GRB 230919A
GCN Circular 34769
Subject
Konus-Wind detection of GRB 230919A
Date
2023-09-26T13:36:05Z (2 years ago)
From
Y. Temiraev at Ioffe Institute <yuri.temiraev@mail.ioffe.ru>
Via
Web form
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 GRB 230919A
(Fermi-GBM detection: The Fermi GBM team, GCN Circ. 34737;
Scotton et al., GCN Circ. 34750;
AstroSat CZTI detection: Navaneeth et al., GCN Circ. 34742;
Swift/BAT-GUANO detection: DeLaunay et al., GCN Circ. 34747;
IPN triangulation: Kozyrev et al., GCN Circ. 34752)
triggered Konus-Wind at T0=61103.312 s UT (16:58:23.312).
The burst light curve shows a multipeaked structure
which starts at ~T0-0.4 s and has a total duration of ~2.4 s.
The emission is seen up to ~4 MeV.
The Konus-Wind light curve of this GRB is available at
http://www.ioffe.ru/LEA/GRBs/GRB230919_T61103/
As observed by Konus-Wind, the burst
had a fluence of 8.37(-2.57,+3.19)x10^-6 erg/cm2,
and a 16-ms peak flux, measured from T0+0.430 s,
of 1.44(-0.72,+0.81)x10^-5 erg/cm2/s
(both in the 20 keV - 10 MeV energy range).
The spectrum of the burst (measured from T0 to T0+8.448 s)
is best fit in the 20 keV - 4 MeV range
by a power law with exponential cutoff model:
dN/dE ~ (E^alpha)*exp(-E*(2+alpha)/Ep)
with alpha = -0.88(-0.25,+0.37)
and Ep = 1452(-629,+1078) keV (chi2 = 69/83 dof).
Fitting by a GRB (Band) model yields the same alpha and Ep,
and an upper limit on the high energy photon index: beta < -2.1
(chi2 = 69/82 dof).
All the quoted errors are at the 90% confidence level.
All the quoted values are preliminary.
GCN Circular 34752
Subject
IPN triangulation of GRB 230919A (short)
Date
2023-09-20T21:46:04Z (2 years ago)
From
Anna Ridnaia at Ioffe Institute <ridnaia@mail.ioffe.ru>
Via
Web form
A.S. Kozyrev, D.V. Golovin, M.L. Litvak, I.G. Mitrofanov, and A.B. Sanin
on behalf of the HEND/Mars Odyssey team,
A. Ridnaia, D. Frederiks, D. Svinkin, A. Lysenko,
and T. Cline on behalf of the Konus-Wind team,
A. Goldstein, M. S. Briggs, C. Wilson-Hodge,
and E. Burns on behalf of the Fermi GBM 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 short-duration GRB 230919A
(Fermi-GBM detection: The Fermi GBM team, GCN Circ. 34737;
Scotton et al., GCN Circ. 34750;
AstroSat CZTI detection: Navaneeth et al., GCN Circ. 34742;
Swift/BAT-GUANO detection: DeLaunay et al., GCN Circ. 34747)
has been detected by Fermi (GBM trigger 716835508), Konus-Wind,
Mars-Odyssey (HEND), Swift (BAT), and AstroSat (CZTI),
so far, at about 61103 s UT (16:58:23).
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:
71.620 (04h 46m 29s) +44.076 (+44d 04' 35")
Corners:
70.812 (04h 43m 15s) +45.562 (+45d 33' 43")
70.802 (04h 43m 12s) +45.703 (+45d 42' 10")
72.402 (04h 49m 37s) +42.484 (+42d 29' 04")
72.411 (04h 49m 39s) +42.324 (+42d 19' 28")
---------------------------------------------
The error box area is 543 sq. arcmin, and its maximum
dimension is 3.6 deg (the minimum one is 3 arcmin).
The Sun distance was 100 deg.
The IPN localization is consistent with, but reduces the area of,
the Fermi-GBM final localization (GCN Circ. 34737).
This localization may be improved.
A triangulation map and HEALPix FITS file are posted at
http://www.ioffe.ru/LEA/GRBs/GRB230919_T61103/IPN/
The Konus-Wind time history and spectrum will be given
in a forthcoming GCN Circular.
GCN Circular 34750
Subject
GRB 230919A: Fermi GBM Observation
Date
2023-09-20T20:49:41Z (2 years ago)
From
Lorenzo Scotton at UAH <lscottongcn@outlook.com>
Via
Web form
L. Scotton (UAH), C. Fletcher (USRA) and C. Meegan (UAH) report on behalf of
the Fermi Gamma-ray Burst Monitor Team:
"At 16:58:23.86 UT on 19 September 2023, the Fermi Gamma-ray Burst Monitor (GBM)
triggered and located GRB 230919A (trigger 716835508/230919707).
which was also detected by AstroSat (Navaneeth et al. 2023, GCN 34742)
and Swift/BAT-GUANO (DeLaunay et al. 2023, GCN 34747).
The Fermi GBM Final Real-time Localization was reported in GCN 34737.
The angle from the Fermi LAT boresight is 120 degrees.
The GBM light curve consists of multiple peaks
with a duration (T90) of about 2.9s. The time-averaged spectrum
from T0-0.06 to T0+1.34 s is best fit by
a power law function with an exponential high-energy cutoff.
