GRB 230709C
GCN Circular 34187
Subject
GRB 230709C: BALROG localization (Fermi Trigger 710617111 / GRB 230709735)
Date
2023-07-09T22:19:05Z (2 years ago)
From
Jochen Greiner at MPE <jcgrog@mpe.mpg.de>
T. Preis, B. Biltzinger, J. Burgess & J. Greiner (all MPE Garching) report:
The public trigdat data of the Fermi Gamma-ray Burst Monitor (GBM) trigger
710617111 at 17:38:26 on 09 July 2023 were automatically fitted for spectrum
and sky location with BALROG (Burgess et al. 2018, MNRAS 476, 1427;
Berlato et al. 2019, ApJ 873, 60).
The best-fit position (1 sigma statistical errors) is:
RA(2000.0) = 267.1+/-6.5 deg
Decl.(2000.0) = -71.4+/-1.1 deg
We estimate an additional systematic error of 1 deg.
Further details are available at:
https://grb.mpe.mpg.de/grb/GRB230709735/
The Healpix map can be downloaded from:
https://grb.mpe.mpg.de/grb/GRB230709735/healpix
The location parameters are available as JSON at:
https://grb.mpe.mpg.de/grb/GRB230709735/json
GCN Circular 34191
Subject
GRB 230709C: AstroSat CZTI detection
Date
2023-07-10T09:12:13Z (2 years ago)
From
Gaurav Waratkar at IIT Bombay <gauravwaratkar@iitb.ac.in>
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 a short GRB 230709C which was also detected by Fermi-GBM (Trig. 710617111; Preis et al., GCN Circ. 34187).
The source was clearly detected in the 20-200 keV energy range. The light curve peaks at 2023-07-09 17:38:26.94 UTC. The measured peak count rate associated with the burst is 3742 (+1196, -481) counts/s above the background in the combined data of all quadrants, with a total of 280 (+65, -56) counts. The local mean background count rate was 337 (+34, -54) counts/s. Using cumulative rates, we measure a T90 of 0.33 (+0.30, -0.03) s. We caution that there was a 0.3 s readout dead time in CZTI before the detection of the burst. Hence, the T90 can be as large as 0.63 s for this GRB, with a lower limit of 0.30 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.
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 34198
Subject
GRB 230709C: Fermi GBM Final Localization
Date
2023-07-10T20:07:49Z (2 years ago)
From
Peter Veres at University of Alabama in Huntsville <veresp@gmail.com>
The Fermi GBM team reports the detection of a likely SHORT GRB
"At 17:38:26.82 UT on 09 July 2023, the Fermi Gamma-ray Burst Monitor (GBM)
triggered and located GRB 230709C (trigger 710617111/230709735), which
initially was classified as a non-GRB trigger by the flight software.
The on-ground calculated location, using the Fermi GBM trigger data,
is RA = 267.56, Dec = -70.47 (J2000 degrees, equivalent to J2000 17h 50m, -70d 28'),
with a statistical uncertainty of 1.44 degrees.
The angle from the Fermi LAT boresight is 131 degrees.
The skymap can be found here:
https://heasarc.gsfc.nasa.gov/FTP/fermi/data/gbm/triggers/2023/bn230709735/quicklook/glg_skymap_all_bn230709735.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/bn230709735/quicklook/glg_healpix_all_bn230709735.fit
The GBM light curve can be found here:
https://heasarc.gsfc.nasa.gov/FTP/fermi/data/gbm/triggers/2023/bn230709735/quicklook/glg_lc_medres34_bn230709735.gif"
GCN Circular 34199
Subject
GRB 230709C: Fermi GBM Detection
Date
2023-07-10T20:12:24Z (2 years ago)
From
Peter Veres at University of Alabama in Huntsville <veresp@gmail.com>
P. Veres and C. Meegan (both UAH) report on behalf of
the Fermi Gamma-ray Burst Monitor Team:
"At 17:38:26.82 UT on 09 July 2023, the Fermi Gamma-ray Burst Monitor (GBM)
triggered and located GRB 230709C (trigger 710617111/230709735).
The on-ground calculated location, using the Fermi GBM trigger data (GCN #34198) is consistent with the location reported by Preis et al., GCN #34187.
The GBM light curve consists of a single emission episode with a duration (T90)
of about 0.19 s (50-300 keV). The time-averaged spectrum
from T0-0.06 to T0+0.19 s is best fit by
a power law function with an exponential high-energy cutoff.
