GRB 250716A
GCN Circular 41109
Subject
Konus-Wind detection of GRB 250716A
Date
2025-07-17T15:32:45Z (3 months ago)
From
Dmitry Svinkin at Ioffe Institute <svinkin@mail.ioffe.ru>
Via
Web form
D. Svinkin, D. Frederiks, A. Lysenko, A. Ridnaia,
A. Tsvetkova, M. Ulanov, and T. Cline
on behalf of the Konus-Wind team, report:
The bright, long-duration GRB 250716A
(Fermi-GBM detection: Fermi GBM team, GCN 41099;
Mukherjee and Meegan, GCN 41102)
triggered Konus-Wind at T0=5348.122 s UT (01:29:08.122).
The burst light curve shows a multipeaked structure
which starts at ~T0-91 s and has a total duration of ~235 s.
The emission is seen up to ~20 MeV.
The Konus-Wind light curve of this GRB is available at
http://www.ioffe.ru/LEA/GRBs/GRB250716_T05348/
As observed by Konus-Wind, the burst
had a fluence of 2.39(-0.09,+0.09)x10^-4 erg/cm2,
and a 64-ms peak flux, measured from T0+2.544 s,
of 4.26(-0.33,+0.33)x10^-5 erg/cm2/s
(both in the 20 keV - 10 MeV energy range).
The time-averaged spectrum of the burst
(measured from T0 to T0+88.064 s)
is best fit in the 20 keV - 10 MeV range
by the GRB (Band) model with the following parameters:
the low-energy photon index alpha = -1.25(-0.04,+0.04),
the high energy photon index beta = -1.78(-0.04,+0.03),
the peak energy Ep = 554(-84,+93) keV
(chi2 = 124/97 dof).
The spectrum near the maximum count rate
(measured from T0+0.256 to T0+4.096 s)
is best fit in the 20 keV - 10 MeV range
by the GRB (Band) model with the following parameters:
the low-energy photon index alpha = -0.78(-0.06,+0.07),
the high energy photon index beta = -1.59(-0.03,+0.03),
the peak energy Ep = 726(-113,+139) keV
(chi2 = 106/86 dof).
All the quoted errors are at the 68% confidence level.
All the quoted values are preliminary.
GCN Circular 41108
Subject
GRB 250716A: Swift-XRT afterglow detection
Date
2025-07-17T15:12:43Z (3 months ago)
From
Phil Evans at U of Leicester <pae9@star.le.ac.uk>
Via
email
M.A. Williams (PSU), S. Dichiara (PSU), J.A. Kennea (PSU), J.P. Osborne
(U. Leicester), K.L. Page (U. Leicester), A.P. Beardmore (U.
Leicester), A. D'Ai (INAF-IASFPA), S. Campana (INAF-OAB), A. Melandri
(INAF-OAR) and P.A. Evans (U. Leicester) reports on behalf of the
Swift-XRT team:
Swift-XRT has performed follow-up observations of the
Fermi/GBM-detected burst GRB 250716A. We searched for X-ray sources in
2.6 ks of Photon Counting (PC) mode data. The total exposure at the
position of the afterglow (see below) is 2.6 ks, obtained between
T0+79.5 ks and T0+91.7 ks.
An uncatalogued X-ray source is detected within the GOTO error region
and is above the RASS 3-sigma upper limit at this position, and is
therefore likely the GRB afterglow. Using 2790 s of PC mode data and 2
UVOT images, we find an enhanced XRT position (using the XRT-UVOT
alignment and matching UVOT field sources to the USNO-B1 catalogue):
RA, Dec = 66.77171, -46.56649 which is equivalent to:
RA (J2000): 04h 27m 05.21s
Dec(J2000): -46d 33' 59.4"
with an uncertainty of 2.7 arcsec (radius, 90% confidence). This
position is 1.9 arcsec from the GOTO position.
The light curve can be modelled with a power-law decay with a decay
index of alpha=2.755 (+0.015, -0.755).
