July 2025 - vsnet-grb-info - ooruri.kusastro.kyoto-u.ac.jp

[vsnet-grb-info 39260] LIGO/Virgo/KAGRA S250726ak: Upper limits from Swift/BAT-GUANO
by GCN Circulars 30 Jul '25

30 Jul '25

TITLE: GCN CIRCULAR NUMBER: 41204 SUBJECT: LIGO/Virgo/KAGRA S250726ak: Upper limits from Swift/BAT-GUANO DATE: 25/07/30 17:57:00 GMT FROM: Maia Williams at PSU <mjw6837(a)psu.edu> Maia Williams (PSU), Samuele Ronchini (PSU), Gayathri Raman, James DeLaunay (PSU), Tyler Parsotan (NASA GSFC), Jamie A. Kennea (PSU), Aaron Tohuvavohu (Caltech) report: Swift/BAT was observing 99.9% of the GW localization probability ([Bilby.multiorder.fits](https://gracedb.ligo.org/api/superevents/S250726ak/f…) at merger time. A fraction 40.74% of the GW localization posterior is contained inside the BAT coded FoV. The LVK 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](https://iopscience.iop.org/article/10.3847/1538-4357/aba94f)). 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. Using the NITRATES analysis ([DeLaunay + Tohuvavohu 2022, ApJ, 941, 169](https://iopscience.iop.org/article/10.3847/1538-4357/ac9d38)), we searched for emission on 8 timescales from 0.128s to 16.384s in the interval [-20,+20] seconds around the merger time. We find no evidence for a signal, and derive the following upper limits. We quote the 5-sigma flux upper limits in the 15-350 keV band, weighted over the GW localization, for four spectral templates (soft, normal, and hard GRB-like templates described in [arXiv:1612.02395], and spectral shape from GRB170817A [arXiv:1710.05446]) and for four time bins. In units of 10^-7 erg/s/cm^2: |time_bin (s) |soft |normal|hard |GRB170817 |-|-|-|-|-| |0.256 |12.10 |7.77 |6.83 |8.74 |1.024 |6.19 |3.97 |3.49 |4.46 |4.096 |3.34 |2.15 |1.89 |2.41 |16.384 |2.10 |1.35 |1.18 |1.51 The upper limits as function of sky position are plotted here, alongside the GW localization: https://zenodo.org/records/16614782 The solid and dashed lines indicate the 90% and 50% GW contour levels, respectively. The corresponding fits file is also included. 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/41204. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 39259] LIGO/Virgo/KAGRA S250725l: Upper limits from Swift/BAT-GUANO
by GCN Circulars 30 Jul '25

30 Jul '25

TITLE: GCN CIRCULAR NUMBER: 41203 SUBJECT: LIGO/Virgo/KAGRA S250725l: Upper limits from Swift/BAT-GUANO DATE: 25/07/30 17:54:00 GMT FROM: Maia Williams at PSU <mjw6837(a)psu.edu> Maia Williams (PSU), Samuele Ronchini (PSU), Gayathri Raman, James DeLaunay (PSU), Tyler Parsotan (NASA GSFC), Jamie A. Kennea (PSU), Aaron Tohuvavohu (Caltech) report: Swift/BAT was observing 100.0% of the GW localization probability ([Bilby.offline0.multiorder.fits](https://gracedb.ligo.org/api/superevents/S2…) at merger time. A fraction 38.64% of the GW localization posterior is contained inside the BAT coded FoV. The LVK 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](https://iopscience.iop.org/article/10.3847/1538-4357/aba94f)). 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. Using the NITRATES analysis ([DeLaunay + Tohuvavohu 2022, ApJ, 941, 169](https://iopscience.iop.org/article/10.3847/1538-4357/ac9d38)), we searched for emission on 8 timescales from 0.128s to 16.384s in the interval [-20,+20] seconds around the merger time. We find no evidence for a signal, and derive the following upper limits. We quote the 5-sigma flux upper limits in the 15-350 keV band, weighted over the GW localization, for four spectral templates (soft, normal, and hard GRB-like templates described in [arXiv:1612.02395], and spectral shape from GRB170817A [arXiv:1710.05446]) and for four time bins. In units of 10^-7 erg/s/cm^2: |time_bin (s) |soft |normal|hard |GRB170817 |-|-|-|-|-| |0.256 |9.96 |6.98 |6.25 |7.72 |1.024 |5.08 |3.56 |3.19 |3.94 |4.096 |2.74 |1.92 |1.72 |2.13 |16.384 |1.71 |1.20 |1.08 |1.33 The upper limits as function of sky position are plotted here, alongside the GW localization: https://zenodo.org/records/16614280 The solid and dashed lines indicate the 90% and 50% GW contour levels, respectively. The corresponding fits file is also included. 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/41203. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 39258] LIGO/Virgo/KAGRA S250727dc: Upper limits from Swift/BAT-GUANO
by GCN Circulars 30 Jul '25

