GRB 250625A

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

At 16:04:57 UT on 25 Jun 2025, the Fermi Gamma-ray Burst Monitor (GBM) triggered and located GRB 250625A (trigger 772560302.510236 / 250625670).

The on-ground calculated location, using the Fermi GBM trigger data, is RA = 257.2, Dec = 27.0 (J2000 degrees, equivalent to J2000 17h 08m, 27d 00'), with a statistical uncertainty of 6.9 degrees.

The angle from the Fermi LAT boresight is 28.0 degrees.

The skymap can be found here:
https://heasarc.gsfc.nasa.gov/FTP/fermi/data/gbm/triggers/2025/bn250625670/quicklook/glg_skymap_all_bn250625670.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/bn250625670/quicklook/glg_healpix_all_bn250625670.fit

The GBM light curve can be found here:
https://heasarc.gsfc.nasa.gov/FTP/fermi/data/gbm/triggers/2025/bn250625670/quicklook/glg_lc_medres34_bn250625670.gif

M. Ferro (INAF-OAB), R. Brivio (INAF-OAB), J. J. DeLaunay (PSU),
R. Gupta (NASA GSFC), J. A. Kennea (PSU), D. M. Palmer (LANL),
B. Sbarufatti (INAF-OAB) and M. H. Siegel (PSU) report on behalf of
the Neil Gehrels Swift Observatory Team:

At 16:04:56 UT, the Swift Burst Alert Telescope (BAT) triggered and
located GRB 250625A (trigger=1327910).  Swift slewed immediately to the burst.
The BAT on-board calculated location is 
RA, Dec 261.519, +22.265 which is 
   RA(J2000) = 17h 26m 04s
   Dec(J2000) = +22d 15' 55"
with an uncertainty of 3 arcmin (radius, 90% containment, including 
systematic uncertainty).  The BAT light curve showed a complex
structure with a duration of about 8 sec.  The peak count rate
was ~2200 counts/sec (15-350 keV), at ~2 sec after the trigger.

The XRT began observing the field at 16:06:56.2 UT, 119.8 seconds after
the BAT trigger. Using promptly downlinked data we find an uncatalogued
X-ray source with an enhanced position: RA, Dec 261.50871, 22.26763
which is equivalent to:
   RA(J2000)  = 17h 26m 02.09s
   Dec(J2000) = +22d 16' 03.5"
with an uncertainty of 1.9 arcseconds (radius, 90% containment). This
location is 35 arcseconds from the BAT onboard position, within the BAT
error circle. This position may be improved as more data are received;
the latest position is available at https://www.swift.ac.uk/sper.  We
cannot determine whether the source is fading at the present time. 

A power-law fit to a spectrum formed from promptly downlinked event
data gives a column density in excess of the Galactic value (5.47 x
10^20 cm^-2, Willingale et al. 2013), with an excess column of 8
(+10.81/-7.26) x 10^21 cm^-2 (90% confidence).

UVOT took a finding chart exposure of 150 seconds with the White filter
starting 124 seconds after the BAT trigger. No credible afterglow candidate has
been found in the initial data products. The 2.7'x2.7' sub-image covers 100% of
the XRT error circle. The typical 3-sigma upper limit has been about 19.6 mag.
The 8'x8' region for the list of sources generated on-board covers 100% of the
XRT error circle. The list of sources is typically complete to about 18 mag. No
correction has been made for the expected extinction corresponding to E(B-V) of
0.055.

This is co-detection with Fermi/GBM (GCN #40824
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 ).

Burst Advocate for this burst is M. Ferro (matteo.ferro AT inaf.it).
Please contact the BA by email if you require additional information
regarding Swift followup of this burst. In extremely urgent cases, after
trying the Burst Advocate, you can contact the Swift PI by phone (see
Swift TOO web site for information: http://www.swift.psu.edu/)

V.Lipunov, E.Gorbovskoy, A.Kuznetsov, K.Zhirkov, I.Panchenko, N.Tiurina, P.Balanutsa, V.Topolev, D.Vlasenko, 
G.Antipov,  A.Sankovich, Yu.Tselik, Ya.Kechin, V.Senik, A.Chasovnikov, K.Labsina, I. Gorbunov (Lomonosov MSU),
O.Gress, N.Budnev (ISU),
C.Francile,  F. Podesta, R.Podesta, E. Gonzalez  (Observatorio Astronomico Felix Aguilar (OAFA),
A. Tlatov, D. Dormidontov (Kislovodsk Solar Station of the Pulkovo Observatory),
A.Sosnovskij (CrAO),
A. Gabovich, V.Yurkov (Blagoveschensk Educational StateUniversity),
D.Buckley (SAAO),
R.Rebolo (The Instituto de Astrofisica de Canarias),
L.Carrasco, J.R.Valdes, V.Chavushyan, V.M.Patino Alvarez, J.Martinez,
A.R.Corella, L.H.Rodriguez (INAOE, Guillermo Haro Astrophysics Observatory) 

