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"23602 results found.
- EP250831a: NOT optical observations and tentative afterglow candidate
- EP250827b: Contemporaneous detection of EP X-ray flare EP250827b and ZTF transient ZTF25abmpngy/AT2025wkm
- GRB 250901A: SVOM detection of a burst
- EP250901a: Mephisto optical upper limits
- GRB 250830C: AstroSat CZTI detection of a long burst
- EP250831a: EP-FXT follow-up observation
- EP250831a: Swift-XRT observations
- LIGO/Virgo/KAGRA S250831cc: Coverage and upper limits from MAXI/GSC observations
- GRB 250831A: Swift-XRT counterpart detection
- GRB 250831A: SVOM/COLIBRÍ (FM-GFT) optical upper limit
- GRB 250831A: SVOM/VT upper limit with VHF data
- GRB 250831A: SVOM detection of a soft burst
- LIGO/Virgo/KAGRA S250830bp: Coverage and upper limits from MAXI/GSC observations
- LIGO/Virgo/KAGRA S250830bp GLADEnet Completeness: Potential Host Galaxies in the 90% Credible Volume
- LIGO/Virgo/KAGRA S250830bp: NED Galaxies in the 4-Update Localization Volume
- LIGO/Virgo/KAGRA S250830bp: Identification of a GW compact binary merger candidate
- EP-WXT trigger 01709200994: confirmation of a stellar flare by BOOTES-6
- GRB 250830B: MAXI/GSC detection
- LIGO/Virgo/KAGRA S250830m: Identification of a GW compact binary merger candidate
- GRB 250830A / MAXI J0853+337: MAXI/GSC detection
- GRB 250828B: Swift-BAT refined analysis
- LIGO/Virgo/KAGRA S250725j: Observations with the NSF-DOE Vera C. Rubin Observatory
- GRB 250808B: SVOM detection of a burst through offline search
- EP250828a: Optical counterpart detection with Kinder observations
- EP-WXT trigger 01709200800 : KAIT optical observations
- EP250828a: KAIT optical upper limit
- EP250827a: Swift/UVOT Detection
- EP250828a: Seimei/TriCCS optical counterpart detection
- GRB 250828B: Swift detection of a burst
- EP250827a: STEP/T80S Confirmation of fading optical counterpart
- EP250828a: Optical upper limit with Kinder observations
- EP250827a: LCO observations show fading optical counterpart
- EP250827a: Preliminary analysis of the EP-WXT and EP-FXT observations
- LIGO/Virgo/KAGRA S250827fo: Identification of a GW compact binary merger candidate
- EP250827a: confirmation of optical rebrightening with LCO
- EP250827a: GOTO observation of the optical afterglow
- EP250827A: An optical rebrightening was detected by LCO.
