GCN Circulars
GCN Circulars are rapid astronomical bulletins submitted by and distributed to community members worldwide. They are used to share discoveries, observations, quantitative near-term predictions, requests for follow-up observations, or future observing plans related to high-energy, multi-messenger, and variable or transient astrophysical events. See the documentation for help with subscribing to or submitting Circulars.
To navigate to a specific circular, enter the associated Circular ID (e.g. 'gcn123', 'Circular 123', or '123').
Advanced Search
To narrow the search results, use advanced search syntax. This allows for specifying which circular field to search (submitter, subject, and/or body). For additional information, refer to the advanced search documentation.
Advanced Search Examples (click to copy):
subject:"Swift"body:"GRB"submitter:"Judith Racusin"12321 results found.
- GRB 250219A: NUTTelA-TAO / BSTI Optical Limits
- Fermi trigger No 761805304: Global MASTER-Net observations report
- GRB 250221A: 1.6m Mephisto optical detection
- GRB 250221A: AKO Optical Upper Limit
- GRB 250221A: Swift/UVOT Detection
- EP250220a: Liverpool Telescope upper limits
- GRB 250219A: GRANDMA/Kilonova-Catcher upper limits
- IceCube-250207A: MASTER flaring blazar QSOJ0854+2006 with Zhirkov effect
- EP250220a: 1.6m Mephisto observations
- EP250220a: Liverpool Telescope optical upper limits
- EP250220a: Optical upper limit with Kinder observations
- Swift GRB250221.15: Global MASTER-Net OT detection
- Swift GRB250221.15: Global MASTER-Net observations report
- EP250220a: Xinglong optical upper limit
- EP250220a: Global MASTER-Net observations report
- GRB 250219A: Swift/UVOT Upper Limits
- GRB 250219A: OHP/T193 optical upper limit
- GRB 250219A: 1.6m Mephisto optical upper limits
- GRB 250219A: Swift-XRT observations
- LIGO/Virgo/KAGRA S250206dm: Upper limits from MSU cubesats observations
- GRB 250217C: Swift-XRT observations
- GRB 250217C: COLIBRÍ/DDRAGO Upper Limits on the Optical Counterpart
- GRB 250217C: DDOTI Upper Limits on the Optical Afterglow
- Transient SVOM/sb25021804: COLIBRÍ/DDRAGO Optical Upper Limits on the Optical Counterpart
- GRB 250213A: Swift-XRT observations
- LIGO/Virgo/KAGRA S250206dm: AZT-33IK Target Optical Observations
- Fermi GRB 250217C: Global MASTER-Net observations report
- IceCube-Cascade 250215A: Upper limits from a search for additional neutrino events in IceCube
- Fermi GRB 250217A: Global MASTER-Net observations report
- GRANDMA/OPD observations of GRB250215A
- Fermi GRB 250216A: Global MASTER-Net observations report
- EP250212a: FTW optical and NIR upper limits
- GRB 250215A: Swift/UVOT Upper Limits
- GRB 250215A: COLIBRÍ/DDRAGO Optical Upper Limits on the Afterglow
- GRB 250215A/EP250215a: 1.6m Mephisto optical observation report
- GRB 250213A: COLIBRÍ/DDRAGO Optical Upper Limits on the Afterglow
- EP250215a: Global MASTER-Net observations report
- Fermi GRB 250215A: Global MASTER-Net observations report
- Fermi trigger No 761206993: Global MASTER-Net observations report
- EP250207b: Xinglong optical upper limit
- Fermi GRB 250214A: Global MASTER-Net observations report
- EP250212a: Xinglong optical upper limit
- EP250212a: Global MASTER-Net observations report
- GRB 250205A: VIRT Optical Upper Limit
- GRB 250205A: Leavitt Observatory optical upper limit
- EP250207b: VLA radio upper limits
- EP250212a: Liverpool Telescope optical upper limits