MASTER-Tavrida robotic telescope  (Global MASTER-Net: http://observ.pereplet.ru, Lipunov et al., 2010, Advances in Astronomy, vol. 2010, 30L)  located in Russia (Lomonosov MSU, SAI Crimea astronomical station) started inspect of the Fermi GRB 250625A ( Fermi GBM team, GCN 40824
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 ) errorbox  16256 sec after notice time and 16277 sec after trigger time at 2025-06-25 20:36:14 UT, with upper limit up to  14.7 mag. The observations began at zenith distance = 22 deg. The sun  altitude  is -20.8 deg. 

The galactic latitude b = 33 deg., longitude l = 49 deg.


Real time updated cover map and OT discovered available here: 
https://master.sai.msu.ru/site/master2/observ.php?id=2916483

We obtain a following upper limits.  

Tmid-T0  |      Date Time      |          Site       |             Coord (J2000)          |Filt.| Expt. | Limit| Comment
_________|_____________________|_____________________|____________________________________|_____|_______|_______|________

   16367 | 2025-06-25 20:36:14 |      MASTER-Tavrida | (17h 25m 02.21s , +22d 17m 15.8s) |   C |   180 | 14.7 |        
Filter C is a clear (unfiltred) band. 


The observation and reduction will continue. 
The message may be cited.

A.P. Beardmore, P.A. Evans, M.R. Goad and J.P. Osborne (U. Leicester) 
report on behalf of the Swift-XRT team.

Using 2454 s of XRT Photon Counting mode data and 3 UVOT
images for GRB 250625A, we find an astrometrically corrected X-ray
position (using the XRT-UVOT alignment and matching UVOT field sources
to the USNO-B1 catalogue): RA, Dec = 261.50887, +22.26729 which is equivalent
to:

RA (J2000): 17h 26m 2.13s
Dec (J2000): +22d 16' 02.3"

with an uncertainty of 2.3 arcsec (radius, 90% confidence).

This position may be improved as more data are received. The latest
position can be viewed at http://www.swift.ac.uk/xrt_positions. Position
enhancement is described by Goad et al. (2007, A&A, 476, 1401) and Evans
et al. (2009, MNRAS, 397, 1177).

This circular was automatically generated, and is an official product of the
Swift-XRT team.

A. Moskvitin, O. Spiridonova (SAO RAS),
report on behalf of a GRB follow-up collaboration.

We observed the field of the GRB 250625A (The Fermi GBM team, 
GCN 40824
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 ; Ferro et al., GCN 40825
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 ) with SAO RAS 1-m telescope 
Zeiss-1000 equipped with CCD-photometer. We obtained 6 x 300 sec. 
exposures in Rc band on June 25, 20:39:03--21:12:11 UT 
(t_mid - T0 = 4.8447 hours).

Withtin the enhanced XRT error circle (Beardmore et al., GCN 40827
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 ) 
we detect single object with the coordinates:
R.A. (J2000.0) =  17:26:02.1
Dec. (J2000.0) = +22:16:03.6 +/- 0".3
and brightness of R = 22.97 +/- 0.17, possible GRB OT.
Observations are ongoing to confirm variability of the object.

Preliminary photometry is based on the nearby USNO-B1.0 
and has not corrected for the Galactic extinction.

R.A.       Dec. (2000)   R2
17:26:06.4 +22:16:29.4   14.75
17:26:03.7 +22:15:09.9   15.42
17:26:10.0 +22:13:56.8   15.03
17:26:01.4 +22:18:39.0   14.59

L. P. Xin, H. L. Li,  Y. L. Qiu, C. Wu, Y.N. Ma, Z. H. Yao, X. H. Han, Y. Xu, J. Wang, P. P. Zhang, W. J. Xie, Y. J. Xiao, H. B. Cai, L. Lan, J. S. Deng, J. Y. Wei (NAOC), J. Palmerio (CEA), A. Li (BNU) report on behalf of the SVOM/VT team

SVOM/VT performed a Target of Opportunity observation of GRB 250625A detected by Swift-BAT（Ferro et al., GCN 40825
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 ) and Fermi-GBM (GCN #40824
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 ). The observation began at 2025-06-25T16:50:36 UTC, 45.7 minutes after the trigger, in the VT_B (400nm-650nm) and VT_R (650nm-1000nm) channels simultaneously.

The optical counterpart (Moskvitin et al., GCN 40828
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 ) within the errorbox of Swift/XRT (Beardmore et al., GCN 40827
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 ) was detected in the 38*70 sec stack image with a magnitude of VT_B=22.5+/-0.15 mag in AB magnitude with a mid time of 69 min after the burst. 

