GRB 250725A
GCN Circular 41200
Subject
GRB 250725A: AstroSat CZTI detection
Date
2025-07-30T10:10:49Z (25 days ago)
From
Gaurav Waratkar at IIT Bombay <gauravwaratkar@iitb.ac.in>
Via
Web form
M. Tembhurnikar (IUCAA), G. Waratkar (IITB), A. Vibhute (IUCAA), V. Bhalerao (IITB), D. Bhattacharya (Ashoka University/IUCAA), A. R. Rao (IUCAA/TIFR), and S. Vadawale (PRL) report on behalf of the AstroSat CZTI collaboration:
Analysis of AstroSat CZTI data with the CIFT framework (Sharma et al., 2021, JApA, 42, 73) showed the detection of a long-duration GRB 250725A which was also detected by Fermi/GBM (Fermi GBM Team, GCN Circ. 41150), Swift/BAT (Evans et. al., GCN Circ. 41152), Konus/Wind (Frederiks et. al., GCN Circ. 41166), and SVOM/GRM (Wang et. al., GCN Circ. 41164).
The source was detected in the CsI anticoincidence (Veto) detector in the 100-500 keV energy range. The light curve contained two peaks with the strongest peak at 2025-07-25 01:51:36.83 UTC. The measured peak count rate associated with the burst is 500 (+81, -28) counts/s above the background in the combined data of all quadrants, with a total of 3013 (+264, -366) counts. The local mean background count rate was 1367 (+9, -7) counts/s. We measure a T90 of 10.0 (+0.6, -1.3) s from the cumulative Veto light curve.
The source was also faintly detected in the CZT detectors in the 20-200 keV energy range.
CZTI is built by a TIFR-led consortium of institutes across India, including VSSC, URSC, IUCAA, SAC, and PRL. The Indian Space Research Organisation funded, managed, and facilitated the project.
CZTI GRB detections are reported regularly on the payload site at:
http://astrosat.iucaa.in/czti/?q=grb
GCN Circular 41198
Subject
GRB 250725A: PRIME near-infrared observations
Date
2025-07-29T20:55:52Z (a month ago)
From
Joe Durbak at UMD <gcn.joedurbak@gmail.com>
Via
Web form
J. Durbak (UMD), O. Guiffreda (UMD), N. Passaleva, M. El Kabir, A. S. Kutyrev (NASA/GSFC), E. Troja (U Rome), S. B. Cenko (NASA/GSFC)
Following the Fermi GBM (GCN 41150) and Swift BAT (GCN 41152), we observed the transient field in J and H filters with PRIME ~24 hours after Fermi and Swift detection.
At the position of the optical counterpart reported by MASTER-Net (GCN 41151), we detect a low-significance uncatalogued source in H-band. Using nearby VISTA Hemispherical Survey (VHS) and 2MASS stars for preliminary calibration we derive the following magnitude and limit, not corrected for Galactic extinction:
| Filter | Mag(AB) | Calibration Survey |
|--------|--------------|--------------------|
| J | > 20.6 | VHS |
| H | 20.6 +/- 0.3 | 2MASS |
PRIME is a 1.8m telescope with 1.56 square degree FOV (0.5 arcsec/pixel) located in Sutherland, South Africa at the South African Astronomical Observatory (SAAO) (Kutyrev et al. 2023, Yama et al. 2023, Durbak et al. 2024).
We thank the Osaka University observers at PRIME and the staff at SAAO for their support with these observations.
GCN Circular 41170
Subject
GRB 250725A: Swift-XRT refined Analysis
Date
2025-07-25T19:07:22Z (a month ago)
From
Phil Evans at U of Leicester <pae9@star.le.ac.uk>
Via
email
S. Dichiara (PSU), J.A. Kennea (PSU), D.N. Burrows (PSU), K.L. Page (U.
Leicester), A.P. Beardmore (U. Leicester), V. D'Elia (SSDC & INAF-OAR),
B. Sbarufatti (INAF-OAB), C. Salvaggio (INAF-OAB) and P.A. Evans report
on behalf of the Swift-XRT team:
We have analysed 7.4 ks of XRT data for GRB 250725A, from 828 s to 53.2
ks after the trigger. The data comprise 64 s in Windowed Timing (WT)
mode with the remainder in Photon Counting (PC) mode.
The light curve can be modelled with an initial power-law decay with an
index of alpha=1.14 (+/-0.06), followed by a break at T+13.4 ks to an
alpha of 2.2 (+0.4, -0.3).