- EP250212a: EP-WXT detection and FXT follow-up observation of a fast X-ray transient
- GRB250101A: Radio upper limits from GMRT observations
- EP trigger 10202399251 (possibly EP250212a): NOT J-band upper limit
- Fermi GRB 250212A: Global MASTER-Net observations report
- GRB 250205A: Calapai Observatory, Massa S. Giorgio (Messina), upper limit
- Fermi trigger No 760945500: Global MASTER-Net observations report
- Integral GRB250211.89: Global MASTER-Net observations report
- LIGO/Virgo/KAGRA S250206dm: continued in SOAR galaxy targeted observations and identification of one possible transient
- LIGO/Virgo/KAGRA S250206dm: Kinder confirmation of a possible artefact in AT 2025bbo
- Konus-Wind detection of GRB 250206A
- EP250207b: Global MASTER-Net observations report
- GRB 241128A: VIRT Optical Upper Limit
- EP250207A: Upper limits from Fermi-GBM Observations
- GRB 250209A: MAXI/GSC detection (possible detection of an X-ray flare from 1RXS J145110.3+310648)
- Fermi GRB 250210A: Global MASTER-Net observations report
- LIGO/Virgo/KAGRA S250206dm: Upper limits from GECAM Observations
- IceCube-250207A: Upper limits from a search for additional neutrino events in IceCube
- LIGO/Virgo/KAGRA S250206dm: Global MASTER-Net observations report
- IceCube Alert 250207.09: Global MASTER-Net observations report
- LIGO/Virgo/KAGRA S250206dm & FRB 20250206A: MASTER observations and possible mother galaxy
- Fermi-LAT Gamma-ray Observations of IceCube-250207A
- GRB 250206A: Swift-XRT observations
- LIGO/Virgo/KAGRA S250206dm: FRB 20250206A BOOTES-5 and 2.2m CAHA optical upper limits
- GRB 250205A: 1.3m DFOT optical upper limit
- GRB 250207B: Swift-XRT observations
- CHIME/FRB source FRB 20250206A detected less than 1 minute after LIGO-Virgo-Kagra (LVK) S250206dm, however the probability of spatial coincidence is order 0.1%
- LIGO/Virgo/KAGRA S250206dm: DDOTI Upper Limits
- Konus-Wind detection of GRB 250204B
- IGO/Virgo/KAGRA S250206dm: Virtual Telescope Project upper limit for the Neutrino IceCube Candidate
- LIGO/Virgo/KAGRA S250206dm: DDOTI Upper Limit for the Neutrino IceCube Candidate
- LIGO/Virgo/KAGRA S250206dm: No counterpart candidates in INTEGRAL SPI-ACS prompt observation
- LIGO/Virgo/KAGRA S250206dm: COLIBRÍ/DDRAGO Observations of the AT 2025azn Optical Candidate
- GRB 250129A: Continued AbAO and Mondy optical observations
- LIGO/Virgo/KAGRA S250206dm: SAGUARO Detection of Two Potential Optical Counterparts
- GRB 250207B: MAXI/GSC detection
- LIGO/Virgo/KAGRA S250206dm: Upper limits from Fermi-GBM Observations
- Fermi-LAT Gamma-ray Observations of IceCube-250203A
- LIGO/Virgo/KAGRA S250206dm: Coverage and upper limits from MAXI/GSC observations
- GRB 250205A: REM NIR upper limit
- GRB 250205A: Swift/UVOT Upper Limits
- GRB 250205A: GOTO optical upper limits
- EP 250108A: Upper limits from Fermi-GBM Observations
- GRB 250129A: 7DT Detection and Medium-band SED of Afterglow
- Swift GRB250129A: MASTER 4 days observations report
- LIGO/Virgo/KAGRA S250201i: Coverage and upper limits from MAXI/GSC observations
- EP250108A / SN 2025kg: Upper limits from a neutrino search with IceCube
- GRB 250127A: EP-FXT second observation epoch and confirmation of the x-ray afterglow fading
- GRB 250128B: SAO RAS Zeiss-1000 and CrAO ZTSh optical upper limits
- GRB 250128B: VLA radio upper limit
- Ep250125A: 1.3m DFOT optical upper limit
- GRB 250128B: TNG optical upper limit
- GRB 250127A: CrAO and Terskol optical upper limits
- GRB 250128B: NOT optical upper limit