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"12334 results found.
- GRB 251208D: Swift-XRT observations
- GRB 251129A: e-MERLIN C-band observations
- LAT GRB251208.43: Global MASTER-Net observations report
- GRB 251208D: LCO optical upper limits
- SVOM GRB251208D: Global MASTER-Net observations report
- SVOM GRB251206.86: Global MASTER-Net observations report
- GRB 251203C: Swift/UVOT Upper Limit
- Konus-Wind detection of GRB 251118A
- Swift GRB251205A: Global MASTER-Net observations report
- GRB 251203C: SVOM/COLIBRÍ (FM-GFT) optical upper limit
- GRB 251201B: SALT spectroscopic redshift z = 1.599
- GRB 251203C: J-band observations with WINTER
- GRB 251203C: LCO optical afterglow confirmation
- GRB 251203B: Swift-XRT observations
- GRB 251203C: LCO optical upper limits
- GRB 251203B: LCO optical upper limits
- SVOM GRB251203.77: Global MASTER-Net observations report
- SVOM GRB251203B: Global MASTER-Net observations report
- Fermi GRB 251202B: Global MASTER-Net observations report
- GRB251129A/EP251129a: Swift UVOT detection
- GRB 251202A: Swift/UVOT Detection
- GRB 251201B: Swift/UVOT Detection
- Fermi-LAT Gamma-ray Observations of IceCube-251130A
- Fermi GRB 251202A: Global MASTER-Net observations report
- IceCube-251130A: Upper limits from a search for additional neutrino events in IceCube
- Swift GRB 251201B: Global MASTER-Net observations report
- SVOM GRB251201.19: Global MASTER-Net observations report
- Fermi GRB 251130B: Global MASTER-Net observations report
- IceCube Alert 251130.75: Global MASTER-Net observations report
- EP251130a: Swift-XRT counterpart detection
- EP251130a: Global MASTER-Net observations report
- GRB 251129A: Swift-XRT afterglow detection
- EP251129a: Global MASTER-Net observations report
- SVOM GRB251129A: Global MASTER-Net observations report
- Fermi GRB 251128A: Global MASTER-Net observations report
- GRB 251126A: OHP/T193 optical observations and tentative spectroscopic redshift
- GRB 251126A: Swift/UVOT Detection
- EP251124a: Pan-STARRS ri-band imaging and photometry
- Fermi GRB 251127A: Global MASTER-Net observations report
- Swift GRB 251126A: Global MASTER-Net observations report
- GRB 251125B: COLIBRÍ further observations and photometric redshift upper limit of z < 3
- EP251124b: NOT r- and z-band optical upper limits
- Fermi GRB 251125B: Global MASTER-Net observations report
- EP251124b: Global MASTER-Net observations report
- EP251124a: Xinglong GWAC-F60A optical observation
- Fermi GRB 251125A: Global MASTER-Net observations report
- EP251124a: NOT r- and z-band optical upper limits
- EP251124a: Global MASTER-Net observations report
- EP251124a: Swift-XRT observations
- EP251124a: Optical upper limit with Kinder observations
- Fermi GRB 251124a: Global MASTER-Net observations report
- LIGO/Virgo/KAGRA S251105aj: SVOM/VT optical observations and preliminary results on SVOM J2320.0-2901
- EP251124a: GROWTH-India Telescope optical upper limits
- GRB 251122A / EP251122a: EP-FXT counterpart detection
- GRB 251122A/EP251122a: Additional, deeper LCO optical r band upper limit
- GRB 251122A / EP251122a: LCO optical upper limits
- EP251122a: Global MASTER-Net observations report
- GRB 251122A/EP251122a: SVOM/C-GFT upper limit
- Fermi trigger No 785388351: Global MASTER-Net observations report
- GRB 251118A: Swift/UVOT Detection
- GRB 251118A: Swift-XRT afterglow detection
- GRB 251117A: Swift-XRT observations
- EP251118a: Global MASTER-Net observations report
- LAT GRB251118.86: Global MASTER-Net observations report
- Fermi GRB 251118B: Global MASTER-Net observations report
- LIGO/Virgo/KAGRA S251112cm: Upper limits from Glowbug gamma-ray observations
- GRB 251115A: Swift-XRT observations
- LAT GRB251117.51: Global MASTER-Net observations report
- GRB 251116B: SVOM/VT optical upper limit
- GRB 251116C: Swift-XRT observations
- GRB 251116C: SVOM/VT optical upper limit
- GRB 251111A: Mondy optical upper limit
- GRB 251116B: LCO optical upper limits
- GRB 251116C: LCO optical upper limits
- SVOM GRB251116C: Global MASTER-Net observations report
- IceCube-Cascade 251112A: Upper limits from a search for additional neutrino events in IceCube
- Fermi GRB 251115A: Global MASTER-Net observations report
- Konus-Wind detection of GRB 251108C
- Fermi trigger No 784717756: Global MASTER-Net observations report
- LIGO/Virgo/KAGRA S251112cm: Swift XRT observations, 20 X-ray sources
- Fermi GRB 251114A: Global MASTER-Net observations report
- Fermi GRB 251113A: Global MASTER-Net observations report
- GRB 251112A: Swift/UVOT Upper Limits
- LIGO/Virgo/KAGRA S251112cm: Detection of two young transients by BlackGEM/MeerLICHT: AT2025adgp and AT2025adgq
- GRB 251112B: MAXI/GSC detection
- LIGO/Virgo/KAGRA S251112cm: Coverage and upper limits from MAXI/GSC observations
- Swift Trigger 1413695: a possible GRB 251112A
- LIGO/Virgo/KAGRA S251112cm: Upper limits from Fermi-GBM Observations
- Fermi trigger No 784621743: Global MASTER-Net observations report
- GRB251111A: 1.3m DFOT optical upper limit
- SVOM GRB251111.42: Global MASTER-Net observations report
- GRB 251111A: Swift-XRT observations
- SVOM GRB251111.22: Global MASTER-Net observations report
- GRB 251111A: KAIT optical upper limit
- GRB 251106A: Swift/UVOT Upper Limits
- IceCube-Cascade 251107A: Upper limits from a search for additional neutrino events in IceCube
- Fermi trigger No 784329591: Global MASTER-Net observations report
- Fermi trigger No 784279167: Global MASTER-Net observations report
- SVOM GRB251108.54: Global MASTER-Net observations report
- SVOM GRB251106.83: Global MASTER-Net observations report