Gamma-ray Burst 250602A

(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:     Mon 02 Jun 25 03:05:00 UT
NOTICE_TYPE:     Fermi-GBM Flight Position
RECORD_NUM:      51
TRIGGER_NUM:     770526276
GRB_RA:          114.983d {+07h 39m 56s} (J2000),
                 115.696d {+07h 42m 47s} (current),
                 113.571d {+07h 34m 17s} (1950)
GRB_DEC:         +71.733d {+71d 43' 60"} (J2000),
                 +71.673d {+71d 40' 22"} (current),
                 +71.848d {+71d 50' 52"} (1950)
GRB_ERROR:       10.87 [deg radius, statistical plus systematic]
GRB_INTEN:       398 [cnts/sec]
DATA_SIGNIF:     16.30 [sigma]
INTEG_TIME:      1.024 [sec]
GRB_DATE:        20828 TJD;   153 DOY;   25/06/02
GRB_TIME:        11071.31 SOD {03:04:31.31} UT
GRB_PHI:         321.00 [deg]
GRB_THETA:       115.00 [deg]
DATA_TIME_SCALE: 1.0240 [sec]
HARD_RATIO:      0.64
LOC_ALGORITHM:   3 (version number of)
MOST_LIKELY:      95%  GRB
2nd_MOST_LIKELY:   3%  Generic Transient
DETECTORS:       0,1,0, 0,1,0, 0,0,0, 0,0,0, 0,0,
SUN_POSTN:        70.35d {+04h 41m 23s}  +22.21d {+22d 12' 21"}
SUN_DIST:         55.71 [deg]   Sun_angle= -3.0 [hr] (East of Sun)
MOON_POSTN:      153.06d {+10h 12m 15s}  +13.37d {+13d 22' 03"}
MOON_DIST:        62.44 [deg]
MOON_ILLUM:      40 [%]
GAL_COORDS:      143.54, 29.45 [deg] galactic lon,lat of the burst (or transient)
ECL_COORDS:      101.72, 49.31 [deg] ecliptic lon,lat of the burst (or transient)
LC_URL:          http://heasarc.gsfc.nasa.gov/FTP/fermi/data/gbm/triggers/2025/bn250602128/quicklook/glg_lc_medres34_bn250602128.gif
COMMENTS:        Fermi-GBM Flight-calculated Coordinates.  
COMMENTS:        This trigger occurred at longitude,latitude = 198.83,0.78 [deg].  
COMMENTS:        The LC_URL file will not be created until ~15 min after the trigger.

GCN NOTICE

TITLE:           GCN/FERMI NOTICE
NOTICE_DATE:     Mon 02 Jun 25 03:05:17 UT
NOTICE_TYPE:     Fermi-GBM Ground Position
RECORD_NUM:      61
TRIGGER_NUM:     770526276
GRB_RA:          117.610d {+07h 50m 26s} (J2000),
                 118.177d {+07h 52m 42s} (current),
                 116.490d {+07h 45m 58s} (1950)
GRB_DEC:         +62.600d {+62d 36' 00"} (J2000),
                 +62.534d {+62d 32' 02"} (current),
                 +62.727d {+62d 43' 36"} (1950)
GRB_ERROR:       7.77 [deg radius, statistical only]
DATA_SIGNIF:     20.60 [sigma]
DATA_INTERVAL:   1.024 [sec]
GRB_DATE:        20828 TJD;   153 DOY;   25/06/02
GRB_TIME:        11071.31 SOD {03:04:31.31} UT
GRB_PHI:         319.00 [deg]
GRB_THETA:       106.00 [deg]
E_RANGE:         44.032 - 279.965 [keV]
LOC_ALGORITHM:   4173 (Gnd S/W Version number)
SUN_POSTN:        70.35d {+04h 41m 23s}  +22.21d {+22d 12' 21"}
SUN_DIST:         51.54 [deg]   Sun_angle= -3.2 [hr] (East of Sun)
MOON_POSTN:      153.07d {+10h 12m 16s}  +13.37d {+13d 21' 59"}
MOON_DIST:        55.03 [deg]
MOON_ILLUM:      40 [%]
GAL_COORDS:      154.07, 30.60 [deg] galactic lon,lat of the burst (or transient)
ECL_COORDS:      106.34, 40.72 [deg] ecliptic lon,lat of the burst (or transient)
LC_URL:          http://heasarc.gsfc.nasa.gov/FTP/fermi/data/gbm/triggers/2025/bn250602128/quicklook/glg_lc_medres34_bn250602128.gif
POS_MAP_URL:     http://gcn.gsfc.nasa.gov/notices_f/gbm_gnd_loc_map_770526276.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 NOTICE