A spectrum formed from the PC mode data can be fitted with an absorbed
power-law with a photon spectral index of 1.72 (+0.09, -0.08). The
best-fitting absorption column is 2.7 (+2.3, -2.1) x 10^22 cm^-2, at a
redshift of 5.26, in addition to the Galactic value of 9.2 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 4.0 x
10^-11 (4.7 x 10^-11) erg cm^-2 count^-1.
A summary of the PC-mode spectrum is thus:
Galactic foreground: 9.2 x 10^20 cm^-2
Intrinsic column: 2.7 (+2.3, -2.1) x 10^22 cm^-2 at z=5.26
Photon index: 1.72 (+0.09, -0.08)
If the light curve continues to decay with a power-law decay index of
2.2, the count rate at T+24 hours will be 4.0 x 10^-3 count s^-1,
corresponding to an observed (unabsorbed) 0.3-10 keV flux of 1.6 x
10^-13 (1.9 x 10^-13) erg cm^-2 s^-1.
The results of the XRT-team automatic analysis are available at
http://www.swift.ac.uk/xrt_products/01336720.
This circular is an official product of the Swift-XRT team.
GCN Circular 41169
Subject
GRB 250725A: Fermi GBM Observation
Date
2025-07-25T17:08:33Z (a month ago)
From
Matt Godwin <msg0028@uah.edu>
Via
Web form
Matt Godwin (UAH), R. Sonawane (IISER TVM) and C. Meegan (UAH) report on behalf of
the Fermi Gamma-ray Burst Monitor Team:
"At 01:51:34.81 UT on 25 July 2025, the Fermi Gamma-ray Burst Monitor (GBM)
triggered and located GRB 250725A (trigger 775101099/250725077).
which was also detected by Swift XRT (Evans et al. 2025, GCN 41152), Konus-Wind (Frederiks et al. 2025, GCN 41166),
and Fermi LAT (Airasca et al. 2025, GCN 41161). The Fermi GBM on-ground location is consistent with the Swift XRT position.
The redshift observed by VLT (Thakur et al. 2025, GCN 41160) is z = 5.26.
The angle from the Fermi LAT boresight is 24 degrees.
The GBM light curve consists of one main peak and a weaker secondary peak with a duration (T90)
of about 9.5 s (50-300 keV). The time-averaged spectrum
from T0+0.003 to T0+11.904 s is best fit by
a Band function with Epeak = 161 +/- 7 keV,
alpha = -0.47 +/- 0.05, and beta = -2.7 +/- 0.2.
The event fluence (10-1000 keV) in this time interval is
(1.18 +/- 0.03)E-05 erg/cm^2. The 1-sec peak photon flux measured
starting from T0+1.7 s in the 10-1000 keV band is 18 +/- 0.4 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/"
GCN Circular 41167
Subject
GRB 250725A: Swift-BAT refined analysis
Date
2025-07-25T16:18:21Z (a month ago)
From
Rahul Gupta at NASA GSFC <rahul.gupta@nasa.gov>
Via
Web form
T. Parsotan (GSFC), S. D. Barthelmy (GSFC),
P. A. Evans (U Leicester), R. Gupta (GSFC),
H. A. Krimm (NSF), S. Laha (GSFC/UMBC),
A. Y. Lien (U Tampa), C. B. Markwardt (GSFC),
M. J. Moss (GSFC), D. M. Palmer (LANL),
D. Sadaula (GSFC/UMBC), T. Sakamoto (AGU)
(i.e. the Swift-BAT team):
Using the data set from T-239 to T+963 sec from the recent telemetry downlink,
we report further analysis of BAT GRB 250725A (trigger #1336720)
(Evans, et al., GCN Circ. 41152). The BAT ground-calculated position is
RA, Dec = 35.459, -82.786 deg which is
RA(J2000) = 02h 21m 50.1s
Dec(J2000) = -82d 47' 10.4"
with an uncertainty of 1.0 arcmin, (radius, sys+stat, 90% containment).
The partial coding was 34%.
The mask-weighted BAT light curve shows multi-peaked emission episode starting
~T-2 sec, with a sharp rise and a structured decay extending over ~12 seconds.
T90 (15-350 keV) is 9.58 +- 0.25 sec (estimated error including systematics).
