Gamma-ray Burst 240227A

(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 27 Feb 24 04:40:44 UT
NOTICE_TYPE:     Fermi-GBM Flight Position
RECORD_NUM:      49
TRIGGER_NUM:     730701620
GRB_RA:           33.050d {+02h 12m 12s} (J2000),
                  33.289d {+02h 13m 09s} (current),
                  32.555d {+02h 10m 13s} (1950)
GRB_DEC:         -43.917d {-43d 55' 00"} (J2000),
                 -43.804d {-43d 48' 14"} (current),
                 -44.151d {-44d 09' 02"} (1950)
GRB_ERROR:       11.68 [deg radius, statistical plus systematic]
GRB_INTEN:       400 [cnts/sec]
DATA_SIGNIF:     14.80 [sigma]
INTEG_TIME:      0.512 [sec]
GRB_DATE:        20367 TJD;    58 DOY;   24/02/27
GRB_TIME:        16815.16 SOD {04:40:15.16} UT
GRB_PHI:         329.00 [deg]
GRB_THETA:        40.00 [deg]
DATA_TIME_SCALE: 0.5120 [sec]
HARD_RATIO:      0.28
LOC_ALGORITHM:   3 (version number of)
MOST_LIKELY:      97%  GRB
2nd_MOST_LIKELY:   1%  Generic Transient
DETECTORS:       1,0,0, 0,1,0, 0,0,0, 0,0,0, 0,0,
SUN_POSTN:       339.73d {+22h 38m 56s}   -8.54d {-08d 32' 19"}
SUN_DIST:         58.21 [deg]   Sun_angle= -3.6 [hr] (East of Sun)
MOON_POSTN:      186.67d {+12h 26m 41s}   -2.03d {-02d 01' 39"}
MOON_DIST:       128.34 [deg]
MOON_ILLUM:      94 [%]
GAL_COORDS:      264.11,-66.63 [deg] galactic lon,lat of the burst (or transient)
ECL_COORDS:        7.97,-52.43 [deg] ecliptic lon,lat of the burst (or transient)
LC_URL:          http://heasarc.gsfc.nasa.gov/FTP/fermi/data/gbm/triggers/2024/bn240227195/quicklook/glg_lc_medres34_bn240227195.gif
COMMENTS:        Fermi-GBM Flight-calculated Coordinates.  
COMMENTS:        This trigger occurred at longitude,latitude = 258.80,-21.25 [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 27 Feb 24 04:41:02 UT
NOTICE_TYPE:     Fermi-GBM Ground Position
RECORD_NUM:      59
TRIGGER_NUM:     730701620
GRB_RA:           33.140d {+02h 12m 34s} (J2000),
                  33.369d {+02h 13m 29s} (current),
                  32.665d {+02h 10m 40s} (1950)
GRB_DEC:         -47.450d {-47d 27' 00"} (J2000),
                 -47.338d {-47d 20' 14"} (current),
                 -47.684d {-47d 41' 00"} (1950)
GRB_ERROR:       3.80 [deg radius, statistical only]
DATA_SIGNIF:     14.80 [sigma]
DATA_INTERVAL:   0.512 [sec]
GRB_DATE:        20367 TJD;    58 DOY;   24/02/27
GRB_TIME:        16815.16 SOD {04:40:15.16} UT
GRB_PHI:         332.00 [deg]
GRB_THETA:        37.00 [deg]
E_RANGE:         44.032 - 279.965 [keV]
LOC_ALGORITHM:   4173 (Gnd S/W Version number)
SUN_POSTN:       339.73d {+22h 38m 56s}   -8.54d {-08d 32' 19"}
SUN_DIST:         59.57 [deg]   Sun_angle= -3.6 [hr] (East of Sun)
MOON_POSTN:      186.67d {+12h 26m 42s}   -2.03d {-02d 01' 44"}
MOON_DIST:       125.38 [deg]
MOON_ILLUM:      94 [%]
GAL_COORDS:      270.32,-64.22 [deg] galactic lon,lat of the burst (or transient)
ECL_COORDS:        4.66,-55.38 [deg] ecliptic lon,lat of the burst (or transient)
LC_URL:          http://heasarc.gsfc.nasa.gov/FTP/fermi/data/gbm/triggers/2024/bn240227195/quicklook/glg_lc_medres34_bn240227195.gif
POS_MAP_URL:     http://gcn.gsfc.nasa.gov/notices_f/gbm_gnd_loc_map_730701620.fits
COMMENTS:        Fermi-GBM Ground-calculated Coordinates.  
COMMENTS:        In the LAT Field-of-view.  
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.  
COMMENTS:           
COMMENTS:        NOTE: This GBM event is temporally(1.0<100sec) coincident with the INTEGRAL_SPIACS event (trignum=10593).

