the NITRATES paper for brief descriptions and interpretation of sqrt(TS), DeltaLLHPeak, and DeltaLLHOut.
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 #33983
G. Waratkar (IITB), P K. Navaneeth (IUCAA), A. Vibhute (IUCAA), V. Bhalerao (IITB), D. Bhattacharya (Ashoka University/IUCAA), A. R. Rao (IUCAA/TIFR), and S. Vadawale (PRL) report on behalf of the AstroSat CZTI collaboration:
Analysis of AstroSat CZTI data with the CIFT framework (Sharma et al., 2021, JApA, 42, 73) showed the detection of a bright short GRB 230616A which was also detected by INTEGRAL/SPI-ACS (Trig 10287) and Swift/BAT-GUANO (Tohuvavohu et al., GCN Circ. 33982).
The source was clearly detected in the 20-200 keV energy range. The light curve peaks at 2023-06-16 20:37:58.765 UTC. The measured peak count rate associated with the burst is 6385 (+1349, -1043) counts/s above the background in the combined data of all quadrants, with a total of 307 (+42, -47) counts. The local mean background count rate was 431 (+29, -43) counts/s. Using cumulative rates, we measure a T90 of 0.06 (+0.01, -0.01) s.
The source was also clearly detected in the CsI anticoincidence (Veto) detector in the 100-500 keV energy range.
CZTI is built by a TIFR-led consortium of institutes across India, including VSSC, URSC, IUCAA, SAC, and PRL. The Indian Space Research Organisation funded, managed, and facilitated the project.
CZTI GRB detections are reported regularly on the payload site at: http://astrosat.iucaa.in/czti/?q=grb
GCN Circular #33988
P. A. Evans (U. Leicester) reports on behalf of the Swift team:
Swift has initiated a ToO observation of the IPN GRB 230616A. Automated analysis of the XRT data will be presented online at https://www.swift.ac.uk/ToO_GRBs/00021576
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 IPN 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 #34006
P. D'Avanzo (INAF-OAB), M.G. Bernardini (INAF-OAB), D.N. Burrows (PSU), J. D. Gropp (PSU), S. Dichiara (PSU), A.P. Beardmore (U. Leicester), J.P. Osborne (U. Leicester), E. Ambrosi (INAF-IASFPA) and P.A. Evans (U. Leicester) report on behalf of the Swift-XRT team:
Swift-XRT has performed follow-up observations of the IPN-detected burst GRB 230616A in a series of observations tiled on the sky. The total exposure time is 4.6 ks, distributed over 4 tiles; the maximum exposure at a single sky location was 2.0 ks. The data were collected between T0+111.3 ks and T0+140.7 ks, and are entirely in Photon Counting (PC) mode.
Three uncatalogued X-ray sources have been detected, however none of them is above the RASS limit or shows definitive signs of fading. Therefore, at the present time we cannot identify which, if any, is the afterglow. Details of these sources are given below:
Source 1:
```
  RA (J2000.0):  192.1005  =  12:48:24.12
  Dec (J2000.0): +5.4365  =  +05:26:11.4
  Error: 8.2 arcsec (radius, 90% conf.)
  Count-rate: 0.0177 [+0.0053, -0.0045] ct s^-1   
  Distance: 1675 arcsec from IPN position.
  Flux: (6.8 [+2.1, -1.7])e-13 erg cm^-2 s^-1 (observed, 0.3-10 keV)
```
Source 2:
```
  RA (J2000.0):  192.2299  =  12:48:55.18
  Dec (J2000.0): +6.0936  =  +06:05:36.9
  Error: 5.1 arcsec (radius, 90% conf. [Enhanced position])
  Count-rate: 0.0125 [+0.0046, -0.0037] ct s^-1   
  Distance: 820 arcsec from IPN position.
  Flux: (4.2 [+1.5, -1.3])e-13 erg cm^-2 s^-1 (observed, 0.3-10 keV)
```
Source 3:
```
  RA (J2000.0):  191.8031  =  12:47:12.74
  Dec (J2000.0): +5.5136  =  +05:30:48.9
  Error: 6.0 arcsec (radius, 90% conf.)
  Count-rate: (5.7 [+3.5, -2.5])e-3 ct s^-1   
  Distance: 1769 arcsec from IPN position.
```
The results of the XRT-team automatic analysis of the tiled XRT observations, including a position-specific upper limit calculator, are available at https://www.swift.ac.uk/xrt_products/TILED_GRB00112.