The counterpart is also detected in VT_R band in the stack image, but it has some contaimination from the blooming light from the nearby bright source. More detailed data analysis is on going. 

Our photometry was not corrected for Galactic extinction.

The Space Variable Objects Monitor (SVOM) is a China-France joint mission led by the Chinese National Space Administration (CNSA, China), National Centre 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. VT was jointly developed by Xi'an Institute of Optics and Precision Mechanics (XIOPM), CAS and National astronomical observatories (NAOC), CAS. 

D. B. Malesani (DAWN/NBI and Radboud), A. Martin-Carrillo (UCD), A. de Ugarte Postigo (LAM), G. Corcoran (UCD), B. P. Gompertz (Birmingham), D. Xu (NAOC), M. A. Diaz Teodori (NOT and Turku Univ.), report on behalf of a larger collaboration:

We observed the position of the X-ray and optical afterglow (Beardmore et al., GCN 40827
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 ; Moskvitin & Spiridonova, GCN 40828
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 ) of GRB 250625A (Ferro et al., GCN 40825
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 ; Fermi GBM team, GCN 40824
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 ) using the Nordic Optical Telescope, using the “standby” StanCam instrument.

In a sequence of 3 exposures of 200 s each, with mean time 2025 Jun 25.948 UT (6.67 hr after the trigger), we detect no object consistent with the X-ray afterglow, down to a limiting magnitude z > 21 AB, calibrated against the Pan-STARRS catalog.

V.Lipunov, E.Gorbovskoy, A.Kuznetsov, K.Zhirkov, I.Panchenko, N.Tiurina, P.Balanutsa, V.Topolev, D.Vlasenko, 
G.Antipov,  A.Sankovich, Yu.Tselik, Ya.Kechin, V.Senik, A.Chasovnikov, K.Labsina, I. Gorbunov (Lomonosov MSU),
O.Gress, N.Budnev (ISU),
C.Francile,  F. Podesta, R.Podesta, E. Gonzalez  (Observatorio Astronomico Felix Aguilar (OAFA),
A. Tlatov, D. Dormidontov (Kislovodsk Solar Station of the Pulkovo Observatory),
A.Sosnovskij (CrAO),
A. Gabovich, V.Yurkov (Blagoveschensk Educational StateUniversity),
D.Buckley (SAAO),
R.Rebolo (The Instituto de Astrofisica de Canarias),
L.Carrasco, J.R.Valdes, V.Chavushyan, V.M.Patino Alvarez, J.Martinez,
A.R.Corella, L.H.Rodriguez (INAOE, Guillermo Haro Astrophysics Observatory) 

MASTER-Tavrida robotic telescope  (Global MASTER-Net: http://observ.pereplet.ru, Lipunov et al., 2010, Advances in Astronomy, vol. 2010, 30L)  located in Russia (Lomonosov MSU, SAI Crimea astronomical station) was pointed to the Swift GRB 250625A ( M. Ferro et al., GCN 40825
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 ) errorbox  16240 sec after notice time and 16278 sec after trigger time at 2025-06-25 20:36:14 UT, with upper limit up to  14.7 mag. The observations began at zenith distance = 22 deg. The sun  altitude  is -20.8 deg. 

MASTER-OAFA robotic telescope  located in Argentina (OAFA observatory of San Juan National University) was pointed to the Swift GRB 250625A errorbox  35307 sec after notice time and 35345 sec after trigger time at 2025-06-26 01:54:01 UT, with upper limit up to  18.9 mag. The observations began at zenith distance = 60 deg. The sun  altitude  is -53.1 deg. 

The galactic latitude b = 28 deg., longitude l = 45 deg.


Real time updated cover map and OT discovered available here: 
https://master.sai.msu.ru/site/master2/observ.php?id=2916460

We obtain a following upper limits.  

Tmid-T0  |          Site       |Filt.| Expt. | Limit| Comment
_________|_____________________|_____|_______|______|________

   16368 |      MASTER-Tavrida |   C |   180 | 14.7 |        
   35435 |         MASTER-OAFA |   C |   180 | 18.5 |        
   35630 |         MASTER-OAFA |   C |   180 | 18.2 |        
   35825 |         MASTER-OAFA |   C |   180 | 18.9 |        
   36026 |         MASTER-OAFA |   C |   180 | 18.6 |        
Filter C is a clear (unfiltred) band. 


The observation and reduction will continue. 
The message may be cited.

Matt Godwin (UAH), O. Mukherjee (USRA) and C. Meegan (UAH) report on behalf of
the Fermi Gamma-ray Burst Monitor Team:

"At 16:04:57.51 UT on 25 June 2025, the Fermi Gamma-ray Burst Monitor (GBM)
triggered and located GRB250625A (trigger 772560302/250625670).
Which was also detected by Swift BAT/XRT (Ferro et al. 2025, GCN 40825
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 ) and SVOM/VT (Xin et al. 2025, GCN 40830
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 ).
The Fermi GBM on-ground location is consistent with the Swift position.