The time-averaged spectrum from T-1.77 to T+9.50 sec is best fit by a power law
with an exponential cutoff. This fit gives a photon index 0.81 +- 0.19, and
Epeak of 207.2 +- 105.6 keV (chi squared 38.63 for 56 d.o.f.). For this model
the total fluence in the 15-150 keV band is 5.0 +- 0.1 x 10^-06 erg/cm2 and
the 1-sec peak flux measured from T+0.06 sec in the 15-150 keV band
is 12.5 +- 0.6 ph/cm2/sec. A fit to a simple power law gives a photon index of
1.15 +- 0.05 (chi squared 49.20 for 57 d.o.f.).
All the quoted errors are at the 90% confidence level.
The results of the batgrbproduct analysis are available at
https://swift.gsfc.nasa.gov/results/batgrbcat/BAT_refined_circular/1336720
GCN Circular 41166
Subject
Konus-Wind detection of GRB 250725A
Date
2025-07-25T15:53:14Z (a month ago)
Edited On
2025-07-25T17:11:22Z (a month ago)
From
Dmitry Frederiks at Ioffe Institute <fred@mail.ioffe.ru>
Edited By
Judith Racusin at NASA/GSFC <judith.racusin@nasa.gov> on behalf of Dmitry Frederiks at Ioffe Institute <ddfrederiks@gmail.com>
Via
email
D. Frederiks, A.Lysenko, A. Ridnaia, D. Svinkin,
A. Tsvetkova, M. Ulanov, and T. Cline,
on behalf of the Konus-Wind team, report:
The long GRB 250725A (Fermi-GBM detection:
The Fermi GBM team, GCN 41150;
Swift detection: Evans et al., GCN 41152;
SVOM/GRM observation: Wang et al., GCN 41164)
triggered Konus-Wind (KW) at T0=6698.029 s UT (01:51:38.029).
The burst shows a multi-peaked structure with a total duration of ~12 s.
The emission is seen up to ~1.5 MeV.
The Konus-Wind light curve of this GRB is available at
http://www.ioffe.ru/LEA/GRBs/GRB250725_T06698/
As observed by Konus-Wind, the burst had
a fluence of (1.19 ± 0.10)x10^-5 erg/cm^2 and
a 64-ms peak energy flux, measured from T0 + 0.512 s,
of (4.16 ± 0.41)x10^-6 erg/cm^2/s (both in the 20 keV - 10 MeV energy range).
The time-integrated spectrum (measured from T0 to T0+16.640 s)
is best fit in the 20 keV - 15 MeV range by a GRB (Band) function
with the following model parameters:
the low-energy photon index alpha = -0.41 (-0.13,+0.15),
the high energy photon index beta = -2.75 (-0.25,+0.18),
the peak energy Ep = 155 (-9,+9) keV,
chi2 = 89/97 dof.
Assuming the redshift z=5.26 (Thakur et al., GCN 41160)
and a standard cosmology with H_0 = 67.3 km/s/Mpc, Omega_M = 0.315,
and Omega_Lambda = 0.685 (Planck Collaboration, 2014),
we estimate the burst isotropic energy release E_iso to (5.85 ± 0.49)x10^53 erg,
the isotropic peak luminosity L_iso to (1.30 ± 0.13)x10^54 erg/s, and
the rest-frame peak spectral energy Ep,z to (970 ± 56) keV.
With the obtained estimates, GRB 250725A is consistent with 68% prediction bands
of both 'Amati' and 'Yonetoku' relations for the sample of >300 long KW GRBs
with known redshifts (Tsvetkova et al., 2017; Tsvetkova et al., 2021),
see http://www.ioffe.ru/LEA/GRBs/GRB250725_T06698/GRB250725A_rest_frame.pdf
All the quoted errors are estimated at the 68% confidence level.
All the presented results are preliminary.
GCN Circular 41164
Subject
GRB 250725A: SVOM/GRM observation
Date
2025-07-25T14:18:41Z (a month ago)
From
Chenwei Wang at IHEP <cwwang@ihep.ac.cn>
Via
Web form
SVOM/GRM team: 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 GRB 250725A (SVOM trigger reference: sb25072501) at 2025-07-25T01:51:36.300 UTC (T0), which is also detected by Fermi/GBM (Fermi GBM Team, GCN#41150), Swift/BAT (P. A. Evans et al., GCN#41152) and Fermi/LAT (A. Holzmann Airasca et al., GCN#41161).
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 followed by a narrow spike with a T90 of 9.7 +/-0.3 s in the 15-5000 keV band.
