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"16157 results found.
- GRB 251001B: Swift/UVOT Detection
- GRB 251001B: COLIBRÍ optical observations
- GRB 251001B: GTC/OSIRIS+ spectroscopic redshift z = 2.162
- GRB 251001B: SVOM/VT optical observation
- GRB 251001B: NOT optical observations
- GRB 251001B: Further GOTO observations of optical counterpart.
- 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 250910A / EP250910a: VLT/X-shooter host galaxy redshift z = 0.592
- GRB 250925A: MAO/AZT-22 optical observations
- GRB 250925A: Mondy I-band optical observations
- GRB 250916A: SVOM/VT optical observation
- GRB 250924A: SVOM/GRM observation
- GRB 250920C: ULL-ASTRO-MASTER early detection of the optical afterglow with LCO 40-cm telescope at Siding Spring Observatory
- GRB 250925A: Swift/UVOT Upper Limits
- GRB 250925A: Mondy and AbAO optical observations
- GRB 250925A: SVOM/GWAC-F60A upper limit
- 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: 1.5m OSN optical detection and redshift with the 10.4m GTC/OSIRIS+
- GRB 250919A / EP250919a: Global MASTER Net before, during and after trigger optical observations
- GRB 250925A: COLIBRÍ optical photometry of the afterglow
- GRB 250925A: Optical Observations via Virtual Telescope Project, Italy
- GRB250925A: Liverpool Telescope optical observations
- GRB 250925A: NOT optical afterglow candidate
- GRB 250925A: Leavitt Observatory optical upper limit
- GRB 250922A: SVOM/GRM observation
- GRB 250924A: 1.6m Mephisto optical upper limits
- GRB 250924A: SAO RAS optical observations
- GRB 250924A: NOT optical observations
- GRB 250924A: SVOM/VT optical observation
- GRB 250924A: J-band detection with WINTER
- GRB 250924A: KAIT optical observations
- GRB 250924A: Mondy optical observations, afterglow fading
- GRB 250924A: Kilonova-Catcher optical afterglow detection
- GRB 250920C: Kilonova-Catcher optical afterglow detection
- GRB 250922B: SVOM/GRM observation
- GRB 250920C: TRT optical observation
- GRB 250924A: COLIBRÍ optical observations
- GRB 250919A / EP250919a: further LCO optical observation
- GRB 250924A: DDOTI Detection of the Optical Counterpart
- GRB 250924A: Swift detection of a burst with an optical counterpart
- GRB 250920B: AbAO optical upper limits
- GRB 250920C: KAIT optical observations
- GRB 250920C: VLT redshift confirmation z = 1.399
- EP250911a: e-MERLIN radio observations
- GRB 250920B: CrAO ZTSH optical observations
- GRB 250920C: SALT redshift confirmation
- GRB 250920C: COLIBRÍ optical observations
- GRB 250920B: SAO RAS optical observations
- GRB 250920C: NIR observations with WINTER
- GRB 250920B: NIR observations with WINTER
- GRB 250920C: PRIME near-infrared detection
- GRB 250916A: Swift/UVOT Detection
- GRB 250916A: CrAO ZTSh R-band optical observations
- GRB 250916A: SAO RAS Zeiss-1000 optical observations
- GRB 250920B: Asiago optical observations
- GRB 250920B: Kitab-ISON optical upper limit
- GRB 250917B: Mondy and Zeiss-1000 SAO RAS optical observations, optical observations, afterglow candidate
- GRB 250920C: SVOM/GRM observation
- GRB 250920C: GTC/OSIRIS+ spectroscopic redshift z = 1.40
- GRB 250917B: KAIT optical upper limit
- GRB 250920C: GROWTH-India Telescope optical observations
- GRB 250916A: FTW optical and NIR observations of the counterpart
- GRB 250920B: FTW optical and NIR observations of the counterpart
- GRB 250920C: Optical counterpart detection by LCO
- GRB 250920A: SVOM/GRM observation
- GRB250920C: LCOGT Optical Detection
- GRB 250920B: SVOM/C-GFT optical observations
- GRB 250920C: GOTO optical counterpart candidate
- GRB 250919A / EP250919a: LCO optical observation
- GRB 250920B: Swift detection of a burst with a bright optical counterpart.
- GRB 250919A/EP250919a: SVOM/VT optical observation
- GRB 250919A / EP250919a: MASTER bright afterglow detection 24h after GRB time
- GRB 250916A: Mondy R-band optical observations
- GRB 250918A: SVOM/GRM observation
- GRB 250919A/EP250919A: Swift/UVOT afterglow detection
- GRB 250919A: Swift-XRT afterglow detection
- EP250919a/GRB 250919A: Gemini/GMOS-S spectroscopic redshift z = 1.145
- GRB 250919A: SVOM/GRM observation of a very bright GRB
- EP250919a: Einstein Probe detection of an X-ray transient
- The EP-WXT trigger 01709243841: Las Cumbres discovery of the optical counterpart
- GRB 250916A: Fermi GBM Observation
- GRB 250916A: KAIT optical observations
- GRB 250916A: NuSTAR detection of the prompt emission
- GRB 250916A: further SAO RAS optical observations
- GRB 250917B: Swift/UVOT Upper Limits
- GRB 250916A: OSIRIS+/GTC redshift z = 2.015
- GRB 250916A: Swift-XRT observations
- GRB 250916A: MAO/AZT-22 optical observations
- GRB 250916A: SAO RAS optical observations
- GRB 250916A : GIT optical observations
- GRB250917B: WFST optical observations
- GRB 250916A: GOTO optical counterpart candidate
- EP250827b: VLA Observations
- LIGO/Virgo/KAGRA S250818k: HCT optical follow-up
- GRB 250912A: SVOM/COLIBRÍ (FM-GFT) optical observations