GCN Circulars
GCN Circulars are rapid bulletins submitted by and distributed to the community. See the documentation for help with subscribing to or submitting Circulars.
Search for Circulars by submitter, subject, or body text (e.g. 'Fermi GRB').
To navigate to a specific circular, enter the associated Circular ID (e.g. 'gcn123', 'Circular 123', or '123').
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"- The EP-WXT trigger 01709132387 is likely a flaring star
- Fermi GRB 250307A: Global MASTER-Net observations report
- Konus-Wind detection of GRB 250306A
- GRB 250307A: Fermi GBM Final Real-time Localization
- GRB 250306A: Swift-BAT refined analysis
- GRB 250306A: NuSTAR detection of the prompt emission
- EP250304a: MeerKAT detection of a possible radio counterpart
- IceCube-241016A: MASTER flaring blazar 5BZU J073038.29-320820.2 with Zhirkov effect
- GRB 250305A: AstroSat CZTI detection
- EP250302a:Xinglong optical observations
- GRB 250306A: AstroSat CZTI detection
- Fermi trigger No 762963055: Global MASTER-Net observations report
- Fermi Gamma-ray Burst Monitor trigger 762963055/250306591 is not a GRB
- Swift GRB 250306A: Global MASTER-Net observations report
- LIGO/Virgo/KAGRA S250207bg: Update-5 NED Galaxies in the Localization Volume
- GRB 250306A: Swift detection of a burst
- LIGO/Virgo/KAGRA S250207bg: Updated Sky localization
- GRB250101A: Radio upper limits from VLA observations
- LIGO/Virgo/KAGRA S250306ej: Retraction of GW compact binary merger candidate
- GRB 250305A: SVOM/GRM observation of a burst
- The EP-WXT trigger 01709132323 is likely a flaring star
- EP250304A: Upper limits from Fermi-GBM Observations
- Fermi GRB 250305A: Global MASTER-Net observations report
- Fermi-LAT Gamma-ray Observations of IceCube-250302A
- GRB 250305A: Fermi GBM Final Real-time Localization
- EP250302a: Optical Observations at CrAO and SAO RAS
- GRB 250219A: SVOM/C-GFT optical upper limit at early phase
- EP 250304A: Optical counterpart detection by LCO
- EP250302A: 1.3m DFOT optical afterglow detection
- IceCube-250302A: Upper limits from a search for additional neutrino events in IceCube
- EP250304a: refined analysis of the EP-WXT and EP-FXT observations
- Konus-Wind detection of GRB 250222A
- EP250304a: REM NIR upper limits
- IPN triangulation of GRB 250222A
- EP250304a: Swift/UVOT detection of an optical counterpart with a rising light curve
- EP250302a: Mondy Continued Optical Observations
- EP250304a: VLT/X-shooter redshift z = 0.200
- EP250304a: Swift-XRT detection of a fading X-ray source
- EP250304a: TRT optical counterpart detection
- LIGO/Virgo/KAGRA S250304cb: Identification of a GW compact binary merger candidate
- EP250304a: Global MASTER-Net observations report
- EP250304a: Einstein Probe detection of an X-ray transient
- The EP-WXT trigger 01709132212 is not a real source
- EP250302a: SVOM/VT optical observation
- LIGO/Virgo/KAGRA S250223dk and Swift/BAT-GUANO ID 762004910: Swift/UVOT Upper Limits
- EP250302a: SAO RAS optical observations
- EP250302a : GIT optical follow-up
- EP250302a: VLT/X-shooter redshift confirmation
- EP250225a: the candidate optical counterpart is an AGN
- EP250302a: Kinder optical follow-up observations
- LIGO/Virgo/KAGRA S250302av: 2 counterpart neutrino candidate events from an IceCube neutrino search
- EP250302a: Swift/UVOT detection
- EP250302a: NUTTelA-TAO Early Measurments
- EP250302a: optical observation from the INAF Asiago Observatory
- EP250302a: REM NIR upper limits
- IceCube-241113A: MASTER flaring blazar 5BZB J1311+0853 with Zhirkov effect
- EP250302a: Mondy Observations and Optical Light Curve
- EP250302a: VLT/MUSE optical redshift z = 1.131
- INTEGRAL: end of scientific operations
- EP250302A: VLT near-infrared observations
- EP250302A: VLT/X-shooter tentative redshift
- EP250302a: OHP/T193 optical and spectroscopic observations
- EP250302a: Global MASTER-Net observations report
- EP250302a: Xinglong F60B optical observation
- EP250302a: Swift-XRT observations of a fading X-ray source
- EP250302a: Einstein Probe detection of an X-ray transient
- EP250302a: SVOM/C-GFT optical observations
- GRB 250226A: GRANDMA Optical Observations
- EP250302a: Montarrenti Observatory optical detection
- Fermi GRB 250302A: Global MASTER-Net observations report
- EP250302a: FTW optical and NIR detection
- EP250302a: Nanshan/HMT optical counterpart detection
- IceCube-250302A - IceCube observation of a high-energy neutrino candidate track-like event
- GRB 250302A: Fermi GBM Final Real-time Localization
- GRB 250228A: Fermi GBM Final Localization
- The EP-WXT trigger 01709132140 is likely a flaring star
- LIGO/Virgo/KAGRA S250206dm: early X-ray upper limits from Einstein Probe WXT and preliminary results of FXT observations
- GRB 250225B: VLT near-infrared afterglow confirmation
- EP250228a: Optical observations with Kinder and Swift/UVOT
- Konus-Wind detection of GRB 250226A
- GRB 250225B: EIRSAT-1 GMOD Detection
- GRB 250226A: KAO Optical Upper Limit
- GRB 250226A: AbAO AS-32 Optical Upper Limit
- EP250227a: Global MASTER-Net observations report
- EP250223A: Upper limits from Fermi-GBM Observations
- EP250227a: TRT optical upper limit
- GRB 250225B: VLT/HAWKI near-infrared observations
- EP250227a: Optical upper limits with Kinder observations
- EP250227a: NOT optical observations
- EP250227a: Einstein Probe detected of a fast X-ray transient
- EP250228a: updates on the EP observations
- GRB 250226A: Fermi GBM Observation
- EP250225a: EP-FXT follow-up observation
- EP250223a: J band upper limit by SYSU 80cm telescope
- EP250228a: Swift/XRT localisation
- EP250228a: Global MASTER-Net observations report
- EP250228a: Einstein Probe detection of an X-ray transient
- GRB 250226A / EP250226a: LCO detection of the afterglow
- LIGO/Virgo/KAGRA S250227e: Updated Sky localization
- LIGO/Virgo/KAGRA S250226dl: Updated Sky localization