TITLE: GCN CIRCULAR
NUMBER: 41194
SUBJECT: GRB 250728A: Swift-XRT observations
DATE: 25/07/29 09:59:23 GMT
FROM: Phil Evans at U of Leicester <pae9(a)star.le.ac.uk>
M.A. Williams (PSU), J.P. Osborne (U. Leicester), K.L. Page (U.
Leicester), A.P. Beardmore (U. Leicester), A. Melandri (INAF-OAR), T.
Sbarrato (INAF-OAB), P. D'Avanzo (INAF-OAB), S. Dichiara (PSU), J.A.
Kennea (PSU) 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 250728A, collecting 3.1 ks of Photon
Counting (PC) mode data between T0+14.6 ks and T0+28.2 ks.
One uncatalogued X-ray source has been detected within the estimated
3-sigma Fermi/GBM error region (394 arcsec), it is below the RASS limit
and shows no definitive signs of fading. Therefore, at the present time
we cannot confirm this as the afterglow. Details of this source are
given below:
Source 3:
RA (J2000.0): 260.9895 = 17:23:57.48
Dec (J2000.0): +16.2004 = +16:12:01.6
Error: 6.7 arcsec (radius, 90% conf.)
Count-rate: (1.98 [+1.26, -0.93])e-3 ct s^-1
Distance: 154 arcsec from Fermi/GBM position.
Flux: (1.34 [+0.85, -0.63])e-13 erg cm^-2 s^-1 (observed, 0.3-10 keV)
Two uncatalogued sources were also detected too far from the GRB
position to be likely afterglow candidates.
The results of the XRT-team automatic analysis of the XRT observations,
including a position-specific upper limit calculator, are available at
https://www.swift.ac.uk/ToO_GRBs/00021852.
This circular is an official product of the Swift-XRT team.
View this GCN Circular online at https://gcn.nasa.gov/circulars/41194.
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TITLE: GCN CIRCULAR
NUMBER: 41193
SUBJECT: GRB 250727A: SVOM/ECLAIRs refined analysis
DATE: 25/07/29 08:16:33 GMT
FROM: SVOM_group <svomgroup(a)bao.ac.cn>
M. G. Bernardini (INAF-OAB, LUPM), N. Dagoneau, D. Turpin (CEA), J.-L. Atteia, M. Brunet (IRAP), L. P. Xin (NAOC), J. X. Cao (GXU)
Using the event-by-event data downloaded through the X-band ground station, we report further analysis of ECLAIRs observations of GRB 250727A (SVOM burst-id sb25072701).
The burst that triggered ECLAIRs onboard (Cao et al. GCN 41176) consists of a long soft bump detected mainly below 30 keV, with a duration of T90 = (115.1 -8.2 +14.2) s in the 4-30 keV energy band.
The time-averaged spectrum from T0-10 s to T0+100 s (T0 = 2025-07-27T10:55:41.923s) in the energy range 5-50 keV is best fitted by a powerlaw model with index 2.3+/-0.4. With this model, the total 4-50 keV fluence is (1.4+/-0.1)e-7 erg/cm^2.
The spectrum can be equally fit by a blackbody model with temperature 2.4+/-0.5 keV. With this model, the total 4-50 keV fluence is (1.1+/-0.1)e-7 erg/cm^2.
All the quoted errors are at the 68% confidence level.
We note that the calibration of SVOM/ECLAIRs is undergoing thus these results are preliminary.
The Space-based multi-band astronomical 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 CNES, CEA-IRFU, CNRS-IRAP, CNRS-APC.
The SVOM/ECLAIRs point of contact for this burst is: Maria Grazia Bernardini (INAF-OAB, LUPM) (maria.bernardini at inaf.it)
View this GCN Circular online at https://gcn.nasa.gov/circulars/41193.