GCN NOTICE

TITLE:           GCN/FERMI NOTICE
NOTICE_DATE:     Tue 27 Feb 24 04:46:53 UT
NOTICE_TYPE:     Fermi-GBM Final Position
RECORD_NUM:      0
TRIGGER_NUM:     730701620
GRB_RA:           69.590d {+04h 38m 22s} (J2000),
                  69.671d {+04h 38m 41s} (current),
                  69.424d {+04h 37m 42s} (1950)
GRB_DEC:         -61.170d {-61d 10' 11"} (J2000),
                 -61.123d {-61d 07' 22"} (current),
                 -61.267d {-61d 16' 02"} (1950)
GRB_ERROR:       3.63 [deg radius, statistical only]
GRB_DATE:        20367 TJD;    58 DOY;   24/02/27
GRB_TIME:        16815.16 SOD {04:40:15.16} UT
GRB_PHI:         315.00 [deg]
GRB_THETA:        13.00 [deg]
E_RANGE:         44.032 - 279.965 [keV]
LOC_ALGORITHM:   41731 (Gnd S/W Version number)
SUN_POSTN:       339.74d {+22h 38m 57s}   -8.54d {-08d 32' 13"}
SUN_DIST:         82.50 [deg]   Sun_angle= -6.0 [hr] (East of Sun)
MOON_POSTN:      186.72d {+12h 26m 52s}   -2.05d {-02d 03' 06"}
MOON_DIST:       100.84 [deg]
MOON_ILLUM:      94 [%]
GAL_COORDS:      271.48,-39.41 [deg] galactic lon,lat of the burst (or transient)
ECL_COORDS:       21.48,-79.59 [deg] ecliptic lon,lat of the burst (or transient)
LC_URL:          http://heasarc.gsfc.nasa.gov/FTP/fermi/data/gbm/triggers/2024/bn240227195/quicklook/glg_lc_medres34_bn240227195.gif
LOC_URL:         http://heasarc.gsfc.nasa.gov/FTP/fermi/data/gbm/triggers/2024/bn240227195/quicklook/glg_locplot_all_bn240227195.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:        In the LAT Field-of-view.  
COMMENTS:        This is likely a Short GRB.  
COMMENTS:           
COMMENTS:        NOTE: This GBM event is temporally(1.0<100sec) coincident with the INTEGRAL_SPIACS event (trignum=10593).

GCN Circular #35814
The Fermi GBM team reports the detection of a likely SHORT GRB
At 04:40:15 UT on 27 Feb 2024, the Fermi Gamma-ray Burst Monitor (GBM) triggered and located GRB 240227A (trigger 730701620.164308 / 240227195).
The on-ground calculated location, using the Fermi GBM trigger data, is RA = 69.6, Dec = -61.2 (J2000 degrees, equivalent to J2000 04h 38m, -61d 12'), with a statistical uncertainty of 3.6 degrees.
The angle from the Fermi LAT boresight is 13.0 degrees.
The skymap can be found here: https://heasarc.gsfc.nasa.gov/FTP/fermi/data/gbm/triggers/2024/bn240227195/quicklook/glg_skymap_all_bn240227195.png
The HEALPix FITS file, including the estimated localization systematic, can be found here: https://heasarc.gsfc.nasa.gov/FTP/fermi/data/gbm/triggers/2024/bn240227195/quicklook/glg_healpix_all_bn240227195.fit
The GBM light curve can be found here: https://heasarc.gsfc.nasa.gov/FTP/fermi/data/gbm/triggers/2024/bn240227195/quicklook/glg_lc_medres34_bn240227195.gif
GCN Circular #35821
D. Svinkin, D. Frederiks, A. Ridnaia, 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,
E. Bozzo and C. Ferrigno, on behalf of the INTEGRAL SPI-ACS GRB team, report:
The short-duration GRB 240227A (Fermi-GBM detection: The Fermi GBM team, GCN 35814) was detected by Fermi (GBM trigger 730701620), Konus-Wind, and INTEGRAL (SPI-ACS) at about 16815 s UT (04:40:15).
We have triangulated it to a preliminary, 3 sigma error box whose coordinates are:
```
 ---------------------------------------------
  RA(2000), deg                 Dec(2000), deg
 ---------------------------------------------
 Center:
   18.683 (01h 14m 44s) -34.040 (-34d 02' 23")
 Corners:
   19.224 (01h 16m 54s) -35.743 (-35d 44' 35")
   18.820 (01h 15m 17s) -32.316 (-32d 18' 58")
   18.123 (01h 12m 29s) -32.337 (-32d 20' 15")
   18.499 (01h 14m 00s) -35.765 (-35d 45' 54")
 ---------------------------------------------
```
The error box area is 2.02 sq. deg, and its maximum dimension is 3.53 deg (the minimum one is 35 arcmin). The Sun distance was 43 deg.