The SVOM/GRM light curve can be found here:
https://www.bursthub.cn//admin/static/svgrb250725A.png
In addition, the position of this burst, as determined by Swift/BAT (RA= 35.47808, DEC= -82.79131, GCN#41152), is located at about 78 degrees from the SVOM optical axis, which is outside the ECLAIRs field of view.
With this localization, the time-averaged spectrum from T0-2 to T0+12 s is best fitted by a power law function with an exponential high-energy cutoff. The power law index is -0.61 +0.15/-0.16 and the cutoff energy, parameterized as Epeak, is 323 +73/-51 keV. The event fluence (10-1000 keV) in this time interval is (8.11 +0.88/-0.80)E-06 erg/cm^2.
With the redshift z = 5.26 by VLT/FORS2 (A. L. Thakur et al., GCN#41160), the Eiso (from 1 keV to 10 MeV in rest frame) of this burst is (4.13 +0.58/-0.48)E53 erg. Thus GRB 250725A is more consistent with Type II GRBs in the 'Amati' relation diagram, as shown at:
https://www.bursthub.cn//admin/static/grb250725A_amati.png
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: Chen-Wei Wang (IHEP)(cwwang@ihep.ac.cn)
GCN Circular 41163
Subject
GRB 250725A: Global MASTER-Net: First Optical Synchronous Observatios of Short GRB.
Date
2025-07-25T13:30:56Z (a month ago)
From
Vladimir Lipunov at Moscow State U/Krylov Obs <lipunov@xray.sai.msu.ru>
Via
email
V.M.Lipunov (Lomonosov MSU, SAI, Moscow), E.Gorbovskoy, N.Tiurina,
A.Kuznetsov, A.Sankovich, G.Antipov, P.Balanutsa, P. Rudominskaya, A.Chasovnikov, V.Topolev, K.Zhirkov, Ya.Kechin, V.Senik, D.Vlasenko (Lomonosov MSU),
C.Francile, F. Podesta, R.Podesta, E. Gonzalez (OAFA),
D.Buckley, (SAAO, South Africa)
O.Gress, N.Budnev (ISU, Irkutsk),
A.Sosnovskij (Crao RAS),
A. Tlatov, D. Dormidontov (Kislovodsk Solar Station of the Pulkovo Observatory),
A. Gabovich, V.Yurkov (Blagoveschensk Educational StateUniversity),
V.M.Pillet (The Instituto de Astrofisica de Canarias, Spain),
L.Carrasco, J.R.Valdes, V.Chavushyan, V.M.Patino Alvarez,
J.Martinez,A.R.Corella, L.H.Rodriguez (INAOE, Guillermo Haro Astrophysics
Observatory, Mexico)
MASTER-OAFA robotic telescope (Global MASTER-Net: http://observ.pereplet.ru,
Lipunov,V.G. Kornilov, E.S. Gorbovskoy, N.V. Tyurina, A.S. Kuznetsov, "ASTRONOMICAL ROBOTIC NETWORKS and OPERATIVE MULTICHANNEL ASTROPHYSICS. Based on the example of the global MASTER network.", The Moscow State University Publishing House. In the series "Works of Outstanding Scientists of Moscow State University", http://www.pereplet.ru/lipunov/625.html#625) located in Argentina (Rudominskaya et al., GCN 41157) and in the South Africa, SAAO; Busckley et al., GCN 41151;) was pointed to the
GRB250725A (Fermi GBM 41150, Swift GCN 41152).
As we noted out the earlier (Rudominskaya et al., GCN 41157), the gamma-ray burst turned out to be a short GRB (Thakur et al., GCN 41160).
Thus, we have images before, during and after GRB250725A.
Now the processing of wide-field and polarized frames continues.
See also optical observations by Li et al. GCN 41158; Perez-Garcia et al. GCN 41159.
The message may be cited.
GCN Circular 41162
Subject
GRB 250725A: Swift/UVOT Upper Limits
Date
2025-07-25T12:27:21Z (a month ago)
From
s.shilling@lancaster.ac.uk
Via
Web form
S. P. R. Shilling (Lancaster U.) and P. A. Evans (U. Leicester)
report on behalf of the Swift/UVOT team:
The Swift/UVOT began settled observations of the field of GRB 250725A
880 s after the BAT trigger (Evans et al., GCN Circ. 41152).