This circular is an official product of the Swift-XRT team.
GCN Circular #34046
A.S. Kozyrev, D.V. Golovin, M.L. Litvak, I.G. Mitrofanov, and A.B. Sanin on behalf of the MGNS/BepiColombo and HEND/Mars Odyssey teams,
J. Benkhoff on behalf of the BepiColombo team,
D. Svinkin, D. Frederiks, A. Ridnaia, A. Lysenko, and T. Cline on behalf of the Konus-Wind team,
E. Burns on behalf of the IPN,
E. Bozzo and C. Ferrigno, on behalf of the INTEGRAL SPI-ACS GRB team,
S. Barthelmy, J. Cummings, H. Krimm, D. Palmer, and A. Tohuvavohu on behalf of the Swift-BAT team,
and
W. Boynton, C. Fellows, K. Harshman, H. Enos, R. Starr, and A.S. Gardner on on behalf of the GRS-Odyssey GRB team, report:
The bright, short-duration GRB 230616A (Swift-BAT/GUANO detection: Tohuvavohu et al., GCN Circ. 33982; AstroSat-CZTI detection: Waratkar et al., GCN Circ. 33983) was detected by Swift (BAT), Konus-Wind, INTEGRAL (SPI-ACS), AstroSat (CZTI), Mars-Odyssey (HEND), and BepiColombo (MGNS) at about 74278 s UT (20:37:58). 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:
  192.035 (12h 48m 08s)  +5.683 ( +5d 40' 57")
 Corners:
  192.022 (12h 48m 05s)  +5.663 ( +5d 39' 46")
  192.049 (12h 48m 12s)  +5.714 ( +5d 42' 49")
  192.048 (12h 48m 12s)  +5.702 ( +5d 42' 08")
  192.022 (12h 48m 05s)  +5.652 ( +5d 39' 06")
 ------------------------------------------
```
The error box area is 0.9 sq. arcmin, and its maximum dimension is 4 arcmin (the minimum one is 0.3 arcmin). The Sun distance was 103 deg.
This box may be improved.
The Swift-XRT sources (D'Avanzo et al., GCN Circ. 34006) are outside the IPN box. There are no obvious catalogued host galaxies (from GLADE+ catalog; Dalya et al., MNRAS 514, 1, 1403, 2022) inside the box.
A triangulation map is posted at http://www.ioffe.ru/LEA/GRBs/GRB230616_T74278/IPN
The Konus-Wind time history and spectrum will be given in a forthcoming GCN Circular.
GCN Circular #34091
Y. Temiraev, D. Svinkin, D. Frederiks, M. Ulanov, A. Tsvetkova, A. Lysenko, A. Ridnaia, and T. Cline on behalf of the Konus-Wind team, report:
The short-duration, bright GRB 230616A (Swift-BAT/GUANO detection: Tohuvavohu et al., GCN Circ. 33982; AstroSat-CZTI detection: Waratkar et al., GCN Circ. 33983; IPN triangulation: Kozyrev et al., GCN Circ. 34046) triggered Konus-Wind at T0=74278.259 s UT (20:37:58.259).
The burst light curve shows a multipeaked structure which starts at ~T0-30 ms and has a total duration of ~98 ms. The emission is seen up to ~7 MeV.
The Konus-Wind light curve of this GRB is available at http://www.ioffe.ru/LEA/GRBs/GRB230616_T74278/
As observed by Konus-Wind, the burst had a fluence of 9.11(-1.11,+1.13)x10^-6 erg/cm2, and a 16-ms peak flux, measured from T0+0.028 s, of 1.77(-0.32,+0.33)x10^-4 erg/cm2/s (both in the 20 keV - 10 MeV energy range).
The time-averaged spectrum of the burst (measured from T0 to T0+0.064 s) is best fit in the 20 keV - 7 MeV range by a power law with exponential cutoff model: dN/dE ~ (E^alpha)*exp(-E*(2+alpha)/Ep) with alpha = -0.38(-0.15,+0.17) and Ep = 1725(-257,+286) keV (chi2 = 63/55 dof). Fitting by a GRB (Band) model yields the same alpha and Ep, and an upper limit on the high energy photon index: beta < -2.7 (chi2 = 63/54 dof).
All the quoted errors are at the 90% confidence level. All the quoted values are preliminary.

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Jochen Greiner, last update: 27-Jun-2023 [Disclaimer]