- EP250827a: Swift-XRT counterpart detection
- The EP-WXT trigger 01709200800 is likely a flaring star
- EP250827a: TRT optical observations
- EP250827a: BOOTES-7 early optical dectection
- EP250827a / GRB 250827A: MASTER-OAFA OT observation
- EP250827a: Einstein Probe detection of an X-ray transient
- LIGO/Virgo/KAGRA S250827l: Identification of a GW compact binary merger candidate
- GRB 250806A: HiPERCAM/GTC limits on a possible supernova
- LIGO/Virgo/KAGRA S250818k: SAO RAS BTA z-band observations of AT2025ulz
- LIGO/Virgo/KAGRA S250818k: GTC/OSIRIS Confirmation of Rebrightening of AT2025ulz
- LIGO/Virgo/KAGRA S250818k: VLA upper limits on AT2025ulz
- LIGO/Virgo/KAGRA S250818k: Pan-STARRS imaging confirms re-brightening of SN2025ulz
- GRB 250823A: Swift-BAT refined analysis
- LIGO/Virgo/KAGRA S250818k: Continued Keck I LRIS spectroscopy of ZTF25abjmnps (AT2025ulz)
- GRB 250821B: AstroSat CZTI detection
- GRB 250819A: AstroSat CZTI detection
- EP250821a: MeerKAT radio counterpart
- EP triggers 01709200706 and 01709200707: GOTO confirmation of flaring stars
- GRB 250823A: COLIBRÍ optical observations
- The EP-WXT trigger 01709200706 is likely a flaring star
- GRB 250823A: Swift/UVOT Detection
- LIGO/Virgo/KAGRA S250818k: CFH/MegaCam follow-up observation for AT2025ulz
- LIGO/Virgo/KAGRA S250818k: COLIBRÍ confirmation of rebrightening of AT2025ulz
- GRB 250823A: Fermi GBM Observation
- GRB 250823A: BOOTES6/DPRT early optical detection
- GRB 250823A: Swift detection of a burst
- Konus-Wind detection of GRB 250821B
- LIGO/Virgo/KAGRA S250818k: Rebrightening detected with Gemini/GMOS
- LIGO/Virgo/KAGRA S250818k: J-GEM follow-up observation for AT2025ulz
- LIGO/Virgo/KAGRA S250818k: GTC/OSIRIS Optical Detection of AT2025ulz
- LIGO/Virgo/Kagra S250818k: STEP/T80N upper limits on 2025ulz
- IPN triangulation of GRB 250821B (long/bright)
- GRB 250821A: Kilonova-Catcher optical upper limits
- GRB 250812A: SVOM/ECLAIRs refined analysis
- GRB 250821A: Swift-BAT refined analysis
- LIGO/Virgo/KAGRA S250818k: Pan-STARRS coverage of the skymap and candidate counterparts
- LIGO/Virgo/KAGRA S250818k: NOT optical observations of AT2025ulz
- LIGO/Virgo/KAGRA S250818k: GRAWITA TNG NIR observations of AT2025ulz
- GRB 250821A: NOT z-band upper limit
- GRB 250821A: KAIT optical upper limit
- LIGO/Virgo/KAGRA S250818k: Continued fading and reddening of AT2025ulz from Keck/LRIS imaging observations
- LIGO/Virgo/KAGRA S250818k : Tautenburg observations, upper limits
- LIGO/Virgo/KAGRA S250818k: GOTO counterpart search and upper limits
- GRB 250814A: CMO SAI and SAO RAS izJ observations.
- LIGO/Virgo/KAGRA S250818k: 10 GHz VLA observations of AT2025ulz
- GRB 250821A: Swift detection of a burst
- LIGO/Virgo/KAGRA S250818k: WFST pre-discovery limits and follow-up observations of AT 2025ulz
- LIGO/Virgo/KAGRA S250818k: WINTER J-band observations of AT 2025ulz
- GRB 250818B: 10 GHz VLA detection
- LIGO/Virgo/KAGRA S250818k: Pan-STARRS grizy-band imaging and photometry of AT2025ulz
- LIGO/Virgo/KAGRA S250818k: Swift observations of AT 2025ulz
- LIGO/Virgo/KAGRA S250818k: ATLAS pre-discovery limits for AT2025ulz
- GRB 250814A: Swift/UVOT Upper Limits
- GRB 250813B: Swift/UVOT Upper Limit
- IPN triangulation of GRB 250816A (short)
- GRB 250818B: Kilonova-Catcher optical afterglow detection
- LIGO/Virgo/KAGRA S250818k: Pan-STARRS pre-detection limits for AT2025ulz
- LIGO/Virgo/KAGRA S250818k: Keck I LRIS spectroscopy of ZTF25abjmnps (AT2025ulz)
- GRB 250818B: Swift/UVOT Detection
- GRB 250818B: optical afterglow detection with Lesedi (GOTO25fzq)
- GRB 250818B: TRT Optical Observation
- GRB 250818B: SAO RAS optical observations
- GRB 250818A: Swift-BAT refined analysis