GRB 250607A

H. Yang, O. Godet, S. Guillot (IRAP), D. Turpin (CEA) 

report on behalf of the SVOM team:

The SVOM/ECLAIRs telescope detected GRB 250607A, also detected by Fermi/GBM (GCN 40648
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 ) and SVOM/GRM (GCN 40651
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 ), starting at 2025-06-07T14:00:51 UTC (T0), through an offline targeted search with the event-by-event data downloaded via the X-band ground station.

The burst was detected within several timescales and energy ranges. The best detection is obtained by the image trigger with a signal-to-noise ratio of 7.4 within 4-20 keV over a time window of 10 s starting at T0. This event was not detected onboard because it was too faint and near the edge of the field of view.

The ECLAIRs lightcurve shows a multi-peaked structure lasting around 10 s, with most of the detected photons below 50 keV. 

The localization of the source is RA, Dec = 228.408, -19.894 degrees:

RA (J2000) = 15h13m38s
Dec (J2000) = -19d53m38s

with a 90% C.L. radius of 10.8 arcmin (including systematic error of 2 arcmin added in quadrature). This localization is broadly consistent with that reported by Fermi/GBM (GCN 40648
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 ). The angular separation between the two positions is 15 degrees, which is compatible with the 10.15 degrees statistical uncertainty of the GBM localization. 

The time-averaged spectrum from T0 to T0+10 s in the 5-120 keV is well fitted by a power law with a photon index of 1.6+/-0.2 and a corresponding 4-120 keV fluence of (1.2+/-0.3)e-6 erg/cm^2. The spectral properties measured with SVOM/ECLAIRs are consistent with those reported by SVOM/GRM (GCN 40651
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 ). 

All quoted errors are at the 68% confidence level.

The Space Variable Objects Monitor (SVOM) is a China-France joint mission led by the Chinese National Space Administration (CNSA), French Space Agency (CNES), and the Chinese Academy of Sciences (CAS), which is dedicated to observing gamma-ray bursts and other transient phenomena in the energetic universe. ECLAIRs was developed jointly by APC, CEA, CNES, and IRAP. 

The SVOM/ECLAIRs point of contact for this event is : Hui Yang (hui.yang@cnrs.fr) 

SVOM/GRM team: Wen-Long Zhang, Wen-Jun Tan, Chen-Wei Wang, Shi-Jie Zheng, Yue Huang, Shao-Lin Xiong, Shuang-Nan Zhang (IHEP)

SVOM/ECLAIRs team: Jean-Luc Atteia (IRAP)

report on behalf of the SVOM team:

SVOM/GRM was triggered in-flight by a long burst GRB 250607A (SVOM trigger reference: sb25060704) at 2025-06-07T14:00:56.000 UTC (T0), which is also detected by Fermi/GBM ( Fermi GBM team., GCN #40648
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 ).

With the event-by-event data downloaded through the X-band ground station, the GRM light curve shows that this burst consists of a single pulse with a T90 of 12.60 +7.20/-5.40 s in the 15-5000 keV band.

The SVOM/GRM light curve can be found here:
https://www.bursthub.cn//admin/static/svgrb250607A.png 

In addition, the position of this burst, as determined by Fermi/GBM (RA = 243.84, Dec = -24.71 , GCN #40648
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 ), is located at about 53 degrees from the SVOM optical axis, and outside the ECLAIRs field of view.

With this localization, the time-averaged spectrum from T0-5s to T0+5s is best fitted by a power law function. The power law index is -1.82+/-0.08. The event fluence (10-1000 keV) in this time interval is (1.37 +0.15/-0.15)E-06 erg/cm^2. 

The Space Variable Objects Monitor (SVOM) is a China-France joint mission led by the Chinese National Space Administration (CNSA, China), National Center for Space Studies (CNES, France) and the Chinese Academy of Sciences (CAS, China), which is dedicated to observing gamma-ray bursts and other transient phenomena in the energetic universe. GRM is developed by the Institute of High Energy Physics (IHEP) of CAS.

The SVOM point of contact for this burst is: Wen-Long Zhang (IHEP)(zhangwl@ihep.ac.cn)

The Fermi GBM team reports the detection of a likely LONG GRB.

"At 14:00:55.64 UT on 07 June 2025, the Fermi Gamma-ray Burst Monitor (GBM)
triggered and located GRB 250607A (trigger 770997660/250607584).

The on-ground calculated location, using the Fermi GBM trigger data,
is RA = 243.84, Dec = -24.71 (J2000 degrees, equivalent to J2000 16h 15m, -24d 42'),
with a statistical uncertainty of 10.15 degrees.

The angle from the Fermi LAT boresight is 90 degrees.

The skymap can be found here:
https://heasarc.gsfc.nasa.gov/FTP/fermi/data/gbm/triggers/2025/bn250607584/quicklook/glg_skymap_all_bn250607584.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/bn250607584/quicklook/glg_healpix_all_bn250607584.fit

The GBM light curve can be found here:
https://heasarc.gsfc.nasa.gov/FTP/fermi/data/gbm/triggers/2025/bn250607584/quicklook/glg_lc_medres34_bn250607584.gif"