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"4055 results found.
- LIGO/Virgo/KAGRA S250701bq: Identification of a GW compact binary merger candidate
- LIGO/Virgo/KAGRA S250701bp: Identification of a GW compact binary merger candidate
- LIGO/Virgo/KAGRA S250629bs: Updated Sky localization
- LIGO/Virgo/KAGRA S250629ae: Updated Sky localization
- LIGO/Virgo/KAGRA S250629bs: Identification of a GW compact binary merger candidate
- LIGO/Virgo/KAGRA S250628am: Identification of a GW compact binary merger candidate (duplicate submission)
- LIGO/Virgo/KAGRA S250629ae: Identification of a GW compact binary merger candidate
- LIGO/Virgo/KAGRA S250628am: Updated Sky localization
- LIGO/Virgo/KAGRA S250628am: Identification of a GW compact binary merger candidate
- GRB 250601A: Swift/BAT-GUANO arcminute localization of a likely short burst
- GRB 250530C: BOOTES-7 optical upper limit
- EP-WXT trigger 01709177124: confirmation of a stellar flare by BOOTES-6
- GRB 250527C: Swift/BAT-GUANO arcminute localization of a burst
- EP J1350.0-8622: BOOTES-6/DPRT optical upper limit
- GRB 250424A: COLIBRÍ detection of the associated supernova
- LIGO/Virgo/KAGRA S250328ae: DECam DESGW Candidates (Final Epochs)
- EP250511a: BOOTES-5 optical upper limit
- IceCube-250506A: Upper limits from a search for additional neutrino events in IceCube
- GRB 250504A: EIRSAT-1 GMOD Detection
- IceCube-250429A: Upper limits from a search for additional neutrino events in IceCube
- IceCube-250426A: Upper limits from a search for additional neutrino events in IceCube
- GRB 250424A: EIRSAT-1 GMOD Detection
- IceCube-250416A: Upper limits from a search for additional neutrino events in IceCube
- IceCube-250421A: Upper limits from a search for additional neutrino events in IceCube
- LIGO/Virgo/KAGRA S250328ae: Subaru/PFS Spectroscopic Follow up and Candidates
- SVOM/sb25042207: BOOTES-2 early optical upper limit
- IPN triangulation of GRB 250321D (consistent with the fast X-ray transient EP250321a)
- IceCube-250406A: Upper limits from a search for additional neutrino events in IceCube
- LIGO/Virgo/KAGRA S250331o: Upper limits from Swift/BAT-GUANO
- EP250404a: BOOTES-4/JGT optical afterglow detection
- GRB 250403A: 1.6m Mephisto multi-band optical detection
- LIGO/Virgo/KAGRA S250328ae: DECam DESGW Candidates (Epoch 2)
- GRB 250330B: EIRSAT-1 GMOD Detection
- LIGO/Virgo/KAGRA S250331o: Updated Sky localization
- GRB 250331D: Swift/BAT-GUANO arcminute localization of a burst during slew
- IceCube-250330A: Upper limits from a search for additional neutrino events in IceCube
- LIGO/Virgo/KAGRA S250331o: NED Galaxies in the 3-Initial Localization Volume
- LIGO/Virgo/KAGRA S250328ae: Swift XRT observations, 34 possible X-ray sources
- LIGO/Virgo/KAGRA S250331o: Identification of a GW compact binary merger candidate
- GRB 250330A: BOOTES-7 early optical upper limit
- LIGO/Virgo/KAGRA S250328ae: DECam DESGW Candidates (Epoch 1)
- LIGO/Virgo/KAGRA S250329fl: 2 counterpart neutrino candidate events from an IceCube neutrino search
- LIGO/Virgo/KAGRA S250328ae: NED Galaxies in the 4-Update Localization Volume
- LIGO/Virgo/KAGRA S250328ae: Updated Sky localization
- LIGO/Virgo/KAGRA S250328ae: Identification of a GW compact binary merger candidate
- GRB 250327B: Las Cumbres optical counterpart detection
- LIGO/Virgo/KAGRA S250326y: Updated Sky localization
- LIGO/Virgo/KAGRA S250326y: Identification of a GW compact binary merger candidate
- GRB250322A: STEP/T80S optical limits
- LIGO/Virgo/KAGRA S250206dm: LIGHETR followup observations of AT2025azn
- LIGO/Virgo/KAGRA S250319bu: Updated Sky localization
- LIGO/Virgo/KAGRA S250319bu: Identification of a GW compact binary merger candidate
- GRB 250316A: Swift/BAT-GUANO arcminute localization of a burst
- FRB 20250206A: Nondetection of Repeating Bursts from FRB 20250206A with FAST