A spectrum formed from the PC mode data can be fitted with an absorbed
power-law with a photon spectral index of 2.22 (+0.30, -0.27). The
best-fitting absorption column is 6.9 (+6.4, -5.2) x 10^20 cm^-2, in
excess of the Galactic value of 1.2 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 3.0 x 10^-11 (3.7 x 10^-11) erg
cm^-2 count^-1.
A summary of the PC-mode spectrum is thus:
Total column: 6.9 (+6.4, -5.2) x 10^20 cm^-2
Galactic foreground: 1.2 x 10^20 cm^-2
Excess significance: 1.8 sigma
Photon index: 2.22 (+0.30, -0.27)
The results of the XRT-team automatic analysis of the likely afterglow
are at https://www.swift.ac.uk/ToO_GRBs/00021845/Source1.php.
The results of the full analysis of the XRT observations are available
at https://www.swift.ac.uk/ToO_GRBs/00021845.
This circular is an official product of the Swift-XRT team.
GCN Circular 41106
Subject
GRB 250716A: Lesedi Detection of Fading Optical Transient GOTO25eyp
Date
2025-07-17T11:01:22Z (3 months ago)
From
Amit Kumar at Royal Holloway - UoL/ U of Warwick, UK <amitkundu515@gmail.com>
Via
Web form
Amit Kumar (RHUL), Nikita Rawat (SAAO), David Buckley (SAAO), Justyn R. Maund (RHUL), Danny Steeghs (Warwick) and Raya Dastidar (UNAB) report:
We observed the optical transient GOTO25eyp (AT 2025rhc; Rayson et al., GCN 41103), a candidate counterpart to GRB 250716A (Fermi GBM Team, GCNs 41099, 41102), using the 1-m Lesedi telescope at the South African Astronomical Observatory (SAAO), Sutherland, South Africa. Observations were conducted on 2025 July 17 between 03:08:39 and 04:09:30 UT (~25.66 to ~26.67 hours post-trigger) in g’, r’, i’, and z’ bands (3×360s in g and z, 3×300s in r and i bands).
GOTO25eyp was clearly detected in all individual exposures across the four filters. Preliminary aperture photometry yields the following magnitudes in g’ and r’ bands:
DATE-OBS T-T0 (hrs) Filter Exp (s) Magnitude (AB)
-------------------------------------------------------------------------------------
2025-07-17T03:08:39 25.66 g’ 360s 18.95 ± 0.09
2025-07-17T03:26:56 25.96 r’ 300s 18.67 ± 0.07
These observations indicate a decline of ~0.6 mag over ~8.4 hours since the initial detection reported by GOTO. This fading behaviour suggests a transient origin for GOTO25eyp and is broadly consistent with the temporal evolution expected from a GRB afterglow. We note that we are considering the GOTO L-band (400–700 nm), which approximates the mean wavelength coverage of the g and r filters.
Photometric calibration was performed using reference stars from the SDSS catalogue. Follow-up observations are ongoing, and further analysis is in progress.
Data were obtained using the 1-m Lesedi robotic telescope at the SAAO, equipped with the Mookodi low-resolution spectrograph and imager operating in fully robotic imaging mode. We thank the SAAO Instrumentation and Operations (IO) team for their continued support.
GCN Circular 41104
Subject
GRB 250716A: Swift ToO observations
Date
2025-07-16T23:30:19Z (3 months ago)
From
Phil Evans at U of Leicester <pae9@star.le.ac.uk>
Via
email
P. A. Evans (U. Leicester) reports on behalf of the Swift team:
Swift has initiated a ToO observation of the Fermi/GBM-detected event
GRB 250716A. Automated analysis of the XRT data will be presented online at
https://www.swift.ac.uk/ToO_GRBs/00021845
Any uncatalogued X-ray sources detected in this analysis will be
reported on this website and via GCN COUNTERPART notices. These are
not necessarily related to the Fermi/GBM event. Any X-ray source
considered to be a probable afterglow candidate will be reported via a
GCN Circular after manual consideration.
Details of the XRT automated analysis methods are detailed in Evans et
al. (2007, A&A, 469, 379; 2009, MNRAS, 397, 1177 and 2014, ApJS, 210, 8).
