Gamma-ray Burst 240521B

(All information courtesy of the instrument teams.)

Previous IAU Circulars

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Results of Observations

GCN NOTICE

TITLE:           GCN/FERMI NOTICE
NOTICE_DATE:     Tue 21 May 24 15:09:26 UT
NOTICE_TYPE:     Fermi-GBM Flight Position
RECORD_NUM:      44
TRIGGER_NUM:     737996942
GRB_RA:           27.700d {+01h 50m 48s} (J2000),
                  27.952d {+01h 51m 49s} (current),
                  27.182d {+01h 48m 44s} (1950)
GRB_DEC:         -43.550d {-43d 32' 59"} (J2000),
                 -43.430d {-43d 25' 47"} (current),
                 -43.797d {-43d 47' 48"} (1950)
GRB_ERROR:       23.02 [deg radius, statistical plus systematic]
GRB_INTEN:       115 [cnts/sec]
DATA_SIGNIF:     4.50 [sigma]
INTEG_TIME:      2.048 [sec]
GRB_DATE:        20451 TJD;   142 DOY;   24/05/21
GRB_TIME:        54537.06 SOD {15:08:57.06} UT
GRB_PHI:         265.98 [deg]
GRB_THETA:       135.00 [deg]
DATA_TIME_SCALE: 2.0480 [sec]
HARD_RATIO:      1.51
LOC_ALGORITHM:   3 (version number of)
MOST_LIKELY:      69%  GRB
2nd_MOST_LIKELY:  15%  Solar Flare
DETECTORS:       0,0,0, 0,1,0, 0,0,1, 0,0,0, 0,0,
SUN_POSTN:        58.92d {+03h 55m 40s}  +20.37d {+20d 21' 59"}
SUN_DIST:         69.85 [deg]   Sun_angle= 2.1 [hr] (West of Sun)
MOON_POSTN:      215.48d {+14h 21m 55s}  -16.21d {-16d 12' 19"}
MOON_DIST:       119.97 [deg]
MOON_ILLUM:      96 [%]
GAL_COORDS:      270.64,-69.67 [deg] galactic lon,lat of the burst (or transient)
ECL_COORDS:        3.13,-50.01 [deg] ecliptic lon,lat of the burst (or transient)
LC_URL:          http://heasarc.gsfc.nasa.gov/FTP/fermi/data/gbm/triggers/2024/bn240521631/quicklook/glg_lc_medres34_bn240521631.gif
COMMENTS:        Fermi-GBM Flight-calculated Coordinates.  
COMMENTS:        This trigger occurred at longitude,latitude = 137.33,-14.53 [deg].  
COMMENTS:        The LC_URL file will not be created until ~15 min after the trigger.

GCN NOTICE

TITLE:           GCN/FERMI NOTICE
NOTICE_DATE:     Tue 21 May 24 15:18:21 UT
NOTICE_TYPE:     Fermi-GBM Final Position
RECORD_NUM:      0
TRIGGER_NUM:     737996942
GRB_RA:            9.380d {+00h 37m 31s} (J2000),
                   9.671d {+00h 38m 41s} (current),
                   8.782d {+00h 35m 08s} (1950)
GRB_DEC:         -43.600d {-43d 36' 00"} (J2000),
                 -43.466d {-43d 27' 57"} (current),
                 -43.875d {-43d 52' 29"} (1950)
GRB_ERROR:       22.78 [deg radius, statistical only]
GRB_DATE:        20451 TJD;   142 DOY;   24/05/21
GRB_TIME:        54537.06 SOD {15:08:57.06} UT
GRB_PHI:         263.00 [deg]
GRB_THETA:       122.00 [deg]
E_RANGE:         44.032 - 279.965 [keV]
LOC_ALGORITHM:   41731 (Gnd S/W Version number)
SUN_POSTN:        58.92d {+03h 55m 41s}  +20.37d {+20d 22' 04"}
SUN_DIST:         78.19 [deg]   Sun_angle= 3.3 [hr] (West of Sun)
MOON_POSTN:      215.55d {+14h 22m 13s}  -16.24d {-16d 14' 09"}
MOON_DIST:       115.76 [deg]
MOON_ILLUM:      96 [%]
GAL_COORDS:      311.72,-73.29 [deg] galactic lon,lat of the burst (or transient)
ECL_COORDS:      346.92,-42.82 [deg] ecliptic lon,lat of the burst (or transient)
LC_URL:          http://heasarc.gsfc.nasa.gov/FTP/fermi/data/gbm/triggers/2024/bn240521631/quicklook/glg_lc_medres34_bn240521631.gif
LOC_URL:         http://heasarc.gsfc.nasa.gov/FTP/fermi/data/gbm/triggers/2024/bn240521631/quicklook/glg_locplot_all_bn240521631.png
COMMENTS:        Fermi-GBM Final Position.  
COMMENTS:        This Notice was ground-generated -- not flight-generated.  
COMMENTS:        The LC_URL file should be available by the time this FINAL notice is produced.  
COMMENTS:        This notice was generated completely by automated pipeline processing.  
COMMENTS:        This is likely a Long GRB.