- LIGO/Virgo/KAGRA S250304cb: Upper limits from Swift/BAT-GUANO
- IceCube-250309A: Upper limits from a search for additional neutrino events in IceCube
- IceCube-250309A - IceCube observation of a high-energy neutrino candidate track-like event
- LIGO/Virgo/KAGRA S250207bg: Update-5 NED Galaxies in the Localization Volume
- LIGO/Virgo/KAGRA S250207bg: Updated Sky localization
- LIGO/Virgo/KAGRA S250306ej: Retraction of GW compact binary merger candidate
- IceCube-250302A: Upper limits from a search for additional neutrino events in IceCube
- LIGO/Virgo/KAGRA S250304cb: Identification of a GW compact binary merger candidate
- LIGO/Virgo/KAGRA S250223dk and Swift/BAT-GUANO ID 762004910: Swift/UVOT Upper Limits
- LIGO/Virgo/KAGRA S250302av: 2 counterpart neutrino candidate events from an IceCube neutrino search
- EP250302a: NUTTelA-TAO Early Measurments
- LIGO/Virgo/KAGRA S250206dm: early X-ray upper limits from Einstein Probe WXT and preliminary results of FXT observations
- LIGO/Virgo/KAGRA S250227e: Updated Sky localization
- LIGO/Virgo/KAGRA S250226dl: Updated Sky localization
- LIGO/Virgo/KAGRA S250206dm: Upper limits from SVOM/GRM Observations
- LIGO/Virgo/KAGRA S250223dk: Insight-HXMT/HE sub-threshold detection of a burst (HEB 250223501)
- LIGO/Virgo/KAGRA S250227y: Retraction of GW compact binary merger candidate
- LIGO/Virgo/KAGRA S250227e: Identification of a GW compact binary merger candidate
- LIGO/Virgo/KAGRA S250226dl: Identification of a GW compact binary merger candidate
- LIGO/Virgo/KAGRA S250223dk and Swift/BAT-GUANO ID 762004910: Updated Sky localization and Coincidence with External Event
- LIGO/Virgo/KAGRA S250223dk: DECam optical detections of Swift X-ray sources
- LIGO/Virgo S250223dk: Swift XRT observations, 7 X-ray sources
- LIGO/Virgo/KAGRA S250223dk and Swift/BAT-GUANO ID 762004910: DECam GW-MMADS candidates
- LIGO/Virgo/KAGRA S250223dk and Swift/BAT-GUANO ID 762004910: AstroSat CZTI non-detection and upper limits
- LIGO/Virgo/KAGRA S250223dk and Swift/BAT-GUANO ID 762004910: Magellan upper limits.
- LIGO/Virgo/KAGRA S250223dk: DECam DESGW Candidates
- LIGO/Virgo/KAGRA S250223dk and Swift/BAT-GUANO ID 762004910: Upper limits from Fermi-GBM Observations
- GOTO observations of LVK S250223dk/Swift-BAT RAVEN alert
- LIGO/Virgo/KAGRA S250223dk: DDOTI Upper Limits on the Optical Counterpart
- LIGO/Virgo/KAGRA S250223dk and Swift/BAT-GUANO trigger with ID 762004910: Identification of a GW compact binary merger candidate possibly associated with a sub-threshold Swift/BAT-GUANO trigger
- LIGO/Virgo/KAGRA S250206dm: Upper limits from IceCube neutrino searches
- LIGO/Virgo/KAGRA S250221gb: Retraction of GW compact binary merger candidate
- LIGO/Virgo/KAGRA S250221eb: Retraction of GW compact binary merger candidate
- LIGO/Virgo/KAGRA S250206dm: Upper limits from MSU cubesats observations
- LIGO/Virgo/KAGRA S250206dm: AZT-33IK Target Optical Observations
- LIGO/Virgo/KAGRA S250206dm: observation in AbAO, optical transient near NED/GLADE+ galaxy WISEA J021210.14+514821.7
- LIGO/Virgo/KAGRA S250206dm: MASTER LC AT2025bbo
- LIGO/Virgo/KAGRA S250206dm: DECam GW-MMADS candidates
- LIGO/Virgo/KAGRA S250206dm: FTW observations of counterpart candidates AT2025bbo and AT2025bcx, and of NED galaxies
- LIGO/Virgo/KAGRA S250206dm: NEWFIRM NIR Follow-up of AT2025ber
- LIGO/Virgo/KAGRA S250206dm: GECKO Continued Observaiton with 7DT
- LIGO/Virgo/KAGRA S250206dm: AT 2025bbo observations with WFST
- LIGO/Virgo/KAGRA S250211be: Updated Sky localization
- LIGO/Virgo/KAGRA S250206dm: continued in SOAR galaxy targeted observations and identification of one possible transient
- LIGO/Virgo/KAGRA S250206dm: Kinder confirmation of a possible artefact in AT 2025bbo
- LIGO/Virgo/KAGRA S250211be: Identification of a GW compact binary merger candidate