GRB 240215B
GCN Circular 35739
Subject
GRB 240215B: Swift/BAT-GUANO detection of a burst outside the coded FOV
Date
2024-02-16T18:36:56Z (a year ago)
From
Jimmy DeLaunay at Penn State <delauj2@gmail.com>
Via
Web form
James DeLaunay (PSU), Samuele Ronchini (PSU), Gayathri Raman (PSU), Aaron Tohuvavohu (U Toronto), Jamie A. Kennea (PSU), Tyler Parsotan (NASA GSFC) report:
Swift/BAT did not localize GRB 240215B onboard (T0: 2024-02-15T19:51:43.85 UTC, Fermi trig 729719508)
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 28.8 in a 8.192 s analysis time bin, starting at T0.
NITRATES results are consistent with a burst coming from outside the FOV, with DeltaLLHOut of -28.4.
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 35752
Subject
GRB 240215B: GRBAlpha detection
Date
2024-02-18T21:35:25Z (a year ago)
From
Andras Pal at Konkoly Observatory <apal@szofi.net>
Via
Web form
A. Pal (Konkoly Observatory), M. Dafcikova, J. Ripa, M. Kolar, N. Werner (Masaryk U.), M. Ohno, H. Takahashi (Hiroshima U.), L. Meszaros, B. Csak (Konkoly Observatory), N. Husarikova, F. Munz , M. Topinka, L. Szakszonova, 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.), T. 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 240215B (Swift/BAT detection: GCN 35739; Fermi/GBM detection: GCN 35740; INTEGRAL/SPI-ACS peak detection at 2024-02-15 ~19:51:47) was observed by the GRBAlpha 1U CubeSat (Pal et al. 2023, A&A, 677, 40; arXiv:2302.10048).
The detection was confirmed at the peak time 2024-02-15 19:51:49 UTC. The T90 duration measured by GRBAlpha is 16.5 s and the overall significance during T90 reaches 23 sigma.
The light curve obtained by GRBAlpha is available here: https://grbalpha.konkoly.hu/static/share/GRB240215B_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 35763
Subject
GRB 240215B: Fermi GBM Observation
Date
2024-02-20T16:45:45Z (a year ago)
From
Lorenzo Scotton at UAH <lscottongcn@outlook.com>
Via
Web form
L. Scotton (UAH) and C. Meegan (UAH) report on behalf of
the Fermi Gamma-ray Burst Monitor Team:
"At 19:51:43.85 UT on 15 February 2024, the Fermi Gamma-ray Burst Monitor (GBM)
triggered and located GRB 240215B (trigger 729719508/240215828),
which was also detected by Swift/BAT-GUANO (J. DeLaunay et al. 2024, GCN 35739),
and GRBAlpha (A. Pal et al. 2024, GCN 35752).
The Fermi GBM Final Real-time Localization was reported in GCN 35740,
but was mislabelled as GRB 240215C.
After manual inspection, a more accurate on-ground location was found to be
RA = 309.52, Dec = -48.74, with a statistical uncertainty of 2.54 degrees.
The angle from the Fermi LAT boresight is 94 degrees.
The GBM light curve consists of a single emission episode with a duration (T90)
of about 21 s (50-300 keV). The time-averaged spectrum
from T0-5.5 to T0+21.5 s is best fit by
a power law function with an exponential high-energy cutoff.
The power law index is -1.16 +/- 0.04 and the cutoff energy,
parameterized as Epeak, is 210 +/- 10 keV.
The event fluence (10-1000 keV) in this time interval is
(1.12 +/- 0.04)E-05 erg/cm^2. The 1-sec peak photon flux measured
starting from T0+4.9 s in the 10-1000 keV band is 10.8 +/- 0.4 ph/s/cm^2.
A Band function fits the spectrum equally well
with Epeak= 190 +/- 20 keV, alpha = -1.13 +/- 0.05 and beta = -2.5 +/- 0.3.
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/"