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TITLE: GCN CIRCULAR
NUMBER: 41192
SUBJECT: EP-WXT trigger 01709195487: confirmation of a stellar flare by BOOTES-6 & BOOTES-7
DATE: 25/07/29 07:39:10 GMT
FROM: I. Perez-Garcia at Institute of Astrophysics of Andalusia <ipg(a)iaa.es>
I. Perez-Garcia, S.-Y. Wu, A. J. Castro-Tirado, E. J. Fernandez-Garcia, M.D. Caballero-Garcia, S. Guziy, G. Garcia-Segura, R. Sanchez-Ramirez (IAA-CSIC), Y.-D. Hu (INAF-OAB), C. Perez del Pulgar, A. Castellon, I. Carrasco (Univ. de Malaga), L. Hernandez-Garcia (Univ. de Valparaiso), M. Gritsevich (Univ. of Helsinki), D.-R. Xiong (Yunnan Observatories of CAS), B.-B. Zhang (Nanjing Univ.), P. J. Meintjes and H. J. van Heerden (UFS, South Africa), A. Martin-Carrillo and L. Hanlon (UCD, Ireland) and A. Maury (Space, San Pedro de Atacama), on behalf of a larger collaboration, report:
Following the detection of trigger 01709195487 by EP-WXT (Liang et al. GCN 41173), the 0.6m robotic telescopes BOOTES-7 at San Pedro de Atacama (Chile) responded to the alert on July 27, 07:40 UT (i.e. 2 min after notification and 6 min after the detection). Using SDSS g filter and ATLAS REFCAT2 gmag as a reference, we measure an initial magnitude of 12.2 +/- 0.1. Later, on July 27, 23:55 UT (16.25 hours after BOOTES-7 images) the BOOTES-6/DPRT 0.6m robotic telescope at Boyden Observatory in Maselspoort (South Africa) covered the same region, measuring the same source in the same filter with a magnitude of 13.0 +/- 0.1, confirming the EP X-ray trigger due to a stellar flare.
We thank the staff at San Pedro de Atacama Celestial Observations and Boyden Observatory for their excellent support.
View this GCN Circular online at https://gcn.nasa.gov/circulars/41192.
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TITLE: GCN CIRCULAR
NUMBER: 41191
SUBJECT: GRB 250728A: COLIBRÍ optical upper limit
DATE: 25/07/29 06:26:02 GMT
FROM: Camila Angulo Valdez at UNAM <camiangulo(a)astro.unam.mx>
Camila Angulo (UNAM), Francesco Magnani (CPPM), Rosa L. Becerra (U Roma), Stéphane Basa (UAR Pytheas), William H. Lee (UNAM), Alan M. Watson (UNAM), Fredd Alvarez (UNAM), Jean-Luc Atteia (IRAP), Dalya Akl (AUS), Sarah Antier (OCA), Nathaniel R. Butler (ASU) , Damien Dornic (CPPM), Jean-Grégoire Ducoin (CPPM), Francis Fortin (IRAP), Leonardo García García (UNAM), Ramandeep Gill (UNAM), Noémie Globus (UNAM), Kin Ocelotl López (UNAM), Diego López-Cámara (UNAM), Enrique Moreno Méndez (UNAM), Margarita Pereyra (UNAM), Ny Avo Rakotondrainibe (LAM), Benjamin Schneider (LAM) and Antonio de Ugarte Postigo (LAM):
We imaged the field of the Fermi/Swift GRB 250728A (Pathak et al., GCN Circ. 41190; Ronchini et al., GCN Circ. 41185) using the DDRAGO wide-field imager on the COLIBRÍ telescope. We observed from 2025-07-29 03:29 to 05:34 UTC (from 18.07 to 20.15 hours after the trigger) and obtained 96 minutes of exposure in the i filter.
The data were reduced and coadded with the COLIBRÍ pipeline and analysed with STDWeb/STDPipe (Karpov 2025). The photometry was calibrated using nearby stars from the PanSTARRS DR1 catalog, is in the AB system, and is not corrected for Galactic extinction.