This circular is an official product of the Swift-XRT team.
GCN Circular 41103
Subject
GRB 250716A: GOTO tentative optical counterpart candidate
Date
2025-07-16T20:30:19Z (3 months ago)
From
Ben Rayson at University of Leicester <br155@leicester.ac.uk>
Via
Web form
B. Rayson, D. O’Neill, B. P. Gompertz, A. Kumar, R. Starling, K. Ackley, M. J. Dyer, J. Lyman, K. Ulaczyk, B. Godson, D. Steeghs, D. K. Galloway, V. Dhillon, P. O'Brien, G. Ramsay, K. Noysena, R. Kotak, R. P. Breton, L. K. Nuttall, and J. Casares report on behalf of the GOTO collaboration:
We report on optical observations with the Gravitational-wave Optical Transient Observer (GOTO; Steeghs et al. 2022, Dyer et al. 2024) in response to GRB 250716A (Fermi GBM Team, GCNs 41099, 41102).
Targeted observations were performed beginning at 2025-07-16 17:07:29 UT, (+15.64h post trigger) and continued through to 2025-07-16 19:03:17 UT (+17.57h post trigger). 85 images were taken, across 10 unique pointings, covering 203 sq degrees, within the 90% localisation contour. ~90.0% of the total 2D localisation probability was covered, with an average 5-sigma depth of 19.9 mag.
Images were processed immediately after acquisition using the GOTO pipeline. Difference imaging was performed using deeper template observations. Source candidates were initially filtered using a classifier (Killestein et al. 2021) and cross-matched against a variety of contextual and minor planet catalogs. Human vetting was carried out in real time on any candidates that passed the above checks.
A new optical source GOTO25eyp (AT 2025rhc) is identified within the GBM 90% localisation region, lying on the 16% probability contour. The source was initially detected with magnitude L = 18.20 ± 0.04 AB mag at +16.33h post trigger, before fading to L = 18.26 ± 0.04 AB mag at +17.46h post trigger. In total the source was detected in three consecutive epochs. The measured magnitudes are consistent with a decay rate of ~t^(-0.83±0.09). However, we caution that the measured decay is based on a relatively short temporal baseline and is therefore sensitive to scatter in the photometric measurements. The source is coincident with a faint (g=25.15 AB mag) extended source in the legacy survey with a mean photo z=0.98 ± 0.21.
We find no evidence of the source prior to the GRB trigger time in previous GOTO observations or the ATLAS forced photometry server (Shingles et al. 2021). Due to the absence of pre-trigger detections, possible power-law decay, and the presence of a candidate host galaxy, we propose GOTO25eyp / AT 2025rhc as a candidate optical counterpart for GRB 250716A. Follow-up observations are encouraged.
Magnitudes were calibrated using ATLAS-REFCAT2 (Tonry et al. 2018) and are not corrected for Galactic extinction.
GOTO (https://goto-observatory.org) is a network of telescopes that is principally funded by the STFC and operated at the Roque de los Muchachos Observatory on La Palma, Spain, and Siding Spring Observatory in NSW, Australia, on behalf of a consortium including the University of Warwick, Monash University, Armagh Observatory & Planetarium, the University of Leicester, the University of Sheffield, the National Astronomical Research Institute of Thailand (NARIT), the University of Turku, the University of Portsmouth, the University of Manchester and the Instituto de Astrofisica de Canarias (IAC).
GCN Circular 41102
Subject
GRB 250716A: Fermi GBM Observation
Date
2025-07-16T15:35:42Z (3 months ago)
From
oindabimukherjee@gmail.com
Via
Web form
O. Mukherjee (USRA) and C. Meegan (UAH) report on behalf of
the Fermi Gamma-ray Burst Monitor Team:
"At 01:29:06.25 UT on 16 July 2025, the Fermi Gamma-ray Burst Monitor (GBM)
triggered and located GRB 250716A (trigger 774322151/250716062).
