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"20963 results found.
- GRB 250818B: Swift/UVOT Detection
- LIGO/Virgo/KAGRA S250818k: FTW Fast reddening of AT 2025ulz
- GRB 250818B: optical afterglow detection with Lesedi (GOTO25fzq)
- GRB 250818B: TRT Optical Observation
- Fermi GRB 250816A: Global MASTER-Net observations report
- GRB 250818B: SAO RAS optical observations
- Swift GRB 250818A: Global MASTER-Net observations report
- GRB 250818B: NOT optical observations
- LIGO/Virgo/KAGRA S250818k: FTW optical and NIR observations of AT 2025ulz
- Fermi trigger No 776849714: Global MASTER-Net observations report
- GRB 250818B: KAIT optical observations
- GRB 250818A: Swift/UVOT Upper Limits
- LIGO/Virgo/KAGRA S250818k: Candidates from the Zwicky Transient Facility
- GRB 250813B: SVOM/ECLAIRs refined analysis
- LIGO/Virgo/KAGRA S250818k: Coverage and upper limits from MAXI/GSC observations
- GRB 250818B: SVOM/VT optical observation
- GRB 250814A: Further GRAWITA TNG NIR observations
- GRB 250818B: Swift-XRT afterglow detection
- GRB 250818B: GOTO optical counterpart candidate
- sb25081602: Swift-XRT observations
- Fermi GRB 250814B: Global MASTER-Net observations report
- GRB 250813B: Liverpool Telescope optical upper limits
- GRB 250814A: detection of the afterglow candidate with Liverpool Telescope
- GRB 250814A: GRAWITA TNG NIR observations
- GRB 250812A: SVOM/VT optical continued observation
- GRB 250814A: Mondy optical observations of the candidate counterpart to LVK S250814bg
- GRB 250813B: Calapai Observatory, Massa S. Giorgio (Messina), upper limit
- LIGO/Virgo/KAGRA S250813k: Swift XRT observations, 2 X-ray sources
- GRB 250814A: P200/WIRC observations of the afterglow candidate
- GRB 250814A: possible optical afterglow candidate at Spanish observatories
- GRB 250814A: Possible afterglow candidate from P200/WIRC
- GRB 250814A: Optical observations with MDM Hiltner 2.4m telescope
- Fermi trigger No 776818276: Global MASTER-Net observations report
- Swift GRB250814.32: Global MASTER-Net observations report
- GRB 250814A: J-band upper limit from WINTER
- GRB 250813B: NOT observations of the optical afterglow
- GRB 250813B: SVOM/VT optical observations
- GRB 250813B: VLT X-shooter spectroscopic redshift z = 1.752
- GRB 250814A: DDOTI Optical Upper Limit
- Fermi-LAT Gamma-ray Observations of IceCube-250813A
- GRB 250813B: SVOM/COLIBRÍ (FM-GFT) optical observations
- GRB 250813B: Ondrejov D50 fast decay
- LIGO/Virgo/KAGRA S250813k: NED Galaxies in the 4-Update Localization Volume
- EP250812a: Nickel optical upper limit
- GRB 250812A: VLT X-shooter spectroscopic redshift confirmation z = 2.571
- GRB250812a: STEP/T80S Indication of slow decay of afterglow
- EP250812a: NOT, NTT, and GS observations
- GRB 250812A: Swift/UVOT Detection
- EP250812a: COLIBRÍ detection of the VT candidate and evidence of flattening
- EP250812a: SVOM/VT optical counterpart
- EP250812a: refined analysis of the EP-WXT and EP-FXT observations
- IceCube Alert 250813.14: Global MASTER-Net observations report
- GRB 250812A: Swift ToO observations
- EP 250812a: GOTO optical upper limit
- GRB 250812A: Kilonova-Catcher optical afterglow detection
- EP250812a: Swift-XRT counterpart detection
- GRB 250812A: SVOM/COLIBRÍ (FM-GFT) optical observations
- GRB 250812A: SVOM/VT optical afterglow confirmation
- GRB 250812A: Swift-XRT afterglow detection
- GRB 250812A: TRT likely optical counterpart detection
- Fermi-LAT Gamma-ray Observations of IceCube-250804A
- GRB 250809A: Swift/UVOT Detection
- GRB 250702B: Chandra X-ray Detection
- EP250807a: Global MASTER-Net observations report
- Fermi GRB 250808A: Global MASTER-Net observations report
- GRB 250808A: SVOM/COLIBRÍ (FM-GFT) optical upper limit
- GRB 250808A: Swift-XRT candidate counterpart detection
- GRB 250807A: SVOM/VT optical continued observation
- EP-WXT trigger 01709195487: KAIT confirmation of the stellar flare
- GRB 250807B: Swift/UVOT Detection
- GRB 250807B: Kilonova-Catcher optical afterglow detection
- GRB 250807A: Swift/UVOT Detection
- EP250807a: NTT z-band optical upper limit
- GRB 250806A: Mondy optical observations, and nearby bright galaxy photometry
- Swift GRB250807.45: Global MASTER-Net observations report
- GRB 250807B: NTT optical observations
- EP250807a: EP-WXT detection of a fast X-ray transient
- EP 250807.979: GOTO optical upper limit
- GRB 250807A: SVOM/VT optical observation
- EP250806a: Upper limit from Fermi-GBM Observations
- Swift GRB250807.65: Global MASTER-Net observations report
- GRB 250805A: Kilonova-Catcher optical upper limits
- GRB 250805A: Swift/UVOT Upper Limits
- GRB 250806A: Swift/UVOT U-band detection
- IceCube Alert 250804.84: Global MASTER-Net observations report
- EP#01709198415/EP250806a: Swift-XRT observations
- EP250806a: Global MASTER-Net observations report
- EP250806a: refined analysis of the EP-WXT and EP-FXT observations
- EP250806a: Earlier Detection of the VT Candidate by COLIBRÍ and LS
- GRB 250806A: J-band upper limit from WINTER
- GRB 250806A: KAIT optical upper limit
- GRB 250806A: Kilonova-Catcher optical upper limits
- GRB 250806A: SVOM/COLIBRÍ (FM-GFT) optical upper limit
- GRB 250805A: ESO/VLT observations
- GRB 250804B: Swift-XRT observations
- GRB 250805A: TRT optical upper limits
- GRB 250805A: Swift-XRT observations
- Swift GRB250805.26: Global MASTER-Net observations report
- GRB 250804B: Tiled Swift observations
- Fermi trigger No 776041355: Global MASTER-Net observations report