GRB 230908A
GCN Circular 34679
Subject
GRB 230908A: CALET Gamma-Ray Burst Monitor detection
Date
2023-09-13T04:14:01Z (2 years ago)
From
Yuta Kawakubo at Louisiana State University <kawakubo1@lsu.edu>
Via
Web form
N. Cannady (GSFC/UMBC), A. Yoshida, T. Sakamoto, S. Sugita (AGU),
Y. Kawakubo (LSU), K. Yamaoka (Nagoya U), S. Nakahira (JAXA),
Y. Asaoka (ICRR), S. Torii, Y. Akaike, K. Kobayashi (Waseda U),
Y. Shimizu, T. Tamura (Kanagawa U),
M. L. Cherry (LSU), S. Ricciarini (U of Florence),
P. S. Marrocchesi (U of Siena),
and the CALET collaboration:
The long GRB 230908A (AstroSat CZTI detection: Navaneeth et al.,
GCN Circ. 34645; GRBAlpha detection: Dafcikova et al., GCN
Circ. 34647; Swift/BAT-GUANO detection: Tohuvavohu et al.,
GCN Circ. 34661) triggered the CALET Gamma-ray Burst Monitor
(CGBM) at 16:41:17.84 UTC on 8 September 2023
(http://cgbm.calet.jp/cgbm_trigger/flight/1378226327/index.html).
The burst signal was seen by all CGBM detectors.
The burst light curve shows a single pulse that starts
at T+2.1 sec, peaks at T+4.1 sec, and ends at T+9.6 sec.
The T90 and T50 durations measured by the SGM data are 6.2 +/- 0.6 sec
and 2.7 +/- 0.2 sec (40-1000 keV), respectively.
The ground-processed light curve is available at
http://cgbm.calet.jp/cgbm_trigger/ground/1378226327/
The CALET data used in this analysis are provided by
the Waseda CALET Operation Center located at Waseda University.
GCN Circular 34661
Subject
GRB 230908A: Swift/BAT-GUANO detection of a long burst outside the coded FOV
Date
2023-09-11T16:08:54Z (2 years ago)
From
GAYATHRI RAMAN at PSU <gzr5209@psu.edu>
Via
Web form
Aaron Tohuvavohu (U Toronto), Gayathri Raman (PSU), Jamie A. Kennea (PSU), James DeLaunay (U Alabama), Samuele Ronchini (PSU), Tyler Parsotan (NASA GSFC) report:
Swift/BAT did not localize GRB 230908A onboard (T0: 2023-09-08T16:41:17.84 UTC, CALET detection: trigger no. 1378226327, AstroSat detection: GCN 34645, GRBAlpha detection: GCN 34647)
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 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 76.33 in a 8.192 s analysis time bin, starting at T0 + 2.0482 s.
NITRATES results are consistent with a burst coming from outside the FOV, with DeltaLLHOut of -134.81.
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 34647
Subject
GRB 230908A: GRBAlpha detection
Date
2023-09-09T21:15:07Z (2 years ago)
From
Marianna Dafčíková at Masaryk University <500025@mail.muni.cz>
Via
Web form
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 long-duration GRB 230908A (AstroSat detection: GCN 34645; CALET detection: trigger no. 1378226327; INTEGRAL/SPI-ACS peak detection at 2023-09-08 ~16:41:20 UT) was observed by the GRBAlpha 1U CubeSat (Pal et al. 2023; arXiv:2302.10048).
The detection was confirmed at the peak time 2023-09-08 16:41:21 UTC. The T90 duration measured by GRBAlpha is 8 s and the overall significance during T90 reaches 40 sigma.
The light curve obtained by GRBAlpha is available here:
https://grbalpha.konkoly.hu/static/share/GRB230908A_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 34645
Subject
GRB 230908A: AstroSat CZTI detection
Date
2023-09-09T19:29:37Z (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 a GRB 230908A which was also detected by CALET (Trigger Num. 1378226327).
The source was clearly detected in the CZT detectors in the 20-200 keV energy range. The light curve showed a single burst of emission that peaked at 2023-09-08 16:41:22 UTC. The measured peak count rate associated with the burst is 447 (+173, -19) counts/s above the background in the combined data of three quadrants (out of four), with a total of 1458 (+285, -371) counts. The local mean background count rate was 327 (+5, -9) counts/s. Using cumulative rates, we measure a T90 of 9.5 (+3, -5) s.
The source was also clearly detected in the CsI anticoincidence (Veto) detector in the 100-500 keV energy range. The light curve showed a single burst of emission that peaked at 2023-09-08 16:41:23 UTC. The measured peak count rate associated with the burst is 737 (+71, -75) counts/s above the background in the combined data of three quadrants (out of four), with a total of 4509 (+569, -583) counts. The local mean background count rate was 1096 (+7, -7) counts/s. We measure a T90 of 13 (+5, -2) s from the cumulative Veto light curve.
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