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.
Lucene Examples (click to copy):
subject:"Swift"
body:"GRB"
submitter:"Judith Racusin"
23211 results found.
- AT 2025dws, likely optical counterpart of GRB 250309B: LCO confirmation of fast fading
- GRB 250309B: Fermi GBM Observation
- GRB250309B: One candidate counterpart from the Zwicky Transient Facility
- IceCube-250309A: No candidates from the Zwicky Transient Facility
- Fermi-LAT gamma-ray observations of IceCube-250309A
- GRB 250308A: SVOM/GRM detection of QPO in the tail emission
- EP250308a: Einstein Probe detection of an X-ray transient
- EP250308a: NOT optical upper limit
- EP250304a: MeerKAT detection of a possible radio counterpart
- IceCube-241016A: MASTER flaring blazar 5BZU J073038.29-320820.2 with Zhirkov effect
- EP250302a:Xinglong optical observations
- LIGO/Virgo/KAGRA S250207bg: Updated Sky localization
- GRB250101A: Radio upper limits from VLA observations
- GRB 250305A: SVOM/GRM observation of a burst
- The EP-WXT trigger 01709132323 is likely a flaring star
- Fermi-LAT Gamma-ray Observations of IceCube-250302A
- 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
- EP250304a: Swift/UVOT detection of an optical counterpart with a rising light curve
- EP250302a: Mondy Continued Optical Observations
- 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: Einstein Probe detection of an X-ray transient
- 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: Kinder optical follow-up observations
- LIGO/Virgo/KAGRA S250302av: 2 counterpart neutrino candidate events from an IceCube neutrino search
- EP250302a: Swift/UVOT detection
- 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
- EP250302A: VLT near-infrared observations
- EP250302A: VLT/X-shooter tentative redshift
- EP250302a: OHP/T193 optical and spectroscopic observations
- 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
- EP250302a: Nanshan/HMT optical counterpart detection
- GRB 250302A: Fermi GBM Final Real-time Localization
- 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
- GRB 250226A: KAO Optical Upper Limit
- GRB 250226A: AbAO AS-32 Optical Upper Limit
- 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: Einstein Probe detection of an X-ray transient
- GRB 250225B: VLT/Xshooter imaging
- GRB 250205A / EP250205A: further radio observations with the VLA
- EP250225a: NOT optical candidate counterpart
- EP250226a/GRB 250226A:Xinglong optical follow-up observations
- EP250226a/GRB 250226A: refined analysis of the EP-WXT and FXT observations
- EP250225a: TRT optical upper limits
- EP250226a/GRB 250226A: 1.6m Mephisto observations
- LIGO/Virgo/KAGRA S250206dm: Upper limits from SVOM/GRM Observations
- EP250226a/GRB 250226A: Kinder optical follow-up observations
- LIGO/Virgo/KAGRA S250227e: Identification of a GW compact binary merger candidate
- LIGO/Virgo/KAGRA S250226dl: Identification of a GW compact binary merger candidate
- GRB 250225B: Fermi GBM Observation
- GRB 250225B: REM NIR upper limits
- LIGO/Virgo/KAGRA S250223dk and Swift/BAT-GUANO ID 762004910: Updated Sky localization and Coincidence with External Event
- Konus-Wind detection of GRB 250225B
- LIGO/Virgo/KAGRA S250223dk: DECam optical detections of Swift X-ray sources
- EP250223a: CrAO ZTSH optical observation
- GRB 250225B: VLT optical and near-infrared candidate counterpart
- GRB 250225B: SVOM/GRM observation of a long burst
- GRB 250221A: EP-FXT detection of the X-ray afterglow
- EP250226a/GRB 250226A: COLIBRÍ/DDRAGO Detection of the Optical Counterpart
- EP250226a / GRB 250226A: TRT optical counterpart observation
- LIGO/Virgo S250223dk: Swift XRT observations, 7 X-ray sources
- EP250226a/GRB 250226A: EP-WXT detection and FXT follow-up observation of an X-ray transient
- EP250223a: GMG Optical Observation
- EP250225a: Einstein Probe detected of a fast X-ray transient
- EP250223a: GROWTH-India Telescope optical observations
- EP250215A: J band upper limit by SYSU 80cm telescope
- 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
- EP250223a: Kinder optical follow-up observations
- LIGO/Virgo/KAGRA S250223dk and Swift/BAT-GUANO ID 762004910: Upper limits from Fermi-GBM Observations
- GRB 250119B: VZLUSAT-2 detection