30 Jul '25

TITLE: GCN CIRCULAR NUMBER: 41202 SUBJECT: LIGO/Virgo/KAGRA S250727dc: Upper limits from Swift/BAT-GUANO DATE: 25/07/30 17:49:32 GMT FROM: Maia Williams at PSU <mjw6837(a)psu.edu> Maia Williams (PSU), Samuele Ronchini (PSU), Gayathri Raman, James DeLaunay (PSU), Tyler Parsotan (NASA GSFC), Jamie A. Kennea (PSU), Aaron Tohuvavohu (Caltech) report: Swift/BAT was observing 100.00% of the GW localization probability ([Bilby.offline0.multiorder.fits](https://gracedb.ligo.org/api/superevents/S2…) at merger time. A fraction 100.00% of the GW localization posterior is contained inside the BAT coded FoV. The LVK 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](https://iopscience.iop.org/article/10.3847/1538-4357/aba94f)). 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. Using the NITRATES analysis ([DeLaunay + Tohuvavohu 2022, ApJ, 941, 169](https://iopscience.iop.org/article/10.3847/1538-4357/ac9d38)), we searched for emission on 8 timescales from 0.128s to 16.384s in the interval [-20,+20] seconds around the merger time. We find no evidence for a signal, and derive the following upper limits. We quote the 5-sigma flux upper limits in the 15-350 keV band, weighted over the GW localization, for four spectral templates (soft, normal, and hard GRB-like templates described in [arXiv:1612.02395], and spectral shape from GRB170817A [arXiv:1710.05446]) and for four time bins. In units of 10^-7 erg/s/cm^2: |time_bin (s) |soft |normal|hard |GRB170817 |-|-|-|-|-| |0.256 |0.56 |0.87 |0.79 |0.92 |1.024 |0.28 |0.44 |0.40 |0.47 |4.096 |0.15 |0.24 |0.22 |0.25 |16.384 |0.10 |0.15 |0.14 |0.16 The upper limits as function of sky position are plotted here, alongside the GW localization: https://zenodo.org/records/16612515 The solid and dashed lines indicate the 90% and 50% GW contour levels, respectively. The corresponding fits file is also included. 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/41202. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 39257] LIGO/Virgo/KAGRA S250727dc: Swift-XRT observations, 8 X-ray sources
by GCN Circulars 30 Jul '25