The on-ground calculated location, using the Fermi GBM trigger data,
is RA = 65.72, Dec = -48.56 (J2000 degrees, equivalent to
J2000 4h 22m, -48d 33'), with a statistical uncertainty of 1.00 degrees.
(radius, 1-sigma containment, statistical only; there is additionally a
systematic error which we have characterized as a mixture of two Gaussians,
one with a radius of 1.8 degrees (52% contribution) and one with a radius
of 4.1 degrees (47% contribution) [A. Goldstein et al. 2020, ApJ, 895, 1]).
The angle from the Fermi LAT boresight is 126 degrees.
The GBM light curve consists of two pulses with a duration (T90)
of about 66 s (50-300 keV). The time-averaged spectrum
from T0-3.1 to T0+79.9 s is best fit by
a Band function with Epeak = 1153 +/- 133 keV,
alpha = -1.29 +/- 0.01, and beta = -1.89 +/- 0.03.
The event fluence (10-1000 keV) in this time interval is
(9.9 +/- 0.1)E-05 erg/cm^2. The 1-sec peak photon flux measured
starting from T0+5.5 s in the 10-1000 keV band is 37.9 +/- 0.7 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 41100
Subject
Fermi GRB 250716A: Global MASTER-Net observations report
Date
2025-07-16T02:15:32Z (3 months ago)
From
Vladimir Lipunov at Moscow State U/Krylov Obs <lipunov@xray.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-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) started inspect of the Fermi GRB 250716A ( Fermi GBM team, GCN 41099) errorbox 93 sec after notice time and 128 sec after trigger time at 2025-07-16 01:31:14 UT, with upper limit up to 20.3 mag. The observations began at zenith distance = 65 deg. The sun altitude is -51.6 deg.
The galactic latitude b = -44 deg., longitude l = 255 deg.
Real time updated cover map and OT discovered available here:
https://master.sai.msu.ru/site/master2/observ.php?id=2937727
We obtain a following upper limits.
Tmid-T0 | Date Time | Site | Coord (J2000) |Filt.| Expt. | Limit| Comment
_________|_____________________|_____________________|____________________________________|_____|_______|_______|________
144 | 2025-07-16 01:31:14 | MASTER-SAAO | (04h 21m 01.64s , -48d 49m 17.3s) | C | 30 | 18.7 |
144 | 2025-07-16 01:31:15 | MASTER-SAAO | (04h 23m 46.59s , -49d 04m 32.8s) | C | 30 | 18.9 |
445 | 2025-07-16 01:36:01 | MASTER-SAAO | (04h 10m 39.54s , -50d 08m 38.2s) | C | 60 | 19.1 |
445 | 2025-07-16 01:36:01 | MASTER-SAAO | (04h 13m 29.24s , -50d 23m 52.1s) | C | 60 | 19.3 |
644 | 2025-07-16 01:39:20 | MASTER-SAAO | (04h 19m 15.27s , -48d 35m 54.2s) | C | 60 | 19.1 |
704 | 2025-07-16 01:39:20 | MASTER-SAAO | (04h 19m 15.27s , -48d 35m 54.2s) | C | 180 | 20.1 | Coadd
644 | 2025-07-16 01:39:20 | MASTER-SAAO | (04h 21m 59.51s , -48d 51m 08.0s) | C | 60 | 19.5 |
704 | 2025-07-16 01:39:20 | MASTER-SAAO | (04h 21m 59.50s , -48d 51m 08.0s) | C | 180 | 20.3 | Coadd
723 | 2025-07-16 01:40:39 | MASTER-SAAO | (04h 19m 15.21s , -48d 35m 54.7s) | C | 60 | 19.2 |