The power law index is -0.74 +/- 0.06 and the cutoff energy,
parameterized as Epeak, is 2023 +/- 271 keV.
A Band function fits the spectrum equally well with
Epeak = 1617 +/- 352 keV, alpha = -0.68 +/- 0.08 and beta = -2.43 +/- 0.32.
The event fluence (10-1000 keV) in this time interval is
(3.3 +/- 0.1)E-06 erg/cm^2. The 64-msec peak photon flux measured
starting from T0+0.58 s in the 10-1000 keV band is 12 +/- 2 ph/s/cm^2.
The spectral analysis results presented above are preliminary;
final results will be published in the GBM GRB Catalog:
https://heasarc.gsfc.nasa.gov/W3Browse/fermi/fermigbrst.html
For Fermi GBM data and info, please visit the official Fermi GBM Support Page:
https://fermi.gsfc.nasa.gov/ssc/data/access/gbm/"
GCN Circular 34747
Subject
GRB 230919A: Swift/BAT-GUANO detection of a possibly short burst outside the coded FOV
Date
2023-09-20T17:51:55Z (2 years ago)
From
Jimmy DeLaunay at University of Alabama <delauj2@gmail.com>
Via
Web form
James DeLaunay (U Alabama), Aaron Tohuvavohu (U Toronto), Samuele Ronchini (PSU), Gayathri Raman (PSU), Jamie A. Kennea (PSU), Tyler Parsotan (NASA GSFC) report:
Swift/BAT did not localize GRB 230919A onboard (T0: 2023-09-19T16:58:23.86 UTC, Fermi trig 716835508, AstroSat CZTI GCN 34742)
The Fermi 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 [-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 2022, ApJ, 941, 169), performed on the temporal window [T0-20 s, T0+20 s], detects the burst with a sqrt(TS) of 16.6 in a 1.5 s analysis time bin, starting at T0 - 0.2 s.
NITRATES results are consistent with a burst coming from outside the FOV, with DeltaLLHOut of -0.6 and are consistent with Fermi GBM's localization (GCN 34737).
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 34742
Subject
GRB 230919A: AstroSat CZTI detection
Date
2023-09-20T13:42:29Z (2 years ago)
From
Gaurav Waratkar at IIT Bombay <gauravwaratkar@iitb.ac.in>
Via
Web form
P. K. Navaneeth (IUCAA), G. Waratkar (IITB), 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 GRB 230919A which was also detected by Fermi-GBM (Fermi GBM Team, GCN Circ. 34737).
The source was clearly detected in the CZT detectors in the 20-200 keV energy range. The light curve showed multiple peaks of emission with the strongest peak at 2023-09-19 16:58:23.95 UTC. The measured peak count rate associated with the burst is 1118 (+205, -166) counts/s above the background in the combined data of all quadrants, with a total of 921 (+115, -92) counts. The local mean background count rate was 406 (+10, -15) counts/s. Using cumulative rates, we measure a T90 of 1.58 (+1.38, -0.23) s. We caution that there are two 0.3 s readout dead time windows in CZTI data immediately after the detection of the burst. Hence, the T90 can be as large as 2.96 s for this GRB, with a lower limit of 1.35 s as estimated above by cumulative rates.
The source was also clearly detected in the CsI anticoincidence (Veto) detector in the 100-500 keV energy range. The light curve peaks at 2023-09-19 16:58:23.55 UTC. The measured peak count rate associated with the burst is 1196 (+82, -86) counts/s above the background in the combined data of all quadrants, with a total of 1796 (+193, -200) counts. The local mean background count rate was 1280 (+6, -6) counts/s. We measure a T90 of 2.1 (+1.2, -0.5) s from the cumulative Veto light curve. Note that this result is limited due to the 1 s native resolution of veto data.
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 34737
Subject
GRB 230919A: Fermi GBM Final Real-time Localization
Date
2023-09-19T17:06:22Z (2 years ago)
From
Fermi GBM Team at MSFC/Fermi-GBM <do_not_reply@GIOC.nsstc.nasa.gov>
Via
email
The Fermi GBM team reports the detection of a likely LONG GRB
At 16:58:23 UT on 19 Sep 2023, the Fermi Gamma-ray Burst Monitor (GBM) triggered and located GRB 230919A (trigger 716835508.857072 / 230919707).
The on-ground calculated location, using the Fermi GBM trigger data, is RA = 58.2, Dec = 41.2 (J2000 degrees, equivalent to J2000 03h 52m, 41d 12'), with a statistical uncertainty of 6.7 degrees.
The angle from the Fermi LAT boresight is 120.0 degrees.
The skymap can be found here:
https://heasarc.gsfc.nasa.gov/FTP/fermi/data/gbm/triggers/2023/bn230919707/quicklook/glg_skymap_all_bn230919707.png
The HEALPix FITS file, including the estimated localization systematic, can be found here:
https://heasarc.gsfc.nasa.gov/FTP/fermi/data/gbm/triggers/2023/bn230919707/quicklook/glg_healpix_all_bn230919707.fit
The GBM light curve can be found here:
https://heasarc.gsfc.nasa.gov/FTP/fermi/data/gbm/triggers/2023/bn230919707/quicklook/glg_lc_medres34_bn230919707.gif