TITLE:           GCN/FERMI NOTICE
NOTICE_DATE:     Mon 02 Jun 25 03:06:28 UT
NOTICE_TYPE:     Fermi-GBM Ground Position
RECORD_NUM:      0
TRIGGER_NUM:     770526276
GRB_RA:          115.420d {+07h 41m 41s} (J2000),
                 115.992d {+07h 43m 58s} (current),
                 114.291d {+07h 37m 10s} (1950)
GRB_DEC:         +62.620d {+62d 37' 12"} (J2000),
                 +62.559d {+62d 33' 31"} (current),
                 +62.737d {+62d 44' 13"} (1950)
GRB_ERROR:       5.37 [deg radius, statistical only]
DATA_SIGNIF:     18.30 [sigma]
DATA_INTERVAL:   9.216 [sec]
GRB_DATE:        20828 TJD;   153 DOY;   25/06/02
GRB_TIME:        11071.31 SOD {03:04:31.31} UT
GRB_PHI:         320.00 [deg]
GRB_THETA:       106.00 [deg]
E_RANGE:         44.032 - 279.965 [keV]
LOC_ALGORITHM:   41731 (Gnd S/W Version number)
SUN_POSTN:        70.35d {+04h 41m 23s}  +22.21d {+22d 12' 22"}
SUN_DIST:         50.68 [deg]   Sun_angle= -3.0 [hr] (East of Sun)
MOON_POSTN:      153.08d {+10h 12m 18s}  +13.36d {+13d 21' 43"}
MOON_DIST:        55.75 [deg]
MOON_ILLUM:      40 [%]
GAL_COORDS:      154.01, 29.60 [deg] galactic lon,lat of the burst (or transient)
ECL_COORDS:      105.05, 40.50 [deg] ecliptic lon,lat of the burst (or transient)
LC_URL:          http://heasarc.gsfc.nasa.gov/FTP/fermi/data/gbm/triggers/2025/bn250602128/quicklook/glg_lc_medres34_bn250602128.gif
POS_MAP_URL:     http://gcn.gsfc.nasa.gov/notices_f/gbm_gnd_loc_map_770526276.fits
COMMENTS:        Fermi-GBM Ground-calculated Coordinates.  
COMMENTS:        This is likely a Long GRB.  
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 NOTICE

