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"20967 results found.
- GRB 250916A : GIT optical observations
- GRB250917B: WFST optical observations
- GRB 250916A: Swift ToO observations
- GRB 250917B: Swift-XRT observations
- Fermi GRB 250917B: Global MASTER-Net observations report
- GRB 250916A: GOTO optical counterpart candidate
- GRB 250910A: SVOM/ECLAIRs refined analysis
- EP250916a: Einstein Probe detection of an X-ray transient
- Fermi GRB 250916A: Global MASTER-Net observations report
- EP250827b: VLA Observations
- LIGO/Virgo/KAGRA S250818k: HCT optical follow-up
- SVOM/sb25091517: FRAM-ORM stellar flare - transient observation
- GRB 250912A: SVOM/COLIBRÍ (FM-GFT) optical observations
- GRB 250912A: Swift-XRT observations
- GRB250912A: VLT/HAWK-I follow-up observations
- GRB 250912A: VLT observations
- GRB 250912A: SVOM/GRM analysis suggests a possible short GRB with extended emission
- Fermi GRB 250912A: Global MASTER-Net observations report
- EP250911a: Global MASTER-Net observations report
- EP250911a: Upper limit from Fermi-GBM Observations
- EP250911a: refined analysis of the EP-WXT and EP-FXT observations
- GRB 250911A: MASTER optical counterpart observations
- EP250911a: SAO RAS optical observations
- EP250911a: Swift-XRT observations
- EP250911a: Optical detection with Kinder observations
- GRB 250911A: Swift/UVOT Detection
- GRB 250910A / EP250910a: Swift-XRT afterglow detection
- EP250911a: COLIBRÍ optical observations
- Fermi GRB 250910B: Global MASTER-Net observations report
- EP250910a: Global MASTER-Net observations report
- GRB 250903A: SVOM/ECLAIRs refined analysis
- GRB 250911A: Swift-XRT observations
- GRB 250911A: COLIBRÍ optical counterpart candidate
- GRB 250910A / EP250910a: VLT/HAWK-I near-infrared observations
- GRB 250702B: Late time Chandra observations
- EP250908b/EP#01709240653: Swift/UVOT Detection
- EP#01709240653: Swift-XRT observations
- EP250908c: refined analysis of the EP-WXT and EP-FXT observations
- EP250908c: Global MASTER-Net observations report
- Fermi GRB 250909A: Global MASTER-Net observations report
- EP#01709240652 (possibly EP250908a): FTW optical and NIR observations
- Fermi-LAT Gamma-ray Observations of IceCube-250905A
- GRB 250903A: Swift-XRT afterglow detection
- LIGO/Virgo/KAGRA S250830bp: DECam/SOAR GW-MMADS updates
- EP250905b: EP-FXT follow-up observation
- LIGO/Virgo/KAGRA S250830bp: DECam DESGW Epoch 2 Candidates
- EP250905a: Liverpool Telescope observations
- EP250905a: refined analysis of the EP-WXT and EP-FXT observations
- EP250905b: Global MASTER-Net observations report
- EP250905b: EP-WXT detection of a fast X-ray transient
- EP250905a: FTW one optical and multiple NIR counterpart candidates
- EP250905a: JinShan likely optical counterpart detection
- IceCube Alert 250905.84: Global MASTER-Net observations report
- GRB 250905A: Swift/UVOT Upper Limits
- EP250905a: Global MASTER-Net observations report
- GRB 250901A - SVOM/ECLAIRs refined analysis
- GRB 250904A: Swift/UVOT Detection
- GRB 250903A: Swift/UVOT detection
- Swift GRB250905.09: Global MASTER-Net observations report
- Swift GRB 250904A: Global MASTER-Net observations report
- GRB 250904A: TRT optical counterpart detection
- EP250827a and EP250827b: Upper limit from Fermi-GBM Observations
- EP250827b: Gemini Spectroscopic Confirmation of AT2025wkm as a Ic-BL Supernova
- GRB 250903A: Swift-XRT observations
- EP250903a: Swift-XRT observations
- EP#01709201209: Swift-XRT observations
- EP250903a: retraction of the LCO candidate, and discovery of the likely counterpart
- EP250903a: refined analysis of the EP-WXT and EP-FXT observations
- GRB 250903A: VLT X-shooter spectroscopic redshift z = 1.590
- GRB 250903A: LCO optical afterglow detection
- EP250903a: SVOM/VT optical confirmation
- GRB 250903A: TRT optical counterpart detection
- EP250903a: Global MASTER-Net observations report
- EP250903a: TRT optical observations
- EP 250827B: Detection of supernova counterpart by LCO.
- EP/WXT01709201159: GOTO optical follow-up
- EP250827b / AT 2025wkm: TRT optical observations
- EP250827b: NOT spectroscopic observations and AT 2025wkm classification as a broad-lined type-Ic supernova
- EP250827b: continued Liverpool Telescope observations
- GRB 250831A (SVOM trigger sb25083102): KAIT confirmation of stellar flare
- Fermi GRB 250902B: Global MASTER-Net observations report
- Fermi-LAT Gamma-ray Observations of IceCube-250831A
- GRB 250901A: Swift/UVOT Upper Limit
- GRB 250830B: Swift-XRT afterglow detection
- EP250827b: Liverpool Telescope observations
- EP250828a: Early near-infrared follow-up with MIRAGE on the MDM 1.3m telescope
- EP250901a: refined analysis of the EP-WXT and EP-FXT observations
- GRB 250901A: NOT optical observations
- GRB 250901A: Swift-XRT afterglow detection
- EP250901a: Swift-XRT observations
- LIGO/Virgo/KAGRA S250830bp: DECam GW-MMADS candidates
- EP250827b: Swift observations of AT 2025wkm
- LIGO/Virgo/KAGRA S250830bp: DECam DESGW Epoch 1 Candidates
- EP250827b: Gemini Spectroscopy of AT 2025wkm
- EP250831a: NOT optical observations and tentative afterglow candidate
- EP250827b: FTW Observations of AT 2025wkm
- EP250827b: Contemporaneous detection of EP X-ray flare EP250827b and ZTF transient ZTF25abmpngy/AT2025wkm
- EP250901a: Mephisto optical upper limits
- EP250901a: Global MASTER-Net observations report
- EP250831a: Swift-XRT observations