No optical afterglow consistent with the enhanced XRT position
(Osborne et al., GCN Circ. 41153) is detected in the initial UVOT exposures.
Preliminary 3-sigma upper limits using the UVOT photometric system
(Breeveld et al. 2011, AIP Conf. Proc. 1358, 373) for the first
finding chart (FC) exposure and subsequent exposures are:
Filter T_start(s) T_stop(s) Exp(s) Mag
white_FC 880 1029 147 >21.0
white 880 2562 322 >21.2
v 1036 2439 175 >19.6
b 1134 2537 175 >20.1
u 1110 2340 156 >20.1
w1 1085 2488 175 >19.6
w2 1704 1898 39 >19.5
The magnitudes in the table are not corrected for the Galactic extinction
due to the reddening of E(B-V) = 0.114 in the direction of the burst
(Schlegel et al. 1998).
GCN Circular 41161
Subject
GRB 250725A: Fermi-LAT detection
Date
2025-07-25T10:33:39Z (a month ago)
From
A. Holzmann Airasca at University of Trento and INFN Bari <a.holzmannairasca@unitn.it>
Via
Web form
A. Holzmann Airasca (UniTrento and INFN Bari), F. Longo (University and INFN, Trieste), D. Depalo (Politecnico and INFN Bari) and R. Gupta (NASA/GSFC) report on behalf of the Fermi-LAT Collaboration:
On July 25, 2025, Fermi-LAT detected high-energy emission from GRB 250725A, which was also detected by Fermi-GBM (trigger 775101099 / 250725077, GCN 41150), Swift-BAT (GCN 41152), Swift-XRT (GCN 41153), MASTER-OAFA (GCN 41157), SVOM/VT (GCN 41158), BOOTES-7 (GCN 41159) and VLT/FORS2 (GCN 41160).
The best LAT on-ground location is found to be:
RA, Dec = 34.6, -83.2 (J2000)
with an error radius of 1.1 deg (90 % containment, statistical error only).
This was 24 deg from the LAT boresight at the time of the GBM trigger (T0 = 01:51:34.81 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 0 - 90 s after the GBM trigger is (1.26 ± 0.50) E-5 ph/cm2/s. The estimated photon index above 100 MeV is -2.07 ± 0.40.
The highest-energy photon is a 1 GeV event which is observed ~ 15 seconds after the GBM trigger.
The Fermi-LAT point of contact for this burst is Francesco Longo (francesco.longo@ts.infn.it).
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 41160
Subject
GRB 250725A: VLT/FORS2 spectroscopic redshift z = 5.26
Date
2025-07-25T10:24:26Z (a month ago)
From
Nusrin Habeeb at University of Leicester <nh312@leicester.ac.uk>
Via
Web form
A. L. Thakur (INAF-IAPS), N. R. Tanvir (Univ. of Leicester), A. de Ugarte Postigo (LAM), A. Saccardi (CEA/Irfu), L. Izzo (INAF/OACn and DARK/NBI), A. Kumar (RHUL), S. D. Vergani (LUX-Paris Obs.) report on behalf of the Stargate collaboration:
We observed the optical counterpart (Buckley et al. GCN 41151; Li et al. GCN 41158; Perez-Garcia et al. GCN 41159) of GRB 250725A (Fermi GBM Team, GCN 41150; Evans et al. GCN 41152) using the ESO/VLT UT1 (Antu) equipped with the FORS2 spectrograph.
In a 60 s acquisition image obtained in I-band starting on 2025 July 25 at 07:44:31 UT (5.88 hrs after the burst), the afterglow is well detected with I(AB) = 20.5+/-0.1 mag, calibrated against nearby stars from the SkyMapper catalog.
We obtained a single exposure of 1800 s using grism 300I+11 starting on 2025 July 25 at 08:04:47 UT (6.22 hrs after the burst). In a preliminary reduction of the spectrum, a trough due to Lyman-alpha is visible at 7610AA. From the detection of metals absorption features, which we interpret as due to O I and Si II, plus a tentative Si II* fine structure line, we infer a redshift of z = 5.26. At that same redshift we also detect an absorption feature consistent with Lyman-beta from the host galaxy, within the Lyman forest.
We acknowledge the excellent support from the ESO observing staff in Paranal, in particular Carlos La Fuente and Lorena Faundez.