TITLE:           GCN/FERMI NOTICE
NOTICE_DATE:     Mon 02 Jun 25 03:13:40 UT
NOTICE_TYPE:     Fermi-GBM Final Position
RECORD_NUM:      0
TRIGGER_NUM:     770526276
GRB_RA:          111.670d {+07h 26m 41s} (J2000),
                 112.317d {+07h 29m 16s} (current),
                 110.391d {+07h 21m 34s} (1950)
GRB_DEC:         +67.790d {+67d 47' 24"} (J2000),
                 +67.737d {+67d 44' 13"} (current),
                 +67.890d {+67d 53' 24"} (1950)
GRB_ERROR:       4.88 [deg radius, statistical only]
GRB_DATE:        20828 TJD;   153 DOY;   25/06/02
GRB_TIME:        11071.31 SOD {03:04:31.31} UT
GRB_PHI:         322.00 [deg]
GRB_THETA:       111.00 [deg]
E_RANGE:         44.032 - 279.965 [keV]
LOC_ALGORITHM:   41731 (Gnd S/W Version number)
SUN_POSTN:        70.35d {+04h 41m 25s}  +22.21d {+22d 12' 24"}
SUN_DIST:         52.37 [deg]   Sun_angle= -2.8 [hr] (East of Sun)
MOON_POSTN:      153.14d {+10h 12m 32s}  +13.33d {+13d 20' 05"}
MOON_DIST:        60.50 [deg]
MOON_ILLUM:      40 [%]
GAL_COORDS:      148.03, 28.27 [deg] galactic lon,lat of the burst (or transient)
ECL_COORDS:      101.43, 45.21 [deg] ecliptic lon,lat of the burst (or transient)
LC_URL:          http://heasarc.gsfc.nasa.gov/FTP/fermi/data/gbm/triggers/2025/bn250602128/quicklook/glg_lc_medres34_bn250602128.gif
LOC_URL:         http://heasarc.gsfc.nasa.gov/FTP/fermi/data/gbm/triggers/2025/bn250602128/quicklook/glg_locplot_all_bn250602128.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 Circular #40602
The Fermi GBM team reports the detection of a likely LONG GRB
At 03:04:31 UT on 2 Jun 2025, the Fermi Gamma-ray Burst Monitor (GBM) triggered and located GRB 250602A (trigger 770526276.307432 / 250602128).
The on-ground calculated location, using the Fermi GBM trigger data, is RA = 111.7, Dec = 67.8 (J2000 degrees, equivalent to J2000 07h 26m, 67d 47'), with a statistical uncertainty of 4.9 degrees.
The angle from the Fermi LAT boresight is 111.0 degrees.
The skymap can be found here: https://heasarc.gsfc.nasa.gov/FTP/fermi/data/gbm/triggers/2025/bn250602128/quicklook/glg_skymap_all_bn250602128.png
The HEALPix FITS file, including the estimated localization systematic, can be found here: https://heasarc.gsfc.nasa.gov/FTP/fermi/data/gbm/triggers/2025/bn250602128/quicklook/glg_healpix_all_bn250602128.fit
The GBM light curve can be found here: https://heasarc.gsfc.nasa.gov/FTP/fermi/data/gbm/triggers/2025/bn250602128/quicklook/glg_lc_medres34_bn250602128.gif
GCN Circular #40610
Sahil Atri (U Roma), Rosa L. Becerra (U Roma), Alan M. Watson (UNAM), Camila Angulo Valdez (UNAM), Nat Butler (ASU), Simone Dichiara (Penn State University), Tsvetelina Dimitrova (ASU), Alexander Kutyrev (GSFC/UMD), William H. Lee (UNAM), Océlotl López (UNAM), Margarita Pereyra (UNAM) and Eleonora Troja (U Roma) report:
We observed the field of GRB 250602A detected by Fermi/GBM (Fermi GBM Team, GCN Circ. 40602) with the DDOTI/OAN wide-field imager at the Observatorio Astronómico Nacional on Sierra San Pedro Mártir (http://ddoti.astroscu.unam.mx) on the night of 2025-06-02 UTC.
DDOTI observed the Fermi/GBM error region, covering about 88% of the statistical error region (Fermi GBM Team, GCN Circ. 40602). DDOTI observed the field of GRB 250602A from 04:05 UTC to 06:05 UTC (from T+1.01 h to T+ 3.02 h after the trigger) and obtained a total exposure of 50 minutes, alternating with other scientific programs.
Comparing our observations to the USNO-B1 and Pan-STARRS PS1 DR2 catalogues, we detect no uncatalogued fading sources within the observed field down to a 10-sigma limiting AB magnitude of:
w > 20.0
This value is not corrected for the Galactic extinction.
We thank the staff of the Observatorio Astronómico Nacional on the Sierra of San Pedro Mártir.
GCN Circular #40611