This localization may be improved.
A triangulation map and HEALPix FITS file are posted at http://www.ioffe.ru/LEA/GRBs/GRB240227_T16812/IPN
The Konus-Wind time history and spectrum will be given in a forthcoming GCN Circular.
GCN Circular #35825
V. Lipunov, V.Kornilov, E. Gorbovskoy, K. Zhirkov, N.Tyurina, P.Balanutsa, A.Kuznetsov, V.Senik, D. Vlasenko, G.Antipov, D.Zimnukhov, E.Minkina, A.Chasovnikov, V.Topolev, D.Kuvshinov, D. Cheryasov, Ya.Kechin, Yu.Tselik, A. Sosnovskij (Lomonosov Moscow State University, SAI, Physics Department),
R. Podesta, C.Lopez, F. Podesta, C.Francile (Observatorio Astronomico Felix Aguilar OAFA),
R. Rebolo, M. Serra (The Instituto de Astrofisica de Canarias),
D. Buckley (South African Astronomical Observatory),
O.A. Gress, N.M. Budnev, O.Ershova (Irkutsk State University, API),
L.Carrasco, J.R.Valdes, V.Chavushyan, V.M.Patino Alvarez, J.Martinez, A.R.Corella, L.H.Rodriguez (INAOE, Guillermo Haro Astrophysics Observatory),
A. Tlatov, D. Dormidontov (Kislovodsk Solar Station of the Pulkovo Observatory),
V. Yurkov, A. Gabovich (Blagoveschensk Educational State University)
MASTER-SAAO robotic telescope (Global MASTER-Net: http://observ.pereplet.ru, Lipunov et al., 2010, Advances in Astronomy, vol. 2010, 30L) located in South Africa (South African Astronomical Observatory) started inspect of the Fermi GRB 240227A ( Fermi GBM team, GCN 35814) errorbox 48100 sec after notice time and 48133 sec after trigger time at 2024-02-27 18:02:28 UT, with upper limit up to 18.0 mag. Observations started at twilight. The observations began at zenith distance = 32 deg. The sun altitude is -10.2 deg.
The galactic latitude b = -39 deg., longitude l = 271 deg.
Real time updated cover map and OT discovered available here: https://master.sai.msu.ru/site/master2/observ.php?id=2387115
We obtain a following upper limits.
```
Tmid-T0  |      Date Time      |          Site       |             Coord (J2000)          |Filt.| Expt. | Limit| Comment
_________|_____________________|_____________________|____________________________________|_____|_______|_______|________

   48163 | 2024-02-27 18:02:28 |         MASTER-SAAO | (04h 37m 02.73s , -61d 29m 49.8s) |   C |    60 | 17.6 |        
   48163 | 2024-02-27 18:02:28 |         MASTER-SAAO | (04h 55m 01.13s , -61d 40m 45.7s) |   C |    60 | 17.3 |        
   48243 | 2024-02-27 18:03:47 |         MASTER-SAAO | (04h 21m 16.28s , -59d 36m 59.5s) |   C |    60 | 17.8 |        
   48243 | 2024-02-27 18:03:47 |         MASTER-SAAO | (04h 38m 13.45s , -59d 47m 57.1s) |   C |    60 | 17.4 |        
   48322 | 2024-02-27 18:05:07 |         MASTER-SAAO | (04h 21m 36.67s , -63d 25m 43.7s) |   C |    60 | 18.0 |        
   48322 | 2024-02-27 18:05:07 |         MASTER-SAAO | (04h 40m 47.01s , -63d 36m 37.9s) |   C |    60 | 17.7 |        
```
Filter C is a clear (unfiltred) band.
The observation and reduction will continue. The message may be cited.
GCN Circular #35871
A.S. Kozyrev, D.V. Golovin, M.L. Litvak, I.G. Mitrofanov, and A.B. Sanin on behalf of the MGNS/BepiColombo team,
J. Benkhoff on behalf of the BepiColombo team,
D. Svinkin, D. Frederiks, A. Ridnaia, 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,
and
E. Bozzo and C. Ferrigno, on behalf of the INTEGRAL SPI-ACS GRB team, report:
Using the BepiColombo (MGNS) data we have improved the previous IPN error box (Svinkin et al., GCN 35821).
The coordinates of the updated 3 sigma error box are:
```
 ---------------------------------------------
  RA(2000), deg                 Dec(2000), deg
 ---------------------------------------------
 Center:
   18.725 (01h 14m 54s) -34.410 (-34d 24' 34")
 Corners:
   18.512 (01h 14m 03s) -35.909 (-35d 54' 32")
   18.933 (01h 15m 44s) -33.175 (-33d 10' 30")
   18.900 (01h 15m 36s) -32.912 (-32d 54' 42")
   18.488 (01h 13m 57s) -35.644 (-35d 38' 37")
 ---------------------------------------------
```
The error box area is 561 sq. arcmin, and its maximum dimension is 3.01 deg (the minimum one is 3.4 arcmin). The Sun distance was 44 deg.