In the stacked image, we do not detect any new source in the BAT uncertainty region (Ronchini et al., GCN Circ. 41185) to a 5-sigma limit of:
i > 24.20
Furthermore, at the position of Swift/XRT source #3 (Evans et al., GCN Circ. 41186) at 17:23:57.48 +16:12:01.6 we do not detect a new source to a 3-sigma limit of:
i > 24.75
Further observations are ongoing.
We thank the staff of the Observatorio Astronómico Nacional on the Sierra de San Pedro Mártir and the COLIBRÍ and DDRAGO engineering teams.
COLIBRÍ is an astronomical observatory developed and operated jointly by France (AMU, CNES and CNRS) and Mexico (UNAM and SECIHTI). It is located at the Observatorio Astronómico Nacional on the Sierra de San Pedro Mártir, Baja California, Mexico.
View this GCN Circular online at https://gcn.nasa.gov/circulars/41191.
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TITLE: GCN CIRCULAR
NUMBER: 41190
SUBJECT: GRB 250728A: Fermi GBM Observation
DATE: 25/07/28 22:25:38 GMT
FROM: Vidushi Sharma at NASA GSFC/UMBC <vidushi.sharma(a)nasa.gov>
U. Pathak (IIT Bombay), V. Sharma (NASA GSFC/UMBC) and C. Meegan (UAH) report on behalf of
the Fermi Gamma-ray Burst Monitor Team:
"At 09:25:45.57 UT on 28 July 2025, the Fermi Gamma-ray Burst Monitor (GBM)
triggered and located GRB 250728A (trigger 775387550/250728393),
which was also detected by Swift/BAT-GUANO (Samuele Ronchini et al. 2025, GCN 41185).
The Fermi GBM on-ground location is consistent with the Swift/BAT-GUANO position.
The angle from the Fermi LAT boresight is 80 degrees.
The GBM light curve of a short complex pulse with a duration (T90)
of about 0.6 s (50-300 keV).
The time-averaged spectrum from T0-0.58 to T0+0.32 s is best fit by
a power law function. The power law index is -1.6 +/- 0.1.
The event fluence (10-1000 keV) in this time interval is
(3.5 +/- 0.5)E-07 erg/cm^2. The 64-ms peak photon flux measured
starting from T0-0.064 s in the 10-1000 keV band is 7 +/- 1.2 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/"
View this GCN Circular online at https://gcn.nasa.gov/circulars/41190.
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TITLE: GCN CIRCULAR
NUMBER: 41189
SUBJECT: Fermi trigger No 775387550: Global MASTER-Net observations report
DATE: 25/07/28 20:30:33 GMT
FROM: Vladimir Lipunov at Moscow State U/Krylov Obs <lipunov(a)xray.sai.msu.ru>
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-Kislovodsk robotic telescope (Global MASTER-Net: http://observ.pereplet.ru, Lipunov et al., 2010, Advances in Astronomy, vol. 2010, 30L) located in Russia (Lomonosov MSU, Kislovodsk Solar Station of Pulkovo observatory) started inspect of the Fermi GRB250728.39 (trigger No 775387550,16h 46m 12.00s , +18d 16m 48.0s, R=8.29) errorbox 39041 sec after notice time and 39062 sec after trigger time at 2025-07-28 20:16:48 UT, with upper limit up to 14.2 mag. The observations began at zenith distance = 42 deg. The sun altitude is -26.6 deg.
The galactic latitude b = 35 deg., longitude l = 37 deg.
Real time updated cover map and OT discovered available here:
https://master.sai.msu.ru/site/master2/observ.php?id=2950692
We obtain a following upper limits.
Tmid-T0 | Date Time | Site | Coord (J2000) |Filt.| Expt. | Limit| Comment
_________|_____________________|_____________________|____________________________________|_____|_______|_______|________
39093 | 2025-07-28 20:16:48 | MASTER-Kislovodsk | (16h 48m 00.15s , +18d 23m 15.1s) | C | 60 | 14.2 |
39374 | 2025-07-28 20:21:29 | MASTER-Kislovodsk | (16h 43m 37.13s , +20d 18m 42.0s) | C | 60 | 14.1 |
Filter C is a clear (unfiltred) band.
