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"21793 results found.
- GRB 250924A: Swift/UVOT Detection
- GRB 250924A: J-band detection with WINTER
- GRB 250924A: GROWTH-India Telescope Upper Limits
- 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 250920C: TRT optical observation
- GRB 250924A: COLIBRÍ optical observations
- Swift GRB 250924A: Global MASTER-Net observations report
- GRB 250919A / EP250919a: further LCO optical observation
- GRB 250924A: DDOTI Detection of the Optical Counterpart
- 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
- Fermi GRB 250922B: Global MASTER-Net observations report
- GRB 250920B: SAO RAS optical observations
- GRB 250920C: NIR observations with WINTER
- GRB 250920B: NIR observations with WINTER
- Fermi trigger No 780156732: Global MASTER-Net observations report
- 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: GTC/OSIRIS+ spectroscopic redshift z = 1.40
- GRB 250920C: GROWTH-India Telescope optical observations
- GRB 250916A: FTW optical and NIR observations of the counterpart
- GRB 250920C: Swift/UVOT Detection
- Swift GRB 250920C: Global MASTER-Net observations report
- GRB 250920B: Swift/UVOT Detection
- GRB 250920B: FTW optical and NIR observations of the counterpart
- GRB 250920C: Optical counterpart detection by LCO
- GRB 250920B: SVOM/C-GFT optical observations
- GRB 250920C: GOTO optical counterpart candidate
- GRB 250919A / EP250919a: LCO optical observation
- LIGO/Virgo/KAGRA S250920bq: Coverage and upper limits from MAXI/GSC observations
- Swift GRB 250920B: Global MASTER-Net observations report
- GRB 250919A / EP250919a: MASTER bright afterglow detection 24h after GRB time
- GRB 250916A: Mondy R-band optical observations
- Fermi GRB 250918A: Global MASTER-Net observations report
- GRB 250919A/EP250919A: Swift/UVOT afterglow detection
- GRB 250919A: Swift-XRT afterglow detection
- EP250919a/GRB 250919A: Gemini/GMOS-S spectroscopic redshift z = 1.145
- EP250919a: Global MASTER-Net observations report
- EP250919a: Einstein Probe detection of an X-ray transient
- Fermi GRB 250919A: Global MASTER-Net observations report
- GRB 250916A: KAIT optical observations
- GRB 250917B: VLT/HAWK-I near-infrared observations
- GRB 250916A: further SAO RAS optical observations
- GRB 250912A: SVOM/ECLAIRs refined analysis
- GRB 250917B: Swift/UVOT Upper Limits
- GRB 250916A: OSIRIS+/GTC redshift z = 2.015
- GRB 250916A: Swift-XRT observations
- EP250916a: EP-FXT follow-up observation
- GRB 250916A: MAO/AZT-22 optical observations
- GRB 250916A: SAO RAS optical observations
- 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: Swift/BAT-GUANO localization skymap of a possibly short burst
- 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
- EP250908c: tentative VLT/FORS2 redshift z = 2.87
- 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
- GRB 250910A / EP250910a : VLT/HAWK-I NIR counterpart discovery
- 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