GCN Circular 41159
Subject
GRB 250725A: BOOTES-7 early optical detection
Date
2025-07-25T10:03:36Z (a month ago)
From
I. Perez-Garcia at Institute of Astrophysics of Andalusia <ipg@iaa.es>
Via
Web form
I. Perez-Garcia, E. Fernandez-Garcia, S.-Y. Wu, M. D. Caballero-Garcia, R. Sanchez-Ramirez, S. Guziy, and A. J. Castro-Tirado (IAA-CSIC, Granada), C. Perez del Pulgar (Univ. of Malaga), L. Hernandez-Garcia (Univ. of Valparaiso), M. Gritsevich (Univ. of Helsinki), Y.-D. Hu (GXU), B.-B. Zhang (Nanjing Univ.), and A. Maury (Space Obs., San Pedro de Atacama), on behalf of a larger collaboration, report:
Following the detection of GRB 250725A by Swift, the 0.6m BOOTES-7 robotic telescope at Space Observatory (San Pedro de Atacama, Chile) automatically responded to this high-energy event starting on July 25, 01:52:17 UT (i.e. 41 sec after detection). Series of images in clear filter were gathered and we detect an optical source consistent with the one reported by Buckley et al. (GCN 41151) and Li et al. (GCN 41158). Using GaiaDR3 Gmag as a reference, we measure an initial magnitude of 15.5 +/- 0.1 in the first 10 sec exposure image. In subsequent stacked images of 1 sec images we do not detect any source up to mag 15.7, mid exposure time on July 25, 01:53:27. Further analysis of the additional images is ongoing.
We would like to thank the staff at San Pedro de Atacama Space Observatory for their excellent support.
GCN Circular 41158
Subject
GRB 250725A: SVOM/VT optical candidate
Date
2025-07-25T09:38:16Z (a month ago)
Edited On
2025-07-25T13:23:26Z (a month ago)
From
Huali Li at at NAOC, SVOM <lhl@nao.cas.cn>
Edited By
Judith Racusin at NASA/GSFC <judith.racusin@nasa.gov> on behalf of Huali Li at at NAOC, SVOM <lhl@nao.cas.cn>
Via
Web form
H. L. Li, L. P. Xin, Y. L. Qiu, C. Wu, Z. H. Yao, Y. N. Ma, Y. Xu, J. Wang, P. P. Zhang, W. J. Xie, Y. J. Xiao, H. B. Cai, L. Lan, J. Palmerio (CEA), J. S. Deng, J. Y. Wei (NAOC), R. Z. Li (YNAO), X. L. Chen (YNU) report on behalf of the SVOM/VT team.
SVOM performed a Target of Opportunity observation of GRB 250725A detected by Fermi/GBM (Fermi GBM Team, GCN 41150) and Swift/BAT (Evans et al., GCN 41152). SVOM/VT began observing the field at 2025-07-25 02:27:11 UTC, 36.1 min after the Swift trigger time, in the VT_B (400nm-650nm) and VT_R (650nm-1000nm) channels simultaneously.
An uncatalogued source compared to DESI catalogue, is found using VT X-band data, within the error box of Swift/XRT (Osborne et al., GCN 41153) at R.A., Dec 35.480401, -82.791125 degrees:
RA (J2000) = 02:21:55.30
Dec (J2000) = -82:47:28.05
with an uncertainty of 0.5 arcsec.
The source was consistent with the detection of Buckley et al. (GCN 41151). It was detected in both VT_R and VT_B and fading in VT_R by 0.3 mag within about one hour during our observation. The AB magnitudes are:
Mid time | exposure time | band | mag (AB) | mag err
--------------------|-------------------|------|----------|--------
0.93 hour | 70×13 sec | VT_B | 22.30 | 0.10
0.93 hour | 70×10 sec | VT_R | 19.33 | 0.02
Our measurements are not corrected for Galactic extinction.
Considering the red color of VT_B-VT_R of about 2.9, the burst is supposed to be probable at medium/high redshift (Wang et al. 2020).
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. VT was jointly developed by Xi'an Institute of Optics and Precision Mechanics (XIOPM), CAS and National astronomical observatories (NAOC), CAS.