723 | 2025-07-16 01:40:39 | MASTER-SAAO | (04h 21m 59.40s , -48d 51m 08.0s) | C | 60 | 19.3 |
802 | 2025-07-16 01:41:58 | MASTER-SAAO | (04h 19m 15.12s , -48d 35m 55.6s) | C | 60 | 19.2 |
802 | 2025-07-16 01:41:58 | MASTER-SAAO | (04h 21m 59.30s , -48d 51m 08.5s) | C | 60 | 19.4 |
881 | 2025-07-16 01:43:17 | MASTER-SAAO | (04h 19m 14.99s , -48d 35m 56.7s) | C | 60 | 19.2 |
881 | 2025-07-16 01:43:17 | MASTER-SAAO | (04h 21m 59.18s , -48d 51m 09.2s) | C | 60 | 19.5 |
1549 | 2025-07-16 01:54:25 | MASTER-SAAO | (04h 23m 14.98s , -50d 08m 51.1s) | C | 60 | 19.2 |
1549 | 2025-07-16 01:54:25 | MASTER-SAAO | (04h 26m 05.15s , -50d 24m 04.2s) | C | 60 | 19.3 |
1642 | 2025-07-16 01:55:58 | MASTER-SAAO | (04h 10m 40.25s , -50d 08m 03.6s) | C | 60 | 19.2 |
1642 | 2025-07-16 01:55:58 | MASTER-SAAO | (04h 13m 30.51s , -50d 23m 15.5s) | C | 60 | 19.2 |
1737 | 2025-07-16 01:57:32 | MASTER-SAAO | (04h 24m 02.44s , -48d 13m 28.0s) | C | 60 | 19.2 |
1737 | 2025-07-16 01:57:33 | MASTER-SAAO | (04h 26m 45.90s , -48d 28m 40.4s) | C | 60 | 19.3 |
1830 | 2025-07-16 01:59:05 | MASTER-SAAO | (04h 35m 57.93s , -48d 13m 47.8s) | C | 60 | 19.2 |
1830 | 2025-07-16 01:59:06 | MASTER-SAAO | (04h 38m 41.15s , -48d 29m 00.3s) | C | 60 | 19.3 |
2023 | 2025-07-16 02:02:18 | MASTER-SAAO | (04h 13m 05.25s , -48d 15m 56.4s) | C | 60 | 19.2 |
2023 | 2025-07-16 02:02:19 | MASTER-SAAO | (04h 15m 48.99s , -48d 31m 08.2s) | C | 60 | 19.5 |
2117 | 2025-07-16 02:03:53 | MASTER-SAAO | (04h 14m 31.65s , -46d 20m 24.2s) | C | 60 | 19.1 |
2117 | 2025-07-16 02:03:53 | MASTER-SAAO | (04h 17m 09.42s , -46d 35m 36.2s) | C | 60 | 19.3 |
2210 | 2025-07-16 02:05:26 | MASTER-SAAO | (04h 26m 08.46s , -46d 21m 08.9s) | C | 60 | 19.1 |
2210 | 2025-07-16 02:05:26 | MASTER-SAAO | (04h 28m 46.06s , -46d 36m 20.9s) | C | 60 | 19.4 |
2504 | 2025-07-16 02:10:19 | MASTER-SAAO | (04h 23m 06.32s , -50d 07m 32.2s) | C | 60 | 19.3 |
Filter C is a clear (unfiltred) band.
The observation and reduction will continue.
The message may be cited.
GCN Circular 41099
Subject
GRB 250716A: Fermi GBM Final Real-time Localization
Date
2025-07-16T01:39:42Z (3 months 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 01:29:06 UT on 16 Jul 2025, the Fermi Gamma-ray Burst Monitor (GBM) triggered and located GRB 250716A (trigger 774322151.245036 / 250716062).
The on-ground calculated location, using the Fermi GBM trigger data, is RA = 65.7, Dec = -48.6 (J2000 degrees, equivalent to J2000 04h 22m, -48d 36'), with a statistical uncertainty of 1.0 degrees.
The angle from the Fermi LAT boresight is 126.0 degrees.
The skymap can be found here:
https://heasarc.gsfc.nasa.gov/FTP/fermi/data/gbm/triggers/2025/bn250716062/quicklook/glg_skymap_all_bn250716062.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/bn250716062/quicklook/glg_healpix_all_bn250716062.fit
The GBM light curve can be found here:
https://heasarc.gsfc.nasa.gov/FTP/fermi/data/gbm/triggers/2025/bn250716062/quicklook/glg_lc_medres34_bn250716062.gif