A. Holzmann Airasca (UniTrento and INFN Bari), S. Lopez (CNRS / IN2P3), R. Gupta (NASA GSFC), F. Longo (University and INFN, Trieste), N. Di Lalla (Stanford Univ.), and J. Racusin (NASA GSFC) report on behalf of the Fermi-LAT Collaboration:
On June 02, 2025, Fermi-LAT detected high-energy emission from GRB 250602A, which was also detected by Fermi-GBM (trigger 770526276 / 250602128, GCN 40602).
The best LAT on-ground location is found to be:
RA, Dec = 111.9, 56.9 (J2000)
with an error radius of 0.4 deg (90 % containment, statistical error only). This was 111 deg from the LAT boresight at the time of the GBM trigger (T0 = 03:04:31.31 UT).
The data from the Fermi-LAT shows a significant increase in the event rate that is spatially and temporally correlated with the GBM emission with high significance. The photon flux above 100 MeV in the time interval 3000 - 8000 s after the GBM trigger is (8.2 ± 3.2) E-7 ph/cm2/s. The estimated photon index above 100 MeV is -2.17 ± 0.33.
The highest-energy photon is a 1.6 GeV event which is observed ~ 4800 seconds after the GBM trigger.
The Fermi-LAT point of contact for this burst is Rahul Gupta (rahul.gupta@nasa.gov).
The Fermi-LAT is a pair conversion telescope designed to cover the energy band from 20 MeV to greater than 300 GeV. It is the product of an international collaboration between NASA and DOE in the U.S. and many scientific institutions across France, Italy, Japan and Sweden.
GCN Circular #40612
Jacob Smith (UAH) and C. Meegan (UAH) report on behalf of the Fermi Gamma-ray Burst Monitor Team:
At 03:04:31.31 UT on 02 June 2025, the Fermi Gamma-ray Burst Monitor (GBM) triggered and located GRB 250602A (trigger 770526276/250602128). which was also detected by Fermi-LAT (A. Holzmann Airasca, et al. 2025, GCN 40611). The Fermi GBM on-ground location is consistent with the Fermi-LAT position.
The angle from the Fermi LAT boresight is 111 degrees.
The GBM light curve consists of a single emission episode with a duration (T90) of about 14.6 s (50-300 keV). The time-averaged spectrum from T0+0.003 to T0+8.768 s is best fit by a power law function with an exponential high-energy cutoff. The power law index is -0.9 +/- 0.1 and the cutoff energy, parameterized as Epeak, is 120 +/- 10 keV.
The event fluence (10-1000 keV) in this time interval is (1.7 +/- 0.1)E-06 erg/cm^2. The 1-sec peak photon flux measured starting from T0+0.0 s in the 10-1000 keV band is 5.8 +/- 0.3 ph/s/cm^2.
A Band function fits the spectrum equally well with Epeak= 102 +/- 22 keV, alpha = -0.7 +/- 0.3 and beta = -2.2 +/- 0.2.
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 #40620
Rosa L. Becerra (U Roma), Sahil Atri (U Roma), Alan M. Watson (UNAM), Camila Angulo Valdez (UNAM), Nat Butler (ASU), Simone Dichiara (Penn State University), Tsvetelina Dimitrova (ASU), Alexander Kutyrev (GSFC/UMD), William H. Lee (UNAM), Océlotl López (UNAM), Margarita Pereyra (UNAM) and Eleonora Troja (U Roma) report:
We continued our follow-up campaign of GRB 250602A, detected by Fermi/GBM (Fermi GBM Team, GCN Circ. 40602) with the DDOTI/OAN wide-field imager at the Observatorio Astronómico Nacional on Sierra San Pedro Mártir (http://ddoti.astroscu.unam.mx) on the night of 2025-06-03 UTC.
DDOTI observed the Fermi/LAT error region (Holzmann Airasca et al., GCN Circ. 40611), from 03:51 UTC to 05:01 UTC (from T+24.7 h to T+ 25.9 h after the trigger), obtaining a total exposure time of 48 minutes.
By comparing our observations with the USNO-B1 and Pan-STARRS PS1 DR2 catalogs, and performing image subtraction using a Pan-STARRS PS1 DR2 template, we detect no uncatalogued sources within the observed field down to a 10-sigma limiting AB magnitude of:
w > 20.0
Unfortunately, the Fermi/LAT error region was not included in the field observed on the night of 2025-06-02 UTC (Atri et al., GCN Circ. 40610).
This value is not corrected for the Galactic extinction.
We thank the staff of the Observatorio Astronómico Nacional on the Sierra of San Pedro Mártir.

