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"2790 results found.
- GRB 260818B: SVOM/ECLAIRs refined analysis
- GRB 260818A: SVOM/ECLAIRs refined analysis
- GRB 260818A: SVOM possible detection of a long and faint GRB
- EP260812b: GTC/OSIRIS+ tentative spectroscopic redshift z = 2.034
- GRB 260805D: SVOM/GRM detection of a possible magnetar burst
- EP260812a: NOT and Liverpool Telescope upper limits:
- EP260812b: Einstein Probe detection of an X-ray transient
- GRB 260317A: SVOM/ECLAIRs detection through offline targeted search and its possible association to magnetar 1E 1841-04.5
- GRB 260807A: SVOM/ECLAIRs refined analysis
- GRB 260808B: SVOM/ECLAIRs refined analysis
- GRB 260807A: SVOM possible detection of a faint burst
- GRB 260708A / SN 2026stf: Spectroscopic host redshift z = 0.055 and confirmation of an associated type Ic-BL supernova
- GRB 260802A / EP J223759.5+531421: SVOM/VT optical upper limit
- GRB 260802A/EP J223759.5+531421: SVOM detection of a possible magnetar burst
- GRB 260726A: SVOM ECLAIRs improved position and MXT possible detection of a counterpart
- IceCube-260722A: Classification of ZTF26abjbxfs/SN 2026vts as a Type Ia Supernova
- GRB 260706A: ATCA detection of possible radio counterpart
- GRB 260705A: ATCA radio observations
- GRB 260705A: Candidate Optical Counterpart from SOAR and Gemini-South and Possible Association with GRB 260705B
- GRB 260704A: SVOM/COLIBRÍ (FM-GFT) possible optical counterpart candidate
- GRB 260704A: SVOM detection of a possible GRB
- GRB 260618A: Fermi GBM Observation
- GRB 260618C: SVOM/ECLAIRs detection of a possible burst through on-ground search
- GRB 260610B: VLT/FORS2 spectroscopic observation suggests the non-thermal nature of the optical rebrightening
- GRB 260619A: SVOM possible detection of a faint burst
- Konus-Wind detection of GRB 260616A
- GRB 260610B / AT2026owq: SAO RAS optical observations of possible re-brightening
- GRB260616C: MAXI/GSC detection
- GRB 260610B / AT 2026owq: Possible re-brightening identified from Pan-STARRS observations
- GRB 260610B / AT2026owq: SVOM/VT optical observations
- GRB 260610B / AT 2026owq: COLIBRÍ optical observations
- GRB 260610B / AT2026owq: Early ATLAS observations
- GRB 260604C: GRANDMA further observations
- GRB 260604C: Mondy optical observations: evidence of a possible brightening
- GRB 260603A: SVOM/COLIBRÍ (FM-GFT) photometric redshift z = 3.57
- EP260602a: COLIBRÍ optical observations
- GRB 260601B/EP260601a: Insight-HXMT detection
- GRB 260601B/EP260601a: GECAM-B analysis suggests a possible long duration Type I burst
- GRB 260601B: GECAM-B detection of a burst probably associated with EP260601a
- GRB 260530B: SVOM/GRM detection of a possible bright short GRB
- EP260527a/GRB 260527A: optical upper limit with Kinder observations
- GRB 260527A/EP260527a: FTW optical and NIR observations
- GRB 260527A: GECAM-B detection of a short burst probably associated with EP260527a
- GRB 260516D: GOTO optical counterpart detection
- GRB 260516D: GROWTH-India Telescope optical detection
- GRB 260516D: SVOM possible detection of a burst
- EP260507a: Kinder optical counterpart candidate
- GRB 260310A / AT2026fgk: photometric monitoring and tentative maximum of a possible SN
- GRB 260504B: SVOM detection of a short burst
- GRB 260428A: SVOM/GRM observation of a possible short burst with extended emission
- GRB 260428A: GECAM-B detection of a possible long duration Type I burst
- EP260417a/GRB 260417A: refined analysis of the EP-WXT and follow-up EP-FXT observations
- GRB 260411B: COLIBRÍ optical observations
- GRB 260407B: SVOM/GRM detection of a possible magnetar X-ray burst
- EP260321a: uGMRT observations
- EP260329a: EP-FXT follow up observation
- EP260321a: Upper limits from a neutrino search with IceCube
- EP260321a: VLT imaging and spectroscopy show the variable source to be at z = 0.0343
- EP260321a: further Kinder optical observations
- EP260321a: refined analysis of the EP-WXT and EP-FXT observations, implying a possible supernova shock breakout candidate
- GRB 260310A / AT 2026fgk: COLIBRÍ evidence of a late rebrightening
- EP260314a: COLIBRÍ optical upper limit
- GRB 260310A / AT 2026fgk: COLIBRÍ continuing optical observations
- GRB 260310A/AT 2026fgk: Bok spectroscopic observation
- GRB 260310A / AT 2026fgk: COLIBRÍ optical observations
- GRB 260307B: possible NOT optical counterpart
- GRB 260207A: TESS Detection and Possible VLA Counterpart
- SVOM/sb26030408: SVOM detection of an X-ray transient likely associated with Beta Persei
- GRB 260303A: SVOM detection of a burst
- EP260214a: VLA 6 GHz detection
- GRB 260204A: SVOM/ECLAIRs refined analysis
- EP260128a: Liverpool Telescope optical observations and possible counterpart
- GRB 251208D: SVOM/ECLAIRs refined analysis
- GRB 251208D: SVOM/ECLAIRs refined analysis
- GRB 260109C: LCO optical upper limits
- Swift Trigger 1434591: possible GRB 260109C
- GRB 260103A: SVOM/GRM observation of a possible GRB
- GRB 251230A / EP251230a: further NOT optical observations revealing shallower decay or possible rebrightening
- GRB 251230A/EP251230a: Optical upper limit with Kinder observations
- IceCube-251225A - IceCube observation of a high-energy neutrino candidate track-like event
- GRB 251129A / EP251129a: VLA detection of a radio counterpart
- GRB 251219A: GECAM-B detection of a possible magnetar X-ray burst from SGR 1830-0645
- IceCube-251218A - IceCube observation of a high-energy neutrino candidate track-like event
- EP251214a: EP-WXT detection of an X-ray transient possibly associated with GRB 251214A
- IceCube-251210A - IceCube observation of a high-energy neutrino candidate track-like event
- GRB 251208D: SVOM possible detection of a faint burst
- Swift GRB 251205A : MASTER OT detection with host galaxy
- SVOM/sb25120502: SVOM detection of a faint X-ray transient candidate
- GRB 251203B: LCO optical upper limits
- GRB 251201A: GECAM-B observation of a burst
- GRB 251201A: SVOM/GRM observation of a burst
- IceCube-251130A - IceCube observation of a high-energy neutrino candidate track-like event
- LIGO/Virgo/KAGRA S251105aj: EP-FXT follow-up observations and preliminary results on SVOM J2320.0-2901
- LIGO/Virgo/KAGRA S251105aj: SVOM/ECLAIRs detection of a high-energy transient SVOM J2320.0-2901 through targeted search
- GRB 251118C: Glowbug gamma-ray detection of the fast X-ray transient EP251118A
- GRB 251118C: Swift/BAT rates detection of a burst with a possible association with EP 251118A
- GRB 251118C: SVOM/GRM observation of a possible gamma-ray counterpart of EP251118a
- GRB 251116D: SVOM/GRM observation of a long GRB
- GRB 251119A: SVOM detection of a possible burst
- GRB 251013C: Koshka, SAO RAS, Mondy, and CrAO optical observations, possible SN detection