The power law index is -0.01 +/- 0.07 and the cutoff energy,
parameterized as Epeak, is 1050 +/- 50 keV.
The event fluence (10-1000 keV) in this time interval is
(6.3 +/- 0.1)E-06 erg/cm^2. The 64-ms peak photon flux measured
starting from T0+0.0 s in the 10-1000 keV band is 58 +/- 3 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 34201
Subject
GRB 230709C: GRBAlpha detection
Date
2023-07-11T07:39:09Z (2 years ago)
From
Jakub Ripa <ripa.jakub@gmail.com>
M. Dafcikova, J. Ripa (Masaryk U.), A. Pal (Konkoly Observatory), N. Werner (Masaryk U.), M. Ohno, H. Takahashi (Hiroshima U.), L. Meszaros, B. Csak (Konkoly Observatory), N. Husarikova, F. Munz , M. Topinka, M. Kolar, J.-P. Breuer, F. Hroch (Masaryk U.), T. Urbanec, M. Kasal, A. Povalac (Brno U. of Technology), J. Hudec, J. Kapus, M. Frajt (Spacemanic s.r.o), R. Laszlo, M. Koleda (Needronix s.r.o), M. Smelko, P. Hanak, P. Lipovsky (Technical U. of Kosice), G. Galgoczi (Wigner Research Center/Eotvos U.), Y. Uchida, H. Poon, H. Matake (Hiroshima U.), N. Uchida (ISAS/JAXA), T. Bozoki (Eotvos U.), G. Dalya (Eotvos U.), yyT. Enoto (Kyoto U.), Zs. Frei (Eotvos U.), G. Friss (Eotvos U.), Y. Fukazawa, K. Hirose (Hiroshima U.), S. Hisadomi (Nagoya U.), Y. Ichinohe (Rikkyo U.), K. Kapas (Eotvos U.), L. L. Kiss (Konkoly Observatory), T. Mizuno (Hiroshima U.), K. Nakazawa (Nagoya U.), H. Odaka (Univ of Tokyo), J. Takatsy (Eotvos U.), K. Torigoe (Hiroshima U.), N. Kogiso, M. Yoneyama (Osaka Metropolitan U.), M. Moritaki (U. Tokyo), T. Kano (U. Michigan) -- the GRBAlpha collaboration.
The short-duration GRB 230709C (Fermi/GBM detection: GCN Circ. 34187; AstroSat detection: GCN Circ. 34191) was observed by the GRBAlpha 1U CubeSat (Pal et al. 2023; arXiv:2302.10048).
The detection was confirmed at the peak time 2023-07-09 17:38:26 UTC. The light curve observed by GRBAlpha shows a spike within 1 s bin where the SNR reaches 9 sigma.
The light curve obtained by GRBAlpha is available here: https://grbalpha.konkoly.hu/static/share/GRB230709C_GCN.pdf
All GRBAlpha detections are listed at: https://monoceros.physics.muni.cz/hea/GRBAlpha/ GRBAlpha, launched on 2021 March 22, is a demonstration mission for a future CubeSat constellation (Werner et al. Proc. SPIE 2018). The detector of GRBAlpha consists of a 75 x 75 x 5 mm3 CsI scintillator read out by a SiPM array, covering the energy range from ~50 keV to ~1000 keV. To increase the duty cycle and the downlink rate, the upgrade of the on-board data acquisition software stack is in progress. The ground segment is also supported by the radio amateur community and it takes advantage of the SatNOGS network for increased data downlink volume.
GCN Circular 34209
Subject
GRB 230709C: Swift/BAT-GUANO detection of a short burst outside the coded FOV
Date
2023-07-13T03:09:57Z (2 years ago)
From
Samuele Ronchini at PSU <sjs8171@psu.edu>
Samuele Ronchini (PSU), James DeLaunay (U Alabama), Aaron Tohuvavohu (U Toronto), Gayathri Raman (PSU), Jamie A. Kennea (PSU), Tyler Parsotan (NASA GSFC) report:
Swift/BAT did not localize GRB 230709C onboard (T0: 2023-07-09T17:38:26.82 UTC, Fermi trig 710617111)
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 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 2022, ApJ, 941, 169), performed on the temporal window [T0-20 s, T0+20 s], detects the burst with a sqrt(TS) of 38.3 in a 0.256 s analysis time bin, starting at T0-0.064.
NITRATES results are consistent with a burst coming from outside the FOV, with DeltaLLHOut of -32.55 and are consistent with Fermi GBM's localization (GCN 34198).
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/