GRB 250602A
GCN Circular 40602
Subject
GRB 250602A: Fermi GBM Final Real-time Localization
Date
2025-06-02T03:14:49Z (23 days ago)
From
Fermi GBM Team at MSFC/Fermi-GBM <do_not_reply@GIOC.nsstc.nasa.gov>
Via
email
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
Subject
GRB 250602A: DDOTI Optical Upper Limit
Date
2025-06-02T19:56:39Z (22 days ago)
From
sahil.atri@students.uniroma2.eu
Via
Web form
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
Subject
GRB 250602A: Fermi-LAT detection
Date
2025-06-02T20:13:59Z (22 days ago)
From
Rahul Gupta at NASA GSFC <rahul.gupta@nasa.gov>
Via
Web form
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
Subject
GRB 250602A: Fermi GBM Observation
Date
2025-06-03T01:47:35Z (22 days ago)
From
Jacob Smith at Fermi-GBM Team <jrs0118@uah.edu>
Via
Web form
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
Subject
GRB 250602A: DDOTI Optical Follow-Up of the Fermi/LAT Localization
Date
2025-06-03T15:06:50Z (22 days ago)
From
Rosa L. Becerra at Tor Vergata, Roma <rosa.becerra@roma2.infn.it>
Via
Web form
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 Circular 40637
Subject
GRB 250602A: GECAM detection
Date
2025-06-06T04:33:43Z (19 days ago)
From
zhengchao_astro@foxmail.com
Via
Web form
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).