GCN NOTICE

TITLE:           GCN/FERMI NOTICE
NOTICE_DATE:     Wed 04 Jun 25 14:24:42 UT
NOTICE_TYPE:     Fermi-LAT Offline Position
TRIGGER_NUM:     770526276
GRB_RA:          111.890d {+07h 27m 34s} (J2000),
                 112.417d {+07h 29m 40s} (current),
                 110.850d {+07h 23m 24s} (1950)
GRB_DEC:         +56.940d {+56d 56' 24"} (J2000),
                 +56.887d {+56d 53' 12"} (current),
                 +57.041d {+57d 02' 29"} (1950)
GRB_ERROR:       24.00 [arcmin radius, 90% containment, statistical only]
GRB_DATE:        20828 TJD;   153 DOY;   25/06/02
GRB_TIME:        11071.30 SOD {03:04:31.30} UT
TRIGGER_ID:      0x20000000
MISC:            0x40000000
SUN_POSTN:        72.89d {+04h 51m 33s}  +22.50d {+22d 30' 11"}
SUN_DIST:         44.78 [deg]   Sun_angle= -2.6 [hr] (East of Sun)
MOON_POSTN:      180.22d {+12h 00m 54s}   -0.67d {-00d 40' 07"}
MOON_DIST:        78.66 [deg]
MOON_ILLUM:      64 [%]
GAL_COORDS:      160.25, 27.28 [deg] galactic lon,lat of the burst (or transient)
ECL_COORDS:      104.30, 34.58 [deg] ecliptic lon,lat of the burst (or
+transient)
COMMENTS:        Fermi LAT Offline position.  
COMMENTS:        This Notice was ground-generated -- not flight-generated.  
COMMENTS:        It is the result of human-in-the-loop processing.
COMMENTS:        This is a human generated position of a LAT ground   
COMMENTS:        This source corresponds to GBM trigger.

GCN Circular #40637
Chao Zheng, Chen-Wei Wang, Yan-Qiu Zhang, Shao-Lin Xiong, Yue Huang (IHEP) report on behalf of GECAM team:
GECAM-A detected burst GRB 250602A at 2025-06-02T03:04:31.310 UTC (denoted as T0), which was also detected by Fermi/GBM (Fermi GBM team, GCN #40602).
According to the GECAM-A light curves in about 70-6000 keV, this burst mainly consists of a single pulse with a duration (T90) of about 8.68 s.
The GECAM-A light curve can be found here: https://www.bursthub.cn//admin/static/gecamgrb250602A.png
Gravitational wave high-energy Electromagnetic Counterpart All-sky Monitor (GECAM) mission originally consists of two micro-satellites (GECAM-A and GECAM-B) launched in Dec. 2020. As the third member of GECAM constellation, GECAM-C was launched onboard SATech-01 experimental satellite in July 2022. GECAM mission is funded by the Chinese Academy of Sciences (CAS).

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Jochen Greiner, last update: 06-Jun-2025 [Disclaimer]