The angle from the Fermi LAT boresight is 32 degrees.

The GBM light curve consists of one strong peak and a few weaker peaks with a duration (T90)
of about 5.4 s (50-300 keV). The time-averaged spectrum
from T0-2.0 to T0+5.0 s is best fit by
a power law function with an exponential high-energy cutoff. The power law index is -1.27 +/- 0.05 and the cutoff energy, parameterized as Epeak, is 1301.00 +/- 1190.00

The event fluence (10-1000 keV) in this time interval is
(1.8 +/- 0.1)E-06 erg/cm^2. The 1-sec peak photon flux measured
starting from T0-0.13 s in the 10-1000 keV band is 3 +/- 0.2 ph/s/cm^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/"

Z.P. Zhu, S.Q. Jiang, X. Liu, J. An, D. Xu (NAOC), S.Y. Fu (HUST), J.Z. Liu (XAO) report on behalf of a large collaboration:

We observed the field of GRB 250625A detected by the Fermi/GBM and Swift/BAT (the Fermi GBM Team, GCN 40824
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 ; Ferro et al., GCN 40825
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 ), using the 100cm-C telescope (100C) of the JinShan project, located at Altay, Xinjiang, China. Observations started at 16:11:04 UT on 2025-06-25, i.e., 6.1 min after the BAT trigger, and a series of frames were obtained in the Sloan r-, i-, z-bands.

In the first round of r-band exposures, an uncatalogued optical source is marginally detected within the Swift/XRT enhanced error circle (Beardmore et al., GCN 40827
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 ), which is consistent with the reported optical counterpart by SAO RAS (Moskvitin et al., GCN 40828
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 ) and SVOM/VT (Xin et al., GCN 40830
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 ). The source is not detected in i-band and z-band (see also Malesani et al., GCN 40831
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 ), as well as in the second r-band exposures. Our preliminary results are summarized as follows:

T-mid (hr) | Filter | Mag
0.387        |    r    |       22.5 +/- 0.3
1.237        |    i     |       > 21.7 (5$\sigma$)
1.935        |    z    |       > 20.5 (5$\sigma$)
2.761        |    r    |       > 21.1 (5$\sigma$)

calibrated with nearby Pan-STARRS stars without the Galactic extinction correction.

We acknowledge the excellent support from T.Q. Chen and J.L. He for enabling these observations.

S. Dichiara (PSU), K.L. Page (U. Leicester), A.P. Beardmore (U.
Leicester), M. Capalbi (INAF-OAR), M. Perri (SSDC & INAF-OAR), V.
D'Elia (SSDC & INAF-OAR), J.A. Kennea (PSU), D.N. Burrows (PSU) and
P.A. Evans report on behalf of the Swift-XRT team:

We have analysed 6.0 ks of XRT data for GRB 250625A, from 123 s to 45.1
ks after the   trigger. The data comprise 58 s in Windowed Timing (WT)
mode with the remainder in Photon Counting (PC) mode. 

The light curve can be modelled with a series of power-law decays. The
initial decay index is alpha=0.8 (+1.1, -1.2). At T+174 s  the decay
steepens to an alpha of 6.3 (+/-1.7) before breaking again at T+238 s
to a final decay with index alpha=1.19 (+0.17, -0.15).

A spectrum formed from the PC mode data can be fitted with an absorbed
power-law with a photon spectral index of 1.68 (+0.32, -0.29). The
best-fitting absorption column is  1.7 (+1.3, -1.0) x 10^21 cm^-2, in
excess of the Galactic value of 5.5 x 10^20 cm^-2 (Willingale et al.
2013). The counts to observed (unabsorbed) 0.3-10 keV flux conversion
factor deduced from this spectrum  is 4.3 x 10^-11 (5.2 x 10^-11) erg
cm^-2 count^-1. 

A summary of the PC-mode spectrum is thus:
Total column:	     1.7 (+1.3, -1.0) x 10^21 cm^-2
Galactic foreground: 5.5 x 10^20 cm^-2
Excess significance: 1.9 sigma
Photon index:	     1.68 (+0.32, -0.29)

If the light curve continues to decay with a power-law decay index of
1.19, the count rate at T+24 hours will be 5.0 x 10^-4 count s^-1,
corresponding to an observed (unabsorbed) 0.3-10 keV flux of 2.2 x
10^-14 (2.6 x 10^-14) erg cm^-2 s^-1.

The results of the XRT-team automatic analysis are available at
http://www.swift.ac.uk/xrt_products/01327910.

This circular is an official product of the Swift-XRT team.