This box may be further improved.
Updated triangulation map and HEALPix FITS files are posted at http://www.ioffe.ru/LEA/GRBs/GRB240227_T16812/IPN/
GCN Circular #35874
D. Frederiks, A.Lysenko, A. Ridnaia, D. Svinkin, A. Tsvetkova, M. Ulanov, and T. Cline, on behalf of the Konus-Wind team, report:
The short GRB 240227A (Fermi-GBM detection: The Fermi GBM team, GCN 35814; IPN triangulation: Svinkin et al., GCN 35821; Kozyrev et al., GCN 35871). triggered Konus-Wind (KW) at T0=16812.986 s UT (04:40:12.986).
The burst light curve shows a single multi-peaked emission pulse which starts at ~T0-0.400 s and has a duration of ~0.5 s. The emission is seen up to ~2 MeV.
The Konus-Wind light curve of this GRB is available at http://www.ioffe.ru/LEA/GRBs/GRB240227_T16812/
As observed by Konus-Wind, the burst had the total fluence of 1.72(-0.28,+0.36)x10^-6 erg/cm^2 and a 16-ms peak energy flux, measured from T0+0.032 s, of 8.21(-2.63,+3.09)x10^-6 erg/cm^2/s (both in the 20 keV - 10 MeV energy range).
Since a major part of the burst emission was detected before the trigger, a time-averaged spectral analysis was performed using the KW 3-channel light curve data. Modeling the 3-channel time-integrated spectrum (measured from T0-0.400 s to T0+0.096 s) by a power law with exponential cutoff (CPL) model dN/dE ~ (E^alpha)*exp(-E*(2+alpha)/Ep) yields alpha = -0.47 (-0.24, + 0.28) and Ep = 688(-133,+222) keV.
A multi-channel spectrum near the peak count rate (measured from T0 to T0+0.064 s) is best fit in the 20 keV - 15 MeV range by a CPL model with alpha = -0.12(-0.47,+0.70) and Ep = 759(-233,+403) keV (chi2 = 6.4/10 dof).
All the quoted errors are estimated at the 68% confidence level. All the presented results are preliminary.
GCN Circular #35896
C.C. Cheung, R. Woolf, M. Kerr, J.E. Grove (NRL), A. Goldstein (USRA), C.A.= Wilson-Hodge, D. Kocevski (MSFC), and M.S. Briggs (UAH) report:
The Glowbug gamma-ray telescope [1,2], operating on the International Space= Station, reports the detection of the short GRB 240227A, which was also de= tected by Fermi/GBM, Konus/Wind, INTEGRAL/SPI-ACS, and BepiColombo (GCN 358= 14, 35821, 35871, 35874).
Using an adaptive window with a resolution of 32-ms, the burst onset is det= ermined to be 2024-02-27 04:40:14.152 with a duration of 0.51 s and a total= significance of about 16.3 sigma. The light curve comprises a single peak= .
Using a standard power-law function with an exponential high-energy cutoff = [3] to model the emission over this duration results in a photon index dN/d= E~E^x of x=3D1.0 and a cutoff energy ("Epeak") of 576 keV. The modeled 10-= 10000 keV fluence is 1.5e-06 erg/cm^2.
The analysis results presented here are preliminary and use a response func= tion that lacks a detailed characterization of the surrounding passive stru= cture of the ISS.
Glowbug is a NASA-funded technology demonstrator for sensitive, low-cost ga= mma-ray transient telescopes developed, built, and operated by the U.S. Nav= al Research Laboratory (NRL) with support from the University of Alabama in= Huntsville, USRA, and NASA MSFC. It was launched on 2023 March 15 aboard = the Department of Defense Space Test Program=E2=80=99s STP-H9 to the ISS. = The detector comprises 12 large-area (15 cm x 15 cm) CsI:Tl panels covering= the surface of a half cube, and two hexagonal (5-cm diameter, 10-cm length= ) CLLB scintillators, giving it a large field of view (instantaneous FoV ~2= /3 sky) over a wide energy band of 50 keV to >2 MeV.
[1] Grove, J.E. et al. 2020, Proc. Yamada Conf. LXXI, arXiv:2009.11959 [2] Woolf, R.S. et al. 2022, Proc. SPIE, 12181, id. 121811O [3] Goldstein, A. et al. 2020, ApJ 895, 40, arXiv :1909.03006
Distribution Statement A: Approved for public release. Distribution is unl= imited.

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