The observation and reduction will continue.
The message may be cited.
View this GCN Circular online at https://gcn.nasa.gov/circulars/41189.
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TITLE: GCN CIRCULAR
NUMBER: 41188
SUBJECT: LIGO/Virgo/KAGRA S250727dc: Updated Sky localization
DATE: 25/07/28 17:40:55 GMT
FROM: lucy.thomas(a)ligo.org
The LIGO Scientific Collaboration, the Virgo Collaboration, and the KAGRA Collaboration report:
We have conducted further analysis of the LIGO Hanford Observatory (H1), LIGO Livingston Observatory (L1), and Virgo Observatory (V1) data around the time of the compact binary merger (CBC) candidate S250727dc (GCN Circular 41179). Parameter estimation has been performed using Bilby [1] and a new sky map, Bilby.offline0.multiorder.fits,0, distributed via GCN and SCiMMA notices, is available for retrieval from the GraceDB event page:
https://gracedb.ligo.org/superevents/S250727dc
For the Bilby.offline0.multiorder.fits,0 sky map, the 90% credible region is well fit by an ellipse with an area of 15 deg2 described by the following DS9 region (right ascension, declination, semi-major axis, semi-minor axis, position angle of the semi-minor axis):
icrs; ellipse(06h29m, -35d45m, 2.97d, 1.66d, 27.69d)
Marginalized over the whole sky, the a posteriori luminosity distance estimate is 1389 +/- 318 Mpc (a posteriori mean +/- standard deviation).
For further information about analysis methodology and the contents of this alert, refer to the LIGO/Virgo/KAGRA Public Alerts User Guide https://emfollow.docs.ligo.org/.
[1] Ashton et al. ApJS 241, 27 (2019) doi:10.3847/1538-4365/ab06fc and Morisaki et al. PRD 108, 123040 (2023) doi:10.1103/PhysRevD.108.123040
View this GCN Circular online at https://gcn.nasa.gov/circulars/41188.
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TITLE: GCN CIRCULAR
NUMBER: 41187
SUBJECT: LIGO/Virgo/KAGRA S250727dc: Swift-UVOT detection of a new source, AT 2025smm
DATE: 25/07/28 15:31:25 GMT
FROM: Paul Kuin at MSSL <npkuin(a)gmail.com>
N.P.M. Kuin (UCL-MSSL), M.H. Siegel (PSU), A.A. Breeveld (UCL-MSSL), C.
Gronwall (PSU), N.J. Klingler (NASA/GSFC UMBC CRESST II),F.E. Marshall
(NASA/GSFC), S.R. Oates (Lancaster U.), M. De Pasquale (University of
Messina), M.J. Page (UCL-MSSL), S. Shilling (Lancaster U.), A. D’Aì
(INAF-IAFPA), P. D’Avanzo (INAF-OAB), A.P. Beardmore (U. Leicester), M.G.
Bernardini (INAF-OAB),S. Campana (INAF-OAB), S.B. Cenko (NASA/GSFC), J.J.
Delaunay (PSU), S. Dichiara (PSU), V. D’Elia (ASI-SSDC & INAF-OAR),
R.A.J.Eyles-Ferris (U. Leicester), P.A. Evans (U. Leicester), R. Gayathri
(PSU), D. Hartmann (Clemson University), J.A. Kennea (PSU), S. Laha
(NASA/GSFC),H.A. Krimm (NSF), D. B. Malesani (DTU Space), P. O’Brien (U.
Leicester), J.P. Osborne (U. Leicester), T. Partosan (NASA/GSFC), M. Perri
(ASDC), K.L. Page (U. Leicester), D.M. Palmer (LANL), S. Ronchini (PSU), T.
Sbarrato (INAF-OAB), B. Sbarufatti (INAF-OAB), G. Tagliaferri (INAF-OAB),
E. Troja (U. Tor Vergata, INAF), and A. Tohuvavohu (U. Toronto)report:
Swift observed the high-probability region of LIGO/Virgo/KAGRA S250725dc
starting 65.3 minutes after the trigger date. A new UVOT source was found
in the U band with U = 19.9 +/- 0.3 mag (ABmag) image taken on 2025-07-28
00:34_55 UT at the following position:
RA = 97.47619, Dec = -37.23307 deg, or RA = 06:29:54.3,
Dec = -37:13:55.45 in sexagesimal notation.