GCN NOTICE

TITLE:           GCN/FERMI NOTICE
NOTICE_DATE:     Tue 21 May 24 15:09:44 UT
NOTICE_TYPE:     Fermi-GBM Ground Position
RECORD_NUM:      57
TRIGGER_NUM:     737996942
GRB_RA:           16.330d {+01h 05m 19s} (J2000),
                  16.604d {+01h 06m 25s} (current),
                  15.766d {+01h 03m 04s} (1950)
GRB_DEC:         -44.820d {-44d 49' 11"} (J2000),
                 -44.690d {-44d 41' 22"} (current),
                 -45.088d {-45d 05' 14"} (1950)
GRB_ERROR:       6.74 [deg radius, statistical only]
DATA_SIGNIF:     6.30 [sigma]
DATA_INTERVAL:   4.096 [sec]
GRB_DATE:        20451 TJD;   142 DOY;   24/05/21
GRB_TIME:        54537.06 SOD {15:08:57.06} UT
GRB_PHI:         263.00 [deg]
GRB_THETA:       127.00 [deg]
E_RANGE:         44.032 - 279.965 [keV]
LOC_ALGORITHM:   4173 (Gnd S/W Version number)
SUN_POSTN:        58.92d {+03h 55m 40s}  +20.37d {+20d 21' 59"}
SUN_DIST:         75.63 [deg]   Sun_angle= 2.8 [hr] (West of Sun)
MOON_POSTN:      215.48d {+14h 21m 56s}  -16.21d {-16d 12' 22"}
MOON_DIST:       116.72 [deg]
MOON_ILLUM:      96 [%]
GAL_COORDS:      294.90,-72.09 [deg] galactic lon,lat of the burst (or transient)
ECL_COORDS:      351.86,-46.56 [deg] ecliptic lon,lat of the burst (or transient)
LC_URL:          http://heasarc.gsfc.nasa.gov/FTP/fermi/data/gbm/triggers/2024/bn240521631/quicklook/glg_lc_medres34_bn240521631.gif
POS_MAP_URL:     http://gcn.gsfc.nasa.gov/notices_f/gbm_gnd_loc_map_737996942.fits
COMMENTS:        Fermi-GBM Ground-calculated Coordinates.  
COMMENTS:        This Notice was ground-generated -- not flight-generated.  
COMMENTS:        The LC_URL file will not be created/available until ~15 min after the trigger.  
COMMENTS:        The POS_MAP_URL file will not be created/available until ~1.5 min after the notice.

GCN Circular #36532
FROM: Samuele Ronchini at PSU
Samuele Ronchini (PSU), James DeLaunay (PSU), Aaron Tohuvavohu (U Toronto), Gayathri Raman (PSU), Jamie A. Kennea (PSU), Tyler Parsotan (NASA GSFC) report:
Swift/BAT did not localize GRB 240521B onboard (T0: 2024-05-21T15:08:57.06 UTC, Fermi trigger 737996942).
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).=20
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), detects the burst in a 16.384 s analysis time bin starting at T0 - 12.3 s with a sqrt(TS) of 74.6. An arcminute localization is found with DeltaLLHOut of 984.5 and a DeltaLLH Peak of 1282.7.
See Section 9.1 and Figures 10 and 17 in the NITRATES paper for brief descriptions and interpretations of sqrt(TS), DeltaLLHPeak, and DeltaLLHOut.
The BAT position is RA, Dec =3D 355.6879, -32.7215 deg which is
```
   RA(J2000)  =3D 23h 42m 45.10s
   Dec(J2000) =3D -32=C2=B0 43=E2=80=99 17.4=E2=80=99=E2=80=99
```
with an estimated uncertainty of 3 arcmin radius.
Follow-up observations from other instruments are requested. Swift ToO request has been submitted.
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 #36535
S. Dalessi (UAH), C. Fletcher (USRA), and C. Meegan (UAH) report on behalf of the Fermi Gamma-ray Burst Monitor Team:
"At 15:08:57.06 UT on 21 May 2024, the Fermi Gamma-ray Burst Monitor (GBM) triggered and located GRB 240521B (trigger 737996942/240521631). which was also detected by Swift/BAT-GUANO (Ronchini et al. 2024, GCN 36532). The Fermi GBM on-ground location is consistent with the Swift/BAT-GUANO position.
The angle from the Fermi LAT boresight is 101 degrees.
The GBM light curve single emission episode with a duration (T90) of about 34 s (50-300 keV). The time-averaged spectrum from T0-16 to T0+17 s is best fit by a simple power law function with index -1.64 +/- 0.04.
The event fluence (10-1000 keV) in this time interval is (4 +/- 0.5)E-06 erg/cm^2. The 1-sec peak photon flux measured starting from T0-9.9 s in the 10-1000 keV band is 4.1 +/- 0.4 ph/s/cm^2.
A power law function with an exponential high-energy cutoff fits the spectrum equally well. The power law index is -1.48 +/- 0.11 and the cutoff energy, parameterized as Epeak, is 222 +/- 94 keV.
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/"

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Jochen Greiner, last update: 23-May-2024 [Disclaimer]