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"
24602 results found.
- GRB 250114A: Enhanced Swift-XRT position
- GRB 250114A: REM detection of the optical and NIR counterpart
- LIGO/Virgo/KAGRA S250114ax: Identification of a GW compact binary merger candidate
- Swift GRB250114A: Global MASTER-Net OT detection
- GRB 250114A: LCO optical observations
- GRB 250114A: TRT optical observations
- GRB 250114A: Swift detection of a burst with an optical counterpart
- GRB 250101A: Terskol Zeiss-2000 optical observations
- EP250108a / AT 2025kg: SAO RAS optical observations
- EP241021a: SMA radio observation
- GRB 250113A: SVOM/GRM observation of a long burst
- GRB 250107A: VZLUSAT-2 detection
- EP250109b: optical upper limits with the Liverpool Telescope
- GRB 250106A: Swift-XRT afterglow detection
- EP250111a: KAIT optical observations
- GRB 250109A / EP250109a: Mephisto optical upper limits
- EP250108a: Mephisto detection
- EP250111a: Mondy optical observation
- EP250108a / AT 2025kg: LCO optical observations
- EP250108a / AT 2025kg: Swift UVOT detections
- EP250108a / AT 2025kg (the "kangaroo”): VLT/X-shooter spectroscopic redshift z = 0.176 and LFBOT classification
- EP250111a: NOT likely optical counterpart
- GRB 250101B: Fermi GBM Observation
- GRB 250109A / EP250109a: Terskol (INASAN) and SAO RAS observations
- GRB 250109A / EP250109A: Swift/BAT-GUANO localization skymap of a burst
- GRB 250108A: Swift/XRT afterglow fading
- LIGO/Virgo/KAGRA S250109bi: Updated Sky localization
- LIGO/Virgo/KAGRA S250109f: Updated Sky localization
- LIGO/Virgo/KAGRA S250108eo: Updated Sky localization
- EP-WXT trigger EP250108a:Xinglong optical follow-up observations
- GRB 250101A: CMO RC-500 optical observations
- GRB 250109A: Fermi GBM Observation
- EP250108a: NOT optical observations
- EP-WXT trigger EP250109a:Xinglong optical follow-up observations
- GRB 250109a: GMG Optical Upper Limit
- EP250109a: Swift/UVOT non-detection
- IPN triangulation of GRB 250107D (short/hard)
- EP250108a: Liverpool Telescope likely optical counterpart
- GRB 250108B: Swift-BAT refined analysis
- GRB 250108B: 1.3m DFOT upper limit
- GRB 250108B: REM optical/NIR upper limits
- GRB 250101A: Terskol K-800 optical observations
- EP250109a: Swift/XRT non-detection
- GRB 250108A: Swift/UVOT Upper Limits
- LIGO/Virgo/KAGRA S250109bi: Identification of a GW compact binary merger candidate
- GRB 250108A: NOT optical upper limit
- EP250108a: EP-WXT detection of an X-ray transient
- LIGO/Virgo/KAGRA S250109f: Identification of a GW compact binary merger candidate
- GRB 250108B: Swift-XRT refined Analysis
- GRB 250103A: 1.6m Mephisto optical observations
- GRB 250108A: Swift-XRT afterglow detection
- GRB 250108A:SVOM/VT optical candidate
- LIGO/Virgo/KAGRA S250108eo: Identification of a GW compact binary merger candidate
- GRB 250108B: Swift/UVOT Upper Limits
- GRB 250103A: Swift-XRT afterglow detection
- GRB 250108B: Enhanced Swift-XRT position
- GRB 250108B: Swift detection of a burst
- GRB 250107A: Fermi GBM Observation
- GRB 250107A: Swift/BAT-GUANO arcminute localization of a burst
- GRB 250106A: SVOM/VT 2nd optical deep observation
- GRB 250101A: J band upper limit by SYSU 80cm telescope
- EPWXT01709129925: Xinglong optical observations
- GRB 250106A: NOT optical observations
- LIGO/Virgo/KAGRA S250104v: Updated Sky localization
- GRB 250103B: REM optical/NIR upper limits
- GRB 250101A: REM optical/NIR counterpart detection
- GRB 250106A: Swift-XRT observations
- GRB 250106A: SVOM/VT optical candidate
- The EP-WXT trigger 01709129925 is likely a flaring star
- GRB 250103B: Swift-XRT refined Analysis
- GRB 250103B: LCO/1m optical afterglow candidate detection
- GRB 250103A: Bassano Bresciano Observatory upper limit
- GRB 250103A: Swift-XRT observations
- GRB 250101A: 1.3m DFOT optical afterglow detection
- GRB 241229A: 1.3m DFOT upper limit
- GRB 241228B: 1.3m DFOT Optical observations
- GRB 241228A: 1.3m DFOT upper limit
- LIGO/Virgo/KAGRA S250104v: Identification of a GW compact binary merger candidate
- GRB 250103A: Montarrenti Observatory optical detection
- GRB 250101A: further LCOGT optical afterglow observations
- GRB 250103A: TSHAO optical upper limit
- GRB 250103A: Fermi GBM Observation
- GRB 250103B: LCOGT Optical Upper Limit
- IceCube-250102A: Upper limits from a search for additional neutrino events in IceCube
- EP250101a: Liverpool Telescope optical upper limit
- IceCube-250101A: Upper limits from a search for additional neutrino events in IceCube
- GRB 250101a: Liverpool Telescope optical follow-up
- GRB 250103B: Swift detection of a burst
- GRB 250103A: Xinglong 2.16m Optical Candidate
- GRB 250101B: SVOM/GRM observation
- GRB 250103A: GOTO optical upper limit
- GRB 250103A: SVOM/C-GFT optical upper limit
- GRB 250101A: NUTTelA-TAO / BSTI Optical Limits
- EP241231b: optical upper limit with the Liverpool Telescope
- GRB 250103A: SVOM detection of a long burst (duplicate submission)
- GRB 250103A: SVOM detection of a long burst
- EP250101a: Xinglong optical upper limit
- LIGO/Virgo/KAGRA S241230bd: Upper limits from Swift/BAT-GUANO
- GRB 250101A: Swift-BAT refined analysis
- GRB 250101A: further SAO RAS optical observations