We do not find any source on that location in DSS, using the Vizier
photometry tool, or as a nearby object known to the Minor Planet Center
MPChecker tool. The object has been registered as 2025smm by the Transient
Name Server.
A further Swift observation has been planned.
View this GCN Circular online at https://gcn.nasa.gov/circulars/41187.
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TITLE: GCN CIRCULAR
NUMBER: 41186
SUBJECT: GRB 250728A: Swift ToO observations
DATE: 25/07/28 13:29:08 GMT
FROM: Phil Evans at U of Leicester <pae9(a)star.le.ac.uk>
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 250728A. Automated analysis of the XRT data will be presented online at
https://www.swift.ac.uk/ToO_GRBs/00021852
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.
View this GCN Circular online at https://gcn.nasa.gov/circulars/41186.
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TITLE: GCN CIRCULAR
NUMBER: 41185
SUBJECT: GRB 250728A: Swift/BAT-GUANO arcminute localization of a short burst
DATE: 25/07/28 12:57:19 GMT
FROM: Samuele Ronchini at PSU <sjs8171(a)psu.edu>
Samuele Ronchini (PSU), James DeLaunay (PSU), Aaron Tohuvavohu (Caltech), Jamie A. Kennea (PSU), Tyler Parsotan (NASA GSFC), Maia Williams (PSU) report:
Swift/BAT did not localize GRB 250728A onboard (T0: 2025-07-28T09:25:45.57 UTC).
The Fermi notice, distributed in near real-time, triggered the Swift Mission Operations Center operated Gamma-ray Urgent Archiver for Novel Opportunities (GUANO; Tohuvavohu et al. 2020, ApJ, 900, 1).
Upon trigger by this notice, GUANO sent a command to the Swift Burst Alert Telescope (BAT) to save 200 seconds of BAT event-mode data from [-50,+150] seconds around the time of the burst. All the requested event mode data was delivered to the ground.
The arcmin position of the burst is found with the newly developed pipeline BAT-GLIMPSE: Gamma-ray Localization using Imaging and Mosaic techniques for Pointing and Slew Epochs (Ronchini et. al, in prep). The pipeline makes use of the tools from BatAnalysis ([Parsotan et al. 2025](https://iopscience.iop.org/article/10.3847/1538-4357/ade240)). The source is found with an SNR = 8.1
Independently, the BAT likelihood search, NITRATES (DeLaunay + Tohuvavohu 2022, ApJ, 941, 169), confirms the detection of the burst in a 0.512 s analysis time bin starting at T0 - 0.512 s with a sqrt(TS) of 16.4. An arcminute localization is found with DeltaLLHOut of 42.69 and a DeltaLLHPeak of 35.31.
See Section 9.1 and Figures 10 and 17 in the NITRATES paper for brief descriptions and interpretations of sqrt(TS), DeltaLLHPeak, and DeltaLLHOut.
The BAT position is:
RA, Dec = 260.945, 16.2049 deg
which is
RA(J2000) = 17h 23m 46.80s
Dec(J2000) = 16d 12’ 17.6″
with an estimated uncertainty of 3 arcmin radius.
More details about this burst can be found on the trigger report page here: https://guano.swift.psu.edu/trigger_report?id=775387581
XRT and UVOT follow-up has been requested. Results of follow-up observations will be reported in future circulars.
GUANO is a fully autonomous, extremely low latency, spacecraft commanding pipeline designed for targeted recovery of BAT event mode data around the times of compelling astrophysical events to enable more sensitive GRB searches. A live reporting of Swift/BAT event data recovered by GUANO can be found at: https://www.swift.psu.edu/guano/
View this GCN Circular online at https://gcn.nasa.gov/circulars/41185.
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