GCN Circular 41157
Subject
GRB 250725A: MASTER-OAFA optical detection of very fast afterglow
Date
2025-07-25T08:51:52Z (a month ago)
From
Vladimir Lipunov at Moscow State U/Krylov Obs <lipunov@xray.sai.msu.ru>
Via
email
P. Rudominskaya (Lomonosov, MSU),
C.Francile, F. Podesta, R.Podesta, E. Gonzalez (OAFA),
V.Lipunov (Lomonosov MSU), E.Gorbovskoy,
A.Kuznetsov, G.Antipov, P.Balanutsa, A.Chasovnikov, N.Tiurina,
V.Topolev, K.Zhirkov, Ya.Kechin, V.Senik, D.Vlasenko (Lomonosov MSU),
O.Gress, N.Budnev (ISU),
A.Sosnovskij (Crao RAS),
A. Tlatov, D. Dormidontov (Kislovodsk Solar Station of the Pulkovo Observatory),
A. Gabovich, V.Yurkov (Blagoveschensk Educational StateUniversity),
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-OAFA robotic telescope (Global MASTER-Net: http://observ.pereplet.ru, Lipunov et al., 2010, Advances in Astronomy, vol. 2010, 30L) located in Argentina (OAFA observatory of San Juan National University) was pointed to the GRB250725.08 26 sec after notice time and 45 sec after trigger time at 2025-07-25 01:52:22 UT. On our first (10s exposure) set we found 1 optical transient within Swift error-box (ra=35.3833 dec=-82.7836 r=0.05) brighter than 17.7.
T-Tmid Date Time Expt. Ra Dec Mag
---------|---------------------|-------|-----------------|-----------------|-------
50 2025-07-25 01:52:22 10 (02h 21m 55.67s , -82d 47m 28.1s) 15.8
The 5-sigma upper limit has been about 17.7mag
The automatical light curve is the very fast fall F ~ t^-2
This very similar to short GRB behavior.
The large optical telescope observation is very welcome!
The message may be cited.
GCN Circular 41153
Subject
GRB 250725A: Enhanced Swift-XRT position
Date
2025-07-25T04:33:59Z (a month ago)
From
Phil Evans at U of Leicester <pae9@star.le.ac.uk>
Via
email
J.P. Osborne, A.P. Beardmore, P.A. Evans and M.R. Goad (U. Leicester)
report on behalf of the Swift-XRT team.
Using 1662 s of XRT Photon Counting mode data and 1 UVOT
images for GRB 250725A, 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 = 35.47933, -82.79122 which is equivalent
to:
RA (J2000): 02h 21m 55.04s
Dec (J2000): -82d 47' 28.4"
with an uncertainty of 2.2 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.
GCN Circular 41152
Subject
GRB 250725A: Swift detection of a burst
Date
2025-07-25T02:16:19Z (a month ago)
From
K.L. Page at U Leicester <klp5@leicester.ac.uk>
Via
email
P. A. Evans (U Leicester), N. P. M. Kuin (UCL-MSSL),
K. L. Page (U Leicester) and D. M. Palmer (LANL) report on behalf of
the Neil Gehrels Swift Observatory Team:
At 01:51:36 UT, the Swift Burst Alert Telescope (BAT) triggered and
located GRB 250725A (trigger=1336720). Swift slewed to the burst after
a short delay due to an observing constraint.
The BAT on-board calculated location is
RA, Dec 35.385, -82.784 which is
RA(J2000) = 02h 21m 32s
Dec(J2000) = -82d 47' 02"
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 20 sec. The peak count rate
was ~8700 counts/sec (15-350 keV), at ~0 sec after the trigger.
The XRT began observing the field at 02:03:56.8 UT, 740.4 seconds after
the BAT trigger. Using promptly downlinked data we find an uncatalogued
X-ray source located at RA, Dec 35.47808, -82.79131 which is equivalent
to:
RA(J2000) = 02h 21m 54.74s
Dec(J2000) = -82d 47' 28.7"
with an uncertainty of 3.5 arcseconds (radius, 90% containment). This
location is 49 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.
A power-law fit to a spectrum formed from promptly downlinked event
data gives a column density in excess of the Galactic value (9.21 x
10^20 cm^-2, Willingale et al. 2013), with an excess column of 3.9
(+2.24/-1.95) x 10^21 cm^-2 (90% confidence).
UVOT took a finding chart exposure of 150 seconds with the White filter
starting 879 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
0.115.
Burst Advocate for this burst is P. A. Evans (pae9 AT leicester.ac.uk).