30 Jul '25

TITLE: GCN CIRCULAR NUMBER: 41201 SUBJECT: LIGO/Virgo/KAGRA S250727dc: Swift-XRT observations, 8 X-ray sources DATE: 25/07/30 10:45:29 GMT FROM: Phil Evans at U of Leicester <pae9(a)star.le.ac.uk> P.A. Evans (U. Leicester), J.A. Kennea (PSU), A. Tohuvavohu (U. Toronto), S.B. Cenko (NASA/GSFC), R.A.J. Eyles-Ferris (U. Leicester), K.L. Page (U. Leicester), A.P. Beardmore (U. Leicester), M.G. Bernardini (INAF-OAB), A.A. Breeveld (UCL-MSSL), S. Campana (INAF-OAB), J.J. Delaunay (PSU), M. De Pasquale (University of Messina), S. Dichiara (PSU), P. D’Avanzo (INAF-OAB), A. D’Aì (INAF-IASFPA) , V. D’Elia (ASI-SSDC & INAF-OAR), C. Gronwall (PSU), D. Hartmann (Clemson University), N. Klingler (NASA-GSFC / UMBC / CRESST II), N.P.M. Kuin (UCL-MSSL), S. Laha (NASA/GSFC), S.R. Oates (U. Birmingham), J.P. Osborne (U. Leicester), P. O’Brien (U. Leicester), M.J. Page (UCL-MSSL), G. Raman (PSU) S. Ronchini (PSU), T. Sbarrato (INAF-OAB), B. Sbarufatti (INAF-OAB), M.H. Siegel (PSU), G. Tagliaferri (INAF-OAB), E. Troja (U Tor Vergata, INAF) report on behalf of the Swift team: Swift has carried out 171 observations of the LVK error region for the GW trigger S250727dc convolved with the 2MPZ catalogue (Bilicki et al. 2014, ApJS, 210, 9), using the 'bayestar.multiorder.fits,1' GW localisation map. As this is a 3D skymap, galaxy distances were taken into account in selecting which ones to observe. The observations currently span from 3.9 ks to 157 ks after the LVK trigger, and the XRT has covered 11.5 deg^2 on the sky (corrected for overlaps). This covers 70% of the probability in the imrpoved 'Bilby.offline0.multiorder.fits' skymap, and 69% after convolving with the 2MPZ galaxy catalogue, as described by Evans et al. (2016, MNRAS, 462, 1591). In total, we have detected 8 X-ray sources. Each source is assigned a rank of 1-4 which describes how likely it is to be related to the GW trigger, with 1 being the most likely and 4 being the least likely. The ranks are described at https://www.swift.ac.uk/ranks.php. We have found: * 0 sources of rank 1 * 0 sources of rank 2 (see note) * 3 sources of rank 3 * 5 sources of rank 4 NOTE: The online system reports a rank 2 source: Source S250727dc_X1. However, this in the known blazar BL Lac (the prototype of its class of object). During our observation, its flux was significantly increased compared to the mean value in the LSXPS catalogue, hence the automated classification. However, it is known to be highly variable (e.g. https://www.swift.psu.edu/monitoring/source.php?source=BLLacertae) and the intensities in LSXPS are drawn solely from PC-mode data so are biased towards the lower-intensity states. We have thus reclassified this as rank 4 for this circular. RANK 3 sources ============== These are uncatalogued X-ray sources, however they are not brighter than previous upper limits, so do not stand out as likely counterparts to the GW trigger. | Source ID | RA | Dec | Err90 | Detection Flag | | S250727dc_X5 | 06h 23m 38.04s | -35d 38' 24.1" | 7.7" | GOOD | | S250727dc_X6 | 06h 28m 07.71s | -37d 10' 10.3" | 9.5" | REASONABLE | | S250727dc_X7 | 06h 18m 45.03s | -35d 18' 15.1" | 7.0" | GOOD | RANK 4 sources ============== These are catalogued X-ray sources, showing no signs of outburst compared to previous observations, so they are not likely to be related to the GW trigger. | Source ID | RA | Dec | Err90 | Detection Flag | | S250727dc_X1 | 06h 27m 06.55s | -35d 29' 15.0" | 3.8" | GOOD | | S250727dc_X3 | 06h 34m 35.33s | -37d 17' 12.1" | 8.3" | GOOD | | S250727dc_X8 | 06h 36m 18.37s | -37d 22' 33.4" | 4.5" | GOOD | | S250727dc_X9 | 06h 19m 53.43s | -35d 24' 28.2" | 7.7" | GOOD | | S250727dc_X10 | 06h 20m 08.64s | -34d 37' 54.4" | 5.8" | GOOD | In addition, we took a 1.9 ks exposure of the UVOT source reported by Kuin et al. (GCN Circ. 41187). No XRT counterpart was found, with a 3-sigma upper limit of 3.9e-3 ct/sec (approx 1.6e-13 erg cm^-s s^-1, 0.3-10 keV). The results of the XRT automated analysis, including details of the sources listed above, are online at https://www.swift.ac.uk/LVC/S250727dc This circular is an official product of the Swift XRT team. View this GCN Circular online at https://gcn.nasa.gov/circulars/41201. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 39256] GRB 250725A: AstroSat CZTI detection
by GCN Circulars 30 Jul '25

