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"5814 results found.
- LIGO/Virgo/KAGRA S251112cm: Swift XRT observations, 20 X-ray sources
- LIGO/Virgo/KAGRA S251112cm: Candidates from the Zwicky Transient Facility
- Fermi Gamma-ray Burst Monitor trigger 784717756/251113381 is not a GRB
- GRB 251112A: Swift-XRT refined Analysis
- LIGO/Virgo/KAGRA S251112cm: Detection of two young transients by BlackGEM/MeerLICHT: AT2025adgp and AT2025adgq
- LIGO/Virgo/KAGRA S251112cm: Coverage and upper limits from MAXI/GSC observations
- LIGO/Virgo/KAGRA S251112cm: Initial GOTO-South observations
- LIGO/Virgo/KAGRA S251112cm: NED Galaxies in the 3-Initial Localization Volume
- LIGO/Virgo/KAGRA S251112cm: Identification of a GW compact binary merger candidate
- GRB 251111A: Swift-XRT observations
- GRB 251013C: Chandra X-ray observations and jet break detection
- GRB 251111A: SVOM/COLIBRÍ (FM-GFT) optical counterpart detection
- SVOM GRB251108.54: Global MASTER-Net observations report
- SVOM GRB251106.83: Global MASTER-Net observations report
- GRB 250920C: TERI Gamma-ray detection
- Fermi GRB 251103A: Global MASTER-Net observations report
- GRB 251103B: GROWTH-India Telescope optical upper limits
- GRB 251103B: Swift detection of a burst
- GRB 251103A: BOOTES-2/TELMA optical afterglow
- GRB 251103A: NOT optical afterglow candidate
- Fermi GRB 251102A: Global MASTER-Net observations report
- GRB 250926B: VZLUSAT-2 detection
- GRB 250926A: VZLUSAT-2 detection
- GRB 250925A: VZLUSAT-2 detection
- GRB 251028A: MAXI/GSC detection
- Fermi-LAT Gamma-ray Observations of IceCube-251025A
- EP251027.145: COLIBRÍ optical upper limits
- GRB 251017A: Mondy AZT-33IK and Koshka Zeiss-1000 optical observations
- GRB 251017A: INASAN-Kislovodsk optical observations
- GRB 251026B: Tentative GOTO optical counterpart candidate
- GRB 251025B: MAO/AZT-22 optical observations
- Fermi GRB 251025C: Global MASTER-Net observations report
- GRB 251026A: SVOM/COLIBRÍ (FM-GFT) optical upper limit
- GRB 251025A: SVOM/COLIBRÍ (FM-GFT) optical upper limit
- EP251023b: Global MASTER-Net observations report
- EP251023a: ULL-ASTRO-MASTER detection of the optical afterglow with LCO 40-cm telescope at Teide Observatory
- IPN triangulation of GRB 251016B
- EP251023a: COLIBRÍ optical observations
- EP251021b/GRB 251021A: SVOM/VT optical candidate
- GRB 251023B / MAXI J0451+122: MAXI/GSC detection
- Fermi GRB 251023A: Global MASTER-Net observations report
- EP251023a: Einstein Probe detection of an X-ray transient
- LIGO/Virgo/KAGRA S251021u: Identification of a GW compact binary merger candidate
- Fermi-LAT gamma-ray observations of IceCube-251018A
- GRB 251013C: Leavitt Observatory optical photometry
- GRB 251017A: COLIBRÍ Early Afterglow Detection
- GRB 251017A: Swift detection of a burst with an optical counterpart
- sb25101602: Swift-XRT counterpart detection
- GRB 251011B: SVOM/VT optical upper limit
- LIGO/Virgo/KAGRA S251014cn: NED Galaxies in the 3-Initial Localization Volume
- GRB 251014A: DDOTI Upper Limit
- Fermi GRB 251013C: Global MASTER-Net observations report
- GRB 251011B inspection: MASTER orphan GRB detection
- GRB 251011B : MASTER optical observations
- GRB 251011B: Swift detection of a burst
- GRB 251009B (short): Glowbug gamma-ray detection
- GRB 251009A: Fermi GBM Final Localization
- GRB 250916A: TERI Gamma-ray detection
- GRB 250919A: TERI gamma-ray detection
- EP251006a: Global MASTER-Net observations report
- EP250911a: Koshka Zeiss-1000 Optical Upper Limit
- GRB 250902A: MSU cubesats detection
- Fermi GBM Sub-Threshold Detection of GRB 250910A
- GRB 251003A: Swift detection of a burst
- Fermi GRB 251002A: Global MASTER-Net observations report
- GRB 250930A: SVOM/GRM observation
- GRB 251001B: Swift detection of a burst
- LIGO/Virgo/KAGRA S250830bp: SOAR spectroscopy of two DESGW candidates
- LIGO/Virgo/KAGRA S250818k: further MeerKAT monitoring
- GRB 250925A: MAO/AZT-22 optical observations
- Fermi GRB 250929A: Global MASTER-Net observations report
- GRB 250925A: Mondy I-band optical observations
- GRB 250916A: SVOM/VT optical observation
- LIGO/Virgo/KAGRA S250929c: Identification of a GW compact binary merger candidate
- Fermi-LAT Gamma-ray Observations of IceCube-250926A
- GRB 250924A: SVOM/GRM observation
- LIGO/Virgo/KAGRA S250927cy: Identification of a GW compact binary merger candidate
- LIGO/Virgo/KAGRA S250927ck: Identification of a GW compact binary merger candidate
- IceCube-250926A: Upper limits from a search for additional neutrino events in IceCube
- GRB 250926A: Insight-HXMT detection
- Fermi trigger No 780609036: Global MASTER-Net observations report
- IceCube Alert 250926.52: Global MASTER-Net observations report
- GRB 250920C: ULL-ASTRO-MASTER early detection of the optical afterglow with LCO 40-cm telescope at Siding Spring Observatory
- GRB 250926A: AstroSat CZTI detection
- GRB 250925A: Mondy and AbAO optical observations
- GRB 250925A: COLIBRÍ photometric redshift
- IceCube-250926A - IceCube observation of a high-energy neutrino candidate track-like event
- GRB 250925A: SVOM/GWAC-F60A upper limit
- GRB 250925A/EP250925a: EP-WXT detection
- GRB 250926A: DDOTI Optical Observations and Spatial Coincidence with the Orion Nebula
- GRB 250925A : MITSuME Akeno optical upper limits
- GRB 250925A: JinShan optical observations
- GRB 250925A: COLIBRÍ optical photometry of the afterglow
- Fermi GRB 250926A: Global MASTER-Net observations report
- GRB250925A: Liverpool Telescope optical observations
- GRB 250925A: Leavitt Observatory optical upper limit
- GRB 250925A: GROWTH-India Telescope Upper Limits
- Swift GRB 250925A: Global MASTER-Net observations report
- GRB 250922A: SVOM/GRM observation
- GRB 250924A: 1.6m Mephisto optical upper limits