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.
Search for Circulars by submitter, subject, or body text (e.g. 'Fermi GRB').
To navigate to a specific circular, enter the associated Circular ID (e.g. 'gcn123', 'Circular 123', or '123').
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"35321 results found.
- GRB 251005C: COLIBRÍ optical observations
- Fermi GRB 251006A: Global MASTER-Net observations report
- GRB 251005C: VLT/X-shooter Imaging
- GRB 251003A: LAST optical observations
- GRB 251002A: LAST optical observations
- GRB 251006A: Fermi GBM Final Real-time Localization
- GRB 251005C: SVOM/VT optical candidate
- GRB 251005C: AstroSat CZTI detection
- GRB 251005C: Swift/UVOT Upper Limits
- GRB 250902A: MSU cubesats detection
- GRB 251005C: Swift-XRT refined Analysis
- GRB 251005C: Fermi GBM Observation
- Swift GRB 251005A: Global MASTER-Net observations report
- GRB 251005C: Enhanced Swift-XRT position
- GRB 251005C: GOTO optical upper limits
- GRB 251005C: Swift detection of a burst
- GRB 251005B: Fermi GBM Final Real-time Localization
- GRB 251005A: Fermi GBM Final Localization
- GRB 251002A: Mondy/AZT-33IK optical observations
- GRB 251002A: Insight-HXMT detection
- GRB 251002A: Insight-HXMT detection
- GRB 251003A: J-band detection with WINTER
- GRB 251002A: NIR observations with WINTER
- Fermi GBM Sub-Threshold Detection of GRB 250910A
- GRB 251003A: Swift-BAT refined analysis
- GRB 251001B: NIR observations with WINTER
- GRB 251002A: Calapai Observatory, Massa S. Giorgio (Messina), optical observation.
- GRB 251003A: Swift/UVOT Upper Limits
- GRB 251002A: Swift/UVOT detection
- GRB 251001A: AstroSat CZTI detection
- GRB 251001B: COLIBRÍ further observations and evidence of a multi-wavelength shallow decay
- GRB 251003A: Swift-XRT refined Analysis
- GRB 251003A: COLIBRÍ photometric redshift
- GRB 251003A: GOTO detection of the optical counterpart
- GRB 251002A: Fermi GBM Observation
- GRB 251002A: GOTO detection of optical counterpart
- GRB 251001C: SVOM/GRM observation
- GRB 251003A: Enhanced Swift-XRT position
- GRB 251002A: AKO Early Optical Afterglow Detection
- GRB 251003A: GTC/OSIRIS+ spectroscopic redshift z = 4.412
- GRB 251003A: Kilonova-Catcher optical afterglow detection
- GRB 251002A: Swift-XRT afterglow detection
- GRB 251001B: AbAO optical upper limit
- GRB 251002A: Kilonova-Catcher optical afterglow detection
- GRB 251002A: AbAO optical observations
- GRB 251002A: SVOM/COLIBRÍ (FM-GFT) optical observations
- GRB 251001C: CALET Gamma-Ray Burst Monitor detection
- GRB 251002A: J band observations by SYSU 80cm infrared telescope
- GRB 251002A: OHP/T193 MISTRAL optical afterglow detection
- GRB 251002A: VLT/X-shooter spectroscopic redshift z = 2.178
- GRB 251002A: EP-FXT counterpart detection
- GRB 251003A: LCOGT Optical Detection
- GRB 251003A: COLIBRÍ optical detection of the fading afterglow
- GRB 251003A: 1.5m OSN afterglow candidate
- GRB 251003A: Prompt enhanced Swift-XRT position
- GRB 251003A: Swift detection of a burst
- GRB 251003A: Fermi GBM Final Real-time Localization
- Fermi/SVOM GRB 251002A : MASTER OT earlier detection in 2 polarization filters
- GRB 251002A: BOOTES-6 early optical detection
- GRB 251002A: SAO RAS optical observations
- GRB 251002A: ULL-ASTRO-MASTER early detection of the optical afterglow with the LCO 40-cm telescope at Sutherland Observatory
- GRB 251002A: FRAM-ORM afterglow detection
- GRB 251002A: LCO optical observation
- GRB 251002A: SVOM/VT optical observation
- GRB 251002A: SVOM detection of a burst
- Fermi GRB 251002A: Global MASTER-Net observations report
- GRB 251001B: Swift-BAT refined analysis
- GRB 251001A: SVOM/GRM observation
- GRB 251001A: Insight-HXMT detection
- GRB 251001B: Swift/UVOT Detection
- GRB 251001B: COLIBRÍ optical observations
- GRB 251001B: GTC/OSIRIS+ spectroscopic redshift z = 2.162
- GRB 251001B: Swift-XRT refined Analysis
- GRB 251001B: SVOM/VT optical observation
- GRB 251001B: NOT optical observations
- GRB 251001C: Glowbug gamma-ray detection
- Swift GRB 251001B: Global MASTER-Net observations report
- GRB 251001B: Fermi GBM Observation
- GRB 251001B: Further GOTO observations of optical counterpart.
- GRB 251001B: Enhanced Swift-XRT position
- GRB 250930A: Fermi GBM Final Localization
- GRB 251001B: LCOGT Optical Observations
- GRB 250930A: SVOM/GRM observation
- GRB 251001B: TRT optical afterglow detection and potential host galaxy
- GRB 251001B: GOTO optical counterpart detection
- GRB 251001B: Swift detection of a burst
- GRB 251001B: Fermi GBM Final Real-time Localization
- GRB 251001A: Fermi GBM Detection
- GRB 250910A / EP250910a: VLT limits on the possible associated supernova
- GRB 251001A: BALROG localization (Fermi Trigger 780979261 / GRB 251001112)
- GRB 251001A: Fermi GBM Final Real-time Localization
- GRB 250910A / EP250910a: VLT/X-shooter host galaxy redshift z = 0.592
- GRB 250925A: MAO/AZT-22 optical observations
- Fermi GRB 250929A: Global MASTER-Net observations report
- GRB 250929A: Fermi GBM Final Real-time Localization
- GRB 250926A: CALET Gamma-Ray Burst Monitor detection
- GRB 250925A: Mondy I-band optical observations
- GRB 250916A: SVOM/VT optical observation
- GRB 250926A: triangulation location with Insight-HXMT/HE and Fermi/GBM
- GRB 250924A: SVOM/GRM observation