30 Jul '25

TITLE: GCN CIRCULAR NUMBER: 41200 SUBJECT: GRB 250725A: AstroSat CZTI detection DATE: 25/07/30 10:10:49 GMT FROM: Gaurav Waratkar at IIT Bombay <gauravwaratkar(a)iitb.ac.in> 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 View this GCN Circular online at https://gcn.nasa.gov/circulars/41200. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 39255] GRB 250727A: EP-FXT follow-up observation
by GCN Circulars 30 Jul '25

30 Jul '25

TITLE: GCN CIRCULAR NUMBER: 41199 SUBJECT: GRB 250727A: EP-FXT follow-up observation DATE: 25/07/30 06:15:15 GMT FROM: EP Team at NAOC/CAS <ep_ta(a)bao.ac.cn> Y.-H. I. Yin (NJU), R. D. Liang, W. Yuan (NAO, CAS) on behalf of the Einstein Probe (EP) team: EP-FXT performed a follow-up observation of the SVOM/ECLAIRs-detected burst GRB 250727A (SVOM/sb25072701) (Cao et al. GCN 41176) at 2025-07-29T10:57:54 (UTC), about 48 hours after the SVOM/ECLAIRs trigger, with an exposure time of 3878s. Three FXT candidate sources (Yin et al. GCN 41182) are not detected in this observation. The upper limits are listed as follows. Source 1: EPF_J234436.3-810410 RA (J2000): 356.1514 Dec (J2000): -81.0694 Flux upper limit: 8.78 x 10^-14 erg/s/cm2 (0.5-10 keV) Source 2: EPF_J234357.8-811244 RA (J2000): 355.9909 Dec (J2000): -81.2121 Flux upper limit: 1.03 x 10^-13 erg/s/cm2 (0.5-10 keV) Source 3: EPF_J234541.4-811245 RA (J2000): 356.4225 Dec (J2000): -81.2124 Flux upper limit: 6.40 x 10^-14 erg/s/cm2 (0.5-10 keV) Note: This source is spatially consistent with the candidate counterpart Source 1 (SWIFT J234539.1-811248) detected by Swift/XRT. Launched on January 9, 2024, EP is a space X-ray observatory to monitor the soft X-ray sky with X-ray follow-up capability (Yuan et al. 2022, Handbook of X-ray and Gamma-ray Astrophysics). View this GCN Circular online at https://gcn.nasa.gov/circulars/41199. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 39254] GRB 250725A: PRIME near-infrared observations
by GCN Circulars 29 Jul '25

29 Jul '25

TITLE: GCN CIRCULAR NUMBER: 41198 SUBJECT: GRB 250725A: PRIME near-infrared observations DATE: 25/07/29 20:55:52 GMT FROM: Joe Durbak at UMD <gcn.joedurbak(a)gmail.com> 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. View this GCN Circular online at https://gcn.nasa.gov/circulars/41198. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 39253] LIGO/Virgo/KAGRA S250727dc: DECam GW-MMADS upper limits of AT 2025smm
by GCN Circulars 29 Jul '25