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/)
GCN Circular 41151
Subject
Swift GRB 250725A: Global MASTER-Net OT detection
Date
2025-07-25T02:09:35Z (a month ago)
Edited On
2025-07-25T13:23:13Z (a month ago)
From
Vladimir Lipunov at Moscow State U/Krylov Obs <lipunov@xray.sai.msu.ru>
Edited By
Judith Racusin at NASA/GSFC <judith.racusin@nasa.gov> on behalf of Vladimir Lipunov at Lomonosov Moscow State University <lipunov@sai.msu.ru>
Via
email
D. Buckley
(South African Astronomical Observatory),
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),
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) was pointed to the GRB250725.08 33 sec after notice time and 53 sec after trigger time at 2025-07-25 01:52:29 UT. On our first (10s exposure) set we found 1 optical transient within Swift error-box (ra=35.3833 dec=-82.7836 r=0.05) brighter than 16.0.
T-Tmid Date Time Expt. Ra Dec Mag
---------|---------------------|-------|-----------------|-----------------|-------
58 2025-07-25 01:52:29 10 (02h 21m 55.91s , -82d 47m 28.0s) 15.6
The 5-sigma upper limit has been about 16.0mag
The message may be cited.
GCN Circular 41150
Subject
GRB 250725A: Fermi GBM Final Real-time Localization
Date
2025-07-25T02:01:58Z (a month 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 01:51:34 UT on 25 Jul 2025, the Fermi Gamma-ray Burst Monitor (GBM) triggered and located GRB 250725A (trigger 775101099.80868 / 250725077).
The on-ground calculated location, using the Fermi GBM trigger data, is RA = 31.5, Dec = -85.4 (J2000 degrees, equivalent to J2000 02h 06m, -85d 24'), with a statistical uncertainty of 1.0 degrees.
The angle from the Fermi LAT boresight is 22.0 degrees.
The skymap can be found here:
https://heasarc.gsfc.nasa.gov/FTP/fermi/data/gbm/triggers/2025/bn250725077/quicklook/glg_skymap_all_bn250725077.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/bn250725077/quicklook/glg_healpix_all_bn250725077.fit
The GBM light curve can be found here:
https://heasarc.gsfc.nasa.gov/FTP/fermi/data/gbm/triggers/2025/bn250725077/quicklook/glg_lc_medres34_bn250725077.gif
GCN Circular 41148
Subject
Swift GRB 250725A: Global MASTER-Net observations report
Date
2025-07-25T01:58:44Z (a month ago)
Edited On
2025-07-28T13:23:37Z (a month ago)
From
Vladimir Lipunov at Moscow State U/Krylov Obs <lipunov@xray.sai.msu.ru>
Edited By
Judith Racusin at NASA/GSFC <judith.racusin@nasa.gov> on behalf of Vladimir Lipunov at Lomonosov Moscow State University <lipunov@sai.msu.ru>
Via
email
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-OAFA robotic telescope (Global MASTER-Net: http://observ.pereplet.ru, Lipunov et al., 2010, Advances in Astronomy, vol. 2010, 30L) located in Argentina (OAFA observatory of San Juan National University) was pointed to the Swift GRB250725.08 (trigger No 1336720,02h 21m 32.40s , -82d 47m 02.4s, R=0.05) errorbox 23 sec after notice time and 45 sec after trigger time at 2025-07-25 01:52:22 UT, with upper limit up to 18.3 mag. The observations began at zenith distance = 64 deg. The sun altitude is -50.5 deg.
MASTER-SAAO robotic telescope located in South Africa (South African Astronomical Observatory) was pointed to the Swift GRB250725.08 errorbox 30 sec after notice time and 53 sec after trigger time at 2025-07-25 01:52:29 UT, with upper limit up to 17.0 mag. The observations began at zenith distance = 53 deg. The sun altitude is -46.5 deg.
The galactic latitude b = -34 deg., longitude l = 300 deg.
Real time updated cover map and OT discovered available here:
https://master.sai.msu.ru/site/master2/observ.php?id=2947351
We obtain a following upper limits.
Tmid-T0 | Site |Filt.| Expt. | Limit| Comment
_________|_____________________|_____|_______|______|________
51 | MASTER-OAFA | C | 10 | 18.2 |
58 | MASTER-SAAO | P/ | 10 | 16.1 |
58 | MASTER-SAAO | P\\ | 10 | 16.5 |
67 | MASTER-OAFA | C | 10 | 18.3 |
92 | MASTER-SAAO | P/ | 20 | 16.8 |
92 | MASTER-SAAO | P\\ | 20 | 17.0 |
Filter C is a clear (unfiltred) band.
The observation and reduction will continue.
The message may be cited.