29 Jul '25

TITLE: GCN CIRCULAR NUMBER: 41197 SUBJECT: LIGO/Virgo/KAGRA S250727dc: DECam GW-MMADS upper limits of AT 2025smm DATE: 25/07/29 20:55:32 GMT FROM: xjh(a)andrew.cmu.edu Xander J. Hall (CMU), Lei Hu (CMU), Tomás Cabrera (CMU), Antonella Palmese (CMU), Igor Andreoni (UNC), Keerthi Kunnumkai (CMU), Brendan O’Connor (CMU), on behalf of the Gravitational Wave MultiMessenger Astronomy DECam Survey (GW-MMADS) team DECam observed the southern high probability area of the LVK gravitational wave candidate S250727dc (GCN 41179) using the wide-field Dark Energy Camera (DECam) on the 4m Blanco telescope, as part of the Gravitational Wave Multi-Messenger Astronomy DECam Survey (GW-MMADS; PI: Andreoni & Palmese). Observations started at 2025-07-29 09:39 UTC and cover the 90% probability area (GCN 41188). We inspected the location of AT 2025smm, reported by Swift UVOT (GCN 41187), we find no sources in the ugri-bands. Here we report the following limiting magnitudes, not corrected for Galactic extinction: | Filter | Mag (AB) | |--------|----------| | g | > 22.15 | | r | > 21.46 | | i | > 20.60 | Further analysis is underway. We thank the CTIO and NOIRLab staff for supporting these observations and the data calibration. View this GCN Circular online at https://gcn.nasa.gov/circulars/41197. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 39252] LIGO/Virgo/KAGRA S250727dc: PRIME J-band upper limits of AT 2025smm
by GCN Circulars 29 Jul '25

29 Jul '25

TITLE: GCN CIRCULAR NUMBER: 41196 SUBJECT: LIGO/Virgo/KAGRA S250727dc: PRIME J-band upper limits of AT 2025smm DATE: 25/07/29 18:11:07 GMT FROM: Joe Durbak at UMD <gcn.joedurbak(a)gmail.com> LIGO/Virgo/KAGRA S250727dc : PRIME J-band upper limits of AT 2025smm 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 LIGO/Virgo/KAGRA detection of S250727dc (GCN 41179), we observed a portion of the transient field in J-filter with PRIME ~32 hours after LVK detection. This field was chosen to overlap with the Swift UVOT detection of an uncatalogued source, AT 2025smm (GCN 41187). At the position of AT 2025smm reported by Swift UVOT (GCN 41187), we detect no sources in J-band. Using nearby 2MASS stars for preliminary calibration we derive the following limiting magnitude, not corrected for Galactic extinction: | Filter | Mag(AB) | |--------|--------------| | J | > 19.7 | 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. View this GCN Circular online at https://gcn.nasa.gov/circulars/41196. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 39251] GRB: Clarification on Gamma-Ray Burst Naming Convention
by GCN Circulars 29 Jul '25

29 Jul '25

TITLE: GCN CIRCULAR NUMBER: 41195 SUBJECT: GRB: Clarification on Gamma-Ray Burst Naming Convention DATE: 25/07/29 13:26:05 GMT FROM: Eric Burns at LSU <erickayserburns(a)gmail.com> E. Burns (LSU) and D. Svinkin (Ioffe) on behalf of the InterPlanetary Network; J. Racusin (NASA GSFC) on behalf of the GCN Team Gamma-ray bursts are named following the GRB YYMMDDX format, where the two digit year, month, and day from the detection time at Earth is followed by an alphabetical assignment which iterates, beginning with A in the order of announcement. These are classically assigned when a given event is first reported through GCN Circulars and tracked in catalogs by the InterPlanetary Network (IPN). All signals detected from a specific GRB event should utilize the above defined format. That is, even if an instrument is triggered multiple times or there are multiple instrument triggers, all triggers should be categorized into the same alphabetical assignment (the first announced) once it becomes clear that they belong to the same event. The recent event being commonly referred to as “GRB 250702 B,E,D” (or similar) should be properly referred to only as “GRB 250702B”. This is also true for GRB 250706B which has also been referred to as GRB 250706C. These events are also viewable as groups in the GCN Circulars Event View ([GRB 250702B](https://gcn.nasa.gov/circulars/events/ep250702a), [GRB 250706B](https://gcn.nasa.gov/circulars/events/grb-250706b)). This convention clearly indicates singular events, rather than triggers. This is of great benefit to catalogs, and follows other conventions in transient astrophysics (e.g. supernovae). These rules have been de facto and followed by instrument teams, with the deviation caused by automated submission of GCN Circulars by some teams. An automated GRB Naming Server is in development by the IPN to prevent such issues in the future. View this GCN Circular online at https://gcn.